Thread: ZZ4 Backfiring at higher RPM

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Hello
Looking for some help.
Just got my new ZZ4 350 motor with 750 Holley carb running in my 1940 Ford Coupe and after it warms up and if you rev it up fast in park by hitting the gas and letting off the engine will backfire out the carb and the exhaust with the RPM is up around the 3000to 3500 range. I checked the timing and it is at 10 degrees bftdc. Plug wires are on the right plugs and order.

But I am getting cunfussed when you rev it up and have the timing light running it shows the timing will go up to 50 degrees advanced with the vacuum advance on the distributor hooked up to the timed vacuum port.Is this right? If I hook it to the full Vacuum port it will go up to 45 degrees advanced with it hooked up but still backfires.

Also I have heard that there is two ways to hook up the Vacuum advance on the distributor but I would like to find out the right way. Do you hook it to the timed vacuum port or the full vacuum port on the carb.

Any help would be greatly appreciated

Carnut

Originally posted by Keith Yedica
Hello
Looking for some help.
Just got my new ZZ4 350 motor with 750 Holley carb running in my 1940 Ford Coupe and after it warms up and if you rev it up fast in park by hitting the gas and letting off the engine will backfire out the carb and the exhaust with the RPM is up around the 3000to 3500 range. I checked the timing and it is at 10 degrees bftdc. Plug wires are on the right plugs and order.

But I am getting cunfussed when you rev it up and have the timing light running it shows the timing will go up to 50 degrees advanced with the vacuum advance on the distributor hooked up to the timed vacuum port.Is this right? If I hook it to the full Vacuum port it will go up to 45 degrees advanced with it hooked up but still backfires.

Also I have heard that there is two ways to hook up the Vacuum advance on the distributor but I would like to find out the right way. Do you hook it to the timed vacuum port or the full vacuum port on the carb.

Any help would be greatly appreciated

Carnut

what kind of exhaust system do you have?

Rednck,

We answered his question in detail in another thread. He posted the same question two or three different times. After we answered, we never heard back on the final resolution. No sense going through it again.

Here's the original thread.
http://www.clubhotrod.com/forums/sho...threadid=13826