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Six Pack on center carb only?

OOoo k but that seems to work pretty well for a lot of bracket racers ie sand baggers. I would start with backing off on the timing a bit and I like to run my carb/carbs a bit on the rich side. Changes in the weather seems to not affect them as much as being on the money or a tad lean. If that doesn't work, then do limiters.....easy stuff first. A simple adjustable stop under your loud pedal can be effective too.[/QUOTE I didn't mean to come off snippy, but I'm a firm believer that if everything remains the same
OOoo k but that seems to work pretty well for a lot of bracket racers ie sand baggers. I would start with backing off on the timing a bit and I like to run my carb/carbs a bit on the rich side. Changes in the weather seems to not affect them as much as being on the money or a tad lean. If that doesn't work, then do limiters.....easy stuff first. A simple adjustable stop under your loud pedal can be effective too.
I didn't mean to come off snippy. Sorry if I did. I'm a firm believer that a machine (race car) will repeat it's performance over and over again if (big if) all variables remain the same. When you need to be within a hundredth or so to win a round, backing into an opponent leaves a lot of variables in the equation. When I run N/SS with a class index, I would usually add weight, or short shift, or both in order to slow down to the next closest index. That worked very well. I like the idea of a throttle limiter. I'd still like to know if anyone disconnects the outboards with any success. That seems to be the easiest way, without changing any of my tune-up. After the race, I could simply reattach the vacuum lines and be back to normal.
 
Naw....just thought that it might be something you might try. Some can pull it off consistently and some can't....and I've never been one to hammer the brakes just before the line either but have just let off the gas especially if the win was for sure in the bag. I've been able to make my cars consistent without playing with them between rounds even if the weather changed and have done that with more than a couple. Had one that would run 10.50's but it wasn't consistent so started with timing and jetting up a tad. It slowed down a tenth and became very consistent. Guess there's only one good way to find out if disconnecting the outboards would do what you want. If you're a bit nervous about making it too lean on the just the center carb, fatten it a bit and go for it but I have never heard of anyone hurting the engine just running on the center only. I recall hearing about some doing that to get better mileage on the roads when everyone was running 75+ on the freeways but don't know if that really helped or not. Probably did because they had lead feet everywhere else lol
 
Not sure what frustration did, but on my 500 conversion we drilled the 500 in the same location relative to the venturi as stock, pressed in a piece of 1/8 brake line, inserted a fishing line sinker, then drilled the sinker with the same size hole as the stock center carb had. Worked perfect.
my thoughts were to put some kind of restriction in the hose. whether that would work or not may depend on the vacuum source.
 
I didn't mean to come off snippy. Sorry if I did. I'm a firm believer that a machine (race car) will repeat it's performance over and over again if (big if) all variables remain the same. When you need to be within a hundredth or so to win a round, backing into an opponent leaves a lot of variables in the equation. When I run N/SS with a class index, I would usually add weight, or short shift, or both in order to slow down to the next closest index. That worked very well. I like the idea of a throttle limiter. I'd still like to know if anyone disconnects the outboards with any success. That seems to be the easiest way, without changing any of my tune-up. After the race, I could simply reattach the vacuum lines and be back to normal.

It’ll slow way way down on just a 2 barrel. My 12.0 car went 13.7 one day when the outboards failed to open. Needless to say that took the excitement right out of it. That was on a 4412 center also.
 
When you learn how to use a throttle limiter, it's very accurate. I could move my N/SS cross ram car .01. Backed it from 10.1x to 11.0 more than once.
Doug
 
When I had my engine dyno'd it made 590 hp, then he made a pull just on the center carb 390 hp
But that was with stock center carb.
 
Just a thought, used to break apart the old glass fuses & drill a small hole in metal end & push the end into vacuum hoses to limit vacuum when screwing around in late 70’s to kinda bypass the emmision controls.
 
I had a light car with a small block and a brake. When I put a better converter in it , it stepped up to 6.30s 1/8, and the track started making noise about getting a license. I didn't want one so i disconnected the secondaries on my gold claw with blue sleeves ( i think 850cfm ). Car slowed from high 6.30s to low 6.50s. I would disconnect yours and find out what it does, just put in new plugs and check lean/rich. Also, engine masters says you can lose 130hp with the wrong air filter and fan (engine masters episodes 20 and 27).
 
When I had my engine dyno'd it made 590 hp, then he made a pull just on the center carb 390 hp
But that was with stock center carb.
i'm surprised you could get 390hp. what was the manifold vacuum at 390hp? those center carbs are only 250cfm @ 1.5"hg.
 
I had a light car with a small block and a brake. When I put a better converter in it , it stepped up to 6.30s 1/8, and the track started making noise about getting a license. I didn't want one so i disconnected the secondaries on my gold claw with blue sleeves ( i think 850cfm ). Car slowed from high 6.30s to low 6.50s. I would disconnect yours and find out what it does, just put in new plugs and check lean/rich. Also, engine masters says you can lose 130hp with the wrong air filter and fan (engine masters episodes 20 and 27).

Big difference between running a small block on the front half of an 850 vs a 500 incher on the front half of a 750. Given the shitty distribution on the six pack manifold on the big motors I would be afraid of havin a lean cylinder or two.
 
Big difference between running a small block on the front half of an 850 vs a 500 incher on the front half of a 750. Given the shitty distribution on the six pack manifold on the big motors I would be afraid of havin a lean cylinder or two.
Never ran a 6pak, but I read everything back in the day and there were gobs of distribution tricks for that manifold, gotta agree with ‘hemi’.
 
Even the 4 bbl intakes back then sucked but there were some that were better than others. That's just one reason I like to run a bit on the rich side. A plug check will help seeing that but rather run on the rich/safe side than lean to go faster....
 
i'm surprised you could get 390hp. what was the manifold vacuum at 390hp? those center carbs are only 250cfm @ 1.5"hg.
I couldn't tell you that lew, wasn't there for that pull.
 
i'm surprised you could get 390hp. what was the manifold vacuum at 390hp? those center carbs are only 250cfm @ 1.5"hg.

That run was just for grins and giggles and I've thrown the dyno sheet away, so there is no record left of the vacuum. I'd have to put a new room in the shop if I kept every dyno sheet.

The center carburetor is (and was on that dyno run) 350 cfm, and the outboards are 500 cfm, so 1350 cfm total. So then, this equates to about, what, a 960 cfm 4-bbl? I knew exactly once.
 
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That run was just for grins and giggles and I've thrown the dyno sheet away, so there is no record left of the vacuum. I'd have to put a new room in the shop if I kept every dyno sheet.

The center carburetor is (and was on that dyno run) 350 cfm, and the outboards are 500 cfm, so 1350 cfm total. So then, this equates to about, what, a 960 cfm 4-bbl? I knew exactly once.
the 1350cfm rating is at 3"hg. original rating on the carbs was 250 center, 390 ends at 1.5"hg. but 1030 doesn't market as good as 1350.
 
68hemi gts, i agree, there is a certain amount of risk, but thats why i suggested new plugs and looking at mixture. OP did say his center carb was 500cm, but i dont know if that's at3" or 1.5". And you're right, my 850 was on a single plane intake.
 
The 500 (4412) is basically the front half of a 750. I run the same set up on my 511. I've struggled a bit with getting the distribution dialed on the big motor at cruise. WOT seems ok. The manifold acts maxed out. I've also ran a single plane (tm6) with a 1050/4150. It runs much more even. although ET wise, it's pretty much a wash. Not saying just the 2 barrel won't work, not sure I would deliberately try it on "my" 500 cuber without being able to monitor EGT's on all the holes though. I think dialing back the outboards would be my first move.

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68hemi gts, i didn't realize the"500cfm " 2bbl was that small. I just don't think restrictions only will slow him down a half second. Maybe he needs three tiny little twinky-dink air cleaners, and a big-*** fan, lol.
 
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