Big timing mark discrepancy
Thread Starter
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Joined: Jan 2008
Posts: 99
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From: Chesapeake Virginia
Big timing mark discrepancy
I just rebuilt my heads and installed headers. When I put everything back together and set the timing factory spec (0 degrees) the engine idled great but had a really bad hesitation and backfired through the carb on acceleration. I tried many things to fix it, but it ultimately came down to timing. I had to set the timing to about 18 degrees before TDC to make it run well. I had never adjusted the timing on this car since I bought it 18 mos ago and have no idea what it read prior to the work I did.
Any ideas on reasons why the timing needs to be (or just reads that way in error) so far advanced?
Any ideas on reasons why the timing needs to be (or just reads that way in error) so far advanced?
Burning Brakes
Joined: Jan 2003
Posts: 755
Likes: 32
From: Roswell Georgia
I'm a little confused. According to your profile, your '70 Vette engine is a 350/300 which has a factory specified crank advance of 4 degrees, not zero degrees. By chance, did you set the initial crank advance and forget to disconnect the vacuum advance? That would account for the 18 degrees your seeing now. BTW, there is a excellent sticky on setting timing at the top of this forum.
Since you live just around the corner, so to speak, in Chesapeake, PM me if you need some hands on assistance. Are you a member of the Beachcombers Corvette Club? There are plenty of members in the area that would be glad to help you out.
Good luck!
Since you live just around the corner, so to speak, in Chesapeake, PM me if you need some hands on assistance. Are you a member of the Beachcombers Corvette Club? There are plenty of members in the area that would be glad to help you out.
Good luck!
Thread Starter
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Joined: Jan 2008
Posts: 99
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From: Chesapeake Virginia
I'm a little confused by your reply. What do you mean by total of 36?
I still have significant hesitation at load and intend to keep advancing timing until it pings and then back it off to optimal performance. Do you agree?
I still have significant hesitation at load and intend to keep advancing timing until it pings and then back it off to optimal performance. Do you agree?
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
most of us take timing to the next level and actually set it to specifications that are known to be the best for the small block chevy. it involves initial timing, total timing, vacuum advance and centrifigual advance....there is a sticky on timing read it several times .....it usually takes several readings to get it all straight and then get a dial back light and start the fun.....we can help from there.....you may also want to verify TDC if you think the harmonic balancer has slipped......a dial back timing light has a dial on the timing light that allows the "flash" to appear at "0" degrees when it actually is at something else.....we do use this since the degree maker isn;t big eonough to go all the way to 36*
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Thread Starter
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Joined: Jan 2008
Posts: 99
Likes: 0
From: Chesapeake Virginia
I read that sticky a long time ago and to be honest, I didn't really get it. Now that I've been into this issue in depth, I'll read it again and give it a shot! Thanks for the advice.