The Dark Side: V8, V6 & 4 Cylinder Engine Conversions and related radical modifications (brakes, transmission, suspension, drivetrain) for MGB, MGA, Midget and all other MG models. Purists beware!
Started my new 302 but it won't idle below 2000 rpm. 600cfm Holley, new everything - seems to run hot and stumbles when throttle is stabbed. Runs strong other than this, but what could be wrong? Choke is off, accel pumps work ok, cam is broken in ok.
Just my opinion --but 600 cfm is big for 302s, Im running a 500cfm Edelbrock and runs fine, not really a Holley fan anyway --- Have you checked for vacuum leaks ? Is it brand new engine ? Maybe others can be more help --good luck
new engine - here's specs that may help: 302 +0.040 bore; Edelbrock rpm heads port matched; Edelbrock RPM flat hydraulic cam, welded steel 1-5/8" hdrs, 31.5" each tube, jet hot coated; hypereutectic pistons; balanced etc; Mallory 6al ign; Mallory distributor; Holley 600 4bbl with manual choke; Edelbrock Performer intake. only vacuum other than advance is the breather. Everything's new except block and crank. Could the breather be drawing too much air?
yes - all new. Only vacuum connections are to distributor advance (Mallory) and pcv valve.
check the idle adjustment on the secondary's, there is a small screw on the bottom of the base plate. take the carb off look on the bottom of the base plate there is a small slotted screw on the bottom.if you are running a healthy cam it helps by opening the plates on the secondary's so the idle mixture screw will work.
Jim
Get a vacum gauge. They are cheap and really help in these cases. They come with instructions on how to ferret out a host of maladies.
Pete
Craig,
I'll send you my 'back up' copy of Tuning Holley Carbs DVD and you'll be able to tune it correctly.
If it's not the carb or a vacuum leak, then too much timing will make it idle high also.
10-14 BTDC should be in the ballpark with a stock type distributor, set at idle. There could be a leak at one of the intake manifold end seals - especially if the heads or block are shaved. That would make for one mean vacuum leak, which will give you a high idle and hot running (lean).
I agree with Greg about vacuum leak. More than likely under the carb base at the gasket or any large port going into the intake manifold.
Dann BCC
All good ideas, but first make sure that the throttle linkage is not preventing the carb from fully returning to idle. Also, the carb needs a return spring itself, and not rely on a spring built onto the throttle cable.
A 600 Holley with vacuum secondaries will run well on a 302, especially if if it is hotter than stock.
Wayne
Wayne, a partially open throttle would not cause a lean condition.
Dann
Dann,
I agree, but my point was in reference to idle speed and to check the simpler things first. Everyone seems to be stuck on a vacuum leak (which can cause fast idle), but I just presented another possibility that could cause the original problem presented and is very simple to fix.
And now that I re-read the original post, I'm all wet. It almost has to be a vacuum leak.
Wayne