I had a little detonation going on so i reduced my intial timing from 12* to 8*. That got rid of the detonation but now i have spark knock/pinging. I am running a .040" compressed head gaskets, will a .062" head gasket fix this problem?

I figure if i can get rid of the detonation with with just adjusting timing then with a new head gasket i should be set and have no worries. I was also at the time running the old points distributor but now have an HEI which i havent gotten hooked up yet (wiring isn't my thing.) By the way this is a carbed motor and a pretty long duration cam (240/246).

Thanks, Chas

 

Going to a thicker gasket can reduce your compression ratio slightly. If you have a little detonation it may help, but I think the real issue is your timing curve/fuel mixture. What's your compression ratio ?

 

Get better gas!

 

im running sunoco 93 octane

right now the static compression raito is 11.22:1 using a .040" and with a .062" head gasket it will come down to 10.6:1. Im thinking my fuel/mixture should be good but i dont have a wide band sensor to verify. i want to tune my carb but need the car to run descent before i can tune it.

thanks, chas

 

Sunoco 260 GT100 octane unleaded

 

the only fuel that is over 93 octane around me is at the strip 1hr away.

 

I found my dynamic compression ratio to be 8.25:1 is that good? I read something saying that it needs to be around 7.5-8.5 for pump gas.

Thanks, Chas

 

Dynamic is on the high side, but probably ok. What temps is the engine running at? Do you have vacuum advance? What does your advance curve look like (when is all your mechanical timing in)?

Try adding a bottle of octane boost, and see if that helps. That will help you determine if its just inadequate fuel, or if you have something else causing detonation problems - ie. too much heat, timing too high, advancing too fast, too much timing under a load, etc. Under some of those conditions, the octane booster may make it go away, and others it won't. It will help to narrow down the cause to a mechanical/hardware issue, or a tuning problem.

My 350 was pretty tempermental in hot weather sometimes when it had the 305 heads on it (compression was also around 11.25 like yours). What I did was to use a vacuum advance MSD (vac unit can be added to a Pro Billet like I did) and set the initial timing down around 8* or so... with the cam I had, which was slightly smaller than yours, it should have been around 15* initial. I had the vac advance hooked up to manifold vacuum, so under low load the advance was higher (around 20* at idle) but came back down low enough not to cause detonation problems when a big load was put on it. Its a bit of a bandaid, and I changed the heads to a set that dropped it down to about 10:1, but it still worked quite well. I still use the vacuum advance the same way now, even though it has no detonation issues anymore.

 

im running at 180* constant and the timing kicks in completely at 2500 and advances it 8*.