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931 coming back to life!?
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TurboC  



Joined: 28 May 2004
Posts: 22
Location: Clearwater FL

PostPosted: Tue Jun 01, 2010 7:08 pm    Post subject: 931 coming back to life!? Reply with quote

Ok this may be a long post...

I am the second owner of an 82 931 that I bought from a local (now non existent) Porsche dealer in 1984.
The engine went in 1986 and I have had it in my garage ever since.
It is in very good to pristine condition.
I think the color is called bronze?

It came with the full leather interior, sport seats, 16" anodized flat wheels etc.
I put in Eibach springs in the front, Weltmiester torsion bars in the rear, Koin adjustable shocks all around, rear Welt. swaybar, urethane bushings etc.
The car sat low (wouldnt clear tall speed bumps) but rode nice and handled great. I owned a few 928's since then, and the ride was as good if not better and just as quiet.

A combo of too much boost and a wet ecu (or what its called) while racing killed it. I was racing a Vette and winning, and suddenly the car jerked, massive detonation, melted pistons. Limped home at 25mph and its sat the last 24 years now.

What I want to do is find some cosmetic items first then do the mechanicals last.
So if anyone has suggestions on the following:

-Repair the cracked dash, it was cracked in 1984 when I bought it, had a dash overlay

-install power door locks

-install newer style mirrors

-install newer style door handles, dr side was always hard to open

-replace the hatch (started leaking) with a 968 one

-install rear hatch release

-install cruise control

-replace f&r bumpers w/euro, esp front w/ lights

If anyone has suggestions for where to get those parts the cheapest please let me know!

Then to the mechanicals.
I havnt decided what engine to put in yet.

But, I do have, brand new still in the wrapper an Okrasa stroker crank, Okrasa/Mahle pistons and rings, and Carillo rods.
I did love the power of the 931 when the boost was up, but compared to many cars of today that power is probably not as much as Id like. Though how many bored and stroked 931's are there?

So I may sell the stroker kit if I got a good price for it.

I know it may be sacrilage, but I have a spare CTS-v LS3 available that puts out 630hp and is pretty stock and reliable. Not sure what 630hp in this light a car would be like or if it would ever hook up. Its just an option. Stock the car ran 150mph with a bit over 150hp. 4x that amt would assume it would do 200+?

The stock engine did get great milage though, and hit 37mpg on one trip in 1985. Coming from a 1966 GTO w/ a big block Chevy in it, that was amazing.

In the mean time, I would like suggestions on where to look, who to ask about mods like, "what are the largest brakes/calipers I can use while retaining the stock 16" wheels?" I love the gold wheels with gold paint. Looks very "Porsche" if you know what I mean. While I love the GTR look, the body is just too perfect to cut up IMHO and mount flares.
I like a stock looking car that has amazing performance. Sleepers are the best.

My last and only post here was 6 years ago so you can see Im rather out of touch on where to go for what I need but have a limited budget.

The sad thing about the car that bugged me even in 1984, was the Dealer had no warranty with it or one I could even buy. At 2 years old the dash had cracked, turbo replaced, seals replaced and then I bought it. It only had 11,000 miles on it! Then over the next year the rear hatch started to leak. The engine went shortly after that, but partially my fault.
I thought it odd such an expensive car for the day would have dashs crack, rear hatches seperate and leak, etc. When the engine went it had 49k miles on it, as it does today. Also back then no one had a fix for the hatch it was "replace it". No internet to search on either!

Look forward to all your input!

Thanks
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Nein37  



Joined: 29 Dec 2009
Posts: 513
Location: New London, CT

PostPosted: Tue Jun 01, 2010 11:41 pm    Post subject: Reply with quote

http://www.youtube.com/watch?v=PCSFz_YycYA
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1981 931 CGT replica, OEM CGT intercooler, .8 BAR WG spring, GTS Headlights, Innovative Wide band A/F, A/C delete, 16" Fuchs, Weltmeister 200lb lowering springs, Bilstein HDs front, Koni Sport rears.
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ideola  



Joined: 01 Oct 2004
Posts: 15462
Location: Woodstock IL

PostPosted: Tue Jun 01, 2010 11:54 pm    Post subject: Reply with quote

I have two stroked 931s in the works, same basic setup on each:
  • 6.35mm add'l stroke added to rod journals, offset ground stroker crank
  • Crower rods
  • Custom 8:1 pistons from Diamond
  • 87.5mm overbore

Stroker project 1
Stroker project 2

Most of your questions regarding what can be done with respect to suspension, brakes, etc. are covered with lots of cross references in the Performance Upgrades thread.

I would be interested to know more about your stroker setup. Longer rods or offset ground crank? CR on the pistons?

Regarding the dash, the best option I've seen for refinishing is the work done by Robert Budd's Classic 9 Leathershop, a local resource to me. I am also a reseller of his products and a customer <- that link has pix of a C9L dash freshly installed in my "941".
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15 981 GTS | 88 924S SE | 82 931 Holbert | 82 931 Rallye | 81 937 | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 80 US 931 | 80 931 GTR | 79 Sebring | 78 D-Prod Replica | 78 w/D-Prod kit | 78 Poli-Form | 78 Limited Edition | 77 Martini


Last edited by ideola on Wed Jun 02, 2010 2:23 am; edited 1 time in total
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Rasta Monsta  



Joined: 12 Jul 2006
Posts: 11332
Location: PacNW

PostPosted: Wed Jun 02, 2010 1:54 am    Post subject: Reply with quote

Welcome to the Board. Where are you located.
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  • Shaggy (1980 931) - Got Boost?
  • Red (1987 924S) - Pro44/Spec944
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TurboC  



Joined: 28 May 2004
Posts: 22
Location: Clearwater FL

PostPosted: Wed Jun 02, 2010 8:21 am    Post subject: Reply with quote

I am in the Tampa Bay area of FL.

As to the specifics of the crank and rods, I actually dont know! This was a "kit" offered back in 1985/6 by Ottenger to bore/stroke this engine.
Thus the crank is Ottenger, the pistons are by Mahle to Ottenger's specs, and the rods are Carillo.
I do remember being told you had to clearance the block, but dont know if thats due to rod or journel increases? A combo?

Thats I guess what I meant by a rare b&s 931, using parts that were used "back in the day"... LOL

I hope to have her washed and buffed soon and will post some photos.

Just to clarify my former post, the kit was made by and through Ottenger, and they called the crank and Okrasa stroker crank. Dont know why, just was. Some called the pistons the same, Okrasa pistons made by Mahle for Ottenger. If that makes any sense.

I also saw a post by Carl/Gegge? and he mentioned this crank: "Ideola has a crank with 90,75mm stroke and Oetting sold one that got 92,5mm"

SO I would assume if hes right, my crank the latter
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ideola  



Joined: 01 Oct 2004
Posts: 15462
Location: Woodstock IL

PostPosted: Wed Jun 02, 2010 9:16 am    Post subject: Reply with quote

Yeah, not sure if the Ott was due to offset journals or longer rods, or both. The thing to do would be to compare the rod length (center-to-center) to stock, eyeball the rod journals compared to a stock crank, and measure the piston pin centerline to the crown. That would tell us a lot about what you've got. Not surprised to hear you would need to clearance the block, leads me to believe the journals are offset ground. I'm not aware that Carillo made 924 rods (I've checked their catalog), so it would be interesting to know as well if they match OEM or are different. Pix would be nice too
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15 981 GTS | 88 924S SE | 82 931 Holbert | 82 931 Rallye | 81 937 | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 80 US 931 | 80 931 GTR | 79 Sebring | 78 D-Prod Replica | 78 w/D-Prod kit | 78 Poli-Form | 78 Limited Edition | 77 Martini
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TurboC  



Joined: 28 May 2004
Posts: 22
Location: Clearwater FL

PostPosted: Wed Jun 02, 2010 9:43 am    Post subject: Reply with quote

I can take pics, and plan to, but cant upload to my computer for some reason.

From what I remember, the rods alone were $750 in 1986.

Maybe someone who can spec all the parts should take a look?
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TurboC  



Joined: 28 May 2004
Posts: 22
Location: Clearwater FL

PostPosted: Wed Jun 02, 2010 10:29 am    Post subject: Reply with quote

This co, BRD was who I bought it from! And this is what it must be?
This says a different stroke than mentioned before and my kit from BRD has Carillo rods, not modified stock ones
The pistons are as described below:

"The motor was punched out with Dr. Ottinger’s high quality Okrasa 2300 stroker kit, which raises the displacement from the stock 1984 to 2227cc. The stroke is upgraded from 84.4mm to 90.5mm with the beautiful Okrasa stroker crank, a made to size forging that’s a work of art. The crank is Nitrided for extra strength, and is a piece to install and forget.

Much-modified stock connecting rods are used. They are lightened, polished, carefully sized and shot-peened for added durability. Larger (by 2mm) 88.5 Mahle autothermic pistons from the Okrasa kit were used, a high quality die cast design with steel inserts to control expansion. They allow a much closer tolerance to the cylinder wall than a forged piston, with better cold sealing and noticeably lower noise levels due to reduced piston slap. The pistons are originally intended for use with the "flat" 924 head and when used with the Turbo head yield a compression ratio of 7.5:1, lower even than the 110hp motor’s stock 8.5:1. This was upped to 9.7:1 in the BRD motor by "decking" or milling the top of the block by 2mm, effectively raising the piston up closer to the combustion chamber. This approach is not without repercussions, as the shorter distance now requires a Dial-in Cam adjustable cam sprocket to correct cam timing and a shorter timing belt."
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!tom  



Joined: 28 Aug 2006
Posts: 1869
Location: Victoria, BC Canada

PostPosted: Fri Jun 04, 2010 2:40 pm    Post subject: Reply with quote

ideola wrote:
I would be interested to know more about your stroker setup. Longer rods or offset ground crank? CR on the pistons?


You mention longer rods twice in your questions about increasing the displacement.

Please correct me if I'm wrong, but longer rods alone will only increase your compression ratio, and do nothing to your stroke.

The only way to increase the stroke is to do that on the crankshaft, and that would be done either by offset grinding, or making a new crankshaft, or some other technique that results in essentially the same thing.

I would also think that, with a longer stroke crank, you'd need shorter con rods unless you, as mentioned, used different pistons with a different wrist pin location. My understanding is that there is an ideal ratio between con rod length and stroke, so it would be best to increase the con rod length when the stroke is increased, requiring adjustments to the wrist pin height to counteract both adjustments.
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ideola  



Joined: 01 Oct 2004
Posts: 15462
Location: Woodstock IL

PostPosted: Fri Jun 04, 2010 10:10 pm    Post subject: Reply with quote

Yes, you're right about the stroker, the only thing that changes stroke is the rod journal throw. As you point out, in most cases you would need to change either the rod or the piston (or possibly both) to achieve the desired CR. I was under the impression that EMW used a longer rod on their stroker, but not sure now if I inferred that or actually read it somewhere. I do know they used a different rod (and also different pistons), but I've never been able to get specs on the rods they used.

From what I've read, increased rod length often accompanies a stroker "to increase leverage and minimize the high degree of rod angularity created by the increase in stroke. The longer rod also prevents the piston from being pulled out the bottom of the cylinder bore." Although I don't think this latter issue is that much of a concern on our motors. Of course, longer rod means a custom wrist pin location, but that's almost always required anyway to achieve correct CR.

In addition to stroke changes, displacement is also affected by the bore size and potentially any changes to the combustion chamber geometry due to changes in piston (e.g. flat topped vs. dished)...
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15 981 GTS | 88 924S SE | 82 931 Holbert | 82 931 Rallye | 81 937 | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 80 US 931 | 80 931 GTR | 79 Sebring | 78 D-Prod Replica | 78 w/D-Prod kit | 78 Poli-Form | 78 Limited Edition | 77 Martini
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TurboC  



Joined: 28 May 2004
Posts: 22
Location: Clearwater FL

PostPosted: Sat Jun 16, 2012 10:59 am    Post subject: Reply with quote

Well its been right at 2 years since I started this post, and life got in the way to get anything accomplished.
So my 931 has been sitting for 26 years now w/ 49k miles on it. Almost always garaged its in great shape.

I am wondering who anyone suggests to speak to these days about doing the rebuild.
I still have the stroker crank, Carillo rods and Mahle pistons sitting in their original wrappers.
If I could build this and get a good 300+ hp, keep it reliable and maintain reasonable milage, I think Id rather keep the Porsche engine over a chevy swap.

But this will have to be a ground up workup.
Using this stroker kit I still would want to have the head ported, probably a better TB, different turbo, ECU, DIS and even add power steering if possible.

So who is the go to guy to speak to these days?
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ideola  



Joined: 01 Oct 2004
Posts: 15462
Location: Woodstock IL

PostPosted: Sat Jun 16, 2012 1:22 pm    Post subject: Reply with quote

I'm planning a trip to the Daytona area right around 25 June. I know it's a few hours from Clearwater, but I'm coming all the way from Michigan...perhaps we could connect? I would really love to photograph the bits that you have for archival purposes. I'd be happy to compare notes in person, over the phone or via email.

As for building your engine, I would suggest contacting Redbone Garage in the Orlando area. They rebuilt the motor in my 937 when the previous owner scored a cylinder wall. They're located at 2523 Industrial Boulevard Orlando, FL 32804 (407) 299-0619

Please PM me, I'd love to discuss further.
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15 981 GTS | 88 924S SE | 82 931 Holbert | 82 931 Rallye | 81 937 | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 80 US 931 | 80 931 GTR | 79 Sebring | 78 D-Prod Replica | 78 w/D-Prod kit | 78 Poli-Form | 78 Limited Edition | 77 Martini
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TurboC  



Joined: 28 May 2004
Posts: 22
Location: Clearwater FL

PostPosted: Sat Jun 16, 2012 4:05 pm    Post subject: Reply with quote

PM sent
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TurboC  



Joined: 28 May 2004
Posts: 22
Location: Clearwater FL

PostPosted: Sat Jun 16, 2012 4:10 pm    Post subject: Reply with quote

Did a google on Redbone and not only are they listed on Ripoff Report but are rated as an F with the BBB.
Soooooo maybe not? LOL
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ideola  



Joined: 01 Oct 2004
Posts: 15462
Location: Woodstock IL

PostPosted: Sun Jun 17, 2012 12:33 am    Post subject: Reply with quote

I hadn't heard a lot of bad stuff about Redbone...searches on Rennlist do show mixed reviews. The motor in my 937 seems to be very strong, so no complaints yet about the work they did on it.

Another place that came up with high marks is "Zotz", which apparently is now called "German Excellence", although I don't know where they are and have no personal experience with them.

As for head work, I have a guy up here in Detroit who works for Roush. He does all of my work now (on the side, not thru Roush), and has done a couple of heads for some of my customers who have purchased the big valve kit. If you can't find a suitable shop locally, I can help coordinate for you.
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15 981 GTS | 88 924S SE | 82 931 Holbert | 82 931 Rallye | 81 937 | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 80 US 931 | 80 931 GTR | 79 Sebring | 78 D-Prod Replica | 78 w/D-Prod kit | 78 Poli-Form | 78 Limited Edition | 77 Martini
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