73.5 7R case/ heads?

[raspy2point2]

Can I use my CIS heads off my 911T case for MFI or carbs. What has to be done to the CIS injection ports or do I have to sell the Heads and get other heads that work with either MFI or carbs ? Thanks Chris Early S reg.#205/ R-Gruppe#144

[YTNUKLR]

The '73.5 CIS injector port in the head might work for an MFI injector, but for some reason I think the thread is different, so you'll have to tap/drill it out (I think). I also don't remember if the '73.5 CIS injector port is aiming right at the valve. MFI injectors do.

Otherwise, they will work. Likely need some porting unless you are making an MFI 2.4T.

Cheers
Scott

[Bobboloo]

MFI heads have the injector in the head. It screws in.

CIS heads have the injector mounted in the intake runner. A notch is in the intake port of the head for clearance.

To mount MFI injectors in CIS heads you need to weld up the notch and then tap the heads for injectors.

If your CIS heads need rebuilding it would be cheaper to find a set of MFI heads for cores to start with.


If you go with carbs then no machining is necessary. Just find a set of carb manifolds and mount them.

[Eric911S]

Hello: I have some MFI heads just tell me what you want to use them on. Thanks Eric

[raspy2point2]

Thanks all for the replies-- As I bought a long block; it turns out that the heads had a valve job and new valve guides so I was wondering could they be useful on my hot rod 2.8 liter twin plug engine I want to build. My attention went to the intake flanges because the CIS injector ports are located within the flange of the intake manifold slightly on the side of the two post flange and I thought that might be a problem if I wanted to use these heads for carbs or MFI as the flange is not the usual all flat mating surface for the intake maniflod to sit on. I have heard of welding up unused holes on heads before but I am new to engine rebuilding to different configurations. Thanks Chris Early S Reg #205 R- Grouppe #144

[Eric911S]

Hello: You will have to take the engine apart for the second plug hole. I would have the heads welded at the port then port to suit your engine plans. They will work just fine for carbs but you will have to drill and tap for injectors if you want to use stock MFI stuff. This is not difficult but may cost you more than getting MFI heads and going through them. Hope this helps. Thanks Eric

[YTNUKLR]

Bobby, the 73.5 911T CIS has heads that have the injector mounted directly in the head, like MFI. The later 2.7CIS and 3.0CIS cars do have injectors in the intake runners, on that point I agree.

If you do indeed have a notch in the intake port, it needs to be welded up and blended for use with carbs or MFI.

If anyone can resize, I have a photo of a 3.0 CIS head that has been ported and tapped to run MFI...

Cheers
Scott

[Bobboloo]

Didn't know that Scott. Since I've never owned a 2.4CIS motor that might explain why.

Chris,

Since your building a 2.8 motor then you'll want to port your heads to atleast 36mm in. and 35mm ex. (S spec) You'll also need to fly cut the heads so that the 92mm piston will clear. When you decide whether to go with Carbs or MFI just let the machine shop know and they can prep the heads for either application.

[Eric911S]

Hello: Some of the new pistons don't need the head chamfered as they have a cut made for the 2.4 heads. Just thought you might want to know. You will need to port those heads at least 38mm intake and 36mm exhaust ports. Thanks Eric

[raspy2point2]

Hi Eric-- The P/C's are the 2003 style Mahle 92mm high compression ones. Are these the ones you are talking about not needing one of the prep for head machining processes for 92mm P/c's ? Fly cutting ? Thanks Chris Early S reg. #144