911 SC engine upgrade. What would you do?
 

Yes I know how to search but I do not want to trawl through 1.000 pages :D

I am hoping to get some pointers as to the different paths to take.

My SC decided yesterday to succumb to the head stud problem. I had planned for this to happen around October, but he had other plans.

So off it is for an engine rework. The engine is just fine, no oil usage to speak off good power, etc....

I am in no need for a race monster. This is a street only car that I enjoy for the looks and the nostalgia.

What would you do to the engine?

Is there an easy way to extract some extra power? Would you go for 964 cams? Would you work on the exhaust side?
Or is it all not worth it ans simply rework to standard.

depends on if you need P&C's and what type you have. then I would break it down into 2 categories, one with new PC's and one with old ones. then I would break it down again as far as what induction system you want to go with. carbs, EFI or CIS,

Old p&c and I do not want carbs. I have no issue with CIS but understand it is limited performance wise.

Make it a 3.2 with stock cams and CIS.

You will be VERY pleased. :) :)

sell it and get a 3.2.

I think that when it comes to Cams, CIS is the limiting factory is it not?

964 Cams, (assume you already have Euro SC Pistons?) have the dizzy rebuilt and re-curved, tweak the CIS a little to get good A/F. Done

I am not going to get a Carrera. i drive a SuperCarrera ;o)

Yes indeed; this is a euro car with 204hp (actually 213 on the dyno)

Can you start from the 3.0 casing to move to a 3.2?

When done are there any evident visual clues?

If money was no object. 98 mm P&C, 964 cams, Carrera crank and rod set. Would make a 3,4 and look stock on the outside.

Moved to #1 spot.

Speak to William Knight!

Change cams, early exhaust and verify throttle linkage is properly adjusted.

Actually put some equal length headers (no heat) on her if you don't drive in winter!

In Belgium, it's never really winter. It's never really summer either.

I did 964 cams and SSIs, hollowed out muffler, heat backdate and A/C removal. My goal was more responsiveness (less weight, more power). Next round, I hope to go with ITBs and electronic injection / ignition for the same reasons. I'm not ever going to be a racer, but driving my Targa will always be an event.

Will return 6 empty cases to Malmedy this weekend. May pick up 6 full ones!

SC Upgrade
 

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.

If it's an original car with matching numbers, I would put the engine on a shelf and find a 3.2

I did the same thing (keeping the same jugs) but added 10.5:1 pistons and twins plug with carbs cam and portinghttp://forums.pelicanparts.com/suppo...amingdevil.gif

Yes, its called a short stroke 3.2 (done with displacement)
vs the factory long stroke 3.2 (done with different crank)

Do you not recommend a 964 or a DC19 cam with this combo? I would think the bump in displacement would help support a little more cam than stock.

This was the route I am heading with an '80 RoW big port with Mahle 98mm wedge (Max Moritz style) pistons.

+1

Just food for thought and just talking.

My 81 had the head mating ring surface re-faced with a six thousandths of an inch reduction. I did the math, posted calcs here years ago and it was confirmed. CR went from 9.3:1 to 9.5:1. A mini bump. I would be amazed if it was over a couple of HP increase, but don't know.

What I also don't know is if a 9:8:1 to 10:1 mini bump pushes you into a step change scenario that requires all kinds of tending to, given gasoline octane obscurities I know nothing about.

I'd do this.......
 

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

http://forums.pelicanparts.com/uploa...1470953278.jpg

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

regards,
al

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

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
http://forums.pelicanparts.com/uploa...1454537380.jpg


Original factory 3.0RSR piston

http://forums.pelicanparts.com/uploa...1462749750.jpg

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

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

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

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.

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!

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.

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....

Rich,
You've been PM'd

regards,
al

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.

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 :D

X2 to this ^

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

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.

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

Sounds good - do you have a photograph of either?

http://i197.photobucket.com/albums/a...psxpyxfqps.jpg

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?

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)
http://forums.pelicanparts.com/uploa...1438264048.jpg



(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 ):rolleyes:
http://forums.pelicanparts.com/uploa...1456921465.jpg

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)
http://forums.pelicanparts.com/uploa...1456883580.jpg

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.