Pelican Parts Forums - Head Leak #4 via Leak Down Test

Pelican Parts Forums (http://forums.pelicanparts.com/)

- Porsche 911 Technical Forum (http://forums.pelicanparts.com/porsche-911-technical-forum/)

- - Head Leak #4 via Leak Down Test (http://forums.pelicanparts.com/porsche-911-technical-forum/938525-head-leak-4-via-leak-down-test.html)

Quote:

Originally Posted by DRACO A5OG (Post 9389586)

Miles, allot, over 316,000 :D

Prior rebuild 150,000 miles ago, I got her at 170,000+/-, Wow I put allot of miles on her since 2005 :eek:

Tear it all the way down and do it right. You'll be really peeved if you solve the compression issue only to spin a crank bearing or some other bottom end part. You'll be more than half way through the woods with just the top end.

At that age what's the history of the trans? Fresh clutch is a no-brainer too.

^^^ Noted, I agree totally. Better to do a complete rebuild and give her a fresh start.

She does need a new #8 bearing seal at a minimum, oh the pondering. I know better...

915 has been recently rebuilt, New Clutch Job, Balanced Flywheel and Pressure Plate ( Yeah I know Over Kill ) and modified with the 1 Piece bearing bracket from CMS, Shift like sweet butter :D

A little RANT:

Why would they make a engine gasket kit knowing that 99% the heads would be machined and provide 0.25MM OEM spec cylinder gaskets, I mean WTF?

If one did not read the service manual one would never know that a 0.50MM is recommended after machining and worse the darn Camshaft would be mis-aligned with chain tensioner housing hole for the cam's sprocket/end cap, no?

Okay venting complete.

I think the design of the chain housing does allow for a little bit of misalignment. But when heads are machined down to the minimum, a knowledgeable machinist will suggest maybe the chain housing machined to keep it in line with the cam housing. Or you can eliminate the gasket between the chain housing and the engine case and use sealant like Curil T, Loctite 574, Threebond, etc.

It all depends on how you look at it. The cylinder base gaskets are typically there to not only seal the base but also can get your deck height (top edge of piston vs. top edge of cylinder) where we want it, which is ~1mm. On an unmolested engine the .25mm gasket usually satisfied that need. But when your heads are cleaned up, possibly multiple times, that gasket needs to be thicker to push the cylinder + head assembly outward to align the cam housing with the chain housing.

Or, you can address the issue by making sure your heads & chain housings are cut the same. Problem is, with the shorter heads and shorter chain housing your engine "shrinks" and the chain tensioning assembly needs to take up that additional slack in the chain. A solution there has been to use larger idler sprockets. But that isn't a cheap solution and is usually only needed in drastic situations.

So I agree that ideally the gasket kit should include some varying thicknesses so you can dial in your fitment to the chain housing. The question is, do you want to sacrifice deck height by doing that? Most would answer yes since deck height is not an ultra critical measurement if it's just a little bit too long. Especially on a stock rebuild.

Heck, the engine in my racecar had a bunch of deck height (something like 2.4mm) when I tore it down and it didn't demonstrate terrible problems as a result of it. Bad practice, yes, as a result of a poor selection of parts (Carrera pistons on SC rods with 23mm pin) and most notably it was costing me a substantial loss in compression ratio and mild detonation. But it wasn't going to destroy the engine in short order. My point is that if you're only a teensy bit long on deck height by increasing the base gasket thickness, it's not the end of the world.

Quote:

Originally Posted by DRACO A5OG (Post 9389880)

Oh quite interesting, I never knew you could do something like that.

Outstanding!

I did this on my old Vanagan motor. Worked great, no problems after many years. However....

Not sure if that is a good idea on a Carrera. Remember the top of the cylinders have a taper....

BTW, my '71's motor leaks at the same spot. Very frustrating. Probably because I used curl-t on the head to cam housings. Won't do that again.

Porsche says you can machine .25mm off of the head surface. I don't think you will have any problems with the cam chains at that amount removed. I had 1mm removed from my heads and yea there was some finagling to get the cam end plates installed.

Thanks Fellas allot, really appreciate all the encouragement :-)

Just finished dropping the engine and a kind fellow Pelican is lending me his Stand and Yoke. Dropping it off to boot. God Bless Pelicans!

Engine Stripped down to Tensioner Covers, Cams, Heads, Cylinders and Crank!

UPDATE:

Frère Gilles, brought over his Engine Stand and Yoke, even helped me put it together, Merci Gilles, Merci!

http://forums.pelicanparts.com/uploa...1481438995.jpg

Stripped down & Ready to take apart during the day:

http://forums.pelicanparts.com/uploa...1481439148.jpg

Removed H.E.s to discover this in #4 Exhaust Port: :(

http://forums.pelicanparts.com/uploa...1481439254.jpg

vs # 6:

http://forums.pelicanparts.com/uploa...1481439302.jpg

#4 Intake Side

http://forums.pelicanparts.com/uploa...1481439398.jpg

Top area P-Side, damn #6 looks like it is starting to leak too :eek"

http://forums.pelicanparts.com/uploa...1481439480.jpg

http://forums.pelicanparts.com/uploa...1481439523.jpg

Good News, Cam seals were not leaking, it was #4 spiting oil out to the side and down the back of the chain tensioner cover :D ( Pat on back for doing the Cam Swap correctly )

#1 Intake seal was starting to get sucked in only had 1MM sealing the manifold, BTW the barrel nuts were pretty loose surprisingly.

Miller Time :D

Gotta hate the "loose barrel nut" thing-but now you know what's going on.
Though you'll have to take it apart I'd still suggest trying to torque them
before you do-could be failing studs-course with the mileage etc. they could have been replaced
at a previous rebuild with Dilivar-which of course you'd never try reusing anyway.

Sorry to hear about all this Brother Jim.
Keep us posted.

Will do, If I rebuild, I will just update. if I repair, I will start my repair journey part trois :eek:

Boxed and ready to go

Update:

Removed Pistons, Cylinders and Heads to send out for service:

http://forums.pelicanparts.com/uploa...1481676780.JPG
Started to remove some studs, some just came right off, others I will need heat.

http://forums.pelicanparts.com/uploa...1481676780.JPG
Packed tight.

I believe your Christmas care package should arrive on Thursday

Out of curiosity (given my issues) who are you sending that stuff out to?

Quote:

Originally Posted by Soren Lorenson (Post 9395587)

Out of curiosity (given my issues) who are you sending that stuff out to?

Heads to CGarr, Michigan

Cylinder &a Pistons to Ollie's, Arizona

Quote:

Originally Posted by KTL (Post 9395517)

I believe your Christmas care package should arrive on Thursday

Chistmas Care Package Received Safe and Sound :D

Thank you Master Kevin!

Ripping those pesky heads studs out now :cool:

Yep no problem.

Sorry the Snap On collet style remover doesn't have the M10 x 1.5 collet. Haven't gotten around to buying one yet. I've used the M8 collet for trans case studs and cam housing studs and the thing works fantastico.

Oh I can get that, not a problemo, will donate to the cause :-)

http://forums.pelicanparts.com/uploa...1482283679.JPG
http://forums.pelicanparts.com/uploa...1482283679.JPG
http://forums.pelicanparts.com/uploa...1482283679.JPG
http://forums.pelicanparts.com/uploa...1482283679.JPG
http://forums.pelicanparts.com/uploa...1482283679.JPG

Glad I split the case #8 Main and IMS Bearing seems a bit tired after 186,000 miles but I expected worse.

Finger Nail Test on the Journal, No Grooves :D, Yet to open the rods, but I suspect the same wear, No Biggy, she is getting all new Bearings, Going to take the journal to a local shop for micro polishing and maybe correct the Pully end for me :D

Got some good news, CGarr reported heads have never been cut and Better Yet VALVE stems are within spec. WOo Hoo! :cool: