About this time last year there was a post with a lot of good rod/stroke info..
http://forums.pelicanparts.com/911-engine-rebuilding-forum/184752-camshaft-selection-first-draft.html

Whoa...no kidding! Killer info.

Henry, Why don't you test a Motronic fuel injection system (from 3.2 carrera) on your 2.8SS to see how it performs, and measure fuel mileage? (Can Motronic handle 8500rpm?)

I like MFI, always have, always will.
I'll leave the EFI engine development to those people who like it.
Fuel milaege does not interest me much.

" the fastest way to go broke in business is to get an ever growing percentage of an ever shrinking market"

Money must not be the primary motivation.

http://forums.pelicanparts.com/uploa...1128191890.jpg http://forums.pelicanparts.com/uploa...1128191916.jpg http://forums.pelicanparts.com/uploa...1128191950.jpg

Henry, what did you set the deck height @ on the 2.8SS ?

Thanks, Scott

Henry - howz about posting a link with some video and soundtrack to one of your creations!! I'm sure more than a few of us would like to meditate to that!
Nabil

Meditate? It sounds to me like pornography. http://www.pelicanparts.com/support/smileys/wat3.gif

We all have our weakness!!

Henry,

How would one differentiate between a 2.2 S crank and one from an E or T??

Thanks!

2.2S and E are the same.
pic:
http://forums.pelicanparts.com/porsche-911-used-parts-sale-wanted/240541-2-0-2-2l-counterbalanced-crank-blowout-575-shipped.html

The 2.2T crank does not have counterweights, the flanges of dark metal that hang off opposite each journal. BTW, that one is still available.

Best regards, Scott

Wow! Cool thread. There's not much that I feel that I can add at this point.

Although I wonder if some of the difference in performance between short stroke and the long stroke 911ST motors might be due to the increase rod angularity that Henry describes above. On the other hand, one of the benefits of "longer" stroked motors that Porsche's designers have always appeared to have been sensitive to is that with a "longer" stroke motor it's possible to have a more compact combustion chamber (specifically, by this I mean that the surface area to volume ratio is smaller) which results in improved combustion, reduced emissions and reduced ignition timing for a given level of performance.

Just some unquantified thoughts.

Well?

.040 DECK HEIGHT
AND .070 VALVE TO PISTON CLEARANCE.
THIS IS THE SAME FOR ALL OUR HIGH PERFORMANCE ENGINE.
MOST ENGINE BUILDERS HAVE A SERIES OF NUMBERS THAT THEY ARE COMFORTABLE AND IN MY CASE THESE ARE THEM? THEY? IT? MINE

Henry, I understand that you've used JE pistons for this application but is Mahle P&C's 95mm available for such a application? If so, what's the part #?

Mahle does not make a piston specifically designed for this engine configuration.
They do make a 10.5 to 1 compression, 3.0 RSR piston that you can order in a cylinder with SC bolt spacing that will work for a 2.8 SS engine. Part # from Andial is AND 10398495
Keep in mind that a 10.5 to 1, 3.0 piston was designed for a 70.4mm crank so when you install it on a 66mm crank you will loose static compression.
I have measured a loss from .5 to .58 reduction in comp. ratio when doing this conversion.
10.5 to 1 will now be as high as 10.0 to 1 and as low as 9.9 to 1.

With this engine as with all other engines of custom configuration, if compression ratio is important to you, you must measure it.

Henry Thanks for all the information!!

In your opinion is the mahle 3.0 RSR in which you listed the andial p/n for superior to the JE piston for longevity? Would you recommend the mahle over the JE? I am sure there is a big cost difference, but might there be any other reasons to use/ not use the mahle 3.0 RSR set?

Thanks again!

What about Cosworth pistons in terms of longevity when compared to Mahle? Aren't Cosworth's about the same price?

What its cylinder wall thickness?
Is it CE ring groove delete?

Cylinder wall thickness is stock for 95 mm SC or Carrera.
CE ring is optional. Either way.

Re: IT'S DONE
 

[QUOTE]Originally posted by Henry Schmidt
[B] AFTER OVER A YEAR IT'S DONE

2.8 SHORT STROKE 66 MM STROKE 95 MM BORE

THIS BAD BOY SHOULD MAKE 300+ HORSE POWER AND TURN 8500 RPM

Henry - has this bad boy been on a dyno of some sort by now? Any numbers you can share?

Walt Fricke

(slowly building a similar engine with 3.2 heads and wondering particularly what cam to use, though my pistons are cut for more like 12/1 which might change things)

Henry,

Why did you choose 95mm bore? Why not 98mm or whatever to make 3 liter short stroke?

Why not a 100mm and for that matter 102 ?
This is not Mac Donalds, and you don't have to super size me.
When Porsche took a clean sheet of paper and started to build a super car, the 959, they chose the 95 mm piston and a 67 mm stroke. If I could get the 67 mm crank I'd build that engine too.
I also feel the 95 mm cylinder is more stable (thicker walls) than the 98 mm. We have seen ring seating problems with the 98 that we don't see with the 95 mm.
I guess more is not always better.
Who knows? Could a 60x95 (2.5) be close at hand?
9200 rpm ?
The Benetton 3.5 liter F1 V8 was 50 X 95 mm.

Thanks. ;)

BTW:

Isn't 9.9:1 or 10.0:1 enough?

10.0 to 1 for some applications is enough and maybe too much. But for my taste 10.5 is the target figure and if you can make the engine work and survive then you win.

Henry,


Great write-up.

Thanks for the educaton ! :)

By the way, long over due, thanks for the help at Steets 15 years ago when I blew my 6 motor ( spun a rod - like you suggested)

Good to see your doing well.

Henry - wouldn't an SC case be the same as the 3.O Carrera or early turbo?? I never realized there was much difference. If they're the same I'd think we could get SC cores cheaper, or maybe I'm way off here. Set me straight!
Nabil

It is my understanding that the 930/52 3.0 turbo case is capable of accepting a 6bolt crank whereas the 3.0 sc case can only take 9 bolt cranks. That being said I dont think there is much other difference between the two. Seeing as 9bolt 66mm cranks are rather rare, I think the 956/962 used them it gets expensive fast.

Correct me if I am wrong please.

that's right. The main journals are bigger on the 9 bolt cranks so you can't put a 6 bolt crank in an SC or later case, and as PK said the 66mm 9 bolt cranks are pricey/scarce, whereas 66mm 6 bolts are not. Of course if you are building a motor with a 70.4mm or longer stroke, there is no advantage to starting with a small journaled case that I am aware of, you might as well use a cheap SC or later case.

below is a post from Henry regarding the tradeoffs of journal size.

Henry - Sorry if I missed it but, did you custom order some JE pistons for this engine? I read that the compression is 10.5:1 with the 66mm stroke - did you just order 11:1 pistons for a 70.4mm stroke from JE ?

As well, could I keep using my 40mm Webers if I went with a slightly milder cam? (mostly street car)

Thanks,
Andrew M

Yes, they are custom built by JE.

40s on a mild 2.8 would work if you don't plan to rev it. But why build a 2.8SS if you're not going to rev it?

so, some 46 PMO would be in order then...

Very nice Henry! Thats my style of Porsche 911 engine, gather up a bunch of factory parts (or factory style parts) and build something cool out of them. I have always liked those magnesium stacks much better than the plastic ones. I never use the oil fed tensioners in my own engines.

I'm a big fan of "beauty is as beauty does" but that motor is also easy on the eyes. Nice work Henry!
-Chris

A good 30 years to age that glass shroud would be nicer.
Is that a new one?

A bump for those who haven't read this. I just reread it and still love it.

I just found this old post and thought others might enjoy it.

I love that old school Porsche kit more and more.

With good reason. :)

Indeed; great thread; thank you!

I'd be curious to hear anyone's opinion on how this remarkable and beautiful motor might compare to a 2.8S and 2.8 RSR. I've read everything I can find on the forums by Grady, Steve and others about the 2.8S, and it seems like a fantastic option to build on a 2.7 case, with more reliability than the RSR. The RSR seems a little more high strung compared to the 2.8S--more of a pure race engine--but all three sound brilliant, and this is the first I've ever heard of a short stroke 2.8.

In the long term, one of these directions is the one I will probably take, currently driving a 2.7RS that I love.

Beautiful work!

The 2.8SS can not be built on a 2.7 core. (easily)
It is built using a 3.0 turbo or 3.0 Carrera case.
The benefit of this case is that uses the 3.0 head configuration.
These heads flow better than the 2.7 head because of improved valve angles and bigger valves.
The reason I prefer the 2.8SS over all other 2.8 configurations is that the 66 mm crank is stronger than 2.7 based cranks and the rods have a better rod length to stroke ratio. This ratio reduces rod angularity and increases piston dwell.
Net result: more power, higher functional RPMs (8500) and less destructive forces produced by the pistons.
Big bore/small stroke engines for a given displacement (all other things being equal) produce more horse power. The is why F1 rules specify displacement and max. bore not stroke. Current F1 rules state 2400 cc and a 98 mm max. bore. If you do the math that's a 39 mm stroke (rough guess)

The reason you haven't heard of the 2.8SS before is because it's " The best engine Porsche never built"

They came close with the 959 (95 x 67) and some 956/962.
These were special because they used 9 bolt racing cranks (rare but available) instead of the 6 bolt crank.