When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Bonjour,
Merci Greg for your advises.
I'm preparing the heads and trying to understand honing of the bores procedure and what to buy to do it.
I had a lot to do this week but removal of pistons has been finished few minutes ago :
I finished too late today to correctly inspect the parts... tomorrow...
Have a great day.
Raphaël
Bonjour,
2 bores have several scratches that I can feel with my nail. Except that they all looks great. Very beautiful and clear white surfaces...
The pistons looks nice also. None of the rings were stuck. They all move freely.The side of the pistons seems no to have no wear marks.
I measured them at the 62mm distance of the top of the piston. My micrometer looks to be 0.01mm too optimistic.Or my pistons are still new... I get 6 pistons at 100.00mm (all group 1) and 2 at 99.99mm (1 group 0 and 1 group 1).
I started to measure 4 bores. It is much more difficult than the pistons...
The bottom part of the bores looks to be more worn. About 0.02mm more than the top.
The top looks to be between 100.01 and 100.03mm.
The bottom between 100.2 and 100.04mm.
But I have to check with someone more experimented to make sure I measured the bores correctly. It is not obvious for me.
Bonjour,
2 bores have several scratches that I can feel with my nail. Except that they all looks great. Very beautiful and clear white surfaces...
The pistons looks nice also. None of the rings were stuck. They all move freely.The side of the pistons seems no to have no wear marks.
I measured them at the 62mm distance of the top of the piston. My micrometer looks to be 0.01mm too optimistic.Or my pistons are still new... I get 6 pistons at 100.00mm (all group 1) and 2 at 99.99mm (1 group 0 and 1 group 1).
I started to measure 4 bores. It is much more difficult than the pistons...
The bottom part of the bores looks to be more worn. About 0.02mm more than the top.
The top looks to be between 100.01 and 100.03mm.
The bottom between 100.2 and 100.04mm.
But I have to check with someone more experimented to make sure I measured the bores correctly. It is not obvious for me.
Greg,
After reviewing again, I’m only worry about cylinder 4.
on all other cylinders I have no issue to say that scratches are minor so they are not an issue.
But for cylinder 4, I would be more than happy to consider these scratches minor… here is a better picture.
It is not very beautiful… less deep than what I thought… but not beautiful…
have a nice day,
Raphael
Greg,
After reviewing again, I’m only worry about cylinder 4.
on all other cylinders I have no issue to say that scratches are minor so they are not an issue.
But for cylinder 4, I would be more than happy to consider these scratches minor… here is a better picture.
It is not very beautiful… less deep than what I thought… but not beautiful…
have a nice day,
Raphael
Yeah, those a re a bit nasty....and up in an important part of the bore.
Almost looks like a chunk of broken ring was in there.
You can have that one cylinder overbored to 100.5mm and use a stock factory 100.5mm piston. (If you can find one. Check with Porsche...they might have a single.)
This works fine, with the other cylinders being 100mm....the change in displacement is tiny.
All one needs to do is make sure the weights are all the same.
The other alternative is to put a replacement sleeve in the engine and keep the bore at 100mm.....re-use the piston (although it must also have nicks from whatever was in the combustion chamber._
Both methods work great, if you can find the correct machinist. (A sleeve requires more work and is more technical.)
Yes Greg, for sure, if you have a 9th one you intend to use as a door stop… I could find something else instead for you!!!
😂😂😂
Regretfully, no 9th new piston.
I'll look through my used pistons...one never knows.
Porsche has lots of the 100mm version.... I wonder what they are thinking those are going to be used for?
(Although I've seen GTS engines, with sleeves in all 8 cylinders, with standard pistons.
It seems a bit absurd to not have oversize pistons, now that the engines are all wearing out.
I'll ask at my buddies at Classic and see what making pistons is going to take.
I'd happily take 6-10 sets, all on my own.
I think Freisinger bought years back old sparetools stock from Porsche. In the German 928 community was a discussion lately about their ability to deliver rare parts.
Give them a try.
Will try… thank you
crazy stupid world were they did not anticipate that oversized pistons will be required in the future…
Indeed.
I've been asked that same question about '87 to '95 transmission parts.
Here's some logic, followed by an approach:
1. The damage is not at the very top of the stroke.
2. The engine ran fine, before your head gasket issue, presumably with that damage.
3. What do you have to loose?
Buy a 100mm, group 2, stock piston.
Have that cylinder honed and lapped to the same piston to wall clearances as the rest of the engine. You will be amazed at how much of that damage will disappear.
Match the piston weights.
Put it back together.
Pretend you never saw the "nicks"...it will be fine!
09-04-2022, 07:12 PM
