Lee Zook

I posted last week about an 86 951 I was interested in. While I did not get a PPI, I did do an inspection and compression check. While I found a few items needing attention (most visually apparent is the oil on the crossover pipe) the biggest concern is the compression.

I did a cold test, all plugs removed and throttle open. I got:

#1 135 psi
#2 137 psi
#3 105 psi
#4 135 psi

I did the test on #3 several times to be sure that o ring seated etc and they all came up at 105. I also squirted oil into the cylinder and checked it and it was the same.

I know that compression tests are recommended to be done hot. Should i really expect much improvement?

Also what would be a nominal cost for machining/head work for a valve job? I would do all the wrenching my self.

Thanks

Danno

Yeah, compression checks should be done with the engine hot so all the clearances are at operating specs. But that's typically a 10psi difference, so add that to your numbers. My car at 198k-miles had compression# of 142-147psi right before my disasterous OTC attemp where shattered rings destroyed my #3 cylinder.

So I think your numbers all look pretty good except for that #3. I would follow up with a leakdown test to see what's going on with that #3. Rebuilds are usually in the $2500-3500 range depending on the shop. Another option is getting a rebuilt short-block from <a href="http://www.andersonmotorworks.com" target="_blank">Anderson Motorworks</a> for less than that and throwing it in yourself. So you want to factor these costs into the purchase price of the car.

In many ways, that may be a better option because you'll have a brand new engine that'll last 200k-miles. That in itself may be worth the price of an '86 951 + rebuilds. Because while you can find high-mileage '86 951s for $4500-5500, better samples for $7-8k, or even '87-88 non-S 951s in the $9-12k range, none of them will be as mechanically sound as an '86 951 with a new engine!