Sboxin

Hi all, RE: 1992 Porsche 964 Engine Rebuild

Considering we are not looking for high horse power or spending a lot of money, What input would you offer for our project?

Background:
We are in the process of rebuilding a 1992 964 3.6L engine for my son's 1978 911 race car. The car has been running a 3.2L Aase built stock spec engine for about 5 years - it is still very strong and a class winner for 2 years. But, we need more torque and minor HP increase to still be competitive within the NASA PTA Class. Based on our weight HP is limited to 248 RWHP and torque lower than HP.

Findings:
We purchased a used 3.6L and have disassembled it to inspect and measure. The engine had a known leak down test indicating rings - but we also found valve issues in #5 & 6 and #5 rod bearing excess wear. Cylinders are out of tolerance spec also.

Approach:
After discussing the issues with our local Porsche Indi shop and Don at EBS(and researching the Forums) we have decided to:
1. send the cylinders to EBS for refinishing and increase to 102MM ----- DONE
2. send heads to local racing engine machine shop for reconditioning-guides,grind,etc. -----DONE
3. send crankshaft and rods to machine shop for reconditioning and microfinishing ---- DONE
4. send cams to Webcams for regrind to 20/21 - and maybe rockers for recondition -----DONE
5. replace with JE 12.5CR 102MM piston set ----DONE
6. replace with ARP rod bolts ---DONE
7. replace with EBS racing valve springs ---DONE
8. replace head studs ----DONE
9. replace rod, main and IS bearings ----DONE
10. replace flywheel with Patrick 964/915 custom conversion ----DONE
11. replace front pulley with single belt ---- DONE
12. clean and flush case and valve carrier oil passages ----DONE
13. reassemble by Porsche Indi shop --- In process at Don Jackson Enterprises, Phoenix, AZ ---- DONE
14. wiring conversion by Indi shop --- going to use Patrick conversion harness ----- DONE
15. use existing 915 custom built and geared transmission - rebuilt last year - changed 5th to stock 0.82 - DONE
16. use existing custom 1.75" header system ---- DONE
17. use 964 stock intake and DME ---- DME
18. when conversion to 3.6 is complete take car to Steve Wong for dyno custom chips ---- DONE

I will be posting this thread on several different places for feedback.

http://forums.pelicanparts.com/911-e...pproach-2.html


Thank you for your time to respond.

Sincerely,
Roy Turner
Phoenix, AZ

Matt Romanowski

I have a thing against JE pistons, but other than that, I say it looks pretty good. If you want to spend some more money, cams and an aftermarket FI system (like Haltec) will give you more power and tuning options.

winders

Even you are not ging to set the rev limit high, I would get a set of Pauter rods for it. I would do Aase valve springs an Ti retainers too. That way, if you miss a shift, you have some headroom before you do damage to the motor.

Go with Mahle pistons if you don't have to wait a million years.....

Scott

Sboxin

Matt,

Pistons:
Thanks for starting the discussion -- I too was concerned about choosing the JE pistons. A couple of things persuaded us to go this way -- 1. we currently have JE in the 3.2 race engine and they are working very well, and 2. a discussion with EBS convinced us that JE has made improvements to their process to respond to previous Porsche owner concerns.

There are certainly other options that may be better design and quality, but so far JE seems to fit the budget better.

If there is something we are missing here please let us know?

Cams:
We are leaning toward the Webcam 20/21 grind for high lift and low duration to get a little more torque from the 3.6.

Intake:
We like the current economical 964 fuel injection intake system for the lower power numbers we are striving to get from this build. If we decide in the future that we need increased power this will be one of the first places to start upgrading - more air = more power. We discussed both Carbs and ITBs -- but for now we will stay with the existing FI system -- and let Steve Wong work his magic on producing the RWHP numbers we need for race classing.

In addition, I didn't mention that we have been and will continue to use 100 Octane fuel . This provides a lot of tuning flexibility and a side benefit may be cooler heads (so I have been told).

Thanks again for your input,
Regards,

Sboxin

Scott,

Thank you for your input.

Rods:

I too am a little concerned about Porsche stock rods for a race engine --
-- we do plan to keep RPMs low (6500 limit) to help with engine durability.
-- and we do not plan to tune this built engine to more than 248 RWHP.
If we were looking at >7000RPM and 300RWHP then we would definitely put in the better rods -- maybe in a few years when we do another build.

Valve springs:
And you are absolutely correct on valve springs - the current 3.2 engine has AASCO race springs and TI retainers and probably saved my son on at least 2 money shifts when he was still learning to drive this car.

Do you know what the difference is between the Aase/AASCO springs and the EBS developed valve springs??

Thanks again,
Regards,

winders

You want the rods to help save you when you make that money shift. The best valve springs and retainers won't help a bit if you have a rod failure. Relatively speaking, doing the rods now is cheap.

Scott

Sboxin

Scott,

Thanks for a very important piece of information on the money shift and rod durability!
...back to the budget calculator...

Well, the Aussie wants his dinner, so need to stop for now...

Regards,

J richard

Roy,

Im a bit worried your going to blow right through your 248hp ceiling with those mods. Be interesting to see what Geoffery thinks.

If you are doing new pistons and refurbing the cyl too, what about a 3.8 kit?... You could get more torque out of it down low and not run such big cams...

Sboxin

J,

Thank you for your input.

Yes, with the pistons and cams we could easily go over the 248RWHP ceiling.
I talked to Steve Wong and he assured me he could dial in about any HP during the Dyno tune process. The cam we are talking to Webcams about is supposed to be better for torque rather than HP - low duration and high lift.

If we go ahead and build the engine bottom end strong enough - then future adjustments can put the HP higher for different classes or race organizations or more importantly different car platforms.

The other option is to tune for 91 octane fuel -- but I'd rather have the better cooling ability of the 100 octane fuel. Please, someone correct me if we are not correct about this better head cooling issue?

Thanks again,
Regards,

Matt Romanowski

Octane doesn't cool anything. It's a measure of resistance to detonation.

Something to think about - some motors when detuned just lay down at a certain RPM level. It makes them weird to drive.

Larry Herman

You will go right past your 248 RWHP limit with any mods at all. My RSA had 265 RWHP with a stock motor, re-timed stock cams, headers and a chip. If you don't want to up the HP, I like the idea of puting your money into stronger rods, pistons, valve springs etc, as this will give you a good base motor on which you can mod up later if you decide to.

Veloce Raptor

Actually, on a very hot day, a higher octane fuel will help cool the cylinder heads...

J richard

Roy,

Matt aluded to the issue I was trying to get at. With the cams and higher comp you will be making more power which will require you to cap it to the 248hp with fuel and timing limiting (which is just about all you can do with a chip, I don't think the resonance tuning is mappable) I wonder about the driveability. If you had a stock motor that put out the 248 "naturally" then it would be more flexible in my mind. Granted I've never had to restrict an engine, I don't know if a restrictor is a better means that keeps the driveability. I've built torquer motors but it helps to have more displacement/longer stroke to start. (iirc at 102mm I think you are getting close to a 3.8 bore anyway)

Anyway I'll see if I have any old dumps on my 3.6 cars I think they match larry's if not more with stock internals. I wonder if you talked to geoffery if a reinforced stock bottom end with long tube headders and MOTEC might be the best most flexible and in the long run cheapest bang for the buck...just some thoughts, tough to make LESS power!

Matt Romanowski

There's lots of ways to make less power. Only a few that keep the motor happy and easy to drive.

Sboxin

Thank you for your responses---

Power:
One thing that lead us to the choices of pistons and cams is the HP/Tq numbers we received from a fellow competitor - John D with a 3.6 in a 1974 911. His numbers were 226RWHP and about 216 RW-FtLbs torque. So...we thought we were trying to gain 22 RWHP and 20 LbFt torque with upgraded compression and cam timing.

Today, we are changing our thinking to using the 11.5CR pistons and still doing the 102MM upgrade to result in the 3.8L cylinders.
EDIT: After further discussions with our local Porsche specialist DJ, and Don at EBS we are now staying with the 12.5CR pistons.

Jim,

Thank you, and if its not too much trouble, it would be helpful to see your 3.6 dyno graphs if you can find them.

We are learning a lot during this precess -- and that is one of my son's goals...learn about Porsche engines (I think I have created a lifelong Porsche Enthusiast).

Thanks again,
Regards,
Roy T