Question: 928 Engine Rebuild Level of Difficulty

mtelliott · 12-29-2006, 12:22 PM

Question about the level of difficulty on a 928 Engine Rebuild. How hard (as compared to a 911 engine which I have already done)? Is parts about the same price as 911 prices? Can the block be bored if necessary or does it need special work due to the aluminum? How many miles are the engines usually good for (provided proper maintanance).

And the tranny, is it more complex than a 915? Do they shift better than a 915? Is the auto tranny solid?

I'm just so surprised how inexpensive the 928's are compared to a 911. My 911 is not losing value as I own it however the 928's keep dropping.

Michael

MarkRobinson · 12-29-2006, 01:20 PM

Hi Michael, I've done 928 engines before. no need to replace pistons & such. Engines most never need bore clean up or such: just replace rod&main bearings ($500 or so), engine gasket set ($400), & have the manuals handy for all the torques. Not too bad, very well designed & w/o the tricky through-case o-rings & such associated with the 911 engines.

If you have good compression/leakdown (most do), I'd just opt for a long-block resealing (headgaskets as they deteriorate over time), cam tower gaskets, front/rear main seal, oil pan seal, oil pump seal, new t-belt, waterpump & bolts, rebuild the tensioner, & LOOOOTS of cleaning.

These engines can run indefinately. I've never seen a "bad" 928 engine, only damaged engines from people doing stupid things.
With your prior engine building experience with 911's, (say that's a 10 for this conversation), I'd say a 2v 928 is about a 6, & a 7 or 8 for a 4v. Certainly do the leakdown & spec the vavle stems: this is the only area where you could spend $, but again, never heard of them prematurely failing below 300k miles.
Re-boring & sonnen-honing 928 blocks is pricy: expect 1k min. to do so, & you wont find it anywhere but in LA or a west coast shop. New pistons make 911 piston kits look cheap. LIke I said: compresson/leakdown: if good, leave it alone. You can just remove the rods/pistons & replace rod bearings/bolts, & piston rings (about 700 for all that) & not touch the main bearings, but since you're in there...

Also, rods/pistons/crank on a 928 are built like a forged BBC engine: you'll be impressed.

MarkRobinson · 12-29-2006, 01:22 PM

In a nutshell, don't break the shortblock unless you have valid reason to do so: most of the time, it's not necessary. small barely feel-able scratches might be evident on the outter quadrants of each cylinder: this is common with 20+ year old 928 engines, & unless it's a score that is nearing the width/depth of a paperclip, I'd leave it alone. Keep in mind, the compression ring is around 3/8" below the top of the piston, which is at 0 deck on the block, so there will be a very distict ring of carbon where the compression ring does not scrape.

mtelliott · 12-29-2006, 01:39 PM

I'm intrigued. I'm not into racing and looking for a more comfortable commuter car. I love the 911, but hate driving it in the 90+ degree days. I've heard great things about driving a 928.

I think the next thing to do is take one for a spin.

I love to tinker so I've thought about buying one that needs engine work for high value. Then, either putting in a used engine or doing the engine work myself (or both, put in a used while rebuilding with turbo). I've wanted to go turbo on mine but it doesn't really make sense right now to do it to mine.

Michael

MarkRobinson · 12-29-2006, 01:58 PM

Well, drive one that's had maintenance & updates. you REALLY get what you pay for with 928's. I nice car with updates fetches a nice price (no declining values).
Case in point: my '86.5 car (5speed) has almost 15k on it now, getting the turbo system next month, 2-time concours placer (1st & 3rd) within a month of owning it. I'd sell it for 40k w/o turbo, 50k with.

mtelliott · 12-29-2006, 05:27 PM

Wow. I've seen them locally for under 15K up to 1988.

I'm intruiged by the turbo system. If I purchased one that needed engine work, I would automatically put the system on. Seems like a no brainer.

What are the years that are desireable?

Michael

MarkRobinson · 12-30-2006, 09:14 AM

Yes, most are well under 15k, but most have had many owners, require maintenance, & have wear on them. My car is essentially a new car, & concours winner as well.

'85-86 cars are the biggest bang for the buck as they're cheap, & have a higher power/weight ratio with an exhaust & chips installed. The late '86 cars (like mine), after car number 1000 (last 4 digits of the vin), have the S4 suspension & brakes: big brembo's all around & abs. '85-86 cars can have ABS: optional on the smaller-braked cars. But, finding an clean '85-86 is difficult> try autotrader.com, cars.com, carsearch.com, & porscheclassified.com. Ebay can easily land you a problem car as it's turned into a clearing house for bad examples (but not always).
The '85-86 cars have brakes that are just fine for the street, but if you plan to track the car, you'll need to step up.

Cheers, Mark

rhjames · rhjames's Garage

basically you can get a pre-S model for less than 5 g's, then they work up to the 10g range, then S4's are above that.

Wally Plumley has good advice on purchasing a 928:

Buy the newest model you can afford, whether that be a 79 or a 95 GTS doesn't matter. It's what fits your particular circumstances.

As for Mark's price tag for his ride, "It's only worth what someone is willing to pay for it." (My father's constant quote)

The thing you should remember is this:

Even if you do a rotisorie restoration on one of these, you'll rarely get your investment out of it. That's why they are such fun to play with.

regards--rhjames

mtelliott · 12-30-2006, 10:42 AM

Thanks for the advice. I'm quite familiar with the 911's and pricing. I'm pretty good at sourcing parts and doing most of the work myself. I've got a total of $15k into my 911. Completely rebuilt engine with new P&C's. Awesome car, very strong. Should be able to get at least $12k for it since I have all receipts.

What year did the 928 go to 5.0 engine? Is it worth it from a drivablity standpoint?

I'm going to talk to some folks in PCA who have them, take a few for a drive, and decide what to do next. I wouldn't sell my car until this spring. Targa's just sell better in the spring.

Best case scenario for me is to find one that has a head gasket leak, the person got a really expensive quote to fix, and just want to get rid of it. I love wrenching on them almost as much as I like driving them (all most).

Last questions:
1) Can you pull the engine from the top, or does the entire front come out from the bottom?
2) What exactly is the torque tube?
3) How well does the 5 speed shift?

Michael

MarkRobinson · 12-30-2006, 10:47 AM

'85's is where they started the 5.0. Don't go any older, smaller engines, dated engine mangement, older seats, etc.

'85-86 engines have heads which are on studs: can pull the engine from top (all 928's), or can unbolt & lift-up the engine to pull the heads off the studs (done that once). The engine is bolted via the bellhousing to a steel tube about 8" diameter, which houses the spinning driveshaft. The transaxle (borg-Warner 5speeds from '85 on) bolt to the other end, so the driveshaft is complete encapsulated & supported: very strong. The C5 corvette engineers copied this. All 928's are like this too BTW, though older 928's have ZF transaxles which are notorious for poor syncro wear.

Mark (call me if you want, later today: 512-925-6977. If i don't answer, I'll call the number back when I get the chance & assume it's you.

m21sniper · 12-30-2006, 11:50 AM

I dunno man, it would be hard to go wrong with an 83 Euro 5speed.

300hp, almost 160mph- bone stock.

Or an 84-86 Euro A/T even. 310hp, and a a true 160mph stock.

And the 84 and older US cars are non-interference designs with rock solid and very simple injection systems.

Each has it's own allure, just depends what you want it for.

Then there's me, who lucked out and got a seriously hotrodded(probably even stroked) 83 US A/T at a dealer only auction for $3400 bucks without even knowing it.

When i raced my old partner's 85 US 5.0 i blew his doors off. At a known 13.5 quarter i can even run with a stock 95 GTS 5.4 liter in a quarter mile drag.

mtelliott · 12-30-2006, 05:18 PM

$3400 seems dirt cheap. Wish I could find deals like that.

Mark, if you meant Michael, let me know when a good time to call would be. Was out most of today. Might be able to keep the 911 if I could find one that cheap.

How solid are the automatics? How well do the 5-speeds shift?

Michael

rhjames · rhjames's Garage

my two cents worth, again.

buy what you can afford, but buy the newest model.

a twin to my 80 euro (with exception: the twin had the 300 horse 4.7 liter Euro) sold on eBay for just over $6K. As far as I could tell, it needed paint, but not much else.

as for the older models (K-Jetronic mechanical fuel injection), just crank up the fuel pressure and take on a Corvette without much trouble. Only drawback is fewer cubic inches (CC's) for those year models......Positives are fewer electronic controls to deal with.

I agree with Mark about the 86.5 models (the best of both the old style and new style 928), but again I refer you to my above post.

Would I rather have a GTS, you bet. Could I afford it, not at this time. Would I give up the opportunity to rebuild, diagnose, repair, modify (ad-nauseum...) my 80 Euro, for a prestine GTS?? Maybe, but why would you change a GTS into something that pretty much has what my 80 Euro will be capable in short order?

Take your time shopping, and just remember that these cars are not appreciating in value like a 35 year old LS6 Chevelle.

Your choice.......Enjoy and good luck!!!!

regards---rhjames

MarkRobinson · 01-02-2007, 05:39 AM

HI Michael,

I had signed my name: Mark, then put the "call me" part. I remember your name.

I have no experience with the autos at all, other than the '85 & newer 4-speeds are better than the older ones.

My '85 & up "push" is also focused around the transmissions: I've only had one '81 euro: & the ZF (although low miles) was grindy for 2nd gear. Since 928 tranny's are so pricy & expensive to work on (8+ actual hours to r&r the unit, not even opening it up!), I like the security of a more modern design.

Mark

mtelliott · 01-03-2007, 08:20 AM

How do you tell by the VIN if they are US or Euro?

MarkRobinson · 01-03-2007, 08:26 AM

ZZZ is in the VIN, otherwise...US-spec.

Visually, it will have front fender (behind wheels) running/turnsignal lights, & an asymmetrical fog light on the lower left part of the rear bumper cover, and a medium-size air-foil on the driver's windshield wiper blade

rhjames · rhjames's Garage

As far as VIN #s are concerned, an easy way to verify US versus ROW (Euro) is 928 Specialist website VIN # comparison. They have US VIN 3s listed, no ROW. You could do it by process of elimination, or look for the triple zzz on the later models (pre-mid eighties don't have 14 digit VINs, there for no zzz in the VIN).

Car wise is as Mark put it.

Turn signal (not marker/running--sorry Mark) light in front fender behind the wheel opening.

Non-Porsche OEM marker lights on the sides-front and rear (mine has BMW lights installed on the rear quarters), pre '87 ROWs didn't come with side marker lights per se.

Rear fog light beside the license plate area (left side for left hand drive--right side for right hand drive) (and yes, I have seen pics of one that had rear fog lights on both sides--Mmmmm, wonder if the owner did that??)

KPH speedometer (although this would have been changed out for Federalization---I put one back in my Euro, in keeping with the Euro theme of the car)

Instrument wording (idiot lights) written in German is a dead give-away.

Spoiler on the driver's side wiper (although again, I have seen pics of one with spoilers on both--owner installed??)

Engine stamping numbers is another good way to verify you're looking at a Euro (ROW)--non US. These too, are listed on (928 Specilalists' website/technical specs).

BE sure to visually check the engine stamping #s to verify you're buying a Euro spec engine, as the engine may have been changed out witha US spec, sometime in the lasts 20-odd years??

Hope this helps.

regards---rhjames

mtelliott · 01-05-2007, 01:11 PM

One more question. I've read (on ebay) about 928's having the torque tube replaced? Is this a common maintenance issue?

When I'm ready, I'll probably opt for the late 80's. I'm thinking 87 - 89. Probably look for something local with maintenance history. Ebay is a great place to educate yourself. Get to read a lot of B.S. on people's cars. Some times, you can learn a lot.

MarkRobinson · 01-05-2007, 01:25 PM

Torquetube replacement: no. rebuild: I don't think so. I've heard of people having bearing/hardened grease issues requiring a rebuild, but very uncommon. A normal PPI with test drive (necessary for shocks, tie-rods, PS bushings (get oily & squishy)) will show if there is grinding/whining from the torque tube: always insist on a dealership or experienced 928 mechanic to perform such a PPI.

m21sniper · 01-05-2007, 01:31 PM

Quote:

Originally posted by MarkRobinson
HI Michael,

I had signed my name: Mark, then put the "call me" part. I remember your name. I have no experience with the autos at all, other than the '85 & newer 4-speeds are better than the older ones.

My '85 & up "push" is also focused around the transmissions: I've only had one '81 euro: & the ZF (although low miles) was grindy for 2nd gear. Since 928 tranny's are so pricy & expensive to work on (8+ actual hours to r&r the unit, not even opening it up!), I like the security of a more modern design.

Mark

Just for the record the 4 speed autos were introduced in US cars in 83, and Euro cars in 84.

They are extremely strong transmissions.