engine studders at full accelleration. Too much gas!
Thread Starter
Drifting
Joined: Jul 2012
Posts: 1,255
Likes: 297
From: Slovenia, EU
2017 C3 of Year Finalist
engine studders at full accelleration. Too much gas!
My 71 SB studders when given full throttle. It looks like it gets too much gas. I run quadrajet, edelbrock rpm intake and long tube headers. Everything else is stock. Spark plugs are new.
How can I adjust mixture at full throttle?
Are the secondaries opening too much too soon?
How can I adjust mixture at full throttle?
Are the secondaries opening too much too soon?
Zen Vet Master Level VII
Joined: Mar 2016
Posts: 5,218
Likes: 1,174
From: Southlake, TX
I'd check to see if the choke is fully opening before I'd be adjusting anything. A sticky choke can cause a stutter at WOT.
A quick test, would be when you begin to stutter and you back off the gas does it smooth out?
Is this a recent occurrence or has it always done it?
A quick test, would be when you begin to stutter and you back off the gas does it smooth out?
Is this a recent occurrence or has it always done it?
Thread Starter
Drifting
Joined: Jul 2012
Posts: 1,255
Likes: 297
From: Slovenia, EU
2017 C3 of Year Finalist
The choke works good. The carb would need a good cleanup but otherwise works good.
If I step of the gas the problems stop.
The previous owner had the carb set in a manner in which the secondaries didn't open at all. Probably to save fuel!!!!!
I changed the throttle cable and set it in a way that the secondaries open if I give it full throttle.
If I step of the gas the problems stop.
The previous owner had the carb set in a manner in which the secondaries didn't open at all. Probably to save fuel!!!!!
I changed the throttle cable and set it in a way that the secondaries open if I give it full throttle.
Melting Slicks
Joined: Oct 2005
Posts: 2,056
Likes: 8
From: Redruth Cornwall
How did you adjust the secondary opening rate?
If you rev the car in neutral, do you see the secondary air valve opening? If so you have it set too loose.
The secondary opening should be smooth and progressive and only under engine load ie driving at WOT.
If the PO had it so the actual secondary butterflies didn't open, perhaps they also adjusted the upper air valve so it was also tight and so not opening. Is it possible the stutter you describe is it starving of fuel as in secondary air valve not opening correctly?
If you rev the car in neutral, do you see the secondary air valve opening? If so you have it set too loose.
The secondary opening should be smooth and progressive and only under engine load ie driving at WOT.
If the PO had it so the actual secondary butterflies didn't open, perhaps they also adjusted the upper air valve so it was also tight and so not opening. Is it possible the stutter you describe is it starving of fuel as in secondary air valve not opening correctly?
Last edited by jotto; Aug 1, 2016 at 03:19 PM.
Racer
Joined: Mar 2013
Posts: 423
Likes: 25
From: Boca Raton Florida
Also does it shudder at any rpm on full throttle or only when in higher rpms?
If you can duplicate the issue while in your garage under hard acceleration throttle movements….try spraying a little carb cleaner at the shudder into the carb and see if it goes away…an easy way to determine a lean condition if you can get it to happen with the car stopped and the hood open.
If you can duplicate the issue while in your garage under hard acceleration throttle movements….try spraying a little carb cleaner at the shudder into the carb and see if it goes away…an easy way to determine a lean condition if you can get it to happen with the car stopped and the hood open.
