Low speed bucking
Thread Starter
Instructor
Joined: Mar 2002
Posts: 140
Likes: 1
From: east hampton ct
Low speed bucking
I question for the engine people here. The motor runs great however during deceleration as I get below 1500 rpm I am getting bucking of the engine. Over time I have reduced this thru tuning but is this just the nature of the motor and gearing I have. Car is a 75 with 4 speed and 3:36 gears. Motor is a 383 w/ 10.5 comp. Older Barry Grant 750 vacuum Secondary on an Edelbrock rpm intake manifold. Older AFR 180 heads with full length headers. The cam is a Bullet hydraulic roller 230 @ .050 with 0.570 intake and 0.518 exhaust at a 109 CL. Intake was degreed to 103.
Tech Contributor
Joined: Aug 1999
Posts: 14,380
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From: At my Bar drinking and wrenching in Lafayette Colorado
Try unplugging your vacuum advance and see if the issue stops. Your 16 degree vacuum advance is a bit long - you might need to limit it to no more than 12 degrees (if the problem goes away when you yank the hose off).
Lars
Lars
Is my vette stock?? HAHA
Joined: Oct 2015
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From: Im not allowed to tell you
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I bet your rpm is lower than that and its the gearing you have. What do you have for a 4 speed. M21 or M22. 3.36 and a M21 is a 7.392 final gear ratio. When you start from a dead stop what RPM to you have to get the motor to so it will pull smoothly. Even a 383 isnt going to pull like a 454.
And that cam at a low rpm is going to lope anyway. I had a similar one in my 327 and had to set my idle at 800 rpm to keep the engine and tranny happy
And that cam at a low rpm is going to lope anyway. I had a similar one in my 327 and had to set my idle at 800 rpm to keep the engine and tranny happy
Last edited by Rescue Rogers; Nov 30, 2020 at 09:21 AM.
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