...and one more question: What makes up a 3.0 RS engine?

[dd74]

Is it still MFI? Is it similar to the 2.7 MFI engine?

Thank you.

[Early_S_Man]

Yes, MFI, and true 'S' cams ... except aluminum block! High winding engine to 7300 rpm redline, and a 915 transaxle with 7:31 ring & pinion!

[nick-moss]

Hoping I am right on this but I think there is very little in common with 2.7 motor.

Different valve and port sizes, barrels, cases, stud pcd etc etc.

The 3.0 RS motor is more a Turbo 3.0 with MFI

[Bobboloo]

Take a 3.0 Carrera motor and put on a 2.7RS MFI and S cams, MFI pistons and early exhaust. =3.0RS

Bobby

[Bill Verburg]

You would also need the 9.8:1 pistons.

[nick-moss]

and big port heads and larger throttle bodies...........

[Bobboloo]

The 3.0 RS motor had the same ports (39mm intake) as the 3.0 Carrera. According to John Starkey the MFI was the same as the 2.7 RS motor. I would imagine that they probably ported the throttle bodies where they met the heads to 39mm from the 36mm that was on the 2.7mm but who knows. I doubt that Porsche would have built different throttle bodies just for the sake of homologation. They only needed 100 and most were going to be converted to RSR spec anyway. Anyone got a 3.0RS that could tell us?

The 90mm MFI pistons "were" 9.8:1 and were set up for S cams.

Bobby

[Bill Verburg]

Originally posted by Bobboloo
Take a 3.0 Carrera motor and put on a 2.7RS MFI and S cams, MFI pistons and early exhaust. =3.0RS

Bobby

The Carrera 3.0 motor had 8.5:1 pistons, I've owned a C3 for 26 yrs. and kick myself every day for not buying th C3RS that was on the lot next to it.

[Bobboloo]

You're correct Bill. I originally stated that you would need MFI pistons so as to differentiate from the the 8.5:1 CIS pistons. I think the only 90mm Mahle MFI pistons were the 9.8:1 for the 3.0RS and 10.3:1 for the RSR and the SCRS. But I'm not sure.

I picked the 3.0 Carrera as the closest motor since it had the same ports. Is there a difference between the 3.0 Carrera case and the 75 Turbo case? If so I guess the Turbo case would be the one but the Turbo heads have smaller ports.


Damn a C3RS. How much did they want for it?

Bobby

[Bill Verburg]

The early turbos used the same case as the na C3 w/ the small port heads.

This was in Stuttgart in late 76, they had several new C3s, and a used 2.7RS, and a used C3RS mixed in. I went for the new car, 3 liter for the torque, C3 for the civilized behavior. What a mistake

[Bobboloo]

Just imagine if you could buy a ticket on a time machine. You would be the resident MFI guru as opposed to the CIS guru.

Oh well, I think you've got the best of both worlds (torque vs. HP) with your 3.6. Not much to complain about in that package.

Bobby

[Bill Verburg]

I had a 2.4S MFI before that. It never ran right at all revs at the same time. It could be tuned to run right high or low but never both. To this day MFI has left a bad taste in my mouth. CIS was ok untill it got old, then it needed frquent attention. So far I have been very impressed w/ Motronic.

[nick-moss]

There is a '77 3.0 Carrera for sale here in the UK for £4000, accident damaged but apparently driveable