SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: UltraRed on March 02, 2011, 12:22:14 PM
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What is your opinion about this... I am currently running what is thought to be an unmolested D9TE-AB. Would this work or am i asking for trouble.
Ported D3's with CJ valves
Scorpion pedastal mount roller rockers
Port matched Performer intake(nicely done)
780 Holley Street Avenger carb. Elec. choke. Vacuum secondaries
Custom length comp cams pushrods
Hyd. cam and lifters. Nice choppy idle with good vacuum. Pulls hard to 5500-6000
This is a complete setup that will get you at least 500HP. I'm running flat top pistons and am right around 10:1 compression. The car made 450 lbs of torque at the wheels at 4K. Engine is in the car at this time. I'm wanting the new TFS 325 heads and a big solid roller so I need to sell this stuff first. I'm just north of Nashville, TN.
Let me know...
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If you are saying that you have this:
I am currently running what is thought to be an unmolested D9TE-AB.
And you want to add only this to your current engine:
Ported D3's with CJ valves
Scorpion pedastal mount roller rockers
Port matched Performer intake(nicely done)
780 Holley Street Avenger carb. Elec. choke. Vacuum secondaries
Custom length comp cams pushrods
Hyd. cam and lifters. Nice choppy idle with good vacuum. Pulls hard to 5500-6000
And you are hoping to get this as a result:
This is a complete setup that will get you at least 500HP.
The answer is NO. It will not get you there all by itself. You will not have adequate camshaft, nor will you have adequate compression ratio, nor will you have adequate carburetor.
Set up properly, ported D3's can be nice heads, but you will not attain 500 hp from an OEM D9TE shortblock with little more than a ported D3 head swap plus an aluminun intake. Hell no.
LO
p.s.: If you have a King Cobra Marine 460 with the forged flat tops, you are better on your way, though. :)
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right on. exactly what i needed. Thank you
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Vacuum secondary carbs are junk for jetboats, you need at least an 850 for them, we sell and use the Chinese blueprinted(by us) HP 970 copies with excellent results, they will work well on just about any modified jet boat engine, and are cheaper than the Hollies. The Performer is one of the worst intakes for a jet. It has smaller runners than stock (and much smaller than the heads!). The Weiand Stealth, Crosswind, or Performer RPM Airgap, are miles ahead with any cammed performance engine, especially in a jet. Ya got a decent, mild, CAR setup though. Probable HP, less than 1 HP/cubic inch, in the real world, unless pro built and fully blueprinted. Having a car engine, you are better to off sell it as such, on a car forum. I'm not baggin' on your deal, but internal clearances and most cams will be wrong for a boat too, and I wouldn't want you to get caught up in a pissing contest if you sell it to a boat guy and it doesn't work out. Perhaps I was too harsh.... but it is what it is. TIMINATOR
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Vacuum secondary carbs are junk for jetboats, you need at least an 850 for them, we sell and use the Chinese blueprinted(by us) HP 970 copies with excellent results, they will work well on just about any modified jet boat engine, and are cheaper than the Hollies. The Performer is one of the worst intakes for a jet. It has smaller runners than stock (and much smaller than the heads!). The Weiand Stealth, Crosswind, or Performer RPM Airgap, are miles ahead with any cammed performance engine, especially in a jet. Ya got a decent, mild, CAR setup though. Probable HP, less than 1 HP/cubic inch, in the real world, unless pro built and fully blueprinted. Having a car engine, you are better to off sell it as such, on a car forum. I'm not baggin' on your deal, but internal clearances and most cams will be wrong for a boat too, and I wouldn't want you to get caught up in a pissing contest if you sell it to a boat guy and it doesn't work out. Perhaps I was too harsh.... but it is what it is. TIMINATOR
While I agree with a lot of info here, I have to respectfully disagree with the vacuum secondary comment...
They can be made to work and work extremely well. The problem is that most vacuum secondary carburetors are built with part throttle efficiency in mind. Once this has been tuned out of the set up, they work killer.
The biggest limitation on vacuum secondary performance carbs are parts availability for tuning them to a high RPM torque application. Most of the jetboat engines of late utilize much lower venturi velocities and actually are working way out of their intended design. Which in all honesty is why really high performance jets use so much fuel ( I have been working on this on paper), a vacuum secondary system is where its headed, my buddy's EFI boat uses less fuel than it did when it had an 870 CFM Barry Grant but makes another 150 RPM.....Have not gotten my head wrapped around that one yet, but suspect it was a venturi velocity issue allowing the fuel to just run in like an overflowing toilet.
Not trying to start anything, just throwing out that there are different strokes for different folks.... ;)
GT
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While I agree with a lot of info here, I have to respectfully disagree with the vacuum secondary comment...
They can be made to work and work extremely well. The problem is that most vacuum secondary carburetors are built with part throttle efficiency in mind. Once this has been tuned out of the set up, they work killer.
The biggest limitation on vacuum secondary performance carbs are parts availability for tuning them to a high RPM torque application. Most of the jetboat engines of late utilize much lower venturi velocities and actually are working way out of their intended design. Which in all honesty is why really high performance jets use so much fuel ( I have been working on this on paper), a vacuum secondary system is where its headed, my buddy's EFI boat uses less fuel than it did when it had an 870 CFM Barry Grant but makes another 150 RPM.....Have not gotten my head wrapped around that one yet, but suspect it was a venturi velocity issue allowing the fuel to just run in like an overflowing toilet.
Not trying to start anything, just throwing out that there are different strokes for different folks.... ;)
GT
I concurr whole heartedly. No problems running vac secondaries, even twins too large for the application on a Tunnel Ram, really. Every time I've encountered a carb problem on my boats, or a friends, it's been vacuum leaks somewhere. Base gaskets, intake gaskets, or even carb gaskets themselves. Mechanical secondaries would have NOT fixed the problem, only hidden it.
Vac secondary 4160 carbs work very well on jets, and were original equipment on all of them. To restate the original statement that Vac secondaries "had no place on a jet boat" is not only wrong, it's irresponsible. The vast majority of Marine Rated Holley carbs out there are Vac Secondary, and I'm pretty dead set on NOT running street carbs on ANY boat. There is startling evidence as to why, and I'm not gonna get into that, though I know many of you are running street carbs on your boats with no problems............yet.......... ;)
Ray
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The J tubes are obvious. What are the other differences between street and marine carbs? We always tune the carbs, so any tuning differences would not matter. Unless we plan to use them out of the box, obviously we would never do this.
The 870-EFI gains tell me that he was rich with the 870. Maybe 11-1 . The EFI probably brought him closer to the magic 12.5-1. Was he tuning his 870 with a wideband, or the seat of his pants?
Either vacs or mechs can be tuned adequately. The 4150 vacs have a lot more tunability than the 4160. No carburetor on the planet can compare to EFI! >:D You can tune a carburetor VERY well for any application with the correct tools. (a spark plug and a color chart are not part of this "proper tools" arsenal!"
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Vacuum secs typically do not FULLY open with a normal big block until about 6500 rpm, they are not designed to. Most jets don't turn that many rpm. If you use a light sec. spring to get them to open fully at normal jet rpms, a bog will occur during the transition. During part throttle cruise, the vac secs will open to the same amount as the primaries, the air flow speed will be low, and the economy will suffer. Part of that is because the secs are jetted richer than desired for continous use to help any transition bog while they are opening. The Vac sec carbs will have much less throttle response than double pumpers too. Using a large double pumper allows staying on the primary bores during much higher and lower cruise rpms, the mixture velocity is higher at lower rpms and that promotes torque and economy. You can the use the wrong part on many applications and it will work, just not optimally. If you haven't tried both setups correctly calibrated back to back on the same day, you have no basis to compare. Many aftermarket companies still sell junk parts for their intended applications because they still sell, not because they are correct. There exists a manifold company that still sells several old outdated designs, and promotes them too, even though the newer designs COMPLETELY outrun the old ones in every application. Many peeps buy that stuff based on advertising or advice from peeps that ran the junk when it was state of the art "back in the day", then when the new guy wants more performance, the company will be happy to sell them that too, they got your cash twice, rather than them recomending the correct part from the start. Marine vac sec carbs are used mostly for outdrive applications to minimize the shock to the drive, and help keep from cavitating the prop on the launch. Jets don't need either crutch. If you have never seen how long a vac secondary carb takes to open in actual use or on a flowbench, you can't fully appreciate why many of us won't use one in most applications. My 21 Daytona with the 572 and dominator carb modified to allow much more airflow before the secs opened, could cruise at about 65-68 mph on only the primaries, and fuel mileage was much better than your average 18 footer with a 454. P.S. it ran 113. TIMINATOR
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Vacuum secs typically do not FULLY open with a normal big block until about 6500 rpm, they are not designed to. Most jets don't turn that many rpm. If you use a light sec. spring to get them to open fully at normal jet rpms, a bog will occur during the transition. During part throttle cruise, the vac secs will open to the same amount as the primaries, the air flow speed will be low, and the economy will suffer. Part of that is because the secs are jetted richer than desired for continous use to help any transition bog while they are opening. The Vac sec carbs will have much less throttle response than double pumpers too. Using a large double pumper allows staying on the primary bores during much higher and lower cruise rpms, the mixture velocity is higher at lower rpms and that promotes torque and economy. You can the use the wrong part on many applications and it will work, just not optimally. If you haven't tried both setups correctly calibrated back to back on the same day, you have no basis to compare. Many aftermarket companies still sell junk parts for their intended applications because they still sell, not because they are correct. There exists a manifold company that still sells several old outdated designs, and promotes them too, even though the newer designs COMPLETELY outrun the old ones in every application. Many peeps buy that stuff based on advertising or advice from peeps that ran the junk when it was state of the art "back in the day", then when the new guy wants more performance, the company will be happy to sell them that too, they got your cash twice, rather than them recomending the correct part from the start. Marine vac sec carbs are used mostly for outdrive applications to minimize the shock to the drive, and help keep from cavitating the prop on the launch. Jets don't need either crutch. If you have never seen how long a vac secondary carb takes to open in actual use or on a flowbench, you can't fully appreciate why many of us won't use one in most applications. My 21 Daytona with the 572 and dominator carb modified to allow much more airflow before the secs opened, could cruise at about 65-68 mph on only the primaries, and fuel mileage was much better than your average 18 footer with a 454. P.S. it ran 113. TIMINATOR
Nice!!!! Facts , not opinion!
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Anybody that wants to drop on by during business hrs. can bring their favorite vac. sec. carb. and I'll throw it on the Superflow for ya. All fuel and vestiges of fuel MUST be cleaned out before this! AGAIN THE CARB MUST BE DRY BEFORE YOU DO THE NEXT EXPERIMENT!!!! If you want to try the experiment, take a blow gun and hold the primaries full open, (you do have to have three hands to make this work), find the small brass tube in the outside rear of the passenger side barrel(as installed on a car), blast down air straight into the venturi above that little tube, and see how long it takes to open the secondaries. The amount of air that you are blowing past the tube is smaller in volume than what the carb will ingest during operation, but you are concentrating that air right on the tube, and at a higher speed too. If the secs. open in about 3-5 seconds, that is normal, if you have removed the secondary diaphragms check ball or installed a very light spring, they open quicker but it will take a big pump cam and shooter to try and cover the bog that will result. Or you will have to "pedal" the throttle, or you get the bog or you get a backfire. Otherwise, the big shooter/big pump/big pump cam will only hurt your fuel mileage, but you WILL be smarter than the Holley engineers. AGAIN THE CARB MUST BE COMPLETELY DRY OF FUEL BEFORE DOING THIS TEST!!! We do this for a final test before returning a rebuilt carb to the customer, if you show him the "test" he will probably be saving up for a new carb! TIMINATOR
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I agree 90%. which is as close as you can get on a forum. IMO
You have OBVIOUSLY done a fair amount of testing.
"You can use the wrong part, and it will work. Just not optimally." I agree but EFI is so damn expensive!
Most of us are working with compromises and budgets.
One quick question. WFO aren't we all looking for 12.5 to 1 with no regard to vac, mech, or EFI? Maximum velocity without restriction!
Don't the power valves offset the 14.7 cruise to 12.5 at WFO on the holley vac and mech primaries? Economy vs. power. Therefore the mechanical secondaries would be chasing the same number as the vac secondaries. Neither should be richer than the other. You just do not have control over the 4160 secondaries.
I agree that if you change the opening rate of the vac secondaries you may create a lean condition during the transition.
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At typical jetboat rpm, the secondaries will not be fully open. The main jets control mostly the top rpm/air flow calibration only. When the carbs sec is not fully open, the mixture is controlled mostly by the air jets, and emulsion tubes. Unless the carb has been modified that can't be done. If you pay to have it modified you could have easily bought the correct doublepumper instead. About your statement of unrestricted air flow... carbs are rated with flow cfm at 1.5 inches of mercury vacuum below the carb, in other terms, that is 20.5 inches of water restriction. Standard flowbench protocol is to flow at 28 inches of water(heads, manifolds, etc.). The intake tract will never see that much vacuum at Wide open throttle, nor will the carb, nor do you want it to. You say you want unrestricted air flow(and you should have near that), but you are then recomending a 750 vac sec carb that will never fully open the secondaries and cause a large restriction. HUH? I have not seen even a stock 330 HP jet motor that will not benefit from a good, larger than stock dual plane intake and a 850 carb. We have sold a BUNCH of the blueprinted(by us) Chineese HP 950 clone carbs for use on everything from stock Olds 455s, 454s, and 460s, to 675 HP+ roller motors with alum heads. In every case those carbs outran an 850 Holley. Just for all of your info, the most used by the GM jetboat engines as a stock carb is the Quadrajet 4 bbl. and that flows 810 cfm, the smaller 785 unit was popular on smallblocks. In the case of our foreman's Biesemeyer jet, as an early experiment we installed only a Junk Torker(our opinion) and the HP 950 on an otherwise STOCK 455 Olds with log exhausts, it picked up 2-3 mph. Plug color was too close to change anything, when his ported head, now roller cammed 455 was finished, we installed the same carb and an Olds Crosswind intake on it, again the jetting was very close, only requiring a change to jets of 2 sizes smaller. Most peeps wouldn't have even bothered, but we are anal(in our case we take anal to be short for analyze!). Every post is backed up by a lot of past real world testing. We don't deal in "I think" or "I read", we try everything as much as possible! TIMINATOR
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At typical jetboat rpm, the secondaries will not be fully open. The main jets control mostly the top rpm/air flow calibration only. When the carbs sec is not fully open, the mixture is controlled mostly by the air jets, and emulsion tubes. Unless the carb has been modified that can't be done. If you pay to have it modified you could have easily bought the correct doublepumper instead. About your statement of unrestricted air flow... carbs are rated with flow cfm at 1.5 inches of mercury vacuum below the carb, in other terms, that is 20.5 inches of water restriction. Standard flowbench protocol is to flow at 28 inches of water(heads, manifolds, etc.). The intake tract will never see that much vacuum at Wide open throttle, nor will the carb, nor do you want it to. You say you want unrestricted air flow(and you should have near that), but you are then recomending a 750 vac sec carb that will never fully open the secondaries and cause a large restriction. HUH? I have not seen even a stock 330 HP jet motor that will not benefit from a good, larger than stock dual plane intake and a 850 carb. We have sold a BUNCH of the blueprinted(by us) Chineese HP 950 clone carbs for use on everything from stock Olds 455s, 454s, and 460s, to 675 HP+ roller motors with alum heads. In every case those carbs outran an 850 Holley. Just for all of your info, the most used by the GM jetboat engines as a stock carb is the Quadrajet 4 bbl. and that flows 810 cfm, the smaller 785 unit was popular on smallblocks. In the case of our foreman's Biesemeyer jet, as an early experiment we installed only a Junk Torker(our opinion) and the HP 950 on an otherwise STOCK 455 Olds with log exhausts, it picked up 2-3 mph. Plug color was too close to change anything, when his ported head, now roller cammed 455 was finished, we installed the same carb and an Olds Crosswind intake on it, again the jetting was very close, only requiring a change to jets of 2 sizes smaller. Most peeps wouldn't have even bothered, but we are anal(in our case we take anal to be short for analyze!). Every post is backed up by a lot of past real world testing. We don't deal in "I think" or "I read", we try everything as much as possible! TIMINATOR
This is all good information and you may be 100% correct as far as the bench testing, but at the same time I have had some jets with later model vacuum secondaries and all I can say is there was very little left on the table, I wish I had the list number, but the secondaries were as close to WFO at speed as they could be mechanically and it brought the WFO vacuum numbers down to the 2"h.g. realm....There was no room for more carb. IMHO...The wide band put us at near 13:1 AFR...
The reason for the test was trying to gain even a little fuel efficiency on a whitewater boat with a small block Chevy. Had we been able to increase the fuel economy even a little, we could lighten the boat up a bit by having a smaller load of the 6.2 lb/gal fuel.
What we ended up using was a Dial a Jet of sorts, it was an electronically manipulated metering block and it was adjusted using a wide band o2 (one of the early ones with the fancy LED lights)... :screwy: We were able to cut fuel runs by about 9 gallons a leg, which equated to about 55 pounds... :thumbup: Hell I could have the extra breakfast burrito which made it worth while :thumbup:
No need to defend yourself so strongly, my comment was merely for the weekend warrior who may or may not be on a limited budget trying to get a boat wet but does not want to drop $500-1000 on a properly sized carburetor...I say run it. the 9 HP you may leave on the table will NOT be noticeable in a jet.... (It typically takes 20-30 HP to gain anything in a jet pump application).
GT
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There wasn't any recommendation anywhere in this thread that I found for a 750 vac sec. Only the statement that vac secs can be made to work well. Even the Timinator states that many imperfect combinations can be made to function adequately.
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In regards to the original question, nevermind the 700+/- cfm anything for the jet boat. Instead put a Holley 850 on the 460 jetboat engine, even if the 460 is bone stock. We are not cruising down the highway at 2500 rpm, we are running 4000 rpm & above typical...and so the engine needs to breathe more easily up there.
LO