Makes you kind of wonder why we have few choices on the East Coast.
thanks for the info...the rebuild looks great. I already lined up my 3.2 cylinders for EBS.
Rick
'78 930

I am free this weekend. when will you be working? I'd like to stop by and check out the progress.

btw, what's the address?

Jamie

Sorry for the folks who wanted to help this weekend.....not much happened at all. Engine is pretty much in the same state as above.

The heads are currently getting CC'd and the cam towers cleaned up. Once I get the volume figures, calculate the proper deck height and CR, I can resume.

I'll post when things start happening again, maybe have a friendly weekend gathering.

Charlie,
My first post: Found your BB a few months ago. It's great to have a local site which doesn't seem affiliated with a big group or someone selling something. I have already benifitted and hope to get more real and honest answers here.

I'm intrested in more detail about the P/C's from EBS.

My situation:
I bought my car (83 911SC Euro Cabrolet) in December of 01.
I got it from someone I know and he was selling it because he has no mechanical ability and it became too expensive and frustrating for him to
keep. He bought it in 85 from the importer and has driven it regularly since. He kept meticulous records and I even got most of the recipts for all the work and money he put into the car since he bought it. I later added it up and he spent more than the 30K he paid for the car on repairs and maintenance.



I knew the car was a mess and a big project, but I couldn't refuse the $4,000 price tag.

I have driven it almost daily until May of this year.

The Odometer just recently turned 250K.

My goal is to get it back to it's former glory and drive it!

The main problem with the car was the so-called mechanics who worked on it before I bought it.

In 1996 the previous owner decided that his baby deserved a rebuilt motor. His mechanic told him that it would take more than a month to get the parts to do the job properly. They opted to install a recently rebuilt motor that the mechanic sourced from a salvage operation.

This was the begining of the real problems.
The new motor (Long Block) was from an 82 US version SC.
The engine number (930/16) and the serial number confirmed the year.
They retained the European CIS System.

I assume it ran OK at the time but as the recipts show a newer mechanic started working on it soon after that time. The new mechanic didn't understand the differences between the European CIS System and the US Version with Lambda Control. (I also think the engine number threw him off.) He began swopping parts in the CIS system with the wrong and incompatible parts.

In the year or so since I bought the car I have learned alot about the CIS system and finally got it completely straightened out this past winter.
Because I couldn't easily find the European CIS parts or for a reasonable price, my reaserch told me that it was really the same system used on the 78-79 SC with some additional improvemants. I have not been able to find out what exactly they are except that I know the system pressure regulator on the fuel distributer was improved. The CIS retained the original European Air Box, Air Flow Sensor, and intake runners.

It was running very well until early this spring the engine started missing.
I traced down a bad distributer wire (the green one) This helped but I later learned after getting the engine on an Ocilliscope that #4 was weak.
This was at the same time I was trying to get it through emmissions in Maryland.

After passing emissions I continued to work on the source of the miss.
(Going back I had good compression readings several months earlier. 190-195 psi on all cylinders so I didn't suspect an internal problem.)

Following the emissions test I was able to barrow a leak down tester.
Found that all the cylinders were 97% or better except for #4 which was bad. Air blowing out of the oil tank which indicated a problem with the rings.

I dropped the engine and found that the top ring on #4 was cracked.
No dammage to the cylinder. I also found a round mark on the top of the piston where the intake valve was hitting it and rubbed off the carbon buildup.

After a lot of debating about what to do I ultimately decided to tear down the entire engine. I have measured the crank and found it was well within wear limits. The pistons and cylinders are within wear tollerances and the heads needed a complete valve job with guides. I had a mechanic at Rockville Porsche look at the camshafts. He told me that although they has a few small pits on the lobes that the pits were an original defect in the casting and were of concern.

I concluded that this in fact was a rebuilt engine, but who's definition of rebuilt. Valve guides were shot! The rings were worn, one to the point that it broke.

So here is what I'm doing:
New main and rod bearings and of course seals.
New wrist pin busings on the rods.
New intake and exhaust valves with guides, seals and new springs (I dissasembled cleaned and removed the guides.) Easier than you might think. Jack's machine shop in Kensington installed the guides and refaced the valve seats. They did a great job!
I also bough new rocker arms because the bushings and the faces were worn on the old ones. (I have seen that they can be reconditioned, but the new ones were cheap from vertex.)
New Sprockets and Timing Chains

I am still debating what to do about the P/C's.
Charlie, I am in the same situation that you were in. My Pistons and Cylinders are Alusil. I have read some debates and Cautions about re-using them and honing them. (In fact I think these were honed at one point because the marks are visible at the bottom of the cylinder wher the rings don't rub. The rings were in fact sealing well because of the high compression pressures 190-195 psi. 97%+ on the leakdown.) They are also within the wear limits.
The debate as I read it was that it is bad to hone them. If you don't hone them the new rings have a 50/50 chance of seating and sealing.
This is why they are refered to as disposable.

I have located a new set of the European 9.8-1 Mahle set at Vertex. With my Prefered discount card I paid $35 for I get 10% off the $2200 price they are quoting.

Charlie it seems that you found a new alternative. I have read about the JE Pistons on the Pelican BB. Wayne also mentions this in his engine rebuilding book. I didn't know they could replate the Alusil cylinders. Is that what I read on your post?
If so what did it all cost including shipping?
How long did it take?
Can they bore the Alusil cylinders out before replating?

Before reading your post, I had pretty much made up my mind to reuse the old PC's. You have made me open up this debate again. I'm hopefully ready to start putting it back together this weekend.
Please share with me your thought process.
Thanks! :D

William--

Welcome to the board. It sounds like we can learn a lot more from you than you'll learn from us.

I don't know about that, but I will try and help someone if I can!

William....welcome :lol:

I was in the same boat, wondering what to do about the Alusil P/C's. They measured well within spec and totally reusable. I was walking the line regarding reusing the Alusil P/C's or bumping up the compression using the JE's and replated C's. My main concern was the durability of the replated C's. If you search the archives on Rennlist or Pelican, you may find the post. Steve Weiner has been using replated C's in race engine for quite a while w/o any problems. EBS also told me that the plating process currently used has been improved upon from OEM for better adhesion, durability and consistency. They also have not had any problems with the replated C's. I decided to bite the bullet for another 'while you're in there' upgrade.

Turn around time from EBS for the replated C's and JE's was 30 days. The JE's come with lightweight wristpins, Goetze rings, and circlips. The Alusil C's are bored to remove the old lining, replated and honed back to 95mm. $1900 for the P/C package.

BTW: Successfully reringing used Alusils has been documented a few times on the Pelican BBS. The method recommended to me was to thoroually clean the C's with kerosene and a scotch bright to remove/break the glaze (don't hone using conventional methods). Use a very light lubricant (marvel mystery oil) on the walls/rings during assembly. Break in procedures are pretty much like what Wayne has documented in his book, but continue to vary the RPM and WOT technique as much as possible for the first 1500 miles to ensure thorough seating.

FYI: You can get JE's manufactured in any CR you specify. Wayne and CE recommend a deck height 1.25-1.5mm. JE's compression ratios are calculated from a 1mm deck height.

For Example with 9.8:1 JE's:

1mm Deck Height - CR 9.8:1
1.25 DH - CR 9.5:1
1.50 DH - CR 9.3:1

I think I noted this earlier, but Porsche's CR numbers are actually .25-.50 lower than specified, so our SC's are really around 8.9:1 An approximation for HP increase is 10% per compression point. Fortunately, we can really benefit from a CR increase as we are right in the sweet spot of the CR/HP bell curve.:) That's why the later Euro SC's produce 204 HP.

So, if you are serious about dialing in a specific CR, ask your machine shop or EBS about what you can do to compensate. IF your heads have been milled, get them CC'd. EBS can give you the dome volume of a specific CR piston prior to ordering. I have BA's formula in a spreadsheet that you can plug these values into if you want to play with CR's.

Hope I didn't throw a wrench into the works.......no pun intended :shock:

Charlie, didn't see your post until just now. (I missed it because it's on the 2nd page.)
Thanks!

From what I read in your post it seems like EBS is really completly reconditioning the cylinders by boring, replating and honing to the original toloerances. (Like new!) You may have answered this before, but, did they machine the bottom and top mating surfaces?

I got my lower end back together this past weekend. I'm ready to go on the P/C's.

It looks like my options are:
Go cheap and take my chances with the P/C's I have.
Buy the Euro Mahles from Vertex. (+- 2K with my discount plus shipping.
Probably wait a week.)
Follow you lead with the EBS reconditioned Cylinders and the JE Pistons.
($1900 +_ plus 30 Days.)

A few questions before I decide:
How to find out the CR on the pistons I have. Will any of the numbers on them tell me what I have? I posted this question on another board and the answer was that they were casting numbers.

Does the compression readings somewhat indicate the CR.
I've herd that typical compression psi was 150 psi plus.
I was reading 190-195 psi. Does this indicate anything?
Has anyone seen the US piston and the Euro version CIS piston side by side? If so is there a perceptable difference?


Lastly, Charlie were you able to get anything done over the weekend?

From what I read in your post it seems like EBS is really completely reconditioning the cylinders by boring, replating and honing to the original tolerances.

Correct, that is the process; bore, replate, hone. EBS sends out the C's to a plating company, can't remember the name off hand (not US Chrome).

You may have answered this before, but, did they machine the bottom and top mating surfaces?

I didn’t see it on the spec sheet, so I don't believe so. It will all come out in the deck height measurements anyway.


A few questions before I decide:
How to find out the CR on the pistons I have. Will any of the numbers on them tell me what I have? I posted this question on another board and the answer was that they were casting numbers.

I don’t know if those casting numbers will tell you anything about the piston CR. For the 82 US SC's, Porsche's CR specs are 9.3:1, actually measured the CR is around 8.9:1. You can bump up the CR by lowering the deck height (from the factory, DH was 1.35-1.5), increasing dome volume or decreasing head volume. The Euro SC's had the increased dome volume. To correctly calculate your CR, find out the piston dome volume and your head volume, any competent machine shop can do this for you. You know your bore (95mm) and stroke (70.4mm) and assuming a safe deck height of 1.25-1.5mm, you can plug these values into BA's equation and get your true CR (once you measure your deck height). I can e-mail you a spreadsheet that you can use to calculate your CR. Send me a PM.

Does the compression readings somewhat indicate the CR.
I've herd that typical compression psi was 150 psi plus.
I was reading 190-195 psi. Does this indicate anything?

Check out this thread and responses. Compression readings are probably not a good indicator of true mechanical CR.

http://www.team.net/html_arc/mg-t/200008/msg00184.html
http://www.team.net/html_arc/mg-t/200008/msg00185.html
http://www.team.net/html_arc/mg-t/200008/msg00188.html
http://www.team.net/html_arc/mg-t/200008/msg00189.html


Lastly, Charlie were you able to get anything done over the weekend?

Not on my car :wink: Maybe this weekend…..

Decided to go ahead and keep my old P/C's.
I took a standard hone (One w/ three arms) and lined the cylinder with the green scotch brite pads. I ran it with my cordless drill for about 30-45 seconds (About 20 strokes up and down.) A really fine cleaning or honing.
I installed them all last night. Although there is no real reason to check the deck height (I made no changes to the stock setup which was running in the car.) I might do it just to know and to calculate the CR and you described.

In reading the articles you attached it seems like valve timing has an effect on the compression pressures. If the intake valve is held open longer past BDC the piston will travel up the cylinder some before the compressing the air/fuel. Sorta like shortening the stroke? or reducing the displacement.

I didn't check the valve timing as I took it apart. Maybe I should have?
Does the 190 seem high to you?