rwflier

I am sending my 1-3 cylinder head to Costa Mesa R&D for repair to the #1 cylinder crack and was wondering what the maximum amount of material to take off the head as far as resurfacing goes? Without getting close to valve to piston contact and also to keep compression around 11.3 to11.7:1.

Flat6 Innovations

Heads must be decked perfectly even to maintain combustion balance. if you aren't pulling both heads and machining them equally, don't deck the cylinder head at all.

rwflier

I should clarify my post: it's just one head that needs to be repaired but both heads will be resurfaced (decked); the engine has been pulled and the short block sits on an engine stand. Thanks for the reply.

rwflier

I should clarify my post: it's just one head that needs to be repaired but both heads will be resurfaced (decked); the engine has been pulled and the short block sits on an engine stand. Thanks for the reply.

Pac996

I don't know an answer but can add that possibly there are different head gaskets thicknesses you could use. It's common to have different gasket thicknesses for performance bike engines. I have to figure porsche should have the same sort of trick since changing the compression ratio is easy to do with the gasket. When going to a turbo and such thicker gaskets lower the compression to the desired value. So pretty much if shaving the heads is required then a thicker gasket can save you from too close of a tolerence.

Dharn55

When Costa Mesa R&D repaired my cylinder head 1-3 they did not resurface the deck (I only sent the one head). Why are you having it resurfaced? Are there flaws or damage?

Flat6 Innovations

Outstanding.. Had me really worried there.

There are no multiple thickness gaskets available for the M96 engine due to the MLS construction of the gaskets.

The shop doing the work should be able to advise the material removal.. We have our own parameters as their is no rule book concerning this aspect of the engine.

logray

Found this in the workshop manual regarding head resurfacing, for what it's worth.

permissable surface uneavenness = 0.002"
permissable unevenness after machining = 0.001"
minimum head depth (wear dimension) = 5.5767"
while machining, peak to valley height = 0.0006"

jrgordonsenior

Costa Mesa R&D knows where the limits are. They've done many M96 heads for multiple So Cal performance shops....

Curious, what's their lead time right now?....

Byprodriver

Currently minimal

rwflier

It's a good idea to resurface, according to Steve Baker at Baker Cylinder Heads in Henderson, NV. It provides assurance the head is completely flat for sealing correctly due to heating and cooling of the aluminum.

Quadcammer

pretty horrible way to mess with compression. You can lower compression with a thick headgasket and actually be more prone to detonation due to the changes in the quench.

Macster

With this thinking then it also makes sense to resurface the block surface against which the head fits.

My training in this area had me avoiding removing any metal unless it was clearly called for -- proper checking of the head's surface using a precision surface plate and the appropriate tools was required to thoroughly characterize the surface topology/geometry of the head -- and then removing only the tiniest amount of material needed to bring the head to spec.

Too often though shops will just set the depth of cut to 0.010" or whatever and take a cut.

This affects the compression ratio a bit but it also in the case of these engines affects the IMS to cam shaft chain play. The tension can of course compensate for this but the less metal removed the better off the engine will be.

Sincerely,

Macster.

logray

IIRC, blocks that are sent to LN engineering are surface ground when they perform a Nickies rebore.

Byprodriver

That is correct,