Quote:
Originally Posted by leftybass209
I agree that starting with the carb fast idle is most logical. Most quadrajets just need the proper love and setup. However, there's a whole other list of things just to consider after your rough idle is sorted...
These crate motors are really low compression. They seem to like a lot of timing... in the 14-16+ range i've found after messing with 3 or 4. The engine break in instructions call for weirdly low static timing, and no vacuum advance. Great in theory for racing, and punishing for fuel mileage.
The cam in that 290hp motor is nearly too much for the low compression, and i'd argue the lobe centerline is all wrong as well for the compression.
If the throttle shafts weren't rebushed on that quad, then there may be a vacuum leak around the throttle shaft. Small vacuum leaks may seem like they iron out after a motor warms up, but they can wreak havoc on a cold motor
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Truth, about those little vacuum leaks. I bought a '69 Skylark years ago for the engine and trans for my '68 Skylark. The guy had done all kinds of stuff to it- HEI, rebuilt the carb, etc. I drove it home, and when troubleshooting it later I discovered the vacuum line for the AC/heater control not connected to the nipple on the back of the carb. Couldn't hear that leak, but man it sure smoothed out the idle when I connected it.