Sbc timing issue
Thread Starter
On The Tree
Joined: May 2008
Posts: 104
Likes: 0
From: weatherford, tx
Sbc timing issue 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.
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.
Launching!
Joined: Oct 2006
Posts: 289
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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.
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.
Thread Starter
On The Tree
Joined: May 2008
Posts: 104
Likes: 0
From: weatherford, tx
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.
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.
TECH Addict
Joined: Jun 2009
Posts: 2,012
Likes: 0
From: Tulsa, OK
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.
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.
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