SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: double-d on September 28, 2010, 11:17:31 AM
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18 foot jetboat with jacuzzi yj with american turbine conversion. "A" impelller
463 olds w/ Ga heads Ported quite a bit
180lbs compression.
comp cam 42-231-4, 230@ 50 installed straight up
single Holley 750 DP w/ mech secs, plug color is a nice tan.
Offy turbo thrust manifold. Intake manifold vacuum at idle is 11.5
MSD ignition and dist. +12 advance
Bassett over the transom water injected headers. No thermostat, engine temp is always 100F or less.
This thing runs great but, I can only get this motor to rev to 48-4900 rpm, sure its 61mph, but this thing should get to 6k rpm no?
I'm getting parts to build up a holley 850, and give it some more cfm, anyone think i should try otherwise?
For the olds guys what carbs, impellars and rpms are you running?
thanks
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your gunna need about 700-750hp at 6k to get to 6k and that motor is probably not making that much hp
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Ok, here's the american turbine impellar chart
H.P. 9.5 9.25 AA A B C
150 2900 3050 3200 3600 3800 4050
200 3200 3350 3500 4000 4200 4450
250 3450 3600 3700 4300 4500 4800
300 3800 3950 4050 4550 4800 5100
350 4050 4200 4300 4750 5100 5350
400 4250 4400 4500 5050 5300 5600
450 4450 4600 4700 5250 5500 5850
500 4650 4800 4950 5400 5700 6050
550 4800 4950 5100 5550 5850 N/A
ok 6k is probably too high of an expectation. I think I should at least be able to get it to 5400.
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I wouldn't want to spin an olds to 6k for very long or very many times. And if your plug color is good then I wouldn't swap the Carb, but you can check manifold vacuum on a wot run to see if the Carb is too small. I would take a closer look at the ground strap on the plug and see where the timing mark is and check for speckles on the ceramic and if no detonation maybe put more timing in, what is your total and base timing? The camshaft could be degreed way off if it was installed " straight up" and it could be retarded or advanced, but no way to know without degreeing the camshaft.
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Well, i'll let you know how long it lasts at 6k. If it ever gets there, hahaa :thumbup:
base timing is 12 and full advance is 33.
I haven't degreed it, and i know i should. But installing it straight up is 106 at intake centerline as suggested on the cam card.
Im really leaning toward upping the carb to an 850, i have done a bunch of reseach and it's looking like i need around 800cfm min for the displacement.
I know it varies, but what vac at wide open would indicate too small a carb?
Any olds guys out there runinn' around 5500 rpm with an A impeller
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Impeller efficiency drops like ton of crap at or near 5200 RPM, once over that, your literally just "adjusting" the loading and unloading of the impeller and limiting cavitation...
Your setup sounds very close, maybe the tune is off or your pump is lagging in setup.
A little more info is really needed, but if you are "shooting" for 6,000RPM then I think you will be leaving something on the table..
Shoot for a MPH... More can be done for that. I have seen 540" big blocks not make 6,000 without a lot of tuning and ingenuity with an A impeller...The speed difference from 4900 to 6000 RPM will be negligible if you don't change the pump setup IMHO....
GT
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Well, i'll let you know how long it lasts at 6k. If it ever gets there, hahaa :thumbup:
base timing is 12 and full advance is 33.
I haven't degreed it, and i know i should. But installing it straight up is 106 at intake centerline as suggested on the cam card.
Im really leaning toward upping the carb to an 850, i have done a bunch of reseach and it's looking like i need around 800cfm min for the displacement.
I know it varies, but what vac at wide open would indicate too small a carb?
Any olds guys out there runinn' around 5500 rpm with an A impeller
I think an 850 double pumper is a good call...But wont get you to 6K, why did you pick that RPM BTW, just curious.... :sly:
My dads freinds Olds runs 5200 RPM like it has a governor on it, Berkeley pump with an A Stainless and a Trick plate loader, boat does 70 MPH with three people and a cooler of boat sodas... :thumbup:
I know for a fact it has an 850 dp because I dialed it in... :sly: Also has a 1" open spacer on a Edelbrock Victor intake...
GT
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double-d, You said Offy turbo thrust manifold, and single 750. Is that the single carb tunnel ram ?
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double-d, You said Offy turbo thrust manifold, and single 750. Is that the single carb tunnel ram ?
Single carb tunnel = :thumbdown: :thumbdown: Just my opinion :-\
GT
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Single carb tunnel = :thumbdown: :thumbdown: Just my opinion :-\
GT
Yea, thats kinda what I was gettin at. If thats what he has, its a HUGE plenum to try to feed (for lack of a better term) with a single carb, not to mention the funky flow to the corner cylinders.
Not sayin thats you problem, but if I remember right those manifolds wanted a big carb.
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I bought a new jet boat olds/jacuzzi WJ in 1975--on the test drive, the motor ran 5600 rpms and the sales guy told me I had a strong motor. They didn't have GPS, but it ran a measured mile in just less than 1 minute, so low 60s MPH. Well in year 2, the tach broke and when I replaced, rpms dropped to 4900, but the speed was the same. Hmm, must have been one of those "closer" tachs.
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I bought a new jet boat olds/jacuzzi WJ in 1975--on the test drive, the motor ran 5600 rpms and the sales guy told me I had a strong motor. They didn't have GPS, but it ran a measured mile in just less than 1 minute, so low 60s MPH. Well in year 2, the tach broke and when I replaced, rpms dropped to 4900, but the speed was the same. Hmm, must have been one of those "closer" tachs.
I didn't know they had E bay tachs in 1975.. :sly:
Hi Mark!
Sorry for the jack double d
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ha! they probably had the tach switched to 6 cylinder
i picked 6k because that is what the cam is rated to.
yup single carb tunnel ram. I don't know why people frown on 'em, it's pulling good vac, other then they have no bottom end on the street, on a boat that doesn't matter.
offys carb selector says the manifold only needs a 650-700 with single carb, they don't specify displacement though.
GT so are you saying to go dual carbs? do you know what cam your buddy has? I would be happy with 5200 @ 70! it would be cheaper to change the cam.
here's an article i found, looks like an 850 is the min.
http://www.popularhotrodding.com/tech/0302phr_oldsmobile_455ci_engine_build/index.html (http://www.popularhotrodding.com/tech/0302phr_oldsmobile_455ci_engine_build/index.html)
Dyno Results
STOCK REBUILD
With an Edelbrock Performer manifold,
a Demon 850-cfm carb, MSD ignition,
and Hooker headers
RPM TORQUE HP
3,000 525 300
3,100 522 308
3,200 522 318
3,300 521 328
3,400 525 340
3,500 529 352
3,600 533 365
3,700 532 375
3,800 528 382
3,900 522 388
4,000 516 393
4,100 507 396
4,200 500 400
4,300 492 403
4,400 481 403
4,500 471 404
4,600 459 402
4,700 447 400
4,800 433 395
4,900 424 395
5,000 413 393
5,100 404 393
UPGRADED LEVEL 1- Same as the
stock rebuild, but with COMP cam,
rockers, springs, and pushrods
RPM TORQUE HP
3,000 490 280
3,100 490 290
3,200 494 301
3,300 496 312
3,400 507 328
3,500 527 351
3,600 531 364
3,700 536 377
3,800 538 389
3,900 538 400
4,000 536 408
4,100 526 411
4,200 520 416
4,300 513 420
4,400 507 425
4,500 501 429
4,600 494 433
4,700 485 434
4,800 474 433
4,900 465 434
5,000 456 434
5,100 449 436
5,200 442 438
5,300 435 438
5,400 422 434
UPGRADED LEVEL 2- Same as upgraded level 1,
except for the Offenhauser
Tunnel Ram, and dual Holley 750-cfm carbs
RPM TORQUE HP
3,000 512 292
3,100 514 304
3,200 518 316
3,300 520 327
3,400 526 341
3,500 535 356
3,600 538 369
3,700 541 381
3,800 537 389
3,900 531 394
4,000 526 401
4,100 518 404
4,200 510 408
4,300 505 413
4,400 498 418
4,500 493 423
4,600 488 427
4,700 481 430
4,800 473 432
4,900 464 433
5,000 456 436
5,100 455 442
5,200 450 445
5,300 447 452
5,400 440 452
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double-d,
I really want you to take this for what is is worth, which may be very little to nothing... :-\
Those dyno results if you were to plot them on a curve, cross "too early" to be a real powerhouse in the jet boat application. (look at how early the torque tapers off)....
Automotive thinking will get you into trouble every time. ;)
I have gotten in to too many debates regarding this very subject, so i wont go there...For now.
Your setup is horse power friendly but torque poor. There are a few things that I would look into before going crazy and please do the research before actually changing anything.....
First off, I need some clarification on what you mean by "pulls good vacuum". In what regard? Your vacuum levels with a T/R at speed should be spooky low, like in the -.5" to -1" should be obtainable I would think....If you have a high vacuum number, it would be due to not getting the most out of the T/R or a small carb choice.
Single carb T/R's are notoriously unbalanced, meaning you need to play with rocker arm ratio's and jetting, not to mention spark plug heat ranges and gaps to get them to work right...Not worth the fuss IMHO...
(I know that sounds funny, but I had a 377 SBC that wanted smaller ratio rockers in the corners according to the dyno numbers and pyrometer readings... :screwy:
I want to say it was a camshaft chosen by Mondello Performance, but know nothing about it other than it sounds like it wants to eat up the universe at idle, extremely lumpy...
Jet pumps require a ridiculous amount of torque to achieve their potential, that being said, the torque requirement does not taper off like that of a car or a prop boat. It gets convoluted as hell the more you dig in to it...
Don't focus on RPM, focus on speed, it is a bigger picture way of looking at it, FWIW, you can sometime reduce RPM, but pick up MPH, take a rebuild from a worn pump as an example....
I am not trying to criticize in any way, just trying to point you in a different direction, jets are a different animal than anything with wheels or props...Many will disagree and "they" are wrong.... ;D
GT
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yup single carb tunnel ram. I don't know why people frown on 'em, it's pulling good vac, other then they have no bottom end on the street, on a boat that doesn't matter.
offys carb selector says the manifold only needs a 650-700 with single carb, they don't specify displacement though.
I dont care what Offy says about that manifold, they dont work. Pulling good vac doesnt mean squat when the fuel is falling out of suspension before it gets to the corner cylinders. And yea, I had one (with a 750 on it). Changed to a duel 4 top and the motor was wayyy happier, more responsive and even idled better (with 660s on it). Just look at that manifold for a second. Imagine how the a/f mixture has to travel to reach those corner cylinders. Down the carb, then turn 90 deg, travel all the way to the front or back of the plenum, then another 90 deg turn down into a runner. All while trying to not let the fuel drop out of suspension. Meanwhile every time you stab the throttle, the carb basically shoots fuel directly down the center cylinders runners. I bet if you check your plugs closely the center cylinders look more rich, and the corners look more lean.
Another thing to consider about carb sizing and manifolds. Lets say you had a duel plain intake and a 600 carb. When a cylinder tries to draw air it basically sees a small plenum (half the total size because of the divider) and a 300 cfm carb (it can only draw from half of the carb because of the divider).
Same carb but on a single plain intake, now each cylinder can draw from a larger plenum that is fed by the full 600 cfm.
Your tunnel ram has or should have a divider in the plenum (like a duel plain intake), so basically your feeding each cylinder with a huge plenum and a 375 cfm carb. I know, theres an opening under the divider in there, but because of the huge size of that plenum it doesnt do much to help. Thats why that intake needs a big carb. If you dont mind the imbalance between cylinders they will work OK for cruising around, but not for high performance. Thats why they make a duel 4 top for them.
I would bet that motor would run better with a Victor style single plain intake, like GT said his dads friend has. But if you want to stick with a tunnel ram, get the duel 4 top and another 750.
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WOW !!! This is like porn to me guys. Keep it up ;D
Mmmmm Olds TR's 6K rpm Oh yeah that's what I'm talking about
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WOW !!! This is like porn to me guys. Keep it up ;D
Mmmmm Olds TR's 6K rpm Oh yeah that's what I'm talking about
SERIOUSLY!!! I was thinking the same exact thing. GT and Propless are making me a pitch a tent while learning a shitload in the process. This is awesome. Love this stuff! >:D
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I am in a similar situation with my 21' charger. The Panther pump is fresh with a bronze sleeve, blueprinted, and jeto. Just installed a 502ci ford
that is balanced, seriously ported heads, 10/1 compression, a degreed comp cam( 270-280 dur, 538-554 lift ), Edelbrock Performer RPM, roller
rockers, 12 deg initial- 36 total timing, and 750 vac sec Holley. Machinist with dyno estimates 500hp. Engine is very strong and tune is good
but at WOT 60mph at 5000rpm is all it will do. I am thinking I need at least an 850cfm Dp or possibly street avenger carb. Any suggestions.
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IMO more rpms are not neccesarily the answer ,Your Olds engine will have a much greater chance at sustaining usefull "life" (despite all the oiling mods one could make) partly because of its inherant design, if it was built to make power to a little under 5k and if made to produce enough "grunt" to swing a big Impeller, AA, to 9.5 (which your Jet bowl can accept) It would have a mad hole shot and should move plenty of water to put you close to your speed goal , Were currently building a BBO for a mid west customer and will post up some pics and info on it later call if we can help Tom
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Glass cutter/ Ford lover,
Since you’re enjoying this sooo much, I’m gonna need 4.95 per min, pay pal accepted! Haha need to pay for a dual carb set up!
Gt,
11.5-12 I think is good vac at idle, not sure at wot yet.
I took the choke off the side of the carb a few years back, after some reading last night, i discovered there is a vac circuit there that is now open, I'll plug it with, I don't know what yet, and see if more vac is gained.
If you sbc wanted smaller ratio in the corners, that would equal less air/fuel right?
Sounds like your saying that jet boats need torque at the upper end of the power curve. Since a later-closing intake can enhance top-end torque at the expense of low-end torque has anyone run their cam 4 degrees retarded and had better results?
Right now the plan of attack is to get a vac gauge, that I can read while doing 60+ w/ the 750, then step up to the 850 and check it again.
Propless, I gotta stick with a single carb for now. I’ll check the intake to see if it’s dual plane, but I know Offy made a single plane upper for jet boat use.
I’ll check the plugs and see if the outer cylinders are leaner.
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Glass cutter/ Ford lover,
Since you’re enjoying this sooo much, I’m gonna need 4.95 per min, pay pal accepted! Haha need to pay for a dual carb set up!
Gt,
11.5-12 I think is good vac at idle, not sure at wot yet.
I took the choke off the side of the carb a few years back, after some reading last night, i discovered there is a vac circuit there that is now open, I'll plug it with, I don't know what yet, and see if more vac is gained.
If you sbc wanted smaller ratio in the corners, that would equal less air/fuel right?
Sounds like your saying that jet boats need torque at the upper end of the power curve. Since a later-closing intake can enhance top-end torque at the expense of low-end torque has anyone run their cam 4 degrees retarded and had better results?
Right now the plan of attack is to get a vac gauge, that I can read while doing 60+ w/ the 750, then step up to the 850 and check it again.
Propless, I gotta stick with a single carb for now. I’ll check the intake to see if it’s dual plane, but I know Offy made a single plane upper for jet boat use.
I’ll check the plugs and see if the outer cylinders are leaner.
Not to beat a dead horse here, but vacuum numbers at idle mean nothing....
There is a reason if you want it (engine is under a load at all times on a jet and timing at idle will totally change these numbers)...
And there are several reasons for playing with rocker ratio on some engines, there are times when the dynamics of the induction/exhaust systems simply like it, I don't have any information to back it up other than watched it real time on a dyno.
Use a lead pellet to plug the small hole on the side of the carburetor, the vacuum source was there to pull heat riser heat into the choke housing, it really depends on what choke setpu you have/had...A .177 caliber pellet works well. 8)
Retarding the camshaft may make the situation worse. I gotta run right now, but I will be back.. :thumbup:
GT
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I can turn about 5000 mabey 5500 with an a but im runin a tunel ram and dual 660s and a 540 lift 305 duration cam and c heads with bassets and 10.5 to 1 compression
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for the guys with dual carbs, are the mech or vac secondaries?
its a dual plane upper manifold so that sux. Maybe I'll get my precision sawsall out.
Checked the plugs and they all looked pretty close in color but the ones in the back looked more rich. Definitley not what i was expecting according to what was said.
New vac gauge on the way. So when I run this sumbitch, I should be looking for the lowest amount of vacuum when i romp on it from dead stop or cruz on the primarys then floor it? Obviously its not vac at max rpm. Or do both say something about engine performance? I'm diggin into a holley carb book tonite to find out more on manifold vac.
double D
( . ) ( . )
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for the guys with dual carbs, are the mech or vac secondaries?
its a dual plane upper manifold so that sux. Maybe I'll get my precision sawsall out.
Checked the plugs and they all looked pretty close in color but the ones in the back looked more rich. Definitley not what i was expecting according to what was said.
New vac gauge on the way. So when I run this sumbitch, I should be looking for the lowest amount of vacuum when i romp on it from dead stop or cruz on the primarys then floor it? Obviously its not vac at max rpm. Or do both say something about engine performance? I'm diggin into a holley carb book tonite to find out more on manifold vac.
double D
( . ) ( . )
quick olds and I both have 660s, there mech 1 to 1 (prim and sec open at the same time, kinda like mini Dominators).
As far as I know Offy never made a top that didnt have the divider, even my duel 4 top has it. I dont think I would cut it out, its already suffering from a lack of velocity in that plenum because its to big. Cutting the divider will make it worse (IMO).
Back corners rich would indicate an overly rich mixture. With the low RPM your turning the mixture is sitting around to long in the plenum (lack of velocity, because its to big), the fuel is heavier so it settles to the lowest point (the back of the plenum). I would leave the mixture alone, its better than running the fronts lean. And thats what will happen if you try to tune for a good mixture on the rear cylinders. If you where running higher RPM (moving more air/fuel through the plenum to increase the velocity) and the mixture was a bit leaner, then you would start to see the lean corner/ rich center issue.
Vacuum at max RPM will tell you if the carb is to small, a carb thats to small for the motor will be a restriction and have a higher than normal vac reading. But thats another area of debate that I'm not going to set foot into. Because the rules seam to change when a tunnel ram is involved. :sly: Think about the fact that quick olds is running 1320 cfm of carb on a tunnel ram and turning around the same RPM as GT mentioned with a Victor manifold and 850 cfm. Tunnel rams are different animals and like lots of cfm (IMO).
I think (IMO) you might get a few RPM gain (not to mention better fuel distribution) by switching to a Victor style manifold or even a good duel plain and the 850. Then work on the pump set up to gain speed. Theres more to gained speed wise with the pump set up than by just adding RPM, and the Olds will be happier. What has been done with the jet (besides the conversion), loader ? droop ? diverter ?
Another thing just to think about, when I first put the single 4 tunnel ram on my old boat it lost 150 RPM compared to the duel plain that was on it (same carb). Once I got the duel 4 top and 660s, then the motor came to life. Thats why I hate those manifolds sooo much.
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jetting is 78/84
plug color this week is going to look a bit more rich, it's been 110 outside the last time i ran it, but the rpm has always been the same.
the jet...
stainless A, rex marine performance ramp scoop, 4 degree wedge, and place diveter.
has about fifteen tanks of gas throught it since rebuild.
I'm considering a mini droop.
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I'm not going to get all technical into why I agree Proppy and GT are right on all this. PM me if you want that whole storm. lol.
Leave it at this, T/R's in general are very high rpm only devices that require a TON of compression, Cam, fuel (Both pressure and volume), and forethought into their setup. Not many of these things are very conducive to the Oldsmobile engine, I'm sorry to say.
Vacuum secondary vs mechanical, I run vac, and run inline because I beleive there's inherent bank to bank rich/lean conditions running larger carbs sideways unless you run 1:1 as Proppy does (Firing order comes into play........its a LONG thought process and reasoning behind this).
There's an inherent hate for vac secy's here that really is unfounded, even on T/R's. Trick is spring selection, and that's probably the ONLY info you will gather with a Vacuum Guage that might help with that. Other than that, a Vac guage I don't see doing much for you that a can of WD40 can't in checking for leaks. I did it through trial and error, and the weird setup I have. I duplicated this so my "ship" will have twin setups the same way on 2 engines and jets! Thanks to Proppy and Jim Brock I was able to replicate that arrangement. :thumbup:
The only real insight as to how a T/R is working and to tune it is throttle response, reading your plugs, and performance. You will do this MANY times setting one up right. 2 of those are seat of the pants measurements, only 1 a technical measurement, if you notice. Yes, on a jet boat, pump setup will have a LOT to do with it, just as in a drag car, gearing and tranny issues are involved as well.
Single 4 BBL Tunnel Rams, regardless of what engine and carb on them, IMHO and don't take this the wrong way, are like watching someone else get laid. You get an insight as to what it's all about, you get to be in the room for the show, but you don't get to experience the actual thrill of it for yourself!
Stick with what works on the Olds. A good hi-rise single plane, large carb, cam and compression to work with it, then the pump must match that. I also have a Jacuzzi/Olds combo that will be going through some "changes" over the winter (Among other projects going on). It will stay Jacuzzi/Olds, but as far as where it will end up? A very decent and reliable Hot Rod, but probably nowhere near as fast as others I have laying around.
My .02
Ray
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I'm considering a mini droop.
Based on what? ::)
BTW, If Olds had larger runners in the heads, I would say a tunnel would be the correct answer, but the Olds heads are pretty under designed as far as a high RPM motor is concerned..Just my opinion.
GT
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based getting the pump in the water more and a bit more roost. It seems like the droop snoot is the hot set up, but i don't wanna screw around with cable and linkage BS. I figured a mini droop would be a good comparmise. if it ain't gonna do jack, well thats why I'm here, to figure out what works. :thumbup:
Well, im getting the message that tunnels suck, you ain't hurting my feelings but thats what i'm runnin' at the moment.
It's cheaper to change the manifold then to F around with dual carbs, linkage, finding a dual quad top, blah blah blah.
Ray, the idea i'm planning is using the vac gauge is see how the changes effect the motor. You had mentioned throttle response, plugs and performance. The vac gauge should tell this, since we all know an engine is a big air pump. If I make a change that for example increases manifold vac at wide open throttle then I know it was a change for the better. Vac also helps for sizing power valves.
I asked before if the guys who had tunnel rams and dual carb about there secondaries being vac or mech because IMO 1260 cfm is way over carbed for the volume of air/fuel one cylinder can process. But maybe i don't know shit. If they were vac then the secondarys only open when there is enough vac to do so. Since his boat idled better and better throttle reponse, I was thinking the secondaries where not opening or only at the top end... When the 1 to 1 linkage came into play that but the kabaash on vac seconday theory. Gt mentioned an 850 and a victor doing about the same rpm. Shit i'd rather change a manifold stuff a double A in the pump and rip.
I foundnthis article
http://www.jpmagazine.com/projectbuild/154_0711_455_bigblock_project_murderous_overkill_part_vi/index.html (http://www.jpmagazine.com/projectbuild/154_0711_455_bigblock_project_murderous_overkill_part_vi/index.html)
Although we pushed Welfringer for specifics, we were unable to learn much more than the Edelbrock Torker manifold (PN 2730) underwent Mondello's proprietary blueprinting process. In a nutshell, the intake was port-matched to the cylinder heads using Mondello's gaskets and the plenum and ports were reworked to increase flow-a lot. Mondello also port-matched the Edelbrock Victor manifold (PN 2810) that we tested on Westech's dyno. The Victor was too macho for our engine, proving it needed even more compression, camshaft, and rpm to be happy. The Mondello-modded Torker proved to be an absolutely perfect match for the rest of the combo.
Displacement: 468ci
Bore x stroke: 4.185 x 4.250 inches
Compression ratio: 10.75:1
Rod length, center to center: 6.735 inches
Piston deck height: 0.002-inch
Chamber volume: 77cc
Rod bearing clearance: 0.025-inch
Crank endplay: 0.004-inch
Piston-ring end gap: 0.014-inch (top), 0.018-inch (middle), 0.025-inch (bottom)
Piston-to-wall clearance: 0.005-inch
Camshaft type: Comp Cams solid roller
Valve lift: 0.640-inch (int.), 0.649-inch (exh.)
Duration at 0.050: 268/276 degrees
Lash (hot): 0.020-inch
Lobe separation: 110 degrees
Valve spring (seat): 250 pounds at 1.750-inch
They have a monster cam in this thing and i they say victor is too much and the torker is the way to go. Anyone run a torker and see better results?
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I read that article before..Pretty cool stuff...However, you may disagree here, but trust me on this...This could turn into a month long debate :screwy:
The application of the engine in the article is very different from your jet boat...
Your jet pump will absorb literally everything you throw at it HP wise...That being said, your vacuum levels will be atrociously low because of the engine load...Imagine running your 442 wide open throttle in high gear going straight up the Grapevine and not letting off. That is what you are asking of your boat motor... :screwy: No car buff in there right mind would ever do that, even on a bet...
With all that being said, if the engine load is high, causing low vacuum levels, what would be the best remedy for that? You got it! more air and fuel, so bigger is better (in this case anyways)...
With all do respect to all the automotive enthusiasts, they don't know chit when it comes to a badass jet boat motor tune...
It is very difficult to over carb a big block in a jet, as long as you have good velocity across the venturies, it will work killer, vacuum has little to do with it, but is a great tuning tool...
I'm telling you right now, keep your eyes open for a good used Victor and you will never look back. :thumbup:
The thing I hate about the Torker is the looks, but a great manifold performance wise, the Victor is a better looking piece IMO. :sly:
I would love to see some back to back tests on each, but we all know that's not going to happen... :-\
Another note, a tunnel ram does different things with the air, so 1260 CFM sounds like a lot, it really will not flow those kinds of numbers, but the tunnel ram uses the advantage of working less hard to obtain the air fuel charge accelerating it toward the intake runners....
GT
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based getting the pump in the water more and a bit more roost. It seems like the droop snoot is the hot set up, but i don't wanna screw around with cable and linkage BS. I figured a mini droop would be a good comparmise. if it ain't gonna do jack, well thats why I'm here, to figure out what works. :thumbup:
Not saying it wont work, quite the contrary, just wanted to know what the hull was doing to warrant the droop. What you are doing by adding the droop is change the height of the thrust line (also called the "X" dimension) and quite often adversely effects performance, especially on bow light hulls...
Droops and wedge is a "tune" thing, I seriously doubt any two boats react the same with the same parts....Use what works on yours, not what worked on someone elses, although someone elses is a great starting point if their set up is similar in many ways to yours... :thumbup:
I hope I am not confusing the issue more...I am trying to give real world examples, but I have been programming buildings and working on electronic crap all day, so I could seriously be blowing it out of my ass.. :screwy:
GT
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double-d, Ive been looking for this for you for a bit and finally found it. Heres some more reading for you, http://www.performancemotorsportsnews.com/newsdisplay.php?newsID=177 (http://www.performancemotorsportsnews.com/newsdisplay.php?newsID=177) . Its an article called "the Practical Olds" written by Tim from TUFENUF MARINE PERFORMANCE (AKA TIMINATOR on here), not sure why, but he hasnt been on here in a long time, maybe he dont love us anymore. :sly: There is great info about the Olds motors in there, there inherent issues, how to deal with them, and parts recommendations (look at the section about intakes).
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Picking up 1000 1100 Rpm takes more than a carb or manifold change. Put a nitrous system on with will power to not use it all the time a adjustable plate so you can change HP. You won't need much of a shot to get the rpm you want. Probably he cheapest way and you don't have to use it constantly like a big built engine. Takes will power not to abuse the nitrous, but will haul the mail,like was suggested I wouldn't turn 6 K all the time.
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The majority of Olds "mods" are common sense engine 101 , the rest are IMO can be attributed to Joe Mondello Joe really did pioneer the majority of what makes this motor work , like him or not (not the current "Mondello" administration) Getting the 455 motor to make good power lies mostly in the cylinder heads and valve train , making it live is all about the oiling system , heres Josh making a few of the mods to the 468 (455) aluminum head deal, were building right now , including but not limited to external oil returns (note the returns at the block skirt area) Tom
(https://www.socaljetboats.com/proxy.php?request=http%3A%2F%2Fi147.photobucket.com%2Falbums%2Fr319%2Fjetboatperformance%2FDSC00001-1.jpg&hash=dcc98f66c13493c929922e7ffdef40a79969969c)
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BTW Cant say that Timm doesn't have a good recipe but the majority of Olds "mods" are common sense engine 101 , the rest are IMO can be attributed to Joe Mondello Joe really did pioneer the majority of what makes this motor work , like him or not (not the current "Mondello" administration) Getting the 455 motor to make good power lies mostly in the cylinder heads and valve train , making it live is all about the oiling system , heres Josh making a few of the mods to the 468 (455) aluminum head deal, were building right now , including but not limited to external oil returns (note the returns at the block skirt area) Tom
(https://www.socaljetboats.com/proxy.php?request=http%3A%2F%2Fi147.photobucket.com%2Falbums%2Fr319%2Fjetboatperformance%2FDSC00001-1.jpg&hash=dcc98f66c13493c929922e7ffdef40a79969969c)
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Yeah I would love to squeeze and I had a kit on it a few years ago. I could really find a feesible place for the bottle that wasn't real close to headers, plus I would have killed space for chairs, anchor and what not.I took it off. still got the kit, maybe someday i'll do it up.
Well rigged up the boat with the vac gauge keeping the 750, and t/r on there for now. I got some good base line runs of 13hg at idle and 2hg at wide open doing 59 on gps.
After reading the a practical olds article i saw in there that the timing should be maxed out at 2500-2800. I went back to the msd chart and noticed the ignition curve is stock at doesn't max out until 5k with 21 degrees total advance. My baseline timing is 12, so i bumped it up 14 ran it, gained 1hg at idle but wot was hardly noticable. Bumped it up to 16 degrees and with 15 on the vac the engine sounded healther and starterd better. Got 60 out of it. Then went up 2 jet sizes on the secondaries. that as hardly noticeable. But i didn't do a full throttle kill and check the plugs. I ordered an advance kit to change to a more agressive curve. Any suggestions on timing curves to use. I'll swap to the 850 after that's dialed in.
here is some info i had found on carburation, this i very simalar to what my holley carb book says. I also read 3hg for a 2 barrel and .75hg for dual 4's.
Whether a carburetor never meets its rated airflow capacity or exceeds it is to some degree irrelevant. The key point is that for maximum performance a carburetor must deliver the airflow capacity demanded by the engine. As a general point of reference, if manifold vacuum exceeds 1.5 in/Hg (at WOT) on an engine equipped with a four-barrel, the carburetor is too small; if it falls below 1.5 in/Hg, the carburetor is too large. Obviously, there is at least one hole in that theory because any manifold vacuum level above zero represents a throttled condition, which means an engine won’t produce maximum power. However, if a carburetor is large enough to drop WOT manifold vacuum levels to zero, drivability issues at part throttle may result and low airflow velocities may negatively impact power. The key is to find that magical airflow capacity that keeps air velocities high, without excessively restricting flow.
I contacted comp cams to see if they have any dyno charts of what the hp/ torque numbers look like with the cam -4 straight up and +4 advanced. The guy said they don't have anything. I replied with I find that hard to believe they haven't done that with one single cam in there whole inventory. Please forward to the dyno dept. We'll see what he has to say.
I am leaning to the torker manifold, 850 then maybe the double A. I know the victor is probably better but I think I want to build for torque if double A goes in. But that won't be until next season since my test water, lake hodges closes halloween.
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IMHO you can safely drop below the 1.5" WOT vacuum in a boat without many issues....The reason is again engine load....When it gets to 3/4"to 1" is when things are really happy, think in velocity, not vacuum... :thumbup:
You started the thread by saying you wanted more RPM, and now your saying you want to go to an AA... :screwy: :D
It is my humble opinion again that you stay with the A and use the Torker and the 850. With that combo, you really can't miss as far as the set up...
As for the timing issue, all in by 2,000 or even locked out with a separate ignition switch to get things spinning works with a radical cam...It improves the idle quality and dramatically improves throttle response...
If there are boo-boo's in this post, it is this damn keyboard :banghead: I think someone was using it as a wheel chock or something.. :screwy:
GT
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....all in at 2k, wow that's quick, I'm not going to run that curve first, my compression is too high to try that right off the bat.
Well your starting to talk me out of going for the higher rpm when you said its eaiser to go for speed. Since the olds motor doesn't quite do so hot up in the higher rpm range and its got gobs of torque i figure the double A will be a safer way to go. RPM wise. Swapping the impeller will be the last thing I do. I'll try the can't miss setup first.
I should be there at 3/4 to 1" with the 850
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....all in at 2k, wow that's quick, I'm not going to run that curve first, my compression is too high to try that right off the bat.
Well your starting to talk me out of going for the higher rpm when you said its eaiser to go for speed. Since the olds motor doesn't quite do so hot up in the higher rpm range and its got gobs of torque i figure the double A will be a safer way to go. RPM wise. Swapping the impeller will be the last thing I do. I'll try the can't miss setup first.
I should be there at 3/4 to 1" with the 850
You will be glad you did...
FWIW, my 468 Chevy has 11.5:1 compression and is all in at 1500 RPM with an MSD..I run 50/50 102 AKI and pump gas...Pulls an A to 5250 RPM consistently...No problem...
I can explain why... ;D
A jet pump uses very little horsepower up to about 3,000 RPM, there is a very small load on the engine, not like a four speed car that has to muscle it's way up to speed, think of it like a ridiculous stall converter, it let's things spin before the real work begins... :thumbup:
I will try very hard to not steer you wrong.. ;) I am not a trained professional, but play one on the forums... ;D
GT
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now that's funny! :thumbup: :thumbup:
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I will try very hard to not steer you wrong.. Wink I am not a trained professional, but play one on the forums... Grin
We got lots of other guys for wrong info. Just say the word and we will put you in touch with Vegas crowd. Or Omar (sorry Omar I had to) ;D
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Success! took out the boat this weekend with the light silver spings in the distributor. +16 base timing and 21 advance bushing. So a total advance of 37. Gained gained 200 rpm and maxed at 5100 rpm. Didn't get any MPH readings though, too many fisherman out there and the speed limit is 35.
Swapped over to a piece of shit Ebay 850 Holley knock off mainbody and base plate. Don't buy 'em!! The float bowl screws weren't tapped right, down leg boosters are crooked and the accelerator pump nozzles squirt so wide the fuel doesn't go directly in the carb. Total Junk!! Either way I Gained 100 rpm, peaked at 5200! Vac looks like it dropped down to 1-1.5.
Think I'm going to get the timing up another degree or 2 and lighter on the advance springs. Stickin' with the 750 holley for now, savin' up for a better 850 and the torker intake.
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Success! took out the boat this weekend with the light silver spings in the distributor. +16 base timing and 21 advance bushing. So a total advance of 37. Gained gained 200 rpm and maxed at 5100 rpm. Didn't get any MPH readings though, too many fisherman out there and the speed limit is 35.
Swapped over to a piece of shit Ebay 850 Holley knock off mainbody and base plate. Don't buy 'em!! The float bowl screws weren't tapped right, down leg boosters are crooked and the accelerator pump nozzles squirt so wide the fuel doesn't go directly in the carb. Total Junk!! Either way I Gained 100 rpm, peaked at 5200! Vac looks like it dropped down to 1-1.5.
Think I'm going to get the timing up another degree or 2 and lighter on the advance springs. Stickin' with the 750 holley for now, savin' up for a better 850 and the torker intake.
:thumbup: :thumbup:
GT
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Kinda late butbstay with the a and run it in my opinion tho if Ur gonna run an olds make sure u do the oil return mods to heads block ect so u can run high rpm my motor don't have piling issues anymore 10 at pan drilled the returns and restricted push rods help a lot keep the oil in the pan and run 5500 for a good mile or so i have kinda leafy staying in it longer but I think it'll be fine
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That was good reading and will help when I get around to building a motor this winter. Thanks for bringing this up again Quick Olds. :thumbup:
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Nada prob hit me up if u need help I'll show I what i did to my returns on my heads and block and mondello has the push rods kinda spendy but well worth it and if Ur in my area I'm always ready to help a fellow olds guy or girl :thumbup:
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Yeah got oil mods galore, -8 returns on the back of the heads going back to a 10 qt oil pan, oil restricted cam and main bearings.
what carb size carb your runnin'?
This year I only reduced the timing curve time, she runs a a lot better. I bought an 850 holley and a torker intake but haven't put it on yet.