Advice on 3.6 (early 964) top end rebuild

[GaryR]

I'm trying to get an idea on what will be needed to end the head gasket/case seal problems on a 90 964 3.6 i'm looking at. The engine is very low mileage and in perfect shape other than this (well-known) issue. It seems like the later cylinders have grooves cut in them on both ends, one for a green O-Ring between the case and the jug, the other for a graphite gasket between the head and the cylinder. Would purchasing these cylinders w/matched pistons be the solution? Send the cylinders out to someone to have the grooves cut? Is there a kit out there just for this?

Any info or links would be greatly appreciated!

[Jeff Alton]

Contact Steve at Rennsport Systems, he cam fix this. Mine should get here tonite from him, when they do I will post pics of the mod.

Jeff

[GaryR]

Can you elaborate on this a bit Jeff? I emailed Rennsport but am curious as to what they do. Do they sell the cylinder sets with the grooves cut? Do they machine yours?

Thanks!

[ischmitz]

Read here

http://forums.rennlist.com/rennforums/showthread.php?t=111791

it has been discussed on Pelican as well. I did have my early style cylinders modified and so far no leaks after 10,000 miles.

Ingo

[GaryR]

Thank you Ingo, I spoke with Steve at Rennsport shortly and he explained the process in brief. I'll give that post a look!

[Jeff Alton]

Okay, here is half the story..... only one of 2 boxes showed today. This shows the machining done to the top of cylinder. A 993 head gasket fits the step that is machined in.



Jeff

[GaryR]

Jeff - is there already a place for the "green vitron" O-Ring on the bottom of the cylinder or does Rennsport add that also? And what are those metal upside down mushroom shaped things for?
;-)

Thanks!

[Jeff Alton]

There is a grove at the bottom for the seal already. Them there are the result of valves trying to get intimate with pistons. A half dozen nicley bent exhuast valves!!

Cheers, Jeff

[GaryR]

Got it.. Looks like the best way to go is to have Steve rebuild the heads with new guides and better valves/springs while he has it. What are you doing about new rings? Quick glazebreak on the cylinders and new stock rings?

Its all starting to sound like a plan!

[Jeff Alton]

That is pretty much what I did. Slightly bigger cam from camgrinder here on the board. Stock springs and valves and head rebuild from Rennsport. Just could not justify going with better springs and such as I will be using the factory redline.......... Had Steve clean up P/C set as well.

Jeff