On trouble shooing.

How is an LT-1 any easier to trouble shoot than a 928 engine? Other than loughts of guys have had practice screwing up LT-1s, but not too many have had practice at screwing up a 928 engine?

I've found the L-jetronic EFI to be rather easy to get a hanndle on. It's a very simple system, that is rather rugged and reliable. The ignition system is pretty much a standard high power pointless system, with a distributer. The vacuum lines can be annoying, but thats nothing new. Other than the T-belt, there is nothing realy special. Plus, the 928's arragement makes it far easyer to work on the T-belt than most of the transvers engines out there.

As far as headers go, any header, other than shortys, would ahve to be specialy made. A 928 one wouldn't fit the exaust ports, and an Chevy one wouldn't fit the car's frame. Hum...

If my engine ever goes, and I've got to rebuild it, I think a set of forged chevy pistions, a coated block, and a billet cam would be the way to go. Kinda like the way John did it. By the time I paid for the conversion to Chevy power, I'd be good to go. Maybe?

Oh well. Intersting to say the least.

 

Never! The Porsche is an engineering feat. Like all good German design, it is an engineered package. Anything but the engine that came in it, would not do the car justice. This v8 is a thing of beauty. Maybe my experience with Porsche is still fresh. Maybe if I had a car sans engine, I'd feel differently about it.
Think of it this way. They made too few of these cars to begin with. Putting a mass produced American engine in the car would be tantamount to taking one more 928 out of existence. It would be like putting a Honda engine in a Norton. The Norton has quirks, but also has curves of cast aluminum that give it character.

 

bc,

I'm really not quite sure what you mean when you say the Chebby is easier/cheaper to diagnose and/or repair.

To my mind an internal combustion engine with Bosch FI, and 2 or 4 valves is just that. An engine. Doesn't matter what it says on the valve covers/ cam towers, 'tis just an engine. Sure they all have short cuts, and known issues particular to an engine family, but there's nothing magic going on in the engine compartment.

If you go to a tech who doesn't actually understand what he's doing, then yeah, I suppose he can guess his way through all the 350 Chev problems he barely remembers from the bad tech school he went to. And maybe his boss only charges $50 an hour for goober's labor. Who cares? I wouldn't let one of those bozos check my oil, let alone change it. Would you? Anyone who takes their car to the corner gas station for diagnostic/repair services gets what they pay for and deserve.

The guys who actually build a nice 350 Chev value their time just like the Porsche guys - $80-100 per hour for quality work. Good wrenching ain't cheap. And the technology (OHC, FI, emissions) is all basically the same. Prices? If you march down to the local GM dealer, you'll find part prices that are a page from the Porsche manual - camshaft for a J-car (A J-CAR!)? $375. FI brain for same? $500.

Sure, you can get some cheap parts for a GM car down at NAPA, or AutoZone, but the real good stuff for those motors costs decent $. Last time (not that long ago) I priced out a good quality "crate" GM 350 it was well over $7K by the time you put FI, headers, forged pistons, decent rods, and all that on it. Not to mention adaptation. Cheaper than a factory crate Porsche, by a long shot, but not really less than a nice quality rebuild on a 928 motor.

So, while I agree you can get some more ponies out of a 350, with very minimal (ok, zero) development effort, if the trend continues you'll see the 4.7&5L Porsche engines being brought much closer to their true potential. When that happens, the 350 chev will not have any real advantages, except maybe to save a coupla bucks buying plug wires at PepBoys.


Greg

 

I said it was cheaper to "hot rod" a Chevy...
I also think many more mechanics are good with American engines, than with Porsches...
So let's compare:

High Performance Cam?

Chevy: $150
928: $2,500

High-Performance Intake Manifold:

Chevy: $200
928: $4,000

Forged Stroker Crankshaft, pistons, con rods, rings, etc:

Chevy: $1,500
928: $5,500

Tuned Headers:

Chevy: $200
928: $625

My point is that if I dropped a Chevy engine in my 928, and I decided that I wanted to put high performance cams in it, or an intake manifold, or a supercharger, the parts are bolt-on, inexpensive, etc... If I decide I don't like the cam profile on that cam, heck, I can just take it out and try another one, at only $150 each... The point is, the 928 may have *some* hot-rod parts. But they are outragiously more expensive than the parts to make your Chevy engine just as fast. Now I will agree that they are not as sophisticated, not as reliable, etc... I would never expect a Chevy to be as reliable, or as sophisticated. But I can fool around with it, and make a lot of power. Some of the strokers and supercharged cars out there have blown up. I'm just thinking that if my engine did blow, I would rather that it be a hot-rodded Chevy engine, than a hot-rodded 928 engine. Because I can be back on the road with a $4,000 crate motor, making 400 horsepower. Instead of replacing a $20,000 stroker 928, with all the goodies on it...

 

A Chevy 350 is definitely less sophisticated than a 32V 4 cam, 82" non-metallic belt 928 engine (a good thing) but this makes it MORE reliable - not less! Plus...the small-block would be lighter as well. Particularly if one used the "good" parts like aluminum heads and steel headers...

Harvey
'85S

 

Does anyone know what the design principles of the Porsche V8 was from the begining? What was the ideas on displacement and did they forsee an ultimately higher hp configuration that never came to be reality?

Like many things Porsche, the engine seems "overbuilt" especially at 4.4l. I'm not comparing it only to SBC in which the first time Smokey Yunick viewed it responded that it could never work with stamped rockers in racing conditions. Look at other premium cars and rarely can they be taken up 50% in volume and doubled in hp over stock. This thing is second to the Jaguar V12 in how to make an all aluminum engine so heavy. Did Porsche always invision a 5.4+ liter engine and simply get delayed due to OPEC? Not slamming so don't get defensive, but how did they manage to build a 600lb Al V8. Lexus and Jaguar now make DOHC V8s that can handle hp and do so with a lot less weight. Was it just material for strength, difference in material or a result of engineering before the evolution of computer sim's and stress anaylsis? Again, not picking on the P-car so deffense is not necessary, just trying to figure out why it weighs more than an old cast iron SBC.

 

Sadly Harvey, you are right that you can build a 350 Chev so that it is lighter than a 5L Porsche. Depending on the initial setup (comparing factory to factory) they are usually within 50 lbs, but if you do a SBC with light stuff, it'll make the 928 powerplant look obese. The 928 plant is just heavy, all aluminum or not.

bc,

I will not disagree that it is cheaper to frag a Chev than a Porsche. No argument here.

Once again though, I'm talking overall true, real cost to you, not just some part prices...

~$4k for a GM factory 350hp400ftlb 350CI
~$2k for the swap kit
I assume you have the skills to install it, value your time as you see fit
~$1k for the stuff that you need that doesn't come with the kit
~$3k for a blower kit
~$1k inter/after cooler

~11K$ plus your time. As you know, you'll also spend more time (agreed not as much $) on an ongoing basis wrenching it as a 350 is barely designed to last 70K miles, let alone 300K miles. I'm sure everybody knows some guy that's gotten more out of his SBC, but the GM design life is ~70K. If you completely redo it with really high quality aftermarket parts it should be better.

Take your factory installed Porsche motor out, rebuild it(~$4k), use factory parts, add forced air induction and some very inexpensive (~$1k) fuel upgrades (pump,injectors,fuel reg). Add a blower of your choice (~$2k) and inter/after cooler ~($1k) and some blower hardware ($1k)

Though down 50 ci in displacement, I bet the Porsche puts out nearly the same HP as the Chev, maybe even a bit more since it has better heads, DOHC, superior engine management, etc. I would also bet, that it lasts a lot longer than the Chev with similar output.

I've seen more than a few "swaps" in my time. Half the time, after the bills are all added up, the guy would've saved lots of time and money by improving his original powerplant, as opposed to dropping in the bigger/better engine, with the work it takes to actually get the install right.

The other half the time, it might be helpul in some scenarios, and if it is something within the "family" like sticking a 3.6L turbo motor in a VW Beetle, or a Skyline motor in your 240 SX, it might work out pretty well.

Sure there are a ton of cheap pistons, cams and whatnot available for the 350 chev. But, if you take ALL the costs into consideration, I think you really come out about six to one, half-dozen to the other at best.

And if you factor in the sound of a 2v/4v Porsche v. that of a 350 Chev at 6 grand, the lowered resale pool (I'm sure somebody will want it, but it will be a smaller pool), the fact that it is no longer wholly a Porsche, and other more esoteric considerations, I just don't see the logical case.

If you really dig it, do it. There's nothing wrong with that, hell,it may be fun. But I think it's really difficult to make it into a logical choice (if it's about the money) if you really analyze it. That's all I'm sayin'...

Greg

 

I think the Chevy swap is the same kind of argument as strokers versus supercharging.

I was not really talking about the cost of the conversion.
I was talking more about the end result.

Let's say the end result of a conversion, is a *stock* chevy 350.
Not built to be any more power than the stock 928 motor.

That motor is indeed not as reliable.
It is indeed not a Porsche any longer.

But if it is at the same power level, then you compare your options.

If I want to stroke that 350, to a 383, with a forged crank, and forged pistons, it is cheap to do.
If I want low compression pistons, and a supercharger, I can do that easily too.
If I want to add cams, or an intake, it is much cheaper than on a 928.

My point is that if you make the investment in the conversion, and keep the car for the long haul, you can rebuild it cheaply, if is has problems. If can be hot-rodded chaply as well... The whole "hot-rodding" experience can be cheaper, and you can drag the car, track the car, race the car, and do all the same fun things, but if the engine has problems, it will be a lot cheaper to fix. You could take a hybrid 928 racing, and replace the engine every season.

 

Just curious, does anyone ever consider the reverse? Some time ago I remember seeing a site by a guy who was building steet rod with 928 drivetrain. At the time i saw the site, he was only half done. I wonder if he ever finished it?

FWIW - I agree with most. I'm not a fan of the 928 SBC's. For no more reason than purist snobbery. It would be like my wife getting fake *****, just because her perfectly good real ones got worn out. Sure, they'd look good, but they just arent real. So it is with the 928. It means something to me to be able to look people in the eye when i tell them i own a Porsche without saying, "Its a 928, but....."

But thats just me. Like Ed says, YMMV.

 

I installed a completely rebuilt 94 Chevy LT1 in my 80 928 automatic close to 3 years ago.
FACT
You're not going to get 350 HP out of a 4.5L or 4.7, 928 engine. This was debated on this board some months ago. One can search the archives for the details.
FACT
The conversion I did was less than one third the cost of installing a completely rebuilt 350 HP 32 valve 928 engine.
FACT
My LT1 produces 368 HP, does 0-60 in 4.82 seconds, and 13.1 @ 108.91 MPH in a quarter mile.
It can be modified further, but I'm happy with this performance. Next season, maybe some autocross.
It’s been driven 30,000 miles; and so far, I've had no problems with the 928 chassis, electrical, transmission or the Chevy engine.
The LT1 logging and diagnostic software will run on any windows laptop making troubleshooting and adjustments very easy.
IMHO, it’s a worthwhile alternative for an early model 928 with engine problems.

 

I see no reason why a crate motor from Chevy/Ford/Mopar would not easily make well over 100K miles with the normal combo of performance/street driving.

The low-durability idea is a bit of a farce, far more of these engines see 200K miles w/o major overhaul than see under 100K with major overhaul; attribute poor/proper mantainance and use to that, not build quality and design.

The 300K 928 motor is a bit of a myth too, sure some will see it and alot of piston/cylinders will see it but the upper and lower ends of these engines are pretty standard stuff subject to the same care and abuse as any other engine with similar results.

Timing/ waterpump components will see similar change intervals with a much lower cost for the Chev, Clutch components will offer a high number of choices with lower cost also.

And if you have chronic tinkeritis, the US engine will really shine.

 

All that and a kick-a$$ stereo, too.

 

On the "real Porsche" issue; if you ask some people the 928 ain't a real Porsche no matter whats underhood. so WTF

 

My comment about getting it "worked on" . After you get it in and running which is no small task when it has an electrical issue ......say oil pressure light not working , fuel pump not running where is the problem ?? in the Chevy wiring or the Porsche wiring what color wire turns into which color wire ? What modifications have been done to the fuse relay board ? The Chevy mechanic knows the Chevy part / Porsche guy has wiring diagrams for the Porsche part . Just getting the central warning brain to be happy is a major task when doing a transplant . Paying a mechanic $100 per hour to figure out all the little details adds up very , very quickly and in the end only he knows what he did ..... So for fun , at home , doing your own work it might be "reasonable" and fun , if you have to pay to have it done it is very expensive . And Yes I have several customers with Chevy engines ; Andy founder of Renegade Hybrids , prior owner , used to buy a lot of parts from me (I bought some from him) and I have seen several such conversion cars . Many of us have problems with Smog/ pollution laws which in California make it very difficult to register "hybrid" cars . Just for grins ....try calling repair shops tell them you have a Porsche with a Chevy motor be sure to hold the receiver away from your ear ...........

 

Jim,

Good points.

I'm assuming that we're talking about DIY conversion and maintainance, or even buying an already converted Hybrid and DIY upkeep. Certainly would throw a curve to the equation if your going to pay someone else.