Head Surfaces

[930LDR]

Need some opinions on the condition of these heads and whether or not they should be used. The mating surface has been resurfaced but the face of the combustion chamber domes for cylinders 4-5-6 are pock marked from something having been blasted around in there. The edges of the mating surface on a couple are also somewhat rough. Looks like maybe they were machined one time too many possibly resulting in a slightly more narrow section of mating surface on a couple of them. These have already been rebuilt by my machine shop and they felt they were fine to use (obviously) but I'm looking for some second opinions.

Thanks,

[dhagood]

question for the experts: is that from detonation?

[Steve@Rennsport]

The bottom picture looks like detonation damage; thats a set of heads I would not be using.

[304065]

I agree with Steve. Pockmarks around the small valve are a telltale sign of corrrosion from when the engine sat out in the rain. Pockmarks everywhere suggest detonation or a foreign object getting trapped between the piston and the head, makes a nice pencil holder for your desk.

[930LDR]

Really... there isn't anything that can be done with these? Three out of the six have the pock mark issues and a 4th, maybe 5th, have the symptoms in the bottom picture.

[930LDR]

So what are the ramafications of running a set of heads that look like this? Clearly they aren't pretty, but I'm hearing from my machinist (who worked on the 935s for Garretson) that he wouldn't be worried about bolting these back on.

[Mo_Gearhead]

Quote: "So what are the ramafications of running a set of heads that look like this."
_____________________

IF ..if any of those "pock marks" have (or later develop) sharp edges (as they can lead to carbon buildup) - as the engine temperature builds they can become ignition points - and cause 'detonation.'

In other words - think about the piston NOT being near TDC when the fuel lights off. NOT a good situation.

[CaptainCalf]

If you had a liitle more meat on them to smooth over the rough areas I'd think you could make them work, but from the pics it looks like you may have already run outta real estate

[Walt Fricke]

Rob

If this was a normally aspirated street motor I'd be less worried. But it seems that with a boosted motor you can much more easily run into detonation issues?

What do the pistons look like?

I've reused heads and pistons which had a bolt or two (small, to hold down carburetor stacks)rattling around in the combustion chamber for a couple of laps. Looked kind of ugly, what with dents from the bolt heads, and screw thread marks, but smoothed off the rough edges, discarded the one piston whose top ring land got squished, and things have run fine ever after, both pistons and heads. But no boost, and modest CR for a twin plug carbed race motor.

If you knew why this happened, and how to prevent it happening again, you might be able to make a better informed decision about trade-offs. Were it my motor, I'd not be too worried about most of the erosion, but the substantial pock marking between the exhaust seat and the cylinder edge is really ugly.

You might want to compare the cost of welding some of that up and remachining with the cost of a good used head (which will have to be resurfaced to match what you keep).

[930LDR]

Hey Walt -

Cylinders were pretty clean. Pistons had some evidence of detonation on a few edges. No scaring like the heads though. I ended up picking up a new set of Mahles.

I've actually received feedback from a couple of well known and respected builders (offline) that suggested they would run these on their personal cars but not a customer's.

Honestly I'm leaning towards running them as is although your suggestion on a little welding may not be bad one.

[911pcars]

Heads are aluminum. Aluminum can be welded and remachined.

Question is - Will the cost of this exceed buying a set of good rebuildable heads, then finishing up with needed machining and valve work?

Could be an opportunity to experiment with high compression along with adding combustion-friendly squish areas and compatible pistons. YMMV.

Sherwood

[Jeff Alton]

They look 100% better than a set of 3.2 heads I bought (with out pics) from a fellow on this board who passes himself off as an engine builder..... But I would not run them in that condition.

I ate the cost and donated them to Brian (rarlyl8) where they were perfectly suited to his mock up motor for exhaust fitting.....

[lucittm]

These are desirable RR350 heads. I would use them, if you chose not to use them let me know and I will take the three of them from you.

Thanks,
Mark

[Walt Fricke]

Engine builders are notoriously loathe to put questionable parts into customer engines. Many, if not most, have had bad experiences, even if they got the customer to sign in blood that this was against the expert's recommendation, couldn't be guaranteed, not the right thing to do, etc.

Were the rest of us in that business, we might take that approach also. Life is too short for the aggravation if something goes wrong, and no engine builder wants his engines to blow up. Somehow, the fact that use of the questionable parts was over his objection is not likely to go along with the story that X's motor, built by Y, blew up.