tgilligan

Firing engine up after a top half rebuild. Having some issues with timing settings, idle speed, etc.

Background info:
Stock 5.7 350 small block.
Stock distributor with points.
Intake replaced for Edelbrock Performer
Stock QJet 4 BBL
Stock springs, valves, lifters replaced for CompCams adj rockers, springs, pushrods and hydraulic flat tappet lifters.
Stock cam
Stock crank

Timing marks on balance were validated at TDC for compression stroke and with distributor setting, currently at 10 degrees BTDC. I've been playing with range of 10-16 degrees to see which works best and it varies so I'm having difficult finding the sweet spot. Dwell is at 30 degrees and plugs were gapped to spec.

No issues with crank, spark, fuel etc. At times during a hot start, the engine will increase RPM's to around 2100 and stay there but I've been messing with the idle set screw on the carb a lot to try and find the right setting. At times it will idle smooth at 1000 RPM's with about 14 degrees BTDC, other times it's not a fan of that setting. Seems as if every time I shut it off and let it set and try again, the settings it likes changes.

Vacuum advance is disconnected and plugged and the aftermarket Edelbrock air breather is on the carb. When I mess with the settings with it off the carb, it races up the RPM's when I put the air breather back on. I haven't checked for a vacuum leak but it's possible. I've had a vacuum gauge connected to full manifold vacuum port at the bottom of the carb next to where the PCV hose is routing to ensure I'm getting good readings. How should I check for vacuum leaks elsewhere?

I'm pretty much a novice and really trying to learn so from everyone's experience, what am I doing wrong and what else can I try?

redoldsman

What are your vacuum readings? The most likely place for vacuum leaks is around the intake manifold. Get a can of Berryman's carb cleaner and spray where the intake manifold meets the heads. If you vacuum readings change or your idle changes then you have a vacuum leak. Check the base gasket on the carb also.

oldcutlass

Disconnect your throttle linkage and see if it settles down, your air cleaner may be interfering with it. I would not over advance your initial timing without knowing what it does to your total.