It's a beautiful, bulletproof, and expensive design. There are no bearing caps like you see in an American V8. The bearings, and crankshaft, are held in place by a full length girdle, which bolts to the main section of the block. Cast aluminum oil pan is heavily finned to dissapate heat, and that sump is much larger than an equivalent 4.7 litre V8 from another manufacturer.



Cylinder bores are aluminum. The aluminum, however, has such a high silicon content, that once the bores are finished and honed, the actual wearing surface of the cylinder bore is "glass". These engines hardly ever need attention to the cylinder bore, they are just about wear-proof.


2-valve (16-valve) SOHC 928 motor, initially offered in 4.5 litre, and then 4.7, eventually in 5.0 litre form.


The heads on the early 928 are almost identical to the 944, which was designed after the 928 and which eventually used what was basically 1/2 of the 928 motor. The 944 is a higher compression rig, and the valves can come in contact with pistons if the timing belt breaks. The early model 928, up until the 4-valve motors, is not an interference engine. The 4-valve versions are interference engines, and true to form, when the 928 went to the 4-valve design, so did the 944.

All said and done, the 2-valve engines sound better, pull well in the lower gears, but the 4-valve jobs continue to "pull like a freigt train" all the way to redline.





This "spider intake" system brings cold fresh air in over top of the radiator, into the large oversized filter box, down under the filter box, over to a plenum, up into the plenum, and then finally out through those 8 spiders and into the cylinder head. At the point where air enters the cylinder head, fuel is injected into the air stream.

The spider intake design is lengthened to promote torque. The Euro design is similar, but the runners are not as long, but the power is up by 70. Even without the additional 70-hp, the 1983 928 was the fastest car sold in North America, beating out all turbocharged cars, all Ferrari, Jaguar, Lamborghini, Lotus, Aston Martin, etc.


Here's another view of the spider intake, this one is polished and looks a lot better than mine, but it doesn't run any better! You'll note those spiders are moved to one side or another, so a long handled socket can be used to pull spark plugs. It works, there's just enough space to get the job done.







By comparison, here is a photo of my 1984 944. Note how it looks like 1/2 of the 928 motor, because that's what it is. Due to inherent balance problems with doing this, especially with a large 4-cylinder motor of 2.5 litres (eventually bumped up to 3.0 litre) Porsche used two balance shafts to compensate for internal vibration. I actually ran the car for a while with the balance shafts disconnected, it had full power, and a hint of harmonics at certain rpms, but nothing serious. With the shafts spinning, the motor is turbine smooth.



This is a thing of beauty. It's the bottom end of the 928 V8 motor, and you can see how the full length girdle holds all the bearings and the crankshaft in place. When people wonder what makes a Porsche cost more money, it's machine and casting work, and the labor to get pieces to fit up within tolerances, like this. The 928 was not a cheap mass-produced motor, and neither is the 944. The 928 bottom end remained the same, for all engines produced from 1977 to 1995, ranging from 219-hp to 350+, and it is adequate for race prepared engines producing 400 and 500+ horsepower.


Here is another view of the girdle concept used on the 928 and it's 944 variants. This is a race prepared 944, and you can see some superb workmanship on those "knife edge" crankshaft counterweights. Photo below is the same motor. Pretty awesome piece of work, even in dead stock form. The 944 block has been able to withstand 600-hp in full race turbocharged form, from houses like Kelly Moss.





Here is the 4-cylinder version of the girdle, as used on the 944. Even though the 944 was considered an "entry level" Porsche, you can see Porsche spared no expense when it came to their engine designs. This is a case where engineering dictated to the marketing department what to say, and not vice versa.






In 4-valve trim, the main cam drive cogs remained in the same place they had been in the 2-valve motor, but that second cam is driven by a chain connecting the first and second cams together. This drive chain needs attention on high milage 4-valve engines, but it's a good solution and it works fine.



Here is a magnificient view of a full race 928 4-valve motor, compliments of the Kelly Moss Racing Team. Believe it or not, this motor was destined for a custom built full race 944. Note, it is the same general design as 1/2 of the 4-valve 944. My S2 is a 3.0 litre version of this motor, putting out 208 normally aspirated horsepower (see image below).



ABOVE: View of the 3.0 litre 4-valve 4-cylinder DOHC hemi used in the S2 944.




Here is a pic of M21Sniper's dressed motor, in his 1983 16-valve 4.7 liter 928S. This motor runs VERY STRONG, so if you're in the Philladelphia area, >>>>>>> BEWARE <<<<<<<<


Here's a photo of Heather's 1983 928, hmmm, is it possible the "Snipe" has put his hands on this motor too? I think I see some similarities, and since they're both in Philly, I'm starting to wonder.

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I'm reserving this spot for Rui Costa's photo of his GTS motor!






And now a couple photos of the 16-v heads otherwise known as the 4-valve head. These are essentially the same as on the 944 4-valve or the 928 4-valve. I have a 944 S2 with this head, and they have about the same general amount of torque and pull as tha 2-valve head down low, but the difference is, the 4-valve heads pull like a freight train right up to redline. I suspect the 4-cylinder and V8 cars have the same general characteristics. Where the 2-valve motor is a beautiful thing, the 4-valve is just an improvement in design, power and torque.

I knew the 944 was 1/2 of a 928 motor but I never saw it explained so well. I'm downloading this information for my files.

that exploded view, and the photos of the cylinder bores, and bottom ends really tell a LOT.

Many thanks,

JD

One thing I notice, if the 944 cars (at 1/2 of a 928 motor) are running well and lasting a long time, why didn't they offer the 928 in the same stage of tune as the 944?????

In 1984 that would have made the 928 a 300-hp car, instead of what, 234?? Also, in 1990, it would have made the 928 a 416-hp car, because that 944 S2 produces 208 hp.

This just gives me more reason to believe the 928 is a "detuned" motor and not very highly stressed at all. That may be one reason they seem to be so durable and last so long?

Steve W

I appreciate the information, but I also appreciate the tunes and the sound effects, AWESOME. I love my S2, but that V8 is just brutal. Got to love it, thanks again,

LM944S2

I'd sure like to be your neighbor. Seeing that hardware on the road would be a constant treat to the eyes and ears too.

I have a question for you P, are the 4-cam engines any more of a maintenance hog than the single overhead cam version, and are they any more difficult to keep in tune, repair, and run on a daily basis. I've had good luck with my 1980 16v, and I'm wondering about moving up to a 32-valve job.

JohnLSimmons

1980 928

For a few fleeting moments I was somewhere, not sure where, but it sure was cool

Great site P, I am sending this link around to my friends.

1985 944
Across the pond, London, UK

James

Although the 944 and 928 share a lot of components and philosophy, the early 944 motor is an interference design, while the same year 928 is not. This is due to the 944 being higher compression, and valves get closer to pistons. The 944 is running at a higher state of tune (per cc) than a 928.

Ken

Love those motor sounds, I'm assuming that's a 928?

Mike

Ohh that's nice, I love the sounds and the photos too. I just played through it, haha,

Good reference material.

zooom zoooom

Autoshark
1984 928S Auto

The sounds in this post are awesome, makes me feel as though I'm standing next to a 928. I wasn't expecting that, and had my speakers turned up a bit too loud. I thought a car was about to drive through the room.

cheers, Jay

Since I'm doing some searching today and finding some neat stuff, I thought I would post what Wally Plumley has to say about the 928 block, and how long it should last.

Here is his quote

Regards, Gene






"The 928 block is made of Reynolds 490 high silicon (not silicone) aluminum
alloy. It is precision cast, with controlled cooling for the bores, so as
to bring the silicon to the surface. After boring and honing, the block is
chemically hones to remove a very thin layer of aluminum from the surface
of the bores, leaving a very hard, slightly porous layer of silicon for the
pistons and rings to rub on. Since aluminum does not function well rubbing
against this silicon surface, the aluminum pistons receive a very thin
coating of iron as a wear layer.

Net results:
The cylinder bores are perhaps the longest-wearing ever put in a production
automobile. It is virtually unheard-of for a 928 engine to wear out.
Reboring the cylinders is possible, but requires special care and
knowledge, and usage of a chemical honing treatment to establish the
silicon layer.
Replacement pistons must have an anti-galling wear layer, such as iron,
applied. This coating is rare and expensive in aftermarket pistons.
The block can be bored, and then have iron sleeves installed, but this
eliminates much of the advantage of the Reynolds block."

Wally Plumley
928 Specialists

This is still one of my all time favorite web pages! Love the sound effects too.

TURN UP YOUR SPEAKERS ! Ha ha

The 928 has one of the most durable, but complex blocks of all time. Looking at a small block Chevrolet, by comparison, makes the Chevy look like a tractor motor. The Germans never were noted for making a complex problem simple, they're well known for making a complex problem much more complex than it needs to be, and creating a solution that works well, but is as complicated a soution that can possbily be designed and manufactured. Sheesh, just look at that timing belt replacement requirement, you have to dissassemble half the front end of the motor to do it.

Autoshark

Hey that was fun! The audio surprised me. Good stuff!

Mark Miller 1984 944

Here I am surfing this site, finding lots of really cool stuff, and I stumble upon THIS. What a pleasant surprise, and such a closely held secret in Porsche lore too.

Thanks for posting this, it's awesome.

RT