heads &cylinders (troubling)

I just got off the phone with the gentleman from German Engineering. I got a quote for doing the machine work, valve job ect.
The price he quoted me was reasonable for the valve job.
He said that because of the snapped head stud problem that I would have to send the cylinders in as well to have them all machined and have spacers installed.
That, unfortunately, also makes sense.
What I don't understand is when I told him that the car has 200K on it he said that if I planned on keeping the car for any amount of time that I'd need to replace the pistons and cylinders. Me telling him that the factory Honeing marks were still visable only made him seem sure that my pistons were really worn out and would need replacing.
I just can't afford a set of $2400 pistons and cylinders.
What do all of you think?

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Leland Pate

___79 SC Targa

How can you be sure the honing marks are "factory"? Those cylinders might have been honed and re-ringed. The only way to determine the need for replacement is to measure the pistons and cylinders, and compare the measurements to factory specs.

Leland, did you run a compression test prior to removing the engine? I agree with the previous poster, how do you know the engine hasn't been rebuilt in the past? If you really have 200K on the engine I would thing you would have a wear ridge on the top of the cylinder. Take you fingernail and starting about an inch down from the top of the cylinder, scrape upward and check for a ridge. If there is one, you definitely have enough wear to justify at least cutting the ridge and new rings. Are the pistons stock? Most oversize pistons have the oversize stamped on the top of the piston. If you see an oversize stamp you know it has been thru at least one rebuild.

Kurt V
72 911E

The motor has never been rebuilt.
I have every record on it dating back to 1981.
The lady I bought it from was a very honest and nice person.
You are right though, the only way to tell for sure is to measure them.

Leland,

You need to measure the pistons and cylinders on the thrust areas, that is, the center of the upper and lower surfaces as the pistons and cylinders would normally sit in the engine. For the pistons, measure up an inch from the botton of the skirt. For the cylinders, measure at an inch and two inches up from the bottom of the cylinders. I hope you have the factory spec book for your engine. I believe the max. clearance is about 0.002" ... but I don't find a limit in Bruce's Handbook!

Your contact at German Precision may have an overly pessimistic view of your piston's condition, as Bruce has indicated that Nikasil pistons and cylinders can be re-ringed and last for over 350K miles under best of circumstances.

The Nikasil cylinders and pistons use tight clearnces because of the oil squirters that cool the pistons while running.

It is really too early to have worries, yet, so don't worry! At the worst case, you can still reuse your Nikasil cylinders and put $600 worth of new JE 9.5:1 forged racing pistons in them!

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Warren Hall
1973 911S Targa

Yeah. So quit worrying.

I have a spec book for my car (81-83), and I'd be delighted to get you some numbers from it, but we can't be sure they apply to your car.

Specs are everything though, and you can know, before you make decisions, whether any of your pistons or cylinders have problems. And as Mr. Hall pointed out, a "problem" isn't really a problem.

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'83 SC

If your pistons and cylinders have 200,000 or 50,000 or 300,000 that does not matter. I have seen trash 80,000 miles 3.0 pistons and cylinders and have seen cherry 200,000 miles pistons and cylinders, it comes down to how the owner serviced the motor or how the fuel was working either good or bad, if a fuel system was dumping gas get ready worn ring grooves or never R & R the oil bad cylinder walls and worn piston skirts. CHECK THEM, they are big money because they are the best. Mahle makes one of the best configurations of piston and cylinder wall matching. But CHECK THEM, pick up one of those small white spec books for around $15.00 Porsche calls out "them self's" what is reusable and what is to far gone." Check the pistons skirts and piston ring grooves and the cylinders wear also, cross hatching can either be good or bad.

If you want to raise your compression for more HP and want to save money, then fly cut the heads or you can go to a Forged Hi-Compression pistons, but these only work with Nikasil Cylinders (which you have). Or you going to regrind the cams to 964 profile?

Roy at http://www.motormeister.com

Roy, can you tell me why the crosshatching could be good or bad?

I agree that it is too early to tell the condition.
I'll have to take them up to my mechanic and see.
Thanks again.

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Leland Pate

___79 SC Targa

Even if you do take them to your mechanic, please also see for yourself. Get a micrometer, or caliper, and check those tolerances yourself. If they measured up, I would not hesitate to reuse them. It's an engine for crying out loud. Even if you build it bad, you'll get 100k. By that time you's be General Pate and your SC will be your "track" car with a 3.6. Your daily driver will be a 700 hp electric car when this rebuild wears out.

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'83 SC

Get them measured, that same shop gave my used RS P&C's a good bill of health.

Leland,

Simple rule when you are having to spend money and BIG money ,like pistons and cylinders ...........take your time .

The pattern you see in the cylinder is a good sign but it still can be worn. Pick up a spec book or ask the Porsche mechanic to see his and inspect them with him, he will be making money over all, so he should not mind. Now lets say ONE is bad, well then look for ONE piston or cylinder to match the set. Does it matter if you replace one piston or one cylinder? No, Porsche sells them by single for replacements, just check the pistons' weight, compression ratio and make.

Take your time it may save you money

Roy at http://www.motormeister.com