Henry, thank you for that. That's helpful.

I didn't intend to build a 2.8SS on a 2.7. As I said, the 2.8SS is a new possibility to me, and it's VERY interesting. I have a 2.7RS now, I love it, and have become a huge MFI fan.

Whether I build this new motor on a 2.7 or a 3.0 turbo case is an easy choice since I don't own a second engine yet, and I don't intend to use my existing 2.7 as the core. The idea is to find a core whenever a good opportunity arises, and slowly collect parts, and then slowly build a new high performance motor which would eventually replace the one I have now. If it takes three years to get it done, fine.

A couple more questions if you don't mind.

One thing that appeals about the 2.8S is its longevity, especially if one keeps the revs down. In other threads, Grady and Steve W. have both attested to its durability and power, suggesting a safe 275-280hp is reasonable, without having to refresh every 25-50 hours. It could function in a street car as well as a track/racing car.

How does the 2.8SS compare in that regard? How often would it require refreshing? And if one were to keep the revs limited at or below say 8,000, would that substantially increase the longevity of the motor--or would you just be defeating the point of the engine in the first place by keeping it out of the high end of its usable power band?

The bottom line for me is this: as much as it's far more economical to buy a stock(ish) 3.6, or lightly built 3.2, my ideal dream motor would be a reliable, 300 hp, twin plug MFI race or near-race engine, with super sharp throttle response, a knee-buckling sound, and something sweet to look at. I don't care about fuel economy in this case. Whatever gets me to that goal is where I'll go, be it a 2.8SS or 2.8S, or 2.8RSR or 3.0RSR.

A 2.8 SS should by design out live other 2.8 configurations.
300 horse power is doable and longevity is strictly a function of RPM. There is no reason why a 2.8SS shouldn't last 100K miles if trips to 8000 are few and far between.
For what you are desiring I would guess that a 3.2 SS MFI would be more sensible. Good torque, 7600 red line and and the look feel and sound of the racing RSR.

http://forums.pelicanparts.com/uploa...1162146869.jpg

Henry,
Could you describe in more detail what you think a 3.2SS would be made of?

TIA, John

The engine consist of :
SC, Carrera or 3.3 case.
3.0 (70.4) crank,
3.0, 3.2 or 3.3 heads. (3.2 are the least desirable because of over sized ports and short flanges)
SC rods with ARP bolts (Carrillos if the budget allows)
98 mm pistons and cylinders
Cams to suit your expectations. ( DC 60, 62 or 80 ?)
Supertec twin plug distributor
MFI pump to suit
Throttle bodies 40 X 41.5
Stacks 41.5 x 50 mm
PMO Velocity stacks and air filters.
Quality oil pump (mod SC or larger)

wow looks great henry. I can't wait to get all my parts together to start to build the 3.2 ss turbo

Henry,
Based on the 3.2SS you described, what would be the hp made??

Basically, is the 3.2SS the next logical step "up" in HP vs. the 2.8SS??

Would this set up benefit with the 66mm crank??

Cams and compression will determine ultimate performance but with 10.5 :1 and DC62 cams I would predict 320 at 6900-7100 and 280 + ft/lb.



Would this set up benefit with the 66mm crank??
If revving the engine to 8000+ is important to you.

Have you ever thought about fitting 4 valve watercooled heads on these engines? Can 4 valve heads fit on SC case?

In theory, GTR3 RSR heads should fit. 962 water cooled heads should also fit. Just guessing. You guys with later model experience will have to chime in.

bump , does anybody know what how much work it is to mod SC heads to take MFI injectors?? according to PET, SC's have injectors in the intake runners, not in the heads??

I simple three step machine process is all that is necessary.

Most shops familiar with this process should be able to perform the service for as little as $180.

thanks for that !

3.2 heads for SS
 

I have a set of 3.2 heads to use on my SS 2.8 project. Port sizes seem about right as they are. But I have two questions:

1) The intake ports are not round at the top, to make way for the injectors. There is an indentation. I'm going to use carbs. Should I consider having this area welded and then machined? Some other way of returning them to a cylindrical shape? Because otherwise it will leave a pocket below the carburetor intake manifold.

2) I'm most likely going to run SC cylinders, with the CE rings. But the 3.2s didn't use sealing rings - something was slightly tapered. Was it the head sealing surface, and if so do I need to do something about that or is it OK as is for use with CE rings and stock SC cylinders?

Walt Fricke

The heads are fine. Just order the PMO manifolds that are designed for this application.

The heads are flat, the cylinders have a slight taper. The SC cylinders will work fine.

Henri,

i have 3.2 Heads laying around from a 3.2 junker i bought
they seem perfectly good heads
you mentioned earlier , that those are to big?

what's the drawback of using bigger 3.2 heads??
can't get too much air in there no?

i'm not aiming at the full 300 hp 2.8SS, i'm not that good of a driver, and i want to keep it streetable,but more like a slightly beefed up 2.7RS, 240 maybe 250 HP

you think those 3.2 heads are good for?

I believe that the 41.5 mm intake port on the 3.2 head is too large to promote good port velocity.
High port velocity is necessary for maximum volumetric efficiency.
Port shape and size not just port size is important for engine performance.
Bigger is better only in a full throttle situation. must engines don't run full pedal all the time.
I would recommend a maximum 40 mm port for a 2.8 SS with an intake manifold of 38 mm. This lip at the transition will assist in the control of intake pulses caused by cam overlap and is exaggerated by large duration cams.

Big ports = poor low end possible good high end
small port = good low end possible reduced high end throttle response

Calculate CFM for your projected max RPM and run the smallest port to accomplish that volume.

With a 2.8 @ 7600 RPM 38 mm manifold is appropriate. Add 2 mm to the port for pulse control and you win.

8500 race on a race engine with proper gearing and bigger is better.

that'll definately do for explanation :D

also understand now, how MFI Throttle bodies work on bigger engines , cause i always wondered how that worked , since you can't bore the TB's to big...


38 mm is exactly the size of the TB's, at least the top part ( T TB's) so all that is needed now, is to bore out the lower part below the valve, which shouldn't be a big problem ...

thx again Henri , you're a star !

Walt, I ran into the same problem when putting my Jenveys onto my 3.2 heads (3.4)

I used the PMO insulator/spacer kit as it took care of the problem, so once again Henry knows of what he speaks!!

You will be fine with the PMO kit!

Cheers

Jeff

Does the PMO insulator/spacer kit take care of this problem (if it is a problem)? How?

"1) The intake ports are not round at the top, to make way for the injectors. There is an indentation. I'm going to use carbs. Should I consider having this area welded and then machined? Some other way of returning them to a cylindrical shape? Because otherwise it will leave a pocket below the carburetor intake manifold."

I used their kit for my 2.7 race motor with 38mm intake port heads, but as I recall boring the ports out from 35mm or whatever they were took care of the CIS injector pocket. But the 3.2 heads are big enough as they are for my SS race motor, so unless I do anything that pocket will be there. Sitting below a 41.5mm PMO tall intake runner and the insulators and gaskets that go with it.

Maybe that is not a problem - a kind of partial anti-reversion step? I'm a bit dubious about such serendipity.

And thank you, Henry, for telling me what was beveled. When one is basically an engine assembler rather than a real builder, this is really appreciated.

Walt Fricke

Walt,

The insulator and associated gaskets cover over the cut out for the injector. I guess there there is still a small recess inside the port once you cover it up, but it is sealed at least. I can't think of another bolt on way to fix this problem.

Cheers

On my planned 3.0 MFI engine im using large port SC heads 39mm, as this is a mainly road car low end is important, do you think the 39mm port is sufficient? What should I open the exhaust upto? 37mm? Im using DC40 cams

Some good info here about stack boring

http://forums.pelicanparts.com/porsche-911-technical-forum/306105-mfi-stack-boring.html

Steve

i'm having trouble scoring a 930/52 case
i guess this is the last of the 930 cases that takes the 66mm crank
but if i find another 930 case like an 02 , i guess those would work too, and still be a relatively strong case to work from??

what other good cases are there in the 930/1 to 930/52 range?

Stijn, the case obviously has to be a 3.0L (930 Turbo or Carrera 3.0) case that takes the 6-bolt crank. This is 930/52, 930/02, perhaps others? The flywheel end is recognizably for a 6-bolt crank..kinda like this
http://forums.pelicanparts.com/uploa...1174896625.jpg http://forums.pelicanparts.com/uploa...1174896687.jpg

Cheers
Scott

the problem is i can't see em for sale
so i'm putting up a wanted ad

came up blank for a 52
so needing alternatives

if an 02 works, that's great
does anyone know more case/type numbers that work?
might as well list em in this thread for others

i suspect that higher number is better, due to more revisions/strenght improvements... but in the end, an 02 if done well should hold just the same, they had 260 DIN hp out of hte box, and i suspect there's plenty reserve strenth in the case, right?

Physically the 930/52 and 930/02 are the same. The numbers refer to what engine it was--a Carrera 3.0 (930/02) or a 930 Turbo 3.0 (52).

right, and there will be more 02's around , so i'll hunt for one of those

:D

thanks Scott !


edit,

looks like the other 930 cases are of no use

930-10, 930-20, 930-25 have a housing bore of 65 mm dia and the mainbearings of the crank have 6o mm dia

so the old cranks won't fit in those...

Techincally couldn't you build a 959 out a 930? (with the proper case). Correct me if I'm wrong but you could take a 930, use a short stroke crank, calculate the compression ratio and order the right pistons to achieve 8.3:1 compression (stock 959, though personally I'd be more comfortable closer to 8:1), and twin turbo it, right? The hard part to mimic is the sequential turbos (one big, one small).
Btw, is Motronic injection good for twin turbo? I've seen it done, but is there a better injection (not EFI)?

No. The 959 had 4 valve, water cooled heads, to start. Then there are the myriad other differences. You could mimic bore and stroke, CR, etc. but it wouldn't even be close.

i was refering to bore, stroke, and cr. it would take 962 (or 956?) heads to come even close. obiously you would have a whore part motor to even be able to compare.

But imagine a 2.8 twin turbo...what injection system would any of you use?

Cool; now I see. I'd use any one of number of the EFI systems on the market today.

Are there anyone that could manage a sequential twin turbo system?

it might be possible to build one using solenoids to turn a diverter valve (basically have the exaust split into a fork and have a valve blocking the pipe going to the larger turbo) and sensors coming from the wastegate. anyone know of the porsche design?

someone ask wayne if he knows about the seq. turbos like in his 959. maybe some part diagrams?...

Skip the sequential stuff. Leave it to the manufacture to over complicate the situation. Order the properly sized twins and tune it right. it will be better all around.

Can you offset grind a 70.4 crank to 66-67mm? Maybe offset grind it to a smaller rod journal using the Honda 1.8in rod bearing.

henry, do you think the 66mm 2.0/2.2 crank can handle upwards of 400hp? Shouldn't rebuilding a 3.0 turbo with a 66mm crank and special ordered pistons(7.5CR?) be possible (stock, as in no mods other than crank and pistons...maybe cam) without any complications?

Brett

My understanding is that the 70.4 crank is basically an offset grind from the 66. So you'd have just that much less to work with. Maybe if you went to a smaller journal you could do it. 57mm to 52mm to 45.7/1.8". 52-4.4=47.6=doable?

McInt - the factory reported 620 hp from the 66mm crank in the 1983 2.7L race turbo motor. And 480 from the '74 2.1. Of course, was that the then old and out of regular production forged counterweighted 66mm crank we would purchase used out of a production engine, or something special?

The 66mm crank was reputedly stronger because of more overlap of the rod/crank journal circles. Didn't stop the factory from increasing stroke and power, though.

Walt Fricke

Wow! Do you have any links to more info on the '83 2.7 turbo motor (specifications).

Not right at hand. That information came from my well thumbed Anderson's engine specs table. He gives bore, stroke, some cam info, port and valve size, boost, and peak torque/hp and rpms for same. There are a variety of books setting out various details on the factory racing turbos. In addition to Bruce, Frere has some information. So does Ludvigsen. Aichele only has a little. Starkey's 930 to 935 has a fair amount of information. Doubtless there are others not in my library. None of these authors set out to help gearheads make their own mega hp turbos in their backyards, though. They are more chronicalers of Porsche racing history.

When I thought I would like to make a 2.1L turbo I looked into this stuff. Fascinating, but my wife put her foot down. Too much learning by breaking and blowing up, she said. She was probably right. So I set off to build a SS 2.8. I've been moving slowly. However, for the 2.1 project I never thought the crank would be a problem. They seem pretty stout. I know of a couple of 70.4 cranks which have broken in mag case 2.7s. And the factory had issues with the long stroke 2.8 RSR and its cranks, decreasing rod bearing width and increasing the journal fillet radii among other things in order to beef them up (per the authors).

Everybody who has followed this discussion recognizes the practical advantages of being able to use an SC crank if it could be offset ground to a 66mm throw and live. But this isn't really a discussion about turbos. There is a whole other forum for that. You might want to snoop around there.

Walt Fricke

The crank can easily handle a number like 400 horse power. We built a 2.5 turbo some 10 years ago that made 375 without breathing hard and never had a crank issue. The engine was disassembled after track 60 hr. and showed little or no abnormal wear. If you are looking to build something really trick, grind the rod journals on the 2.2 (66 mm) crank the except 3.0 rods. When you grind the crank properly, you can get a larger radius fillet that will greatly increase the crank rigidity. Knife edge it and it gets almost as light as a non counter weighted crank.
At this point you can install the GT3R Pankl titanium rods [130 mm center to center length] and use a standard piston as you will have restored a the standard dimension to the crank and rod combination. In a 2.5 you use a 90 mm RS piston to get 7.6:1 @ .060 deck.
With a 95mm 8.5 CIS piston (78-79 SC) you get the same CR .7.6:1 @ .060 deck.

For those of you ready to try this modification we have the crank and rods in stock ready to go. Crank is knife edged, oiling mod, GT3R journal mod and heat treated (ion-plasma nitride). Pankls are still in the box. We even have the factory GT3R rod bearings in stock.