Short stroke 3.2

[CamB]

Is there anyone who has actually had it done or who knows the details?

To understand what Mahle do to make the 98mm set, I suggest contacting Andial. I most definitely could be wrong.

This makes sense if you drop the sealing ring and the groove for it when you go from 95 to 98mm cylinders. Carrera's don't have the sealing ring so it must not be absolutely necessary.

This is a picture of a whole p&c - I think I did need sealing rings - I have an invoice for 6x part number 930 104 194 02 but these look to be the ones at the base:



Mahle would simply bore the original casting out to 98mm and omit the groove. They wouldn't necessarily even have to re-bore, just bore it 98mm the first time.

This is what I was told (mechanic has made approx 1/2 dozen short stroke 3.2s).

The cost... well it depends. Assuming you are rebuilding anyway:

1) If you are replacing p&c, the cost of the Mahle 98mm set is <$3000 (I think I paid ~2800??) from Andial. This is offered in:

- CIS friendly with low (single plug) compression. Not sure if twin plug compression available
- carbs/MFI required (for wilder cams up to RSR) for single or twin plug

This compares to Pelican's price for 95mm of $2000 or $2500 (depending on the set). I dunno if Pelican can get the 98mm ones. Thus the difference is probably not much (comparing $2500 to the Andial price). Do some research.

My mechanic was able to tear down my engine, swap 95mm p&c for 98mm and reassemble without needing more than $100 of miscellaneous seals (the engine had been recently rebuilt with the 95mm p&c). So it is just labour which is "free" as an upgrade if you are already paying for a rebuild.

2) If you are not replacing pistons and cylinders... the upgrade is expensive (obviously).

I have no experience with boring and resleaving or boring and replating so have no comment on the cost, etc. But personally, if I was rebuilding an SC that needed new p&c, the change to 98mm would be a no-brainer.

[Doug Zielke]

Cam, I really wish you hadn't been so helpful with all that info.

(Fast forward to this winter....."Damn! These ol' P's & C's sure look worn out, don't they?)

[Bill Douglas]

Cool. Now Doug !!!

[CamB]

Remember, start saying the justification mantra now:

"The only proper way to rebuild an engine is new pistons and cylinders"
"The only proper way to rebuild an engine is new pistons and cylinders"
"The only proper way to rebuild an engine is new pistons and cylinders"

I hope Superman doesn't see this - I am shaping and moulding reason here!!!

Seriously, I am not really the best person to talk to about this - I more or less bought the engine "as is" and have used the opportunity to upgrade the p&c when the engine seller/builder (and I) were both not particularly happy with how the second-hand 95mm p&c sounded. I got a credit on those p&c and paid no labour to upgrade so it was an easy (although still very expensive) decision for me. I also had the added attraction of increasing compression (from 9.5:1 from the 95mm ones to 10.3:1 for the 98mms) and can now take advantage of the twin plugging the engine already had.

I would encourage someone to have a good talk with an expert on this subject - Steve Weiner at Rennsport is probably a pretty good start (and a very helpful guy):

http://www.rennsportsystems.com/~porsche/2f.html

[Wrecked944]

I emailed Andial and asked about reboring and replating 95mm cylinders. here is the reply I received today...

"The cylinders could be rebored I guess but I believe the Mahle 98 mm cylinder had the outer fins a little shorter so that the wall thickness could be kept a certain number. We have heard mixed reviews on the replating subject, some people have had good luck while others have not. "

Doesn't sound very enthusiastic. We really need to find somone who actually provides reboring as a service and ask them. Does anyone know of a shop, mechanic, company that rebores and replates porsche cylinders? This might constitute a "Holy Grail" for SC owners seeking affordable relief from the 3.0 liter straight jacket.

Thanks,

[ChrisBennet]

Originally posted by JanusCole
I emailed Andial and asked about reboring and replating 95mm cylinders. here is the reply I received today...

"The cylinders could be rebored I guess but I believe the Mahle 98 mm cylinder had the outer fins a little shorter so that the wall thickness could be kept a certain number. We have heard mixed reviews on the replating subject, some people have had good luck while others have not. "

Doesn't sound very enthusiastic. We really need to find somone who actually provides reboring as a service and ask them. Does anyone know of a shop, mechanic, company that rebores and replates porsche cylinders? This might constitute a "Holy Grail" for SC owners seeking affordable relief from the 3.0 liter straight jacket.

Thanks,

When I checked with USChrome about reboring and plating they weren't any cheaper than EBS. The issue for SC owners I believe, is that they can't bore out their cyinders because they have the groove at the top. I don't have my digital picture this week or I'd take a picture. If you come by before the 3.0 I'm working goes together you can see what I'm talking about.
-Chris

[Wrecked944]

"The issue for SC owners I believe, is that they can't bore out their cyinders because they have the groove at the top."

(laughing)...Chris, you must realize that for an SC owner on the verge of a top end rebuild (BTW - My engine yolk just came in - hide the power tools !!), this whole debate is like Chinese water torture. Everyone seems to either have rebored cylinders or know someone who does. But I can't find a machine shop to actually DO it for me. And both EBS and Andial said the replacement 98mm cylinders for SC's are out of stock.

Aaaaaaaargh !! It is killing me....

[Doug Zielke]

Originally posted by JanusCole
......And both EBS and Andial said the replacement 98mm cylinders for SC's are out of stock.......

Well now, isn't that just swell.
And after I've spent the last 2 days preparing my credit card for the hit........

[Doug Zielke]

Just a thought here.....
What about obtaining a set from the Fatherland?
Is Max Moritz still in the business?
Herr Kunz, can you help?

[Wrecked944]

Well, the email from Andial came today. So I am guessing they won't have cylinders for a long time. EBS shot me down at least a month ago. So *maybe* they will have something in stock. As per Chris' post, I sent an email to USChrome today just to get any info I could on the process. No reply yet, but that was just an hour ago.

Still trying...

[Wrecked944]

Followup:

The guy who handles Porsche work at USChrome just came back from vacation and called me back. His name is Scott and here is what he said...

US Chrome has a facility in Wisconsin which does, indeed, hone and replate Porsche cylinders. He said they can take a 95mm Alusil cylinder, bore it to 98mm and replate it with Nikasil !! The cost is as follows: Bore to 98mm is $60...Replate and hone is $115. So you should expect to pay $175 per cylinder for a total of $1050. He said the turnaround once they receive the cylinders (AND the new pistons) is about 7-8 business days. He stressed that they need to have your new pistons in hand before they can begin working. So this is a potential bottleneck that the customer needs to avoid up front. If I take CamB's approximation of ~$2800 for a set of 98mm p/c from Andial, then this *may* compare favourably...assuming all else is equal...BIG ASSUMPTION...

Their website with phone numbers, etc is...

http://www.usnicom.com/usbig31.html

Call the Wisconsin office and ask for Scott. He is the Porsche man...

Okay, BIG DISCLAIMER: While this may seem impossible, I actually know less about metallurgy than I do about cars. Can a person know "less than zero"? Perhaps I know things about metallurgy but everything I know is wrong? In any event, you get the idea. I did the calls and emails and leg work on this conversion...but I have no qualifications whatsoever for evaluating the resulting information. So I must pass this along "as is" and hope that someone more knowledgeable can provide the real score.

I genuinely hope this is helpful,

[911nut]

I'll take a stab at the metallurgy concerns.
Nikasil is deposited by using a cladding process in which a plasma torch is used to melt the Ni-Si alloy and deposit it onto the cylinder walls. The final dimension and surface finish of the cylinder diameter are obtained by honing. If there is any contamination present during the cladding process (aluminum oxide, which melts at high temperature or residual cutting fluid) than the Nikasil will not adhere, or "wet" to the cylinder wall. This would cause the plating to flake off in service.
PB

[Doug Zielke]

Janus, thank you for that very good info!

US Chrome has an excellent reputation according to a friend I have in the Aerospace industry.
I just may give "Scott" a call this winter once the motor is apart.

Thanks again for your time tracking all this down.

[ChrisBennet]

Before you get all excited about boring your SC cylinders out to 98mm you should investigate why Engine Builder's Supply said that SC cylinders are not suitable for this. I assume it has something to do with the ring groove SC cylinders have in the top.
-Chris

[Wrecked944]

Hmmm...yes...the Exuberent One speaks with wisdom...I can call back Andial and US Chrome to question it...but I fear I may have reached the limits of my knowledge here...they could probably say something nutty like, "Well, it has to do with the percentage of unobtanium in the cellular wall, etc, etc" and I'd believe it...

Any volunteers to ask more intelligent questions?

BTW - Thanks to Doug Zielke for catching my earlier typo...I intended to say that US Chrome needs to have your new PISTONS in hand before they can work on your cylinders. It is fixed now...sorry about any confusion that was created as a result...

[Wrecked944]

Okay, following Chris' sage advice, I called both EBS and USChrome and asked about the cylinder head ring. Here is what they said:

EBS

The 3.0 liter 95mm cylinders can be bored to 98mm but the reduced piston ring groove will present a weakened mating surface for the cylinder head. No lifeguard on duty. Swim at your own risk.

The 3.2 liter 95mm cylinders had no such piston ring groove and are more suitable candidates for the 98mm conversion and can possibly be attached to SC engines with good results.

USChrome

Cylinders can be machined and plated to whatever specs you want. They've done both kinds of overbores. But you'll need to know what you want and perhaps a consult with an engine expert would be in order (see lifeguard warning above).

Okay, if you have any exaggerated notions about my automotive competence, please read my disclaimer in an earlier post. I can't really evaluate any of these claims for validity. I can only report them as is. For instance, what does "weakened mating surface" mean? Does it mean there is a theoretical weakness or does it mean that overbored cylinders have failed in real life? I looked very closely at CamB's p/c picture, but realized I have no idea what to look for. And if the cylinder head has had a sealing ring attached for 20 years, how will it feel when it suddenly meets one of those "3.2 liter 95mm overbored to 98mm" cylinders who doesn't have a ring? Wasn't the ring there for a reason?

I am flying over uncharted terrain here. Cluefactor Zero, Captain. Perhaps we can lure John Walker or Roland into this and they can settle it in two seconds or less.

Thanks,

[ChrisBennet]

Janus, Are you calling me stupid???



Just kidding
-Chris

[Wrecked944]

Oh, Chris. Jeez...my heart skipped a beat when I saw your post.

As you can imagine, having recently been flamed pretty harshly I have become incredibly gun shy. If I put in any more disclaimers and self-depricating comments into my BBS postings to avoid offending people, folks here will start thinking I am completely retarded (no offense intended to retarded porsche 911 owners)...

[ChrisBennet]

Are you calling me retarded now?

Couldn't resist.

[CamB]

My picture shows that I have no ring.

That seems faintly rude.