blown 944

After looking closely at my cometic hg I've come to the conclusion that the cylinders are moving. The gasket was cut through in perfect circles on the cylinder side on two cylinders. It appears the others were on the way.

I have decided to change my plans regarding trying to seal the cylinders.

I went ahead and cleaned the cooling area of the block, sealed off the water pump openings, and finally did a short fill of block filler. Basically raising the floor by 1.5".

This is a temporary engine and short of creating some sort of deck plate, I don't see a solid solution to be able to run high boost at all.

As most of the heat is transferred at the cylinder tops I'm hoping that it will run cool enough.

So now the current plan is to:

Change head studs
Use wide fire gasket to determine if problem is pseudo solved
Install huge oil cooler under my intercooler

If it appears that this helps, I will then try another cometic or go ahead with the o ringed head and wide fire hg

I'm letting it sit this whole week to harden and installing the oil cooler among other things.

Fingers crossed...

JET951

Thats our conclusion as well Sid,
Every cometic we have used shows the exact same sign that the cylinders were indeed moving and wearing out the raised rings on the steel of the cometic. I still think the cometics are a great headgasket. When they finally fail you can still drive home from the track.
That being said, i think a deckplate is the way to go on the 2.5ltr blocks. or at least some sort of pin around the top of the cylinders to hold them at one with the block.
I am currently using a 944S2 block which has the cylinders siamese together. I have only done 3 track days so far but i believe the siamese will help keep the cylinders from moving.
regards
Sean

blown 944

Sean,

It is my understanding that in addition to the siamesed cylinders, that the floor is also raised in the 3.0 blocks. I have not seen first hand the difference, just what I have read.

If this in fact does work, I will be filling my other block prior to the final hone.

I agree that the cometic is a great hg due to the durability.

It used to take quite a bit more abuse to see these problems with the stock shortblock. Now it's very acute.

pole position

It appears that your high compression with moderate boost on your new motor raised the cylinderpressure significantly more than in your previous set up with high boost only

Looking forward to see if the blockfiller works without cooling problems.

Rogue_Ant

Very high compression combined with a much better flowing head - definitely a lot more cylinder pressure.

Makes me wish I had an in-cylinder pressure-transducer...

Tom M'Guinn

Yes, the 104mm bore blocks have a raised floor. I can post a picture if helpful. They had a bigger water pump too, and did add oil squirters eventually, however, which helped cool from below.

Tom M'Guinn

Can't say I've tried them, but they do make spark plugs with built-in pressure sensors, such as...

http://www.kistler.com/US_en-us/13_P...t-range-7.html

blown 944

Yep, unfortunately. While it's nice at lower boost. Not so much at the hp level I want.


Me too, I've been doing a fair amount of reading and it appears it has been done a few times in the past without negative reports. I should know pretty quick if it holds with a stock type gasket. My main fear is that I am doing it without any deck plate and after already being run in. With the open deck though I can't see too much cylinder distortion happening.

blown 944

those would be pretty cool to try out.

Maybe we should get one or more Josh??

Rogue_Ant

That is very cool... I will take a look at the datasheet this week - perhaps another project to add to the list!
Any pricing for that spark-plug - I don't see it offhand?

refresh951

I bet it is not cheap.

Kistler Instrument Corp.
28714 Magnolia Way
Santa Clarita, CA 91390
USA
Tel. +1 661 296 3429 , Fax +1 661 296 3491
jorge.aldeco@kistler.com

Rogue_Ant

The fun stuff never is! But it helps that most of the analog/digital processing stuff I can build...(and I consider fun)

Thanks!

DLS

I think i have the same problem as you blown 944.
i hope that arp studs and o-ringed block will pin down the cylinders so they will not move around.
we will see this summer if it will help or if i should rip out the engine and replace it with a audi 5 cylinder instead

86 951 Driver

Blown944 you are the shiz. I will never build up a 944 quite up to your level, but its cool that people like you are trying to take these cars to the next level. Now all we need it twin scroll turbos or maybe a twin charged 944??????

blown 944

Depending on what you want, you may very well be going the Audi route. I may too, I can get a builder for 700 and start from there. After a conversation with Dave with CEP today, I am definately setting my sites a little lower unless I go with a 3.0 or larger.

Nah, there have been many before me to push the envelope. I'm just too stupid to read...

I was going to do a twin charge until I used anti lag. Dave (dnovak) will probably do a compound setup. Keep an eye out for that.

I'm just going to focus on the 16v engines, and if they don't do it for me I'll join those who have traded for something else
(powerplant)