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 Too much mechanicl advance
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Kiwi Mal
Cochise

New Zealand
690 Posts

Posted - 27 Dec 2014 :  8:27:26 PM  Show Profile  Reply with Quote
Hi everyone, it's been awhile. I have not been using the bird for a long time and really have put very few miles on the new engine built be Jim Lehart.
The engine is a 462 and has ported E heads with larger valves, solid roller cam-9.5:1 comp. I did have the HEI set up on a distributer machine but it dose not seem right. I am using a MSD HEI ignition module and the factory plate and weights.
I had been running it with 18deg initial but it had a stumble when you started to accelerate. As I said I have just started to have another play and advanced the initial to 20deg and it liked that but I could still feel a very slight flat spot. I thought I would try another 2deg and sort out the vacuum advance at the same time.
With the vacuum advance disconnected I set the initial and then ran the rpms up to see what I was getting for total and was supprised to see it getting a total of 48deg. I can't tell with my timing light exactly what rpm this is happening but I don't think that is important until I can limit the total advance and then want to dial in the speed of the advance.
How do I reduce this by 10deg. The springs reduce the speed of the advance not the total advance, so what else do I need to do ?

Cheers Mal

cortcomp
Coyote

USA
5338 Posts

Posted - 27 Dec 2014 :  10:20:03 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
You need to add a stop (you can read about this in 100 different places). Also, when stumbles are involved, don't rule out the carb as a contributing factor. Sounds like a fun engine!
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Kiwi Mal
Cochise

New Zealand
690 Posts

Posted - 28 Dec 2014 :  5:19:50 PM  Show Profile  Reply with Quote
Thanks cortcomp. I was thinking the carb could be causing the stumble until I played with the timing. I did tap the two holes and fitted allen head bolts that came up through to stop to much advance but this made no difference.

I thought there may have been something about limiting the advance on the tech section of the site but there isn't. I did have a good look at Jim Hands photo of the HEI and I think my centre plate was fitted upside down. Saying that though my centre plate does not contact the weights through the distributers movement which makes me think that the advance is coming in totally uncontrolled. These parts were the factory parts as far as I know. This distributer came with a 1976 400 that I had in the car. Centre plate is a 398 and weights are 053. Photo attached. As you can see there is no contact between the centre plate and weights for quite some movement.

[URL=https://imageshack.com/i/f048VQKMj][/URL]
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