Re: snapping on and off idle

Bill wrote:

> Hi-
>
>    Got a small block chevy with 4 dellortos. It ran fine for most of 
> last year until just before the end of the season when it began to pop 
> a little at idle and on decel and ran rough at part throlle. The carbs 
> were a little leaky and so I ordered 4 rebuild kits and did all of 
> them. No more leaks but the problem persists. It acts sort of like a 
> vaccuum leak but if that's the problem, darned it I can find it. When 
> you first start the motor, there is no popping or snapping but within 
> 30 or 45 seconds it starts, randomly from both sides of the engine. 
> When these things run correctly, there is some minor popping and 
> snapping until the thing warms up (no chokes) then it runs great. This 
> is the opposite. At part throttle, there is a miss and it's running 
> awfully rough. The valves are sjusted correctly and my unisyn says the 
> carbs are synced. Adjusting the idle mixture screws (richer) helps a 
> little but they don't have nearly the effect they should. I sprayed a 
> few shots of carb cleaner around the bases and it seemed like there 
> was a barely noticable change that I couldn't reproduce on a second 
> try. The plugs weren't fouled but I changed them anyway. Same results. 
> Any ideas?
>
> cheers,
> Bill
>

Just a thought but you might try the leak test where the manifold mounts 
to the head also.