m42racer

Now now, don't get your G string all twisted.

It has nothing to do with how low you consider yourself either. It was just the idea of maching on the Pistons still in the engine.

Give me a break!

Peckster

There's more than one reason to replace the belts regularly. I've had to replace rollers too, and I wouldn't have caught that without the belt job.

There aren't many things we can do better than the Porsche engineers.

Tom M'Guinn

I think I could have come up with something better than that nuclear strength snap ring on the thermostat.

Oh, and what about those impossibley-complicated spring-clips holding the distributor cap in place. And while I'm at it, how about that damn oil filter that vomits all over the place everytime you change the oil....

Sam Lin

Flycutting pistons in-engine is not a new process and is quite easily doable.

Tools:

http://www.iskycams.com/category_tem...ategory_id=133

Procedure:

http://www.forcefedhighperformance.com/tech_Isky.htm

Sam

Tom M'Guinn

Sam, thanks for that post. The second link, showing yet another use for duct tape, actaully looks like an effective way to keep the scrap metal shavings out of the motor. I image one of those kits would work or could be adapted for the 951. Who's going to be out guinea pig?

Bengt Sweden

Nice to see for once a car with worse access than the 951!
Wonder how they perform the same operation on the innermost cylinders.
Bengt

m42racer

Not me!! I rather chance the belt not breaking than risk my cylinders with some stray shavings.

jns

m42racer,
Let me know the name of your shop where you take your car so I can sneak in at night with my drill and grinding stones and go to work on your pistons. I would be honored to have your car as the first with the new flycut pistons. It would be an inspiration to us all. Your apology is accepted for criticizing my idea of flycutting pistons in the engine which turned out to be an old and commonplace procedure. You should have done your research first before you started whining. Looks like you learned something after all. I'm proud of you, son.

m42racer

No problem, I take my medicine any way its given.

m42racer

"which turned out to be an old and commonplace procedure."

????

m42racer

JNS,

Everyday I try to live down the reputation we 951 owners have. Then we debate the merits of machining Pistons while still in the Block.

Just how many professional engine builders would do it this way, I'm wondering?

Sam Lin

Yes, it's old and commonplace to flycut pistons in-block. I know engine builders who have done it for longer than the 951 has been around - back then you had to braze your own cutting tools out of a piece of carbide and an old valve, noone made them.

Sam

Tom M'Guinn

I know it sounds crazy, but if the piston is flush with the deck, and duct tape is pushed down tight against the face of the piston and deck, then wouldn't the shavings be sealed out of the motor?

Laust Pedersen

Ingeniously simple, a true sign that it has been around for a long time. Tom, I think you are right for pistons (with outer periphery) flush with the deck, it seals the gap and the other cylinders from the shavings, but it also fixes the piston, so it doesn’t wobble in the cylinder while cutting, although a dedicated plastic wedge in the gap would probably do a better job.
I would imagine it was designed for people converting to high lift and wide cams.

Thanks, excellent references Sam.

Jeff F

Once a crank has been knife-edged, the reciprocating assembly is re-balanced--if it is my car. This is "commonplace." Maybe fly-cutting was done on other models, but not on any making 15 lbs. of boost.

Wes: I just dropped a huge amount of money with your company. How would it seem if I installed all of it, undertook an untested procedure, grenaded something and came back to you with complaints? Not a good idea.

My 2.8 records show it was re-balanced after crossdrilling and a new flywheel installed. It will continue to get that type of care. At 400hp and 7000rpm, I am leaving my combustion chamber and balancing alone until any results are available. Oh, and changing belts. Compared to 928's, it is cheap and easy.

Jeff

'86 951 2.8. Lots of extra stuff. Most from Lindsey.
'87 928 S4. Some extra stuff (Murf SC in progress).
'92 968 Cab. Mostly stock and staying that way.