Can a 2.4MFI induction modified to 2.7MFI?

[farleyd]

Hi to all, might be buying a 1972 2.4T-MFI... and guess whats in my garage? A 2.7RS-spec to be reassembled, but less the MFI.

Can the 2.4T-MFi whole induction system can be modified - stacks, pump, manifold, etc - to be used on the 2.7RS engine? Making it a true 2.7RS?

Thanks for replying.

[Tim Walsh]

what type type of MFI do you have? Any of them can be modified to run on the 2.7RS. If they're not the S type then you have to have your pump rebuilt and possibly the stacks bored out. It's entirely possible. I'm thinking of doing the same thing.

[Jim Richards]

It's something I'm dreaming about, too. Someday.

[RSBob]

Contact Pacific Fuel Injection in San Francisco, Calif. They are considered one of the best and most knowledgeable (sp). 650 588-8880 ask for Gus Pfister.

[zotman72]

Your T plastic stacks are not going to be capable of being expanded. You have find some S or RS stacks. The pump needs a space cam swap and the throttle bodies need expansion. HTH

[Tyson Schmidt]

Zotman's right. Your plastic T stacks are too small and can't be bored out. It's easier to find earlier magnesium stacks and open those up. The throttle bodies can be enlarged, but it's about $1,000. The pump needs the S/RS space cam, and recalibration.
It can all be done, but it's pricey. Probably close to $2500 all tolled.

[Bobboloo]

To elaborate on what Bill said. The T stacks won't do it but the T throttle bodies and injection pump can be modified. The throttles can be bored out from 30mm to 36mm where they meet the cylinder head. The tops of all the T,E & S throttles are all 38mm so nothing is needed there. The hardest thing to round up are the S stacks. (S and RS stacks are the same in 73') You can find them but they are not cheap. Usually in the $1000 range. I know of a set for $900 if your interested.

Another alternative is an E setup. This is something I'm in the process of building right now. A 2.7MFI E motor. Sort of a detuned RS motor if you will. You can get the E stuff much cheaper. I see stacks go for $100 every now and then. (Just bought a set.)

I'm also curious to see how a 2.7 would run with E stacks, throttles and S cams and injection pump. I would think it would move the torque curve lower at the cost of some top end HP. But might be a blast on the street. Kind of a large rally motor if you will.

One other possibilty would be to bore out some E stacks. S stacks measure 42mm> at the top and taper down to >38mm. E stacks measure 38mm> at the top and taper down to >35mm. If you can take out 1.5mm from the inside of the E stack you would have a stack that would measure 41mm>38mm. Pretty dang close.

By the way there is a complete E setup in the want ads for $850 I think.

But like I say You can get E stacks for $100 and a complete T setup for about $500. The only thing is you have to spend the money changing the pump and boring the throttles so you'd still be looking atleast another $1500 or so and we still haven't talked about cams yet which need to match the MFI setup. (another $350)

But to have a true RS motor you need the S stacks.

[fryardds]

Bobby,

I thought the plastic S/RS stacks from '73' were still available to buy from Porsche. Based on your info. I must be mistaken. You are certainly correct about the difficulty finding 'S' stacks. I finally found a set for our '71' and they were expensive.

[Bobboloo]

Brian,

To be honest. I haven't even checked with Porsche as a source for the 72'/73' plastic S stacks. That's an interesting thought though.

Bobby