I have a heads and cam 383 Sbc. With an 850 deamon carb. I've had the engine dyno tuned at a shop a couple years ago but it had a holley 750 in it at the time. And they suggested having it at 35* at full advance.

The engine ran in a camaro for a while with the holley 750 but it had a bronze distributor gear and got worn down and couldn't hold timing. I ran out of money and it set for a couple years. I got the money to fix it finally and I bumped up to an 850 cfm. I pulled the distributor changed the gear and set the timing at 35*. When I take it out on the freeway it detonates under load and pings every once in a while at idle.

I've tried 34*, 35*, and 36*. But it still does it. Do ya'll have any idea what might be causing this? Do you think the bigger carb has something to do with it? And I forgot to say the 850 came off a stock zz4 572. And I haven't changed the jets yet.

 

I'll assume you put in new gas and that the timing marker hasn't moved. Next I would ask: how did you set the timing? Lowest idle you can get, unhook vacuum advance and plug at carb. Set base timing to 14. Rev engine and see what it goes to. 36 is a good number to start with.

What distributor? I have seen worn HEI's go past max advance after you rev a little more. I think it is caused by worn weights. I have never seen this with an aftermarket distributor.

 

Yes I know for sure it's new gas. Timing marker hasn't moved. To set the timing I put it at 25* to fire up initially. I started it. Got it idling. Then put the timing light on it and brought up the rpm's till they it stopped advancing which was 4000. Then I set it at 35*. I am running a Davis Unified Ignition HEI distributor. It has very low miles on it. Probably 10k or so.

 

Every time I've set the timing that's how I've done it and it's always worked. Is that not right?

 

No, that's not how you do it. By running the rpm up and then readjusting the distributor, all you've done is made that setting your new initial setting...like 36 degrees is now your initial advance. Initial should be somewhere around 6-12 degrees.

Have you ever had the distributor curved? Sounds like it needs it. Back off your initial, set it with the vacuum disconnected/plugged. Where do you have the vacuum connected...manifold or ported? Once you've adjusted the distributor for initial....don't move it again. If you aren't getting enough total advance, the problem lies inside it, not with you twisting on it.

 

I think my distributor is mechanical advance only. And is this video incorrect?

 

That's how MSD set the total timing. Skip to 6:02

 

that video has great info in there. listen to what they say cause its correct, so are the other posts on this thread.

 

Come to find out the problem did lie inside the distributor. Thanks for ya'lls help!

 

Glad to hear you got it sorted out. What was the problem?