HansB

Tore down the newly rebuild engine of my track car after 10 hours, cleaned the MLS gasket, (takes a bit more then 10 minutes) and much to our surprise saw on the top side (say over 90 degrees) of the second and third cylinder what almost looked like a laser cut rim of 2 mm (1/10 inch) wide through the first layer of the gasket, following the cylinder circle exactly.

Very clean cut, we even almost missed it.

Any ideas what might have happened?

HansB

Made a drawing to illustrate the damage. Does hardly show on a photo.




Anyone??

anders44

did you try contacting the gasketmaker?

HansB

Good Idea Anders, I did.

For the record:

Cometic anwered :

So, high level detonation. This remains my problem.

Kool

How do you "lift" a head in the engine when it is bolted together? Or more to the point how do you prevent it from lifting?

333pg333

What sort of boost are you running Hans? Did you hear any 'noise' to suggest detonation or see any signs on your pistons? I would think if you had high level detonation you would have more than a nice etching on your gasket. Are you using stock headstuds? Why did you tear it down after only 10 hours?

anders44

also, got egt/afr logs etc?

INURGRL951

JUST CURIOUS I AM RUNNIN A COMETIC HEADGASKET ON MY STREET / TRACK CAR AND WAS WONDERIN THE PURPOSE YOU TOOK YOUR MOTOR APART IN THE FIRST PLACE TO UNCOVER THIS ISSUE..I NOTICED THAT MY PSI A CYLINDER IS LOWER THEN BEFORE AND WAS WONDERIN IF THATS WHY U DECIDED TO TEAR IT DOWN TO INVESTIGATE. AND ALSO THIS IS A BUILT CAR WIT ABOUT 10 HOURS OF TRACK TIME ON IT AND DRIVEN DAILY AND ALSO WHAT WAS THE METHOD AND TORQUE SPEC YOU USED??

HansB

"lifting" of a head is caused by knock. The extra force of the untimely detonations has to go somewhere. If not the HG, then the piston or valves would be damaged.

Many Q's Patrick. I am running a quite conservative 15 psi boost, on what would translate to 93 octane fuel. There is no audible knock, but that is the point with high level detonation, you do not hear it. I am using stock headstuds.

The teardown had two reasons:
After my first morningon the track this year the car did not run properly any more, and when we did a compression test it was 150 - 150 - 150 - 90.
Second reason was that I have had HG/detonation problems before and we wanted to make sure that this rebuild engine was OK.

The inspection showed one floating valve, where some debris was baked on it, and the HG as shown. Both were probably not what caused the poor running, more likely that was a faulty reference mark sender.

No EGT, but AFR logs where ok.

The most likely culprit is the K27/8 turbo, which we suspect to be thermodynamically less efficient. A friend of mine runs the exact same setup (chips, timing, MAF etc, etc.) only a different T04 based turbo, and he has never seen any problems in over 150 track hours.

HansB

This is a track-only car. Torque is by the book.

zoltan944

Head lift is also caused by head bolts stretching under stress (boost) and the head simply comes a bit up. Usually this destroys the gasket but not always. I would look into some different head bolts than stock especially if you keep reusing them

anders44

remember the small turbines produce a ****load of backpressure.

HansB

Agree, that could be a cause, but these were new at the time of the rebuild. I would not think that the moderate amount of boost I run would be too much for new OEM headstuds / bolts

HansB

All points to the K27/8 turbo, but it keeps me wondering how such a commonly used turbo can cause these problems. My current thinking is to spent $1k and replace it. Cheaper than a rebuild.

fast951

HansB, I have personally used a K27/8 on a race car running 19+psi without a issue. I know of others running K27/8 as well. It's a good idea to check the backpressure to be on the safe side, at the same time I would look at other variables causing the detonation (if it's detonating).