rough in gear idle and off idle stumble

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CUDAGUY

CUDAGUY

aka Prince Valiant
Joined
Apr 30, 2009
Messages
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Location
Portland,OR
OK, equipped parts....

225
pushbutton 904
holley 1920 with new accellerator pump
points ignition set to 10* points gapped correctly
valvetrain is 'quiet' (checked it cold when the engine was apart and on the stand)

Issue is backfiring and stumbling if you 'load' the engine suddenly and the idle mixture screw does nothing to improve anything as well as changing the timing. Once you are over 2000RPM or so it smooths out and runs fine.

any suggestions guys?
 
check float level in carb. possible vacuum leak/maybe cracked intake manifold.
still think you need to check the valve lash /.010 intake - .020 exhaust.
these are the first things that come to mind.
 
"Quiet, checked cold" is nowhere near close enough on the valve adjustment. Tune-up parts and technique suggestions in this thread. Carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted here for free download.
 
The carb screws that hols the body to the baseplate are notorious for working loose. If you grab the carburetor and can twist it back and forth seperate from the baseplate, you may have a vacuum leak there. Dan is right about the valve adjustment. It needs to be hot, OR you can subtract about .002" - .003" from the valve lash if adjusting cold and get it spot on.
 
Shouldn't you ADD clearance when adjusting the valves cold? If the parts expand as they get hot I would think both the valves & the pushrods would get longer, causing the clearances to close up. Being long, narrow parts they would expand more than the cast iron block & head. I thought this was the main reason for having the clearances there. The exhaust valve running hotter than the intake valve is why the exhaust valve has a larger clearance setting, isn't it?
 
'64 Cuda said:
Shouldn't you ADD clearance when adjusting the valves cold? If the parts expand as they get hot I would think both the valves & the pushrods would get longer, causing the clearances to close up. Being long, narrow parts they would expand more than the cast iron block & head. I thought this was the main reason for having the clearances there. The exhaust valve running hotter than the intake valve is why the exhaust valve has a larger clearance setting, isn't it?
Click to expand...

Yes. I was havin a stupid moment. :banghead:
 
bumped the timing to 15* and fixed the leaking economizer....problem solved
 
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