Darwantae951

Ok, I know different gauges can read different (and the one I happened to use was about 20+ years old now) so I wasn't too concerned about the numbers, but only about cylinder 1:

1-116
2-125
3-121
4-123

Now I did this myself (first time I've ever done it myself) and the engine was borderline hot, not warm. I know I have an oil burning problem in cylinder one, so I'm guessing that it's my rings?

-Darwin

joonas

Or scrached cylinder wall?

Josh B

Hey Darwin,
You need to get a leak-down tester and check it out that way. That is only a difference of 9 between the high and low cylinders - less than 10%. Have you redone the headgasket on that car? If not I would recommend getting a hardware kit from Rennbay and a widefire headgasket. Then if you need the car as a daily I would pick up a spare head and have it refreshed. The job can easily be done in a weekend and that would be taking it slow. Gives you a great chance to check out your cylinder walls and also your original headgasket is probably pretty nasty looking by now.

V2Rocket

buildup on the valves could prevent them from sealing and thereby dropping compression...usually happens in stop-and-go driven vehicles

marky522

Yeah, i agree with Josh, you need to do a leakdown to see WHERE your loosing compression.

Mark

Darwantae951

Forgot to add that per the advice of someone else, I added a bit of oil to the number one cylinder and compression came up to 125.

Hey Josh, I actually just picked up a widefire headgasket and was debating on putting it on before I took the car back to Texas. How much does a used head and refresh usually run?

Also it isn't the original headgasket on the car, the head was removed by the dealer per POs request to inspect the inside of the engine.

-Darwin

P.S. also this was my first time doing a compression test and I did not know to have the throttle fully open, would this affect numbers overall?

Darwantae951

I'm trying not to picture the worst right now.

luftpirate

Make sure you pull the fuel pump relay to keep gas from getting everywhere, and have it at WOT while you are cranking. Try it again, also inspect the plug on the cyl. with the low results.

Darwantae951

Did and it was very slighly oily (I know the cylinder is burning oil). Also the altitude here is about 3000 ft.

Techno Duck

Rebuild will cost in the area of $150 if you supply the parts (valve guides and stem seals). This includes cleaning the head and milling the deck if necessary. If you are going with a widefire headgasket, i would at the least o-ring the head (costs about $100). The actual usefulness of a widefire headgasket alone is long debated if you go through some older posts, but i think the general consensus is the advantage is useless without an o-ringed head or block.

If you want to save the downtime, i have a good spare cylinder head i can sell to you. Its off my '88 (non S) and was never machined before. PM me if interested.

Darwantae951

PM sent.

Josh B

It is recommended that the throttle be open but from my experience I am not sure that makes a difference. I think that the numbers are not as important as the spread with a compression tester. I've heard a leak-down tester will reveal the picture better of what is going on. Don't forget to buy the hardware kit from Paul or Rennbay - makes things a lot easier. I have a guy here that refreshes heads for $175. He is doing two for me right now. Makes them look real pretty if you glass bead blast them before you take them to the shop. Then they can clean out all the glass

Keithr726

Seriously most 951s with over 100k have scored cylinder walls. I'd say just drive it until its bad then rebuild. Try the test again under different conditions. +1 on the leakdown

MM951

I think its fine, the spread is less then 10%. Are 951s supposed to be in that range?? My 951 is 150 psi on all 4 (-/+ 5psi) but then again it is new..

Do a leak down, but I think its A OK. Drive it till you can't anymore and don't worry about it

zoltan944

The overall numbers are effected by the open throttle. So you would maybe have gotten higher numbers across the board, but still a bit lower reading of cylinder #1.
The difference in cyl #1 from the average of the others is about 5.5%. This was sorta obvious with your #1 plug posted before, but 5.5% would be NOWHERE NEAR what it would take me to pull the head.
As far as it being your first time doing it, it doesn't matter its a no brainer and your results show that you did it correctly.
If you want to know where the loss may be, then a leak down is in order. Should it in fact be some build up on a valve, then Seafoam may be able to fix your problem