What Cam on 72 T with Carbs

[Porsche84]

Hi

I am building a 72 engine as stock except the owner wants to go to carbs instead of MFI. What are the recomendations? Stay with MFI? Go to Carbs? What size carbs? Will the MFI cams work with carbs or do we need to change cams?

Thanks

[Steve@Rennsport]

MFI cams work just perfectly with carbureted cars.

If this car came with MFI, I would have everything professionally rebuilt and reinstall that system for maximum value retention as well as for best drivability.

If not, use 40mm Webers and have them rebuilt by Paul @Performancee Oriented.

[Porsche84]

Hi Steve

I'm concerned about making the MFI run well as I have no experience with them. I know people usually have the pump rebuilt. Does anything else need to be rebuilt? Merry Christmas!

[Steve@Rennsport]

Hi Jerry,

The pump should go to Gus at Pacific FI and the throttle bodies should go to Matt Blast at Eurometrix for rebuilding.

Once thats all done, it should run VERY well once the final adjustments are made. Naturally, this is based on an engine in excellent (perfect) condition.

Merry Christmas to you as well!!

[Henry Schmidt]

A 72 911 with matching numbers is an incredibly valuable piece of kit.
If I was advising your customer I would steer him towards originality.
Supertec can do the complete restoration of the MFI system in house.
The Pumps are rebuilt to factory or performance specs and then calibrated by MFI Werks. The throttle bodies are restored to factory specs and appearance in house as well. Because we do both as a set performance upgrades are easily coordinated.
If you elect to convert to carburetors, new PMO 40mm are the best option.
If you have used Webers 40 mm is also the correct size.
If they need rebuilding we offer that service in house as well.
We have a dedicated department (Terry Soloman) who does machining, fitment and flow bench work start to finish making the process efficient and quick.
Carbs and throttle bodies generally turn around in two weeks and pumps happen in 4 to 6 weeks.
Ancillary parts such as cross bars and linkage are plated to match at no extra charge.
We even build custom systems for those individuals looking for something unique.










Our carb colorizing process restore the carburetors to early factory appearance if desired

[Porsche84]

Thanks Henry, your photos are great. I'll be coming to you (again) for all of my gaskets etc. The customer is watching this thread, we'll see what he says about the MFI. My original concern was that I might be able to make them work correctly. Pelican members like you and Steve certainly can get me thru that.

Merry Christmas

Jerry

[Porsche84]

Here are photos of what I have

[al lkosmal]

Jerry,
You are getting good, professional advice from the best in the biz, so you can take mine with a grain a a salt, but another good alternative is to move forward with the carbs for everyday driver, ease of set-up/maintenance (more people can work/tune carbs than MFI) and then have the MFI system rebuilt to spec and put on the shelf, to retain the originality and value of a nice, old long-hood.

regards,
al

[Matt Monson]

With all the MFI parts still there it would be a no brainer for me. Rebuild the MFI with some performance tweaks. Forget the carbs.

[Henry Schmidt]

Back to the original question: What cams to use.
On a lower compression engine with small ports I like the Solex cams.
For my money the Solex is the best all around factory cams for early Porsche engines.
Two things to consider: Valve pockets, the Solex cams will challenge to valve to piston clearance on "T" pistons.
Next, the MFI pump. The Solex cams seem to work their best with an "E" space cam.
If you're rebuilding the pump, changing the space cam is easy.

If the choice is to change to carburetors I also recommend the Solex cam.

NOTE: There are some misinformed people out there that believe the Solex cam is the same as the "E" cam but that myth is perpetuated by a misprint in a Porsche spec book some 40 years ago.