wsybert

I assume have original cylinders on my 1990 car, therefor no seal ring (head gasket).

If I pull the heads, would I just check for flatness and resurface if necessary?
(I don't believe I have any leaks associated with this surface now.)
Also, is it recommended to machine in the sealing groove.

Adrian's book says you need special tool 9526. Anyone know what this looks like? I know it is some sort of jig to hold the cylinder, just curious how it holds it.

Bill

darth

The way I understand it the sealing ring needs to have a groove cut in the base of the cylinder in order to accomadate it. If you buy a 993 sealing ring kit just provide them to the machine shop doing the work, they should be able to determine what size groove to cut based on the size of the sealing ring (i.e. a big O-ring). If you decide to put a gasket at the top of the cylinder the machine shop will also need these gaskets before hand so they can determine how much to cut away (i.e a machining process called flycut) in order to keep the combustion chamber volume the same. If the machine shop has done this type of work before they may have all the machining specs on hand and documented so they won't need to see the sealing ring and gaskets before hand and they should tell you what kit to buy. Personally I'd stay gasketless if you have no leaks as the system is good and if ain't broke don't fix it. I use to race/rebuild motorcycles and they used the same gasketless system and it worked very well if not better than cylinders with gaskets as long as the head bolt torques were maintained and the 2 sealing surfaces were never allowed to separate. But once they did separated there were problem with burning and warpage and these 2 surfaces need to be perfect to get a good seal. Definitely have the surfaces checked, any good machine shop will do this whether you ask them or not. There are a lot of advantages to not having gaskets - better heat transfer between parts (i.e. head / cylinder) allowing both parts to expand and contract at the same rate provide they are made of the same material, gaskets are used to compensate for any irregularities between the 2 surfaces.

Hope this helps
Bill
90C2
90C2

JasonAndreas

You're supposed to install it on the short 8mm cylinder head studs and the tool cut-out faces the intake valve. What you want is the TSB, "Refacing Cylinder Heads with Use of Tool 9526", February 8, 1994. If you are unable to locate a copy electronically I can probably scan it.

wsybert

Would very much appreciate a scan of the TSP if you can. Thanks.

Curious... If I had to remove the heads from the cylinders. Are there typically any issues on the gasketless heads, once removed? Do they typically need resurfaced?
I am just trying to figure out what I may be getting into if / when I get to this point with my engine.
Thanks.
Bill

Geoffrey

The tool is just a fixture to hold the head in a lathe as it turns to it can be machined. It is held by the cam tower studs.

KirkF

This is the TSB in PDF format.

When I rebuilt my motor I replaced the cylinders with the later style and had the machine shop put the groove into the heads.

As I understand it, the biggest problem with the original style cylinders was that the machined face was a bit too small, so they might tend to warp the heads when they are torqued on. This could lead to leaks. The newer style
has a larger surface and the groove for the steel ring.

(Both the cylinder and the head have a groove)

Kirk

J.PELLEGRINO

For years we have machined the top surface of the old style cylinders to allow for the use of 993 head gaskets. We have never had a problem with any of them to date. We do have a special tool to hold the cylinder in our lathe, but the process is not a big deal.
Good luck, Jerry