3.8 RSR Camshafts in a 964 3.6

edbaus · edbaus's Garage

Hi,

I am looking for information on how a set of 3.8 RSR camshafts would perform in a 964 3.6L.

I will be running the stock injection intake, but using an aftermarket computer to drive it.

The only other modifications to the motor would be a racing exhaust.

I do not want a set of cams that are too agressive, and I am using stock 3.6L pistons.

Does anyone have experience with these.

Thanks

Ed

Bill Verburg · Bill Verburg's Garage

you might want to contact Geoffrey Ring @ Racetek Engineering

He is a Motec oem installer w/ a lot of experience w/ different cams in 964/993 engines using Motec engine management

TRE Cup · TRE Cup's Garage

Could not tell you about that combo, but we have installed the 993 Super Sport grind (Dr cams- Dougherty) , and been very pleased with the results. They added about 25 hp midrange on stock injection

edbaus · edbaus's Garage

the 993 super sport grind is actually the grind I thought I was buying. After getting the cams and contacting Web, I found that they are actually the 993 rsr.

Thanks

Ed

aigel · aigel's Garage

Which ones require "solid" lifters (back to adjusting valves)?

George

TRE Cup · TRE Cup's Garage

we used the adjustable lifters with these cams- Any time you expect to see hard track use, we recommend this change over.

ted · ted's Garage

Quote:

Originally Posted by TRE Cup

Could not tell you about that combo, but we have installed the 993 Super Sport grind (Dr cams- Dougherty) , and been very pleased with the results. They added about 25 hp midrange on stock injection

Dr Cams supplied some Super Cup cams for my non VR 993 3.6.
Otherise stock (windage work on pistons and case) with headers.
With a custom chip it made 306rwhp on 100 octane.
Cam raises the power band, better with short gears too.
Very streetable still.

axl911 · axl911's Garage

Does the cam cause emission problem?

KNIGHTRACE · KNIGHTRACE's Garage

you can meet emissions with the 993 super sport but not the RSR I don't think the RSR will run on stock single butterfly well enough to drive. Porshe never used an RSR cam in anything but 6 butterfly motors. even the 93 RS street motor was 6 butterfly with large cam but the 92 RS was just a stock single butterfly 964 motor. William Knight

Bill Verburg · Bill Verburg's Garage

Quote:

Originally Posted by KNIGHTRACE

you can meet emissions with the 993 super sport but not the RSR I don't think the RSR will run on stock single butterfly well enough to drive. .... William Knight

probably depends on where you live and get tested, the SS is a little more lumpy than RS which barely passes in some places

For Sure RSR needs ITBs and elevated idle speed

Quote:

Originally Posted by KNIGHTRACE

y.....Porshe never used an RSR cam in anything but 6 butterfly motors. even the 93 RS street motor was 6 butterfly with large cam but the 92 RS was just a stock single butterfly 964 motor. William Knight

true, but the MY93 964RS used the same cams and barndoor air sensor as the other n/a 964s, there was a 964 3.8RSR in '93 that had ITB's and used the same cams as the 993RSR and also a 3.8RS which also had ITBs but used a milder cam

993RS used a hot wire mass air sensor, the 993Cup used the same intake but the DME was modified to run off throttle position and manifold pressure, only the 993RSR had ITb's

Mahler9th · 10-31-2017, 08:31 AM

I am pretty sure my 3.8L used RSR-like cam profiles, and it was a single TB engine. I used a larger-than-stock TB (aftermarket BBK 80mm Mustang 5 liter-style which is for sale by the way), and altered the throttle linkage geometry for more progressive part-throttle opening.

My application was primarily racing, but I did drive the car on the street occasionally. Aftermarket ECU. And yest the idle was lumpy and kind of high for street driving.

I bought a used TWM induction system to change it to ITB, then decided on a different class and changed to more modest cams. Sold the TWM.

If I were looking at ITBs now, I'd use the new At Power units. Free bhp relatively speaking.

KNIGHTRACE · KNIGHTRACE's Garage

I can help, I sell cams and have a complete 3.8 RSR motor if needed. however in my opinion if you put either RSR cam standard or sprint it will not work due to the amount of reversion. glad to help and have some custom cams or ITB kits. William Knight 615.969.4917

hda · 02-02-2021, 11:34 AM

Who could make a chip for a 3.6 with 3.8 RSR camshafts?

winders · 02-02-2021, 11:55 AM

Motronic? What is the induction setup? ITBs? Stock?

hda · 02-02-2021, 12:06 PM

Quote:

Originally Posted by winders

Motronic? What is the induction setup? ITBs? Stock?

Stock ECU and stock intake with MAF.

winders · 02-02-2021, 12:25 PM

You need ITBs to run the 3.8 RSR cams......

hda · 02-02-2021, 12:49 PM

Quote:

Originally Posted by winders

You need ITBs to run the 3.8 RSR cams......

I don't think the 3.8 RSR had ITBs.

winders · 02-02-2021, 01:39 PM

Quote:

Originally Posted by hda

I don't think the 3.8 RSR had ITBs.

Here is a photo of an 3.8 RSR sprint engine from Porsche:

You can see the bell crank with rods to the ITBs....

Mahler9th · 02-02-2021, 02:02 PM

I am pretty sure that the engine in that photo used to belong to one of my old friends that co-owned Rennwerks. I don't think all parts and specs were factory at the time the photo was taken.

Those guys at RW got a third overall at Daytona at the beginning of their second season. One of the two co-owners/gentlemen drivers is still racing after all these years... likely the only one in the NASA paddock with a Daytona Rolex at many local events.

As I stated in post #11, I had 3.8 rsr-like cam profiles for a number of years-- with a single TB. I kluged up an 80 BBK TB. Not optimal but it worked fine-- engine made power. I had and still have aftermarket EFI (Haltech).

Depending on design goals, what would be likely more optimal for many would be ITB's, and as I stated in post #11, I'd go with the AT Power units if I were gonna buy ITB's today.

Some, if not all 3.8 rsr specs can be found in Bruce Anderson's book.

For chip work, Steve Wong may be a good place to start. And/or Steve Weiner. They may have answers or be pathways to answers. I still have a picture of the two of them and Matt Monson taken at an RR event.

Was nice to visit with all three in person.

winders · 02-02-2021, 02:28 PM

No, that is an Alex Job Racing engine . The point of the photo is to show the bell crank and the rods going from the bell crank to each set of ITBs.

No one, in good conscience, should suggest that you can get good drivability with a 3.8 RSR cam on a single throttle body setup. The cam in my old 3.6L race engine with a single throttle body setup was not as radical as a 3.8 RSR cam and that thing was useless below 2000 RPM.