KrakHed

I have a holly 750 mechanical secondary carb on my 350bhp 350 (11:1). It has a carb spacer, edlebrock performer intake, and headers. Can anyone suggest a good starting point for jets (primary and secondary) in this carb? I plan to drive it exclusively on the street (no track racing) and pretty often. I already have a detonation problem to deal with at full throttle, so I'm hoping to avoid problems with the carb at the same time.
Any suggestions on the pinging problem would also be appreciated. I've already retarded the timing, set up the engine to run cooler (160), and blocked the vacuum advance. My next steps were going to be to re-curve the distributor to advance later and less as well as possibly doubling up my head gaskets to drop the compression a bit.
Thanks.

-Isaac

:confused:

clem zahrobsky

you can jet up and retard the timing and it may stop the pinging but there is no way you can run 11:1 engine on pump unleaded with any effecentcy. if you live were some gasoline stations sell unleaded race gas of 100 octane and try a 50/50 mixture of it and hi test unleaded. :chevy

Jvette73

When selecting jet size, first check to see what sixe is already in there. Then expieriment with jets sizes 2 sizes above and then two sizes below that if you want to downsize. Always change jets 2 sizes up or down for whats in there to begin with.

11:1 can be tollerable on pump gas if yur cam is big enough. Whats the intake duration on yur current cam? If its too small then you'll get excessive cylinder pressure. Longer intake duration can help reduce cylinder pressure. With a cam big enough to make 11:1 tollerable without ping on a sb, if you run an automatic trans, you will almost definatly need to run a higher stall speed convertor to prevent lag off the line.

Robert N

If you are simply looking for a size to start with that is ideal for the set up, start with the stock sizes called for by Holley and adjust from there.