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The dreadfull timing knock
Thread Starter
Advanced
Joined: Dec 2003
Posts: 73
Likes: 0
From: Keswick Ont
The dreadfull timing knock
Hi All. I just got the rebuilt engine back in the wifes 75 vette, and tried to set it timing at 36 full advance, runs great, but knocks/pings. Its a '75 350 auto with a .480 lift ex/int hei ignition, 10-1 pistons, factory carb. If i set it down to the 20s in timing, it runs fair, and doesnt ping. Im not running high grade fuel at this time, just regular. The distributor is rebuilt too, but stock advance springs are still in there.
Any ideas why i have such a problem setting it at 36 degrees?
Thanks in advance
Andy
Any ideas why i have such a problem setting it at 36 degrees?
Thanks in advance
Andy
Team Owner
Joined: Feb 2005
Posts: 32,519
Likes: 1
From: central America
St. Jude Donor '08-'09
I'm running a similar type of cam in my 72 (the illfamed XE268H) and with 9.5 CR and a performance tuned ignition and carb, I can tell when the gas I get isn't good. If you want a car thats going to perform, you're going to need to run the higher octane fuel. If it is just a cruiser, and you don't get on it, then set the timing lower, and live with lower octane gas.
trw
trw
Melting Slicks
Joined: Apr 1999
Posts: 2,010
Likes: 3
From: Moon Twp. PA USA
My 383 with aluminum heads and 10.25 CR runs fine on 89 octane. May even run on 87, but I'm afraid to try. Cam is CC XE 274.
Total mechanical timing is 36*, all in by 2800 rpm. Vacuum advance gets me +/- 50*.
Total mechanical timing is 36*, all in by 2800 rpm. Vacuum advance gets me +/- 50*.
Team Owner
Joined: Feb 2005
Posts: 32,519
Likes: 1
From: central America
St. Jude Donor '08-'09
Originally Posted by glen242
My 383 with aluminum heads and 10.25 CR runs fine on 89 octane. May even run on 87, but I'm afraid to try. Cam is CC XE 274.
Total mechanical timing is 36*, all in by 2800 rpm. Vacuum advance gets me +/- 50*.
Total mechanical timing is 36*, all in by 2800 rpm. Vacuum advance gets me +/- 50*.
trw
Melting Slicks
Joined: Apr 1999
Posts: 2,010
Likes: 3
From: Moon Twp. PA USA
Originally Posted by AndyMacLeod
Hi All. I just got the rebuilt engine back in the wifes 75 vette, and tried to set it timing at 36 full advance, runs great, but knocks/pings. Its a '75 350 auto with a .480 lift ex/int hei ignition, 10-1 pistons, factory carb. If i set it down to the 20s in timing, it runs fair, and doesnt ping. Im not running high grade fuel at this time, just regular. The distributor is rebuilt too, but stock advance springs are still in there.
Any ideas why i have such a problem setting it at 36 degrees?
Thanks in advance
Andy
Any ideas why i have such a problem setting it at 36 degrees?
Thanks in advance
Andy
Use an adjustable timing light or an accurately marked balancer.
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Thread Starter
Advanced
Joined: Dec 2003
Posts: 73
Likes: 0
From: Keswick Ont
Hi Guys,
Thanks for all the tips. I had read earlier in the forums about some carbs not having full time vacuum at the proper port, and switched to constant vacuum from the manifold. That helped alot, im at 36 full timing now @just over 3000 rpm, with little to no knock, and will play around abit more with higher grade fuel, and lighter springs in the distributor.
Andy
Thanks for all the tips. I had read earlier in the forums about some carbs not having full time vacuum at the proper port, and switched to constant vacuum from the manifold. That helped alot, im at 36 full timing now @just over 3000 rpm, with little to no knock, and will play around abit more with higher grade fuel, and lighter springs in the distributor.
Andy
