compression test numbers

[chocolatelab]

Hi all

Well I decided to have a local porsche shop do the work on the broken head studs. Just dont have the time and room to get it done myself. I promised myself I'll do it one day. Just not this car this day.

Anyway.

One head stud each on 2 cylinders left side broken.

78 sc with 77k miles.

Just got my compression test numbers.

all cylinders but one tested out around 130. Cylinder number 2 tested at 100-105.

Any thoughts from the Pelicans out there?

[craigyirush]

I am no expert, but those number are on the low side.
You might need to check the wear on the P&C's.
I would get a second opinion from a reputable shop, though.

[nineball]

from what i read on this board you want them to be around 150, but don't quote me.

[Hladun]

Compression Test Pressures

Cylinder #2 is a problem.

[scarceller]

Have them do a leak down test as well.

[SC-targa]

These numbers are pre head stud replacement, right?

Are you planning on a valve job while you've got the heads off?

Not sure what you're asking.

Regards,

Jerry

[crashmy911]

no expert. But I think american spec engine. has lower commpression on cylinders. I think 130 is normal! 150 to 160 on euro spec engines. But I could be wrong.

[scarceller]

The 130 isn't the big issue here, it's the the other cyl that's way off down near 100. A leak test will really help give more info on the condition of the cylinders.

The low cyl could be something as simple as a bad Valve Gap or a dirty valve. You want to try to figure out if the low compression is Head/Valve related or Cyl Piston/Ring related

[Hladun]

Originally Posted by crashmy911

no expert. But I think american spec engine. has lower commpression on cylinders. I think 130 is normal! 150 to 160 on euro spec engines. But I could be wrong.

As my table in the link shows, 130 is correct for a 8.5 CR engine and 150 would be more correct for a 9.5 CR (1980+).

[mark waller]

Who did you go to? I emailed a couple of Great shops. Is it at Tom's in Temecula? Hope it works out!

[chocolatelab]

Yes these are pre head stud replacement numbers.

I will be visiting the shop again tomorrow to see how things are getting along.

We will be doing leak down.

I am asking because I want to be as informed as possible when discussing issues and such with the shop.

I will be taking pics and will post.

I really am relying all your assistance to make sure I make the best decisions possible.

Thanks for all your help.

[scarceller]

Was the engine dead cold or warm when compression tested? Both cold and warm test could be useful but the warm test is best.

In the end you really want the shop to try and figure out if this a Cyl/Piston/Rings leak or a head related leak so you can decide what's the best approach to resolving this.

If the broken/loose stud is on the bottom it is possible to repair in car (not easy but possible). You need to remove exhaust system then pull alternator with fan so you can get the air tins out from between the cylinders. If you can get these out you can then see where the stud is threaded into the block. I'm not 100% certain but I think you may be able to get the stud out and then the hard part is inserting the time-sert to repair the bad thread (DO NOT use a helicoil use a TimeSert repair kit) I have repaired these threads before but never in car. However, I do think it may be possible to do the lowers in car.

If it's a lower I'd try fixing the stud(s) in car then drive the car some more and retest comp after a few 100 miles.

[chocolatelab]

Engine is out.

They should have it disassembled shortly.

all questions will be answered then.

Another question. The clutch measured at 6.5. Brand new is 8.

How much life do you all think is left.

[Fast Corners]

Chris,

According to my spec book new was 8.1 mm and the wear limit is achieved at 6.0 mm as long as the wear is even. Maximum runout is 0.6mm. Given this it would be prudent to replace it while the engine is out of the car.

Interesting to me is the car has 77K miles on it and this is most likely the 2nd clutch disk. What does the date stamp on the disk indicate?

[chocolatelab]

Not sure can find out though.

Here's what i have on the clutch from the previous owner.

In 1995 at 62 k miles the clutch was adjusted,replaced fly wheel and flywhhel seal

this is not a daily driver and probably wont see another 5k miles this year.

Any ideas how long it should last? I am sure that is totally dependent on the driver but ballpark?

[GMR911]

My 78 euro 3.0 L tested out at 165,165,165,165,160,155

[Alan Lindquist]

My 1980 SC was tested at 128 (approx) all around except for #2 which was about 95. That was 2005 with 125K on the motor. I've commuted daily and driven it hard but not abused it for 75K miles since then. Now cyl #2 test out as "going along for the ride" as my mechanic puts it. Oil consumption is about the same - 1 qt every 1200 to 1500 miles depending on the outside temperature. Head studs are tight. Oil filler shows puffs of smoke when the cap is removed, so I'm thinking wasted rings. Still runs. Will keep running it and wanting to put a 3.2 in soon.

[chocolatelab]

that is pretty impresive.

they are going to replace the rings since its all out and not too expensive.

It probably just makes sense to put it all back to gether after that just drive it.