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Piston to valve cleance problem. 2.7
I have been trying to get my 2.7 put back together, I have Wayne's book and have read a lot about it on these forums.
The engine went to Ollies, they measured the case, it did not need to be align bored. They installed case savers, decked the case. (they removed .020 off the deck.) machined the spigots and did a vavle job. The best I can tell all they replaced on the heads were the guides and the exhaust vavles and seals of course. I bought an in spec set of Nikasil Mahle P&C's. The originals were Alusil Mahle's. The pistons are CIS, stock ones. I am running stock CIS cams, although they are from another engine.
The problem is that I put the .5mm base gaskets on the cylinders I get a 1.5 mm deck height. Then after assembling the engine and timing the cams I then check the piston to valve clearance. I use the turn the rocker screw method to figure them out. The worst intake clearance I get is about 1mm, most are 1.25. But the real problem is the exhaust valves, I get 1mm on the best one, most are around .5 or .75mm. I have double checked the timing, advancing the timing, retarding the timing on the cams just does not produce much of a difference, and certainly not the extra 1mm I need. I have put another set of stock pistons in the motor and reassembled it, there is not any diffferece in the deck height with them installed. If I move the cylinder heads around I get different readings. But the figures I listed above are the best I can get. If I get the worst case going I can get some exhaust valve clearances at .25mm.
I was wondering if anyone had any suggestions on how to solve this problem? Ask all the questions you want about how and what I did. I am stumped though. The way I see it if I use thicker base gaskets to solve this problem I will have to add another 1mm to the .5mm gaskets I already have and that would give me a deck height of 2.5mm. I don't have any experience with this, but I am afraid that will be too much and might cause detonation, but I don't know.
Anyway, if anyone can help I would appreciate it.
Thanks,
Ray
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76 911S Targa
An ex F1 driver, and Porsche fanatic (my stepfather) once told me that if you listen very carefully on a quiet night you can actually HEAR Porsches rusting in the garage!
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