Low compression on #1

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blk91

Member
Aug 29, 2005
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Howdy all,
My car started idling funning a few weeks ago do to shot wiring on the cps. Fixed the wires that were bad and the car still missed at idle. My Friend that was fixing the harness did a compression test and compression on number 1# was 60. He Did a leak down test and said it appeared the intake valves were the problem. A few people I have talked to found this Highly unlikely. Car has a built motor Wiescos, arps, hks 1.2, manly MM over sized valve springs, and stock springs. Car has been ran in my opinion very conservatively at .95 bar with 550+Lexus and a 60-1 turbonetics bolt on. Any ideas what would be the most likely cause? I wont have the motor apart until next week and I want to get an estimate on what ill need to spend in parts.
Any info would be great
Kanan
 
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blk91

Member
Aug 29, 2005
78
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No none at all what should I check for ? . Also I forgot to add that other than the miss at idle the car runs fine. But I am trying to drive it as little as I can untill I get this figured out.
 
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blk91

Member
Aug 29, 2005
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Do you think that would be somthing that would develop over time?, The car did not miss there first 20k miles I had it. That was about 3k after the motor was built.
 
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blk91

Member
Aug 29, 2005
78
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ca
Not sure head is still on motor what am I looking for? I don't know a ton about internals other than what they are and what they do. My friend might take it apart today and was asking about valve adjustment.
 
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IJ.

Grumpy Old Man
Mar 30, 2005
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I come from a land down under
Turn the crank so the cam is on the back of the lobes for #1 then try and slip a feeler gauge between the cam and the bucket, this will be the "lash" if there's too small or no clearence it will hang a valve open when hot and cause a miss.

As our motors wear the Lash tends to close down as the valves sink into the seat more than the other components wear so you lose clearence over time.
 
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blk91

Member
Aug 29, 2005
78
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Thanks for the info I passed it on to the guy working on the car for me. He said something was off with the shims on the car. He changed somthing and was able to get less than 5% leak down from the 90% it was at before. So things are looking up he said he has to source some new shims and looks like the car will be good to go for at least a while. But getting shims in a smaller town on the weekend most likely isnt going to happen. Should have another update monday.
Again thanks for the info Ian
 
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