2 carbs, idle problems

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Plymouth rat

Well-known member
Joined
May 21, 2008
Messages
206
Location
port colborne, ontario
got a buddy running a 350 with 300 hp, has a weiland high rise with 2 450 holleys, idles at 1100 rpm, as soon as he puts it in gear drops down to nothing rpm, driving him nuts, has 56 jets in them, 65 jets ran to rich, any help or suggestions please...thanks...p-rat
 
Did it idle down with the #65 jets in them ? Does it have a vacume advance dist. ? What type of tranny is he running ? I'd check to see if the advance is working and if there is a significant vacume drop when put into gear.
 
it didnt drop down as much with the 65's but ran way too rich, plugs were soaked, the 56's leaned it out nice, idles great, he has a 350 turbo in it, he plugged the vacuum at the intake, but i believe he said he had 30 lbs before he plugged it off to try it, yes vacuum advance dist.
 
Well, if the dist. cannot advance it will certinly affect the running. How does it run under some RPM's? Does it shift properly?
 
it shifts fine, and on idle has great higher rpm's, the vacuum advance is working, he had a vacuum gauge hooked up on it somewhere, the problem is at 1100 rpm's at idle and he puts it in gear, drops to nothing and stalls, maybe a vacuum, air fuel mixture problem, but runs great at idle...p-rat
 
You may be way past these suggestions, but you have to start somewhere.
1st is the dist hooked up to manifold or ported vacuum?
It needs to be ported, somewhere on the carb where vacuum increases with throttle opening.
With 1100 rpm idle speed he probably is pulling some adv in the dist.
I would disconnect the vacuum to eliminate possible other issues, like vacuum leak, primary butterflies open too much, or secondary butterflies out of adjustment. If you do not experience the high idle with the dist vacuum disconnected and plugged, you will need to grab a timing light. You should not be pulling any vacuum adv at normal idle speeds.
If you will post what you find in these areas, we should be able to get you to a reasonable idle.

good luck,
railroad

If a hammer won't fix it, it's and electrical problem
 
im going out there tonight, i will get railroads info and yours to don, i will post it when i get home, i will also get some pics of his ride, its a 47 ford pickup, chopped ,channeled and sectioned, flip front end, its sharpe, thanks...p-rat
 
This may be not what you want to do but something to try. block off one of the carbs with a flat plate under the base and manifold and see what the thing acts like. If it won't idle correctly with one it sure won't work with 2.
I had a nail head street rod about 30 years ago that whould really launch with one carb disconnected and was a **** with both - but really liked the both at top end. This is a function of cam or not enough cam.
 
Well, with that much of a plenum chamber, your not getting a good air/fuel mixture at low RPM's, I would venture to guess it is a vacuum problem. With all of the tunnel rams I've run, I always had to go up on the idle circuit[starting with the stock jets] and do a considerable amount of jetting and re-jetting to get a all around happy medium from the idle circuit through the intermediate to the top end mixture. He might want to check where his vacuum is on the manifold and whether it is ported or not. The type of cam plays a big role in the vacuum area also.
 
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hey guys, he fixed it, he was told buy the guy at holley not to go more than a turn and a half on the idle screws on each of the carbs, he was in the garage all night playing with them, turned out he had to back them out 3 full turns , eventually he got it where it idles and when he puts it in gear it doesnt stall and will idle, thanks for helping...p-rat
 
You may be way past these suggestions, but you have to start somewhere.
1st is the dist hooked up to manifold or ported vacuum?
It needs to be ported, somewhere on the carb where vacuum increases with throttle opening.
With 1100 rpm idle speed he probably is pulling some adv in the dist.
I would disconnect the vacuum to eliminate possible other issues, like vacuum leak, primary butterflies open too much, or secondary butterflies out of adjustment. If you do not experience the high idle with the dist vacuum disconnected and plugged, you will need to grab a timing light. You should not be pulling any vacuum adv at normal idle speeds.
If you will post what you find in these areas, we should be able to get you to a reasonable idle.

good luck,
railroad

If a hammer won't fix it, it's and electrical problem

Vacuum decreases as throttle opens
 
Adam,
I got away from this thread and missed the last post " vacuum decreases as throttle opens " . This means you are hooked up to manifold vacuum. Normally you DO NOT want this source for your distributor. There should be a hook up on the carb that will have little or no vacuum at idle, but will increase as the throttle is opened. This is the ONE. You will set your base timing with this disconnected and plugged.

This should not affect any carb adjustments, but could help when he puts it in gear, if it is an automatic trans.

Keep posting if you have any problems and I will try to be more alert.

good luck,
 
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