MFI pump conversion for 2.5 S/T

[matteo68]

I have a 2.4 S (013) MFI pump and as some of you will know, I am embarking on a ‘72 2.5 MFI S/T project.

What I need to know is how did the 2.5 MFI race pump (part no. 911.110.222.70 in the Competition Spares List Nov. ‘71) differ from the 013 pump (did it have a special Bosch code?) Is it just a case of fitting a different space cam or was there a lot more to it than that? I have seen some people such as Eisenbrandt in Germany (www.eisenbrandt.eu) offering conversions of earlier Bosch MFI pumps 001-012 to 2.5 spec plus full test and set-up for c. €4,300 plus shipping of the original pump to them, and also conversion of later code pumps for a €500 surcharge. They cannot fit the cold start lever to pumps with code later than 008 however (which I believe is a 2.2S pump?) and I would be grateful for opinions around this modification.

I am also aware of Gus at Pacific Fuel Injection and his top-notch reputation, but was wondering if anyone has had experience of Eisenbrandt on the board?

Finally are there any other routes to getting the correct spec pump without hunting for the NLA / extremely expensive original part?

Thanks.

[Richy]

I know that Bosch made a space cam for the 2.5 engine for the US IMSA series GT cars that is no longer available . I also know that a 2.4 S pump can be easily calibrated to work with a 2.5

[matteo68]

Thanks! I have seen references to real race MFI pumps having codes 1008, 1058, 1076 and 1077 on Elevenparts.com. Hugh Hodges also kindly sent me this link about a real S/T pump which came up for sale on eBay 5 years ago: https://dirtyoldcars.com/1971-1974-p...pump-for-sale/ which confirms what I thought about the prices of these (heaven knows what one would fetch now if it came up for sale!).

An S/T space cam (if one can be found) in my 013 pump may well be the answer I feel.

[RennTyp]

Matteo, the answer to all your MFI questions is just round the corner from you. Go and see Neil Bainbridge at BSMotorsport in Westcott. He knows more about Bosch MFI than anyone else I’ve come across in the UK and has all the Bosch equipment to produce whatever you want including a bespoke space cam. Worth a trip.

Best,

Philip

[JKH]

engine cam choice and port size and everything comes into play first.. Specs of Build

[gled49]

I know Gus at Pacific FI prefers 2.0 pumps for “race” pumps, because of floating rack. He copies the fuel cams and cuts down the fly weights to extend the fuel curve into the high RPM’s. He built 2 for me over the last 30 yrs, a 3.0 & 3.4 RSR spec, each utilized the cold start solenoid on the pump. Running the big engine on the street now, after retiring the car from racing.

[matteo68]

Thanks for the helpful comments. A call to Gus is definitely next on my to-do list then. Maybe he can supply a converted 2.0 pump and I'll sell my 2.4 pump along with all the other MFI parts which I won't need.

[raspy2point2]

Hi Matteo68-- What configuration 2.5 are you going for? Will it be the traditional 66mm crank and 89mm pistons. Or something like 70.4 crank with 86 or 87mm pistons? One way requires cutting the case for pistons ; the other does not. Chris

[matteo68]

So I spoke to Gus on Monday and his advice following a review of my proposed engine spec was as follows:

“ Hi Matt,
With this specifications you do not need a RSR pump You bee fine with the 013 pump.
RSR pumps are for shortstrokes engines with 906 camshafts. If you like a RSR back governor cover can be installed at you pump for looks.
but the pump will then not have a thermostate for warm up running.

I have also bought a complete but dismantled ‘72 S engine principally for the crankcases and will be selling off all the parts we don’t need for the 2.5l high butterfly MFI twin plug long-stroke engine. We will be using the S camshafts rather than Carrera 6 camshafts however, as the car needs to be reasonably tractable and driveable for fast road use.

Regards,
Gus Pfister

Pacific Fuel Injection, Inc.”

So that very neatly answered my question. I may fit GE40 cams instead of S cams but nothing hotter than that (no GE60, RSR or Carrera 6).

Chris, you will have spotted in my comments to Gus that I am proposing a long-stroke 2.5 (2,494 cc / 86.7 x 70.4), per the type 911/70 engine fitted to 911 230 0955 in ‘72 which my car is to accurately replicate as far as possible.

[gled49]

Gus made the same kind of comment to me about the stroke of the engine matching the pump designated for that stroke. 2.0-2.2 pump for 66mm, or 2.4-2.7-3.0 pump for 70.4. He’s selling himself short, my 3.4 uses a 2.0 pump, modified to RSR specs, with a 74.4 stroke, and runs perfect from take off to 8000, now on the street. I believe all things are possible. MFI Werks in Oregon also produces miracles with mixed/matched components. Remember these pumps were designed originally to follow a recipe of components, comp, cams, ports etc.