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#1
11-28-2013, 08:49 PM
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distributor shaft roll pin shearing off?
Has anyone ever heard of the roll pin holding the gear on the distributor shaft shearing off on a Pontiac engine due to heavy weight oil, a high volume oil pump, or any reason at all?
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#2
11-28-2013, 09:30 PM
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Yes, not real common though.
Is it an early 1/8" pin? Pull it and just look it over reinstall a new pin and don't sweat it. Likely had some inclusion to cause it to shear. Definitely look for signs of gear being overly loose on shaft. |
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#3
11-29-2013, 02:58 AM
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I'd be looking for bits of the plastic timing gear or valve stem seal going through the oil pump.
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#4
11-29-2013, 08:23 AM
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You Stilll have a nylon coated cam gear in that motor!!!!
__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
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#5
11-29-2013, 10:32 AM
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Yep. Me. Had 3 of them sheer. Mallory Unilite. Small roll pins though. The new Unilites have a larger roll pin. My engine also has the 80# pump. It pegs at 100 until it warms up. Then it will run 30 at idle and 80 at speed. This engine has run since the 80`s though, so no "bearing wash out" here. Still runs hard today.
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#6
11-29-2013, 10:41 AM
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Thank you for the responses. I Googled the sheared roll pin thing and the only ones that came up were those on Fords and a couple of them were Unilites, so apparently Unilites can be a problem in any brand.
I asked because I am doing some SD clones distributors out of '55/'56 Pontiacs and someone told me I needed to put larger roll pins in, and I had never heard of one shearing off so thought I would ask. |
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#7
11-29-2013, 11:20 AM
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I would install a new oil pump with the p body mod and a new intermediate shaft. AND investigate what ever you found in the oil pan.
__________________
Bull Nose Formula-461, 6x-4, Q-jet, HEI, TH400, 8.5 3.08, superslowjunk |
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#8
11-29-2013, 11:40 AM
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Quote:
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#9
11-29-2013, 12:13 PM
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Roll pins, just like most everything else has different levels of quality and strength.
Always a tradeoff between the diameter of the pin/hole and strength of the actual shaft. I have seen a few mods where the stock pin was replaced with a solid pin that was .0005" larger than the hole in the shaft and pressed in place. Much harder to shear a solid pin of good steel. Tom Vaught
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
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