Chris 911

Hi,
have searched many threads related to 3.8 builds, but look for some updated input. I have tried to reach out to many of the vendors without much luck (Rothsport doesn’t reply at all after three attempts, Colin at 9m responded initially, but after several attempts, no answers since April on either phone or e-mail).

The engine came out of the car to start the build in November. I had already purchased the Mahle 3.8 cylinder and piston set, and have been looking to see what would be a great combination of parts for my engine. I am looking for a good road car, not a track car, but where it has plenty of extra torque and some extra hp (I have a GT4RS that serves as a track tool, so this will be more for spirited road / touring).

Based on Colin’s recommendation, I have purchased the RS Varioram intake, and have been looking at what to combine it with in terms of cams and engine management. Since I need to change the engine management to either a 993RS Motronic and find the wiring harness for it, or opt for Motec, I was leaning towards Motec. Who can supply the wiring and Motec for these cars? I have looked at Rasant, but heard that the quality may be so-so, and the price is high (believe they were out of business for a while, but back now I think).

For cams, a friend of mine with a 993 varioram has opted for the FVD Supersport cams, which is supposedly between the RS and RSR cams. I was thinking maybe the 993 RS cams would be a good fit with the RS varioram and 3.8 kit.

For rods I bought some second hand 993 rods, as they are much lighter than the 964 rods, but anyone have input on what difference it would be between them and Carillos?

I am also looking at what other parts to combine it with, so suggestions / experiences in this are appreciated, and of course from vendors who actually want to sell/respond to inquiries

revolve40

Are you building the motor yourself? I sent my motor to Patrick Motorsports in Phoenix in about a year ago. Nine months later and I'm stoked on the result. I stuck with Motronic and a custom Steve Wong chip. Motec + intake will get you another 20 whp or so but also will cost another $20k. I ended up with 280 whp (using 993ss cams) and am very happy.

Bill Verburg

964 and 993 parts don't mix well at the crankshaft level.

if you are starting w/ a 964 engine, stick w/ 964 crank, rods and pistons, 993 rods do not mate w/ 964 crank, pistons must be designed for the rods used etc.

vram is nice for a stree build as it raises midrange torque, 3.8 102mm cylinders (w/ 109mm bases) are great for similar reason, they build torque everywhere.

ss cams w/ Motec would be the way to go .993 hot film or MAP intake monitoring would also be the way to go w/ ITBs as icing on the cake

Chris 911

Not building it myself (would love to do it, but no time I’m afraid), but have a great engine builder. He has built many engines, but leave it up to me to source the part and select the combination. In hindsight it might have been better finding a shop that would do it according to a known recipe that they are used to.

Some say the intake makes the most difference, others the engine management, they’re both expensive. I think the combination of the other parts is as important to get a good build. Buying the motronic unit and the right chip is not cheap either, and then it’s a question of what combination of overall parts I need for that

Chris 911

Thanks Bill,
Do you have any experience with Carillo rods? Colin suggested the 993 rods with different bearing? And it is a lot lighter than the 964s.

you mention ITB, but does that make sense with the Varioram intake?

Anyone know of a source of Motec and wiring for a 964?

revolve40

They go hand in hand.

I know I'm not Bill, but my motor was built with Carillo rods. No issues. I did machine-fit Mahle P's & C's. Colin at 9m was building custom harnesses for Motec as recently as last year, but seems like you're not getting the customer service you're looking for there. Rasant is the only other option I know that might have some plug-and-play options.

jeff33702

Isn't Rasant done closed?

revolve40

They reopened recently.

spartansix

I would steer clear of ITBs and engine management unless you are having someone like Rothsport or 9m do the whole engine build (and ideally get it running in your car). I've seen too many cars with issue after issue with these systems where the owner ends up spending 20k just trying to get the thing to run right. You can build a fun, reliable motor using 3.8 P&C, Varioram, some slightly hotter cams, lightweight (or mid-weight) flywheel, a high flow cat and primary muffler delete running motronic with a chip, and I'd rather have a reliable car with 20-30hp less than a high strung one with a bit more top end power. It's often cheaper and easier to get the same overall performance gain by making the car lighter, or even better, by regearing the transmission.

Peteinjp

I have Colin’s 3.8 kit and will finally be building it this winter. I suggest you read all of his posts on this forum regarding intake and exhausts because he is the only source of info on the forum they can back it up with actual data. For example, he does not fall into the typical idea that of bigger valves are always better better because as an engineer, he’s also interested in not only flow but velocity. If you read his posts you’ll find that he has tested ITB’s, exhaust etc vs stock and found no gains as even some losses ( street driven engines.) He divides engines into 2 categories based basically on camshaft choice/ rev range usage. I have not found any advice on his part of ITB’s that also have the resonance flap so I may consider that in the future. For now I’m going with stock intake and exhaust and seeing what I can do with internals and managment just to keep it simple and easier to tune. The intake and exhaust are easily changed later.


My said includes a set of 964 heads that Colin ported, 9m Schrick cams, 9m arrow rods, and Mahle piston/cylinders, along with Motec engine management.

I went with Colin’s stuff because the motec comes loaded with a basic map for that particular setup which represents a great value when it come time to tune. It will require some fine tuning but should be close enough off the bat to get things started. Otherwise I would considered a kit from FVD as they can provide tuning for their setups as well while still using motronic.

Rothsport has never responded to my emails or phone messages despite the fact that I own an engine built by them. Colin can be hard to reach by email (particularly when being peppered with questions) but is very responsive on the phone. FVD in Germany has excellent customer service.

As mention above putting money towards a re-gear can really make a huge difference. I’d put money towards that annd stay 3.6 if you can’t swing both.

Pete

targa72e

I can give some short answers to questions.
993 rods will not work with 964 crankshaft as the rod journals on 993 are narrower. You could use 993 crank and rods in 964 case but you cant mix parts.Are your 3.8 Pistons for 964 or 993? You can get aftermarket rods with 964 crank end and 993 pistons end.
If you are not planning on 7K+ power ITBS are not the solution. VarioRam intake is about as good as you can get for sub 7K power.
You did not mention exhaust and muffler. This is just as important at making or killing power as all the rest.
993 SS cams are about as aggressive as you can got with stock fuel injection components.

good luck on build

john

Chris 911

Thanks for good inputs here

The piston and cylinder set is the Mahle 993 11.4:1 slip in set.
Plan to add:
- 993 RS Varioram intake (bought)
- RS clutch and flywheel, as that really changes the feel of the engine (had that in my previous 964 years ago).
- Sport spring set with titanium retainers.
- Heads: Any suggestions?. Colin recommended fitting the 993 valves and 50mm intake to the current 964 heads. Would it make sense to opt for a complete 993 RS head setup?
- Rods - uncertain, hence the question. Given the P/C set, Colin mentioned that he has the 9M rods that work with the cylinder set with the 964 crank. Another solution would be to opt for the GT3 crank, but would still need a rod that would fit the 993 cylinder.
- Cams: It seems as if the SS cams are the way to go here by the feedback.
- Motec, as Pete says, the package from Colin is tried and tested, so this is why I also tried to buy it from him (have found it strange that there has been no response, even on many phone calls and messages to his office).
The exhaust is currently a G-pipe setup with the rest stock. Plan to add a sport cat, but not change the rest. For the use of this car, that will most likely be the best setup. I like the sound of it and don´t believe you can get much more from other exhausts without too much compromise (have another 964 with a full Cargraphic exhaust, and find the sound to be better / deeper with G-pipe).

I´ll try and contact FVD as well to see what input they will give (I´m located in Europe)

Seems to be a vacuum in the market if it´s only 9M and Rasant that offers the harness and Motec for 964s... hmmm.

964George

A friend of mine on here had his 964 engine rebuilt as a 3.8 by RSR
He retained Motronic and the 964 crank but upgraded to a trick oil pump by Auto Verdi
He's very happy with the result, car is discussed in detail in this video.


Regarding engine management, I'm looking at modernizing my 3.6 with a kit from Pie Performance

No affiliation with any of these companies, just passing details on.

s65e90

I'm doing a similar build and gather parts now. I'm not sure the juice is worth the squeeze going from 3.6 to 3.8. Nevertheless, my recipe is:

1. Noonan billet block
2. Billet Extreme Cylinder heads
3. Custom cams
4. Pauter or Pankle rods (still looking at others)
5. Mahle jugs/pistons, would like to spec a piston to keep it just under 12.1 when done.
6. PMO 50mm carbs (simple, works and what I have now, may change to stacks w/ FI later)
7. Stock crank or go 993. Our cranks are awesome, but I'd like to run a regular serp belt and not sure I wanna with the 964 setup.

Some other little odds/ends should make a nice 300+ street car that can take lots of beating on it and be reliable.

Bill Verburg

Except for PMO, nice!

but the weak link in your build is the crank

go for late GT3 crank and GT3 oil pump

you'll have a 4.0 if you sue the GT3 4.0 crank and 102x109mm Mahles cylinders