Timing quandry
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Timing quandry
I've got a rebuilt '78 300 with '87 heads, '87 exhaust manifolds and a Offenhauser 4bbl intake with a Holley 600 carb and a mild CompCams 252H. I can't get any better than 15inches manifold vacuum which indicates late ignition timing - I also get a slight pop out the exhaust when I decelerate, also an indication of late timing. BUT the timing is advanced as far as it will go and the engine still start and run. I'm also concerned that it doesn't have very good lower end torque which the 300 is famous for (even with just an empty trailer hooked on I have to use granny low to get off the line). It idles smooth and runs good mid range though. The local "guru's" seem to be stumped. I talked with CompCams and they say I should be getting 18-20 inches with this cam. Any suggestions would be welcome.
Lead Driver
Joined: Nov 2000
Posts: 6,619
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From: Albuquerque
What's the altitude where you live?
We need to know the actual timing, with and without vacuum advance hooked up at idle.
Also need to be sure the mechanical advance is working and not frozen.
We need to know the actual timing, with and without vacuum advance hooked up at idle.
Also need to be sure the mechanical advance is working and not frozen.
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I'm at 5000 feet. I don't know the actual timing because I set it with a vacuum gauge and tachometer. I don't have a timing light at all. There's a very narrow range of distributor rotation before it dies from either too much advance or retardation, so I'm figuring I must be in the ballpark or it wouldn't run at all. I'm "assuming" the mechanical advance is ok because it's a new distributor but I won't discount that possibility.
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Cargo Master
Joined: Jul 2015
Posts: 3,076
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From: Aransas Pass, Tx
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