engine rebuild problem
 

putting my 930 engine back together.
had the heads rebuilt and ported.
was just curious so I did a leak down on the left side.

LOTS of air leaking past the valves!!!

I think valves leak until they pound their way i to the seats. I've read a handful of threads like this and that seemed to be mentioned in most.
What'd the machine shop that performed the work say about it?

haven't talked to hm. cant until next week

I think you have to run it first before any leakdown test is valid.

+3 above... first drive then if problems occurs , leak down test..

Ivan

Rebuilt heads.......
 

Ty,

A properly rebuilt heads should pass the liquid tests. If you put liquid like water or alcohol over the dome, there should not be any seepage of fluid during the test. If you do, it is not sealing well. This is a basic test before assembly.

Tony

Valve assemblies machined to spec do not leak when assembled.

There should not be leakage from the combustion chamber to the ports, unless there is something physically holding the valve off the seat. They do not need to be run to seat properly.

do we know for sure it is past the valves....? as t77 told me he has the rockers off so above boys are correct no leak -

Ivan

T77..can do it again with a video so we can see it -the leak..

Are you certain the valves are properly adjusted and that you were on the back side of the cam for the cylinder being tested? The valves should not leak on a newly rebuilt head.

red..... i just wrote he has no rocker in ..yet;-)
Ivan

I have tape on the intake ports, its about to blow the tape off.

ok take it of the engine set on the table pour some gas into the each chamber and see where does it leak -is the best you can do now...does not take much time to take it off..It is strange that machine shop would give heads like this??
Ivan

valve leakage
 

I always lap the valves in my self and use Prussion Blue then set valve spring height and reassemble.Do it once and do it right.Then you know.Ciao Fred

good point Fred ..but some of the peeps do not have the tool to do that ,that is why they trust the machine shops to do the job...

Ivan

I reputable guy on here did the heads.
I don't want to say who just in case there really is not an issue

definitely leaking past intake on 1 and 3.
2 was not as bad.

I have just done cam timing, no other rockers installed

ok
just checked again.
its late and had shower so didn't want to stat out there and get sweaty

1 is better. le3aking past rings. I was a bit surprised since they were soaked in oil

3 is still bad. lots blowing out intake port. so I put a rocker on and spun it over a few times but it was still bad.

checked 4, it was tight as a drum

Customer Service......
 

Ty,

Unless you got the job for a bargain, just be thankful. Otherwise, contact the rebuilder and give him an opportunity to fix the problem. Everybody makes mistakes, so allow him to address it. The integrity of your chosen rebuilder will be confirmed by how he handles a situation like this one.

You made a decision by not naming him at the moment. Keep us posted.

Tony

#1 stopped leaking
3 and 6 are leaking.

I guess its back to working on the race car until I get this worked out.

Here is my experience with leakdown and newly rebuilt heads -

http://forums.pelicanparts.com/porsche-911-technical-forum/1053367-chasing-leak-down-after-valve-job.html

I also had a very reputable Porsche engine builder do my heads. Mistakes happen and two of the exhaust valves were not cut all that great. The shop re-cut them.

The frustrating part came next. Lot's of advice that newly rebuilt heads should not leak at all. Not my experience. And torquing the heads down changes the seal as well (non leaking valves would leak and vice versa).

Fortunately after running the engine for a 1000k miles the valves all seated perfectly and my leakdown numbers are great <2%.

Hope that helps some, and best of luck!