911 SC engine upgrade. What would you do?

[al lkosmal]

i'd do this..............



https://www.youtube.com/watch?v=8hMuR3DUArM

regards,
al

Al Kosmal
the x-faktory
koz@x-faktory.com
RGruppe #669
X-Faktory - Home

[wayner]

Speaking for myself, I don't know where the threshold is but from what I understand the main safety net for compression is twin plug heads.

When I was able to look at original high compresion RSR pistons it was pretty obvious that he high compression dome pretty much blocked off half the head area from seeing the spark plug.

On the other hand, the wedge shaped Max Moritz style pistons keep the flame path open with the high part of the piston located at the far end instead of in the middle. Obviously not as much compression but more than stock, yet still a margin for detonation safety that a domed piston does not have without the need for twin plug.

Max style JE piston



Original factory 3.0RSR piston

[Vereeken]

Originally Posted by Spumato

If you are finding yourself in a very similar boat as I was in 2 years ago when my numbers matching engine in my MY74 911 coupe suffered with pulled head studs, then I would follow the same course of action as I underwent:

Obtain low mileage SC for rebuild
Add ARP Head Studs
Add ARP Rod Bolts
Add Titanium Valve Springs
Use High-Flow CIS
Add Carrera Chain Tensioner upgrade
Add real 964 Cams

The 3.2L engine will have more HP, and more top-end, but lacks the peppy punch you will find in a 3.0L. Add that you will probably want a Motronic engine management system on the 3.2L that will add better fuel reliability, while adding complexity.

The 3.0L from an SC 911, when you use an early 70's era SSI setup that goes into a dual in dual out muffler, coupled with a short ring and pinion set 915, and you have one hell of a ride! Trust me as I know firsthand.

What does the 964 cam bring to the table on its own?

[wayner]

The ability to breath better if CIS wasn't in the way???

[gt3racerich]

Originally Posted by al lkosmal

i'd do this..............



https://www.youtube.com/watch?v=8hMuR3DUArM

regards,
al

Al Kosmal
the x-faktory
koz@x-faktory.com
RGruppe #669
X-Faktory - Home

Can you tell me more?
I need to do something with my 3.0/3.2
Thanks, Rich

[Vereeken]

Originally Posted by wayner

The ability to breath better if CIS wasn't in the way???

So a 964 Cam on a Stock CIS is pointless?

[Josh D]

Originally Posted by Vereeken

So a 964 Cam on a Stock CIS is pointless?

I don't think it would be pointless on your high compression big port motor. It would likely move the power band up a few hundred RPM and give a bit more peak HP. With the right exhaust, getting the fuel mixture adjusted right and getting the ignition timing optimal, I would think it would be enough you would feel it.

It's really all about the combination and tuning. Having the RoW CIS gives you a leg up on the US spec CIS.

[otto in norway]

Budget scenarios:

On the cheap:
Stock

A little extra cash:
SSI (or similar pre74 style exhaust)

Some extra cash:
SSI, 964 cams

Even some more extra cash:
SSI, 964 cams, 3.2 set

A lot extra:

1 5/8 exhaust headers (with heat optionally)
3.2 crank with rods
3.4 high comp P/C set
PMO intake TBI
Semi agressive cams


Money no object:
Ask your engine builder to do whatever he can...

Good luck!

[Jcslocum]

Originally Posted by Steve@Rennsport

Make it a 3.2 with stock cams and CIS.

You will be VERY pleased.

Listen to Steve, this is what he does. A 3.2 short stroke motor is very fun. Speak to him about compression ratio as well. A bump would be good but if you get too high, you will need to twin plug it.

Good luck and make sure to let us know what you decide to do.

[will hung]

Originally Posted by Vereeken

So a 964 Cam on a Stock CIS is pointless?

No. But it will shift your power band up a little higher.

My car is a 79 ROW car with a 1981 ROW car's P&C's. The previous owner also added 964 cams. It made really nice power, but it had a noticeable step up in power from 3500 rpm to redline. I added SSI's and the mid-range torque was significantly improved, the car pulls from idle to redline now.

[Vereeken]

Originally Posted by will hung

No. But it will shift your power band up a little higher.

My car is a 79 ROW car with a 1981 ROW car's P&C's. The previous owner also added 964 cams. It made really nice power, but it had a noticeable step up in power from 3500 rpm to redline. I added SSI's and the mid-range torque was significantly improved, the car pulls from idle to redline now.

I do not want to shift power band up higher. Mid-range is what you need me thinks.

The 3.2 on the stock engine case still sounds good.

I have a very original SC with auto-heat (that works!) SSI is a nifty piece of kit but :
a it hangs under the car so only a mechanic gets to enjoy it
b it would mean killing off the auto-heat....

[al lkosmal]

Originally Posted by gt3racerich

Can you tell me more?
I need to do something with my 3.0/3.2
Thanks, Rich

Rich,
You've been PM'd

regards,
al

[arrowSC]

I have an 81 SC (204bhp) with SSIs, and they were one of the first and best mods I did. To address your two concerns:
a. I enjoy the greater torque, response and sound.
b. mine still has autoheat. SSI are free- flowing heat exchangers in the style of the earlier factory exhaust, not race-style headers, so cabin heat is unaffected. Actually not quite true, mine made MORE heat with SSIs.

Originally Posted by Vereeken

I have a very original SC with auto-heat (that works!) SSI is a nifty piece of kit but :
a it hangs under the car so only a mechanic gets to enjoy it
b it would mean killing off the auto-heat....

[Pazuzu]

I'll add a data point on the other end of the engine...

All aluminum clutch. Not just the aluminum Sachs kit, but aluminum (Vidanza) or RSR flywheel as well.
Takes a few days to get used to, but makes the engine revvy in a "my loins tingle" kinda way

[Josh D]

Originally Posted by arrowSC

I have an 81 SC (204bhp) with SSIs, and they were one of the first and best mods I did. To address your two concerns:
a. I enjoy the greater torque, response and sound.
b. mine still has autoheat. SSI are free- flowing heat exchangers in the style of the earlier factory exhaust, not race-style headers, so cabin heat is unaffected. Actually not quite true, mine made MORE heat with SSIs.

X2 to this ^

SSI or even '74 and earlier regular steel heat exchangers work fine with autoheat.

[chris_seven]

Originally Posted by Spumato

Use High-Flow CIS

This is an exercise we are looking at right now and this thread is very interesting.

I would like to understand more about a high flow CIS and what this implies.

If you look back through old articles you will find that Max Moritz in Germany developed a 3.0SC with 180BHP to produce 215BHP.

I know that they fitted their own design of pistons manufactured by Mahle to increase compression and I believe that they also fitted a Micro Dynamics Rising Rate Pressure Regulator but I have not found many other details.

We are building 2 Rally Cars both which will use CIS and we are hoping to obtain about 235 BHP.

We will start with pistons which we will have manufactured at Omega and then experiment with rising rate pressure regs as Micro Dynamics no longer have stock of the units they used to make.

Cylinders may be an issue at 98mm but I guess that they can always be made.

If we have enough budget then Mahle Motorsport seem to make these parts already.

I have read that some of the 928 Fuel distributors have been modified to improve fuel delivery at the top end but without affecting the idle/bottom end but I can't find out how this is done and haven't spent enough time trying to understand the system until now.

Any ideas would be helpful.

Cylinders are more interesting and 98mm is a good idea but I think we will use a rod that uses a 3.0 size pin rather than a 3.2 style rod.

I think that cams are interesting and it seems that there are some cams that work better than a 964 part but again would be interested in learning more.

[wayner]

JE. And Corrillo pistons at 9.5:1 are Max Moritz style and you can spec higher or lower compression

[chris_seven]

Sounds good - do you have a photograph of either?



These are the 10.5:1 Max Moritz pistons at 98mm for a 3.0 litre.

One article say they have a different pin offset to the pistons for a 3.2 but maybe they meant diameter?

[wayner]

3.0 engines use a shorter stroke crank than a factory 3.2, so pin offsets are different depending on what generation of case you start with

If you go to a larger bore piston though, you can turn the 3.0 into what people call a short stroke 3.2 using displacement instead of stroke, and the pin offset remains the same I think?? (Al can confirm)?.


Those pistons in your picture look exactly like my old 9.5:1 pistons.

At 10.5:1 the new ones that I have from the same manufacturer look like this (but require twin plug)




(For comparison here were my lower compression ones - basically like 10.5 with one side shaved off Max Moritz style, to get a safe 9.5:1 with an open flame path)

My 3.0 was VERY health with these pistons. Seat of pants said well into the 200s, and on the straight aways GT3s passed me a lot slower than I would have expected (yet I went twin plug and 10.5:1 anyway )


For cylinder reference, LN engineering is one source, but you can also get stock 3.0 cylinders bored and re-plated to get up to 3.2. through displacement rather than stoke.

JE and Carillo make their pistons in multiple bore sizes

At 10.5:1, here is a comparison of JE (left) vs Carillo (right)

[will hung]

Originally Posted by Vereeken

I do not want to shift power band up higher. Mid-range is what you need me thinks.

The 3.2 on the stock engine case still sounds good.

I have a very original SC with auto-heat (that works!) SSI is a nifty piece of kit but :
a it hangs under the car so only a mechanic gets to enjoy it
b it would mean killing off the auto-heat....

This is false. SSI's will still provide the heat needed for your auto heat. Auto heat is controlled in your interior. The heat exchangers around your exhaust provide the heat. SSI's provide more heat than the stock exchangers. On cool spring and fall nights, if I'm wearing flip flops and I have the foot well blowers on, I can burn my feet. And with their stainless construction, there is less of a chance of exhaust gases leaking into your interior if your exhaust develops a leak.

Plus, the sound. The sound a 911 makes on SSI's is worth the price of admission alone.

As far as power band. What I was getting at was the combination of 964 cams and SSI's created a broad power band from idle to red line and your rotating assembly is still stock.

If you don't need new P&C's, you will spend way less for a set of 964 cams and SSI's then you will for the short stroke 3.2 conversion. But it's your money.