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What CFM carb are you running on your 460

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electrowoman

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« on: June 27, 2008, 10:10:33 PM »
I believe there is more horse power left on the table with my engine.    It's tops at about 5000 RPM's right now, has seen 5200 with the wind at it's back.

 I put on a 750 Holley to get it on the lake.  I think I should have gone with an 800 - 850 double pumper.  My target was 52-5300 rpms, two people on board.  The carb is a tad lean yet and a jet change in the near future. 

I'm just curious what size carb  you guys are running on your 460's and at what RPM's?  My set up is:
750 Holley vac secondaries +  1 inch spacer
Edelbrock RPM air gap intake
Edelbrock RPM heads  with a stud girdle
comp cams xtreme marine cam 278
flat top pistons
mallory ignition,  + msd 6al
Hardin marine logs port matched

My boat is a 23.5 foot Glastron Carlson CV 23,  A impeller berkeley jet.

I believe it weighs around 2000 lbs. that's a number I've seen but not verified.  It's a day cruiser so it isn't a light weight.



« Last Edit: June 27, 2008, 10:54:33 PM by electrowoman »


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« Reply #1 on: June 27, 2008, 11:01:42 PM »
IMO, (which has been known to be worth zilch), that 750 should do the trick. That being said, is it a stock carb, or has it been "tweaked"?. Does it still have the choke horn? what, if any type of arrestor or scoop is on it? and you say it is a little lean, how lean?

My 468 (I know I know a Chevy) has the XM278 w/10.5:1  domes with open chambered heads, Basset headers and a gasket matched high rise and turns exactly 5200 RPM and I'm running a pretty much stock holley 750 DP with the horn milled off and a BG quikjet metering block and I don't think there anything to be had by changing out the carb because there is vertually no vacuum left at WOT  (.6"), a bigger carb is just a bigger hole to pull in more CFM and I don't think there is enough cam to support it, but your situation could be different, being a ford and all (after all, what does a Chevy know, the damn thing is still wearing a Bowtie) ::)

An easy way to find out would be a vacuum guage to see whats she's running flat out.

Agian, just my feelings on the subject.

Its a lot easier to overcarb than to under IMO.
« Last Edit: June 27, 2008, 11:39:56 PM by GT Jets »
  • Boat #1: 1992 Carrera 20.5 Elite (I/O bitches)
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If i get some free time tonight at work, ill play with it and post it for everyone to see.

Time to man up and yank it John!  :banghead:
Ray

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« Reply #2 on: June 27, 2008, 11:09:07 PM »
The carb is still stock other than the secondary spring and 50cc acc. pump.  The plugs are on the  bone white side.  The mains are 70's  I plan on putting in 74's for a trial.

I didn't want to cut the carb up because I may be selling it.

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« Reply #3 on: June 27, 2008, 11:27:31 PM »
Here is an even easier experiment, use a twist tie on the secondary butterfly actuator clip point bent in a vee and tie it around the secondary diaphram body (I use tape) and take it out for a WOT run, then you can "read" how far the secondaries are opening. So cheap and easy you can call it fun!

BTW 70's are short, very short IMO. I would have expected 74-76's

I would keep an eye out for a good used 750 DP and keep the spacer, just make sure the spacer fits the carb nice and smooth and there are no obsructions.

Vacuum secondaries have there place and making tung a breeze because it will only "pull" what it can take, but with low man. vac. you could be leaving a little something on the table, (which is what you said) whereas a mech. sec. is a little more fussy, you can tell right away whats happening do to the instantanious drop in manifold pressure on the mechanical secondary and "feel" where the carb is leaving you "short" in a manner of speaking.
  • Boat #1: 1992 Carrera 20.5 Elite (I/O bitches)
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If i get some free time tonight at work, ill play with it and post it for everyone to see.

Time to man up and yank it John!  :banghead:
Ray

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« Reply #4 on: June 27, 2008, 11:33:42 PM »
In stockish Big blocks in the 450 ci range(give or take) I like 750-800's on a single plane, 800-850's on a dual plane.

A dual plane pulls from only 1/2 of the carb, so you need a bigger carb to get the top end.

Personally my 455 picked up a ton (500 rpm) going from a 750 vac to a worked 850 DP in the boat on a performer dual plane with no spacers.  

I would think you have what you need, I would suggest playing with spacers, secondary springs (I like the purple one, and these do change the CFM of the carb), primary jets, Convert the secondaries to a metering block style so you can change the secondary jets (unless you are lucky enough to have a 3310-1), mill the choke horn, convert to annular discharge, play with the ignition timing.  Also before you do anything make sure the carb is at least at stock jetting (nowadays primaries are 72's for a 3310, some came with 76's in the early days)


My fav carb is the 830 annular (9381) - anything I put it on makes the engine go faster it seems.  

I agree with the vac gauge (I have one in my dash in my boat), if you are pulling over a 1.5 in Hg at WOT, the carb is too small.


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« Reply #5 on: June 27, 2008, 11:38:55 PM »
BTW I was looking at he picture of your engine, do yourself a favor and reroute your fuel line away from the front of the engine, if you ever lose a pulley or a harmonic balancer you will have one of the scariest moments of your life (I have that T-shirt). >:D
  • Boat #1: 1992 Carrera 20.5 Elite (I/O bitches)
  • Boat #2: 19' Bubble deck Jet BBC Berkeley
If i get some free time tonight at work, ill play with it and post it for everyone to see.

Time to man up and yank it John!  :banghead:
Ray

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« Reply #6 on: June 27, 2008, 11:46:08 PM »
Quote
I would think you have what you need, I would suggest playing with spacers, secondary springs (I like the purple one, and these do change the CFM of the carb), primary jets, Convert the secondaries to a metering block style so you can change the secondary jets (unless you are lucky enough to have a 3310-1), mill the choke horn, convert to annular discharge, play with the ignition timing.  Also before you do anything make sure the carb is at least at stock jetting (nowadays primaries are 72's for a 3310, some came with 76's in the early days)


My fav carb is the 830 annular (9381) - anything I put it on makes the engine go faster it seems. 

I agree with the vac gauge (I have one in my dash in my boat), if you are pulling over a 1.5 in Hg at WOT, the carb is too small.


X2,
you have an RPM Airgap, which IMO is the best possible intake for your motor/application, which is why I don't thing bigger is better for this package. I would be really curious to see what the 74's do for you, I'm betting another 150-250 RPM if the rest of the setup is correct (you will be able to get more advance out of the ignition with a bit more fuel).
  • Boat #1: 1992 Carrera 20.5 Elite (I/O bitches)
  • Boat #2: 19' Bubble deck Jet BBC Berkeley
If i get some free time tonight at work, ill play with it and post it for everyone to see.

Time to man up and yank it John!  :banghead:
Ray

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« Reply #7 on: June 27, 2008, 11:51:02 PM »
I forgot to mention, the RPM isn't a true dual plane, and it isn't a single. It falls right in the middle, and an open spacer will make the carb seem even bigger (just like a true dual plane makes the carb seem smaller).
« Last Edit: June 27, 2008, 11:54:03 PM by speedymopars »
21' 74 cheyenne 543 Mopar Berkeley Jet Place diverter

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« Reply #8 on: June 28, 2008, 02:09:46 AM »
The secondaries have the yellow spring and are wide open.  I did the old finger test and there is nothing left. 

 I think I'll move the hoses inside the bulkhead.   There was no room on that side for
the filter is why the hoses and filter were where they are.

The spacer is the 4 hole which is what I ran on the old Torker intake, do you think I should
go to the open?




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« Reply #9 on: June 28, 2008, 06:20:35 AM »
830 dp i think ill check today

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« Reply #10 on: June 28, 2008, 07:33:29 AM »
Both of our Spectra's run older 780 Holley's with the air horns milled flat and radiused.  Stock these come with dual feeds and dual metering blocks.  Notes from the 20' say 74 pri /78 sec jetting.

Usually can be had complete for $50 or less on ebay or craigs.


Cheers, Mark
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« Reply #11 on: June 28, 2008, 04:24:38 PM »
The secondaries have the yellow spring and are wide open.  I did the old finger test and there is nothing left. 

 I think I'll move the hoses inside the bulkhead.   There was no room on that side for
the filter is why the hoses and filter were where they are.

The spacer is the 4 hole which is what I ran on the old Torker intake, do you think I should
go to the open?





I would think that an open spacer would work a little better, probably couldn't tell by "seat of the pants"  ("ASS-ANOMETER') but tuning becomes a little easier with open spacers because of the even pressures on the bores.

And sorry for the criticism on the fuel line routing, seen some scary stuff happen over the years and the eyes focus on possible problems and the mouth throws it at people invited or not ::)

Hate seeing people get hurt, especially if I saw a possible problem.
  • Boat #1: 1992 Carrera 20.5 Elite (I/O bitches)
  • Boat #2: 19' Bubble deck Jet BBC Berkeley
If i get some free time tonight at work, ill play with it and post it for everyone to see.

Time to man up and yank it John!  :banghead:
Ray

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« Reply #12 on: June 28, 2008, 04:48:44 PM »


The spacer is the 4 hole which is what I ran on the old Torker intake, do you think I should
go to the open?


A 4 hole spacer on a torker allows the single plane to work better on the bottom end - a 4 hole on a performer/performer RPM? That is a idle to 4500 RPM manifold at that point. I bet you have great throttle response though (and in a car you would feel great bottom end) and would give you better mileage. It never even crossed my mind that you would be running that combo.

Just take off the spacer and see how it does, then start adding open spacers. In my 440's in a car with a torker it seemed 2 inches open worked best, on a performer, I found it liked 1/2 to 3/4 of an inch.  Your combo WILL vary.

The performer RPM is setup to basically be a performer with about 5/8th -11/16th inch open spacer stock. No spacers on the RPM may in fact give you the best performance.
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« Reply #13 on: June 28, 2008, 06:17:55 PM »
750 demon /stealth intake /5000rpm/will upgrading to an 850 demon soon

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« Reply #14 on: June 28, 2008, 11:52:44 PM »
Keep in mind this is coming from some one that know's next to shit-nothing about mostly stock engines so take this for what it's worth.

1. ditch the 750 vac

2. replace wtih an 850 dp front power valve. Progressive linkage.

3. ditch the 4- hole spacer

4. replace with an 1"  open or better yet 2" Super Sucker spacer.

5. If the RPM Air Gap doesn't already have the plenum devider milled down( I think they do) mill the plenum divider down to 1" below the carb pad.

Sleeper CP

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« Reply #15 on: June 29, 2008, 08:23:04 AM »
454 .030 = 460

Im running a 650 DP with a Edelbrock rpm performer intake ;D

2sav

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« Reply #16 on: June 29, 2008, 09:24:30 AM »
454 .030 = 460

Im running a 650 DP with a Edelbrock rpm performer intake ;D

2sav

Your 650dp maybe a better choice than that 750 vac. I haven't liked vac sec carbs since I had a 780 on my 427 stroker motor in my '69 Mach 1. The engine would only rev to 6,200 +/-. Tried the different springs and nothing seemed to change. I swapped a re-built 850 I had and the first time I speed shifted that thing  was lucky I caught the engine at 7,200 rpm. That carb made that baby a different engine.

If you want performance get rid of the Vac carb.  Also read an article 20+ yrs ago in Car Craft or Hot Rod they had 4 builders build different big blocks and dyno them. The Ford guy put a 750 dp on his 460. At the dyno seccesion he didn't like the power #'s and put an 850 on the engine picked up 50 hp and I think it was only reving 6,500 if that much maybe just 6,000.

Sleeper CP  :)
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« Reply #17 on: June 29, 2008, 01:47:26 PM »
Something I meant to bring up in my previous post but forgot, plug reading on pump gas can be tricky, the way I have been taught to read a plug with pump gas is to put about 10-20% race fuel in with the pump gas because there can be a lot of "oxygenants" in pump gas which prevents a "true" plug reading, the color that you should be looking for is almost a rootbeer brown/rust color, grey can indicate an oil issue, but can also be a little rich, white and shades of white indicate "lean" whereas flat black is rich and gloss black is scary rich.

Run the boat wide open or close for about 30 secs. and do a "hot as you can do safely" shut down. pull a plug and take a digital picture of it, make changes and repeat...

Why the digital picture?, you'll be suprized how little the plug color will change, this will give you a running record.

Would like to hear/read other opinions though...The fuel we get here in the bay area varies big time season to season, so I run a blend of VP race fuel and pump puke.
  • Boat #1: 1992 Carrera 20.5 Elite (I/O bitches)
  • Boat #2: 19' Bubble deck Jet BBC Berkeley
If i get some free time tonight at work, ill play with it and post it for everyone to see.

Time to man up and yank it John!  :banghead:
Ray

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« Reply #18 on: June 29, 2008, 02:45:42 PM »
I believe there is more horse power left on the table with my engine.    It's tops at about 5000 RPM's right now, has seen 5200 with the wind at it's back.

 I put on a 750 Holley to get it on the lake.  I think I should have gone with an 800 - 850 double pumper.  My target was 52-5300 rpms, two people on board.  The carb is a tad lean yet and a jet change in the near future. 

I'm just curious what size carb  you guys are running on your 460's and at what RPM's?  My set up is:
750 Holley vac secondaries +  1 inch spacer
Edelbrock RPM air gap intake
Edelbrock RPM heads  with a stud girdle
comp cams xtreme marine cam 278
flat top pistons
mallory ignition,  + msd 6al
Hardin marine logs port matched
More-so than the carburetor itself, your jet pump will play a big part in how may rpms you will be able to turn your engine.

That being said, I feel that even the bone stock marine-issue 460s should have a Holley 850 double pumper, Holley list # 4781, especially since these jet boat engines run at 5000+/- sustained, the bigger carb is the way to go.  460's respond well to a lot of air, a lot of fuel, and lot of spark...in the engine's stock trim.

The fact that you have a cam, heads, and compression makes me think that the Holley 850 is the minimum that you should have.  Also, the Holley 850 that I am suggesting has progressive mechanical secondary linkage, so you can troll about on the primaries and get decent fuel economy, and also open both primary and secondaries at will whenever you want top-end power.

I run about 1400 cfm on my 0.030" overbore 460 jet boat engine.

LO

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« Reply #19 on: June 29, 2008, 02:54:59 PM »
That being said, I feel that even the bone stock marine-issue 460s should have a Holley 850 double pumper, Holley list # 4781, especially since these jet boat engines run at 5000+/- sustained, the bigger carb is the way to go.  460's respond well to a lot of air, a lot of fuel, and lot of spark...in the engine's stock trim.

The fact that you have a cam, heads, and compression makes me think that the Holley 850 is the minimum that you should have.  Also, the Holley 850 that I am suggesting has progressive mechanical secondary linkage, so you can troll about on the primaries and get decent fuel economy, and also open both primary and secondaries at will whenever you want top-end power.

I run about 1400 cfm on my 0.030" overbore 460 jet boat engine.

LO


I vote for what you and I said.  :)   I second that.

Sleeper CP  :)
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« Reply #20 on: June 29, 2008, 08:18:43 PM »
The 850 will be on the way tomorrow,  what jets do you run?  Do you think 74 in the main and 76 in the back would be ok to start?
Thank you!

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« Reply #21 on: June 30, 2008, 05:29:21 PM »
The 850 will be on the way tomorrow,  what jets do you run?  Do you think 74 in the main and 76 in the back would be ok to start?
Thank you!
If you purchased a brand new Holley carburetor then start with the jetting as received. Do plug readings and go from there.

LO

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« Reply #22 on: June 30, 2008, 05:46:53 PM »
If you purchased a brand new Holley carburetor then start with the jetting as received. Do plug readings and go from there.

LO


If not I'd start in the upper 70's just to be safe. 76-78 or 78 squared. Is it a power valve carb ? If so the primary side can start at 6 jet sizes smaller than the primary, but play it safe and start 4 sizes smaller.

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« Reply #23 on: June 30, 2008, 10:07:57 PM »
The stock jetting in the 850 dps are 80's square. The annular's come with 78's, I needed to get up to 83's square with the dusters engine and one carb.

I would start at 80 and see where you need to go.
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« Reply #24 on: July 10, 2008, 10:46:49 PM »
Any results on the 850 ?

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