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Hi everyone, need your advice again. A 253 HZ with initial advance of 42 degrees at idle and 50 total with the vacuum disconnected. The engine is happy at this idle advance, stalls if its too much lower. I have fitted a new the harmonic balancer in case the balancer had moved, this did not change any of the results. Have also fitted different distributors, also no material change. Car also has the correct carby, but as I said these results are with vacuum disconnected so the carby is not the variable.
I do not know the history of the engine, could the cam timing be out and the ignition timing is trying to compensate, or any other suggestions would be appreciated. Thanks again.
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Originally Posted by: Aussie Dave  Hi everyone, need your advice again. A 253 HZ with initial advance of 42 degrees at idle and 50 total with the vacuum disconnected. The engine is happy at this idle advance, stalls if its too much lower. I have fitted a new the harmonic balancer in case the balancer had moved, this did not change any of the results. Have also fitted different distributors, also no material change. Car also has the correct carby, but as I said these results are with vacuum disconnected so the carby is not the variable.
I do not know the history of the engine, could the cam timing be out and the ignition timing is trying to compensate, or any other suggestions would be appreciated. Thanks again.
I think you are correct with your first guess, if it won't idle at 10-20 degrees the cam timing must be out. Dr Terry |
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Thankyou, I thought it would be best to check before I started pulling everything apart. Appreciate the advice, thanks
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sounds like someone has put the timing chain on to chev specs as in both dots lining up on both cogs. Holden has bottom and top dots about 6 or 7 links apart.
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Thanks, the previous owner was heavily into big block chevs. I will check the cam timing tomorrow, I think Holden is 9 links. Thanks for your thoughts. Regards Dave (this is a possible duplicate reply, my last attempt seems to have disapeared.)
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Originally Posted by: Aussie Dave Thanks, the previous owner was heavily into big block chevs. I will check the cam timing tomorrow, I think Holden is 9 links. Thanks for your thoughts. Regards Dave (this is a possible duplicate reply, my last attempt seems to have disapeared.) yup.. Holden V8s are always 9 links between the links on the timing chain (irrespective of what the bottom chain gear is, as some are quite retarded timing wise) |
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It was very confusing the way GMH did the V8 cam timing. What was wrong with dot-to-dot, this was the waY 6-cyls were done as were SBC V8s.
Anyway for 253/308 it's 9 links from dot to dot INCLUSIVE, not "between".
Dr Terry |
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Thanks Dr Terry, I will try to get at it later today, so it will be interesting to see what I find. Will report back later. Thanks Dave
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Will be interesting to see how far advanced or retarded it is if that is what is done. |
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Checked the cam timing, all ok, 9 links. The crank sprocket has only 1 keyway option. Car is only partly reassembled, next to check another timing light. Currently using snap on with digital advance, I will get out my old timing light and try that.
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