964 cam timing values

[dad]

I just installed 964 cams in my 3.0L 911sc which I recently upgraded to 3.2L and I need to know if the 964 cams are timed different than the stock cams.

[ChrisBennet]

Yes, the 964 cams are timed to 964 specs. I think the setting value is 1.26mm +-0.1 (or is it +-0.2mm?).
-Chris

[911s]

Does anyone know if a 964 grind can be used in a 2.7L? Would any modifications be required? Some have told me that it can, but would like to know the specifics of what would be involved.

[dad]

Thanks for the help Chris, now if I can just figure out the conversion.

[ChrisBennet]

The 964 cam has a higher lift than the SC and thus your valves are more likely to hit your pistons when you miss a shift. It is advisable to replace your valve springs with stiffer "racing" springs when switching to these cams esp if you are going to the track.
-Chris

[911s]

Same deal with 2.7L? Or is it just not possible?

[William Miller]

This may be a basic cam theory question, but:

Can a home mechanic measure the camshaft to determine which cam was in the engine? Chris, you mention higher lift on the 964 cam.
Does that mean the lobe is taller than the standard SC cam? How do the acheive a higher lift by grinding?

I have an engine that has been apart before I bought it. Possibly a few times. While I have it apart I am taking notes to document what exactly is in the engine. One camshaft had writing on one end that said 3.2 911.
I looked this up and they the 3.2 had the same part # as the 3.0 cam.

How can I tell if the camshafts were reground already?
I have the same issue with my pistons and cylinders. How can I find out what the compression ratio is. Before I tore it apart all the cylinders except #4 were at 180-185 psi and holding 97% or better on the leakdown. I have measured and all the clerances are within the wear tollerances. The piston is a KS with a shaped dome top. Looking at Waynes book Page 143 picture 4-8 it looks like it might be the one on the left. The caption states that this is a Montronic piston.
I know my piston has a flat area that faces the intake valve. The #4 piston has a round mark or dent in it where the intake valve was hitting it at this spot.

Is there anyway to cross reference the numbers found on the piston to find out what it is?

The ultimate result was that the top ring on #4 piston broke.
Maybe this was a result of a high lift cam and a weak spring?

Has anyone been here before?
I'm starting to think that I might have a 3.0 block with 3.2 pistons and cylinders, I'm thinking now maybe I have 3.2 heads. The valve guides are shot. Could this combimnation work?

[Wayne 962]

There's a pseudo procedure for measuring the cams in the new Engine Book...

Yes, the 2.7 should be able to use the 964 cams with no problem. I haven't heard of piston / valve clearance being a problem, but of course, you would want to check during assembly regardless...

-Wayne

[William Miller]

A few clarifications:
I do not have 3.2 cylinders. They have the grove for the head gasket.
I looked up the 3.2 head the picture looks like it has a place for the knock sensor to go. So I don't think I have this.

I still think I may have the 3.2 pistons. I think the wrist pins will tell me because waynes book shows that the wrist pin diameter is a little bigger on the 3.2. As I recall the bushing in the top end of the rod seems thinner than some of the pictures I have seen. I'll measure that next!

Wayne I'll also look up the cam measuring procedure.
Thsnks for the help!