924Board.org

[FRporscheman]

Hi guys, this looks like a great board, so I'll be reading a lot in the days to come. I've spent a few years on Rennlist, so please forgive my web etiquette.

I bought my first Porsche (a 944) 2.5 years ago, and sold it .5 years ago. It was an early model with the 924 interior. I bought my current 968 just over 1 year ago. My dad bought his 928 about 12 years ago I think, and my mom's 944 entered the family 20 years ago. I was driven to and from elementary school in her 944, so I know 944s like the back of my hand.

Since selling the 944 and just going with the 968, I've been very happy but I've missed the old-school factor. Plus I've always wanted to have a turbo-something. And I always sort of liked the funky skinny 924, so I thought a 931 could be interesting. Then one of my friends said he's selling a 1982 931 for $700, which has decent paint, decent interior (both of which I don't care about), and a partially disassembled engine. The whole point of getting a second Porsche would be to be my toy, so I engine work just makes it more desireable for me.

Anyway the car is an 82, with 5 lugs, 4 discs, and a blown turbo. Here come my questions:

1. I've read the turbos are worthless unless you use fully synthetic oil. Couldn't I just replace the blown turbo with an aftermarket one, or a 951's turbo or something? I wouldn't want to use full synth unless I've rebuilt the engine with all new seals and gaskets.

2. I probably would want to fully rebuild the engine, instead of replacing the turbo and calling it a day. Is a 931 engine particularly hard to rebuild? While rebuilding it, I suppose I might as well dump the cash to use upgrade goodies where applicable. What kind of stuff could I do to raise performance, and where would the parts come from? I.e., are there low-compression pistons I could get to allow bigger turbos, or some special vw crank with larger stroke, etc.


I have done a lot of work on my old 944 and my 968, like clutches, headgaskets, but I've never rebuilt an engine. Thanks for all your input!
_________________
'93 968
'84 944
82 MB 300td

[ideola]

Welcome aboard! And yes, this is a MUCH better board than that other one you mentioned.

The 82 931 is the best way to go, being a series II...better throttle body, better turbo unit, and purportedly improved exhaust manifold that was not as susceptible to cracking.

That said, that is prob'ly the first thing I would check...if the exhaust manifold is cracked, you better find a good replacement (they're rare as hen's teeth), otherwise you'll have a perpetual boost leak. And no, they're not repairable, at least judging by the lack of success of folks on this board (do a search).

The turbo rebuild will cost you a minimum of $300 from a reputable shop. Again do a search on this board to find one near you. I used Michigan Turbo in Grand Rapids. They quoted me $300 over the phone, it cost me $450 for one, and they wanted $600 for the other, which I declined.

I would have no fear of putting synthetic oil in the car even if I didn't do a full rebuild. That said, if the engine is already partly dismantled, go ahead and rebuild the whole thing. Get yourself the factory service manuals and the parts catalog on CD. If you can't find a source via search, PM me.

Performance mods, the best thing to do is to rebuild the wastegate with a 1.2 bar spring, add a boost controller, an intercooler, and possibly some sort of fuel enrichment like a methanol injection kit. Again, search is your friend for more details on all of these subjects, especially in the performance enhancement forum.

On my wide body project, I've already increased stroke and bore for hopefully some add'l low end grunt, and I had custom pistons made. If you want details on this let me know, but it's spendy.

$700 seems a little high to me for a car with a blown motor. I'd try to wear 'em down a bit...

Good luck. Oh yeah, search is your friend.
_________________
erstwhile owner of just about every 924 variant ever made

[Min]

I'd find one without a blown motor to test drive before purchasing one you have to assemble. That way you know if you like how the car feels. Buying a assemble yourself car is fine and all, but its sure nice to know what the end product will feel like before sinking money into it.

Min
_________________
Custom means it didn't come from a box.
1980 n/a with EDIS and Megasquirt II Injection. 7 different colors and counting.

[Chrenan]

The bottom end on a 931 is the same as the 924 (block, crank, and I think even rods). That part of the rebuild is not high on the difficulty scale.


Bottom end disassembly


Bottom end disassembly – caps removed


Bottom end disassembly – crank and pistons removed


Bottom end disassembly – top


Block back from machine shop – top exhaust side


Block back from machine shop – top intake side


Block back from machine shop – bottom exhaust side


Block back from machine shop – bores


Bottom end assembly – crank


Bottom end assembly – crank


Bottom end assembly – oil pickup


Bottom end assembly – oil pickup


Bottom end assembly – 9.3:1 euro spec pistons


Bottom end assembly – 9.3:1 euro spec pistons


Bottom end assembly – rear crank seal


Bottom end assembly – oil pump and front crank seal


Bottom end assembly – oil pan intake side


Bottom end assembly – oil pan exhaust side


Bottom end assembly – oil pan front


Bottom end assembly – oil pan back


Bottom end assembly – crankcase breather
_________________
1987 951 - M193 Version for Japan

[Lizard]

I would recommend that you convert to EFI as you rebuild, a rebuild is a very good idea as I would be willing to bet you have broken piston rings in there as is.

with regards to the turbo it has a unique hot side, so unless you build a custom exhaust manifold you cannot run anything but a stock unit. if you go with EFI you can upgrade the compressor side and eliminate the bulky BOV off the intake side.

rebuilding the engine is just like any other, however I would recommend that you have new hoses put on all the turbo hoses as they will leak oil.

you will not be able to run Synthetic right after the rebuild.
_________________
3 928s,

[ideola]

chrenan, you show off! pix look great, man! good inspiration for my wide body project!

[Lizard]

the main reason I recommend converting to EFI while doing the rebuild is because the CIS parts have all been sitting for awhile and who is to say it will run right once together, as well all the issues with the DITC box.

If you do convert to EFI now have the spot for injectors machined out and then the injector hole opened slightly to have a Bosch injector sit in this hole that way the injector will sit further in and you will not have as much fuel hitting the wall and deatomizing.

I agree it is easier to do EFI on an engine which is already running but we have other members who could give a base running MAP if he uses MS,

if he bolts everything up with the CIS and finds that the car wont start no this no that he will be chasing electrical gremlins and troubleshooting the CIS for awhile,
_________________
3 928s,

[Chrenan]

I think that is the deciding factor, how long has the CIS been sitting? If it is totally gummed up, you could spend as much time and effort trying to get the CIS going as getting the EFI up and running.

Long term, I think I will have to go to EFI eventually, I can't see the CIS working forever. One major problem with the fuel distributor and I'll have to learn lots about EFI.
_________________
1987 951 - M193 Version for Japan

[ideola]

Lizard, Chrenan, good points...good clarification.
_________________
erstwhile owner of just about every 924 variant ever made

[FRporscheman]

I'd love to do the EFI conversion eventually, but I can't afford to spend on a purchase, rebuild, turbo AND EFI all at once. That will definitely put me in the poor house.

The car has been sitting for a few years, I think. The engine was running when the PO started disassembly. The current owner thinks the PO was trying to replace the turbo, then lost interest and sold it. I've met the owner and I know him on Rennlist too - he's trustworthy. It seems I could theoretically just finish the turbo work, bolt it back together and hope the CIS still works. I hate CIS so much. My brother's 85 GTI also has CIS and it drives both of us nuts.

Well if I do buy the car, it'd be good to know what kind of costs to expect. Assuming I do all the work myself, except for special stuff like machine work, how much do you reckon it would cost to rebuild the engine?

About the exhaust manifold. If it's going to crack, and if it's the only thing prohibiting a new turbo, then I would just have a new manifold made. Is there a source for aftermarket manifolds/headers? Like for racing?

When I go to see the car in person, what things should I look for? As in, what are the typical problem spots? Also, what kind of details hint to special options and packages? All I remember right now is that it had discs and 5-lug spider web wheels.
_________________
'93 968
'84 944
82 MB 300td

[Lizard]

if the car has been sitting for more than 1 year I would not even bother attempting it without doing EFI, if you get it running you will have to probably spend almost as much money on the CIS as you would to convert to EFI, I am not saying you cannot get the car going on it, but it is unlikely that it would run perfectly and at the very least you would need to dismantle and clean the WUR, or replace it.

Converting to EFI doesnt cost all that much and you dont have to get all the items at once.
_________________
3 928s,

[Chrenan]

The guys posting on this thread (Lizard, Ideola) have lots of 924 experience and can help with many questions, as can lots of other folks on the board, so no reason to be too worried going in. I can tell you, I wouldn't have done as much work and kept my 924 as long without this board.

For a rebuild, call EBS Racing and ask about a 931 rebuild kit. That is a good start, costs around $400. Then you'll need a turbo rebuild, not sure about those costs as I have a 924, not 931. Then you'll want to replace most of the coolant hoses, those aren't super expensive, but some of them aren't cheap. The pricey stuff really is the fuel related stuff, the 2 pumps, WUR, injectors, ddistributor, none of it comes cheap. I hear what you are saying though, I didn't do EFI when I rebuilt my engine because I didn't want to complicate the process too much, and cost is always a factor with a hobby car. Maybe rebuild the engine and when it is close to done try to find someone parting out a recently running 931 and buy the fuel system? Long shot, but you never know.
_________________
1987 951 - M193 Version for Japan

[931Tony]

FRPorscheman,
I agree with some of the guys that $700 might be a little steep for one with the engine apart.

I disagree with ideola on one point though, I STRONGLY suggest you don't put synthetic in an engine without a full rebuild. The reason for this being that regular oil builds deposits over time, switching to synthetic oil will do a great job of cleaning all those deposits out but it will also cause seals to leak, oil rings to leak, etc. Really not a pretty sight, it'll turn a great running engine into one leaking, smoking SOB.

As far as the CIS/EFI debate goes I've been recording my process in getting my 931 started after 3 years of sitting in the garage. My determination is to get it running well on CIS parts, then I plan on converting to EFI. I'll start some postings soon (and maybe a How-To or two) if it'll help.

FInally, ideola, I'd love to hear more about your engine build, sounds interesting!

but either way FRporscheman, keep us posted. H

[ideola]

[Smoothie]

I've had the same experience regarding synthetic (specifically Mobil 1) as ideola. I started using Mobil 1 in it when I got the car in fall of '92 and have had no oil leak problems. -And I have no idea if/when the engine's ever been rebuilt - as far as I know, it never was. In fact this is the tightest engine I've ever had in terms of both leakage and consumption by oil burning..every other car I've owned has leaked and burned at least some oil and all of them were run with non-synthetic. I suspect that some of the fear of synthetic-caused-oil-leakage may only be legend passed down from the early days of synthetics and they've been reformulated long since to reduce, if not eliminate the problem.

Based on my own experience (no oil leaks and 10+ years on my current turbo) I would switch right to a full synthetic if only replacing the turbo and to full synthetic right after a dino break-in if rebuilding the engine.
_________________
"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox