67 911s Engine: Carbs to MFI

JackMan · 01-07-2018, 06:40 AM

I have a rebuilt 1967s engine w the following goodies: 2.2 liter pistons (84mm at 9.8:1 compression), 2.7 liter heads (year unknown) and Solex cams. I do not have carbs for the engine. But I do have a complete 1970-71 911s MFI pump and MFI accoutrements. The engine was rebuilt 10 years ago and put on a shelf.

I have all the machine work and receipts to prove the rebuild by a reputable engine builder.

I plan to send the MFI pump out to be rebuilt and configured to work with my engine/exhaust set up along with twin plugging the engine. The engine will run on pump gas.

I'm curious if I need to replace the cam towers to work with MFI cams or can I modify the cam towers to work with MFI cams.

Your thoughts please.

wj

CASair · 01-07-2018, 10:28 AM

find some weber IDS carbs, that thing will scream

. $$ wise it will be about the same as doing all the mods and rebuilding the MFI pump

356RS · 356RS's Garage

3 things you need to do: 1, Heads must be drilled to fit the MFI injectors; 2, Left cam needs the extended end for the MFI drive belt pulley ; 3, Left cam tower only needs the MFI drive pulley seal kit installed.

Matt Monson · 01-08-2018, 06:40 AM

Quote:

Originally Posted by CASair

find some weber IDS carbs, that thing will scream

. $$ wise it will be about the same as doing all the mods and rebuilding the MFI pump

Other than being correct for a 67S there’s nothing special about IDS carbs. Back then the racecars did not use them. Would be a waste of money on a build like this.

He should do what Mark said. Or sell all the MFI parts to fund a set of PMOs.

Jon B · 01-08-2018, 11:12 AM

Quote:

Originally Posted by 356RS

3 things you need to do: 1, Heads must be drilled to fit the MFI injectors; 2, Left cam needs the extended end for the MFI drive belt pulley ; 3, Left cam tower only needs the MFI drive pulley seal kit installed.

4: Figure out how to mount an MFI pump on a crankcase not designed to support one.

JackMan · 01-08-2018, 11:37 AM

Hmmm, so you guys would all agree to just sell the MFI stuff, buy PMO carbs and live happily ever after? My intention of going MFI wasn't for the HP but to have an MFI car in my fleet. My understanding is the MFI setup makes for make quicker throttle response.

ficke · ficke's Garage

I would use Italian made Weber carbs, You do not need IDS with the fuel dump enricher, with the heads you are running. MFI would be a royal PIA both in money and time for little gain. MFI is cool, is the cool factor worth a stack of Ben Franklins? might be? but it will be a large stack compared to a set 40 IDA's
Carbs will have close to the same throttle response as MFI and are way easier to set up for your engine.
I have had some bad experiences in quality control with PMO's and do not recommend them.

JackMan · 01-09-2018, 05:20 AM

Ficke, how long ago did you use PMOs and on what type of engine/exhaust set up. I have a set of PMOs on my 3.0 75 backdate to 70 and they work awesome. The PMOs were purchased new last year.

356RS · 356RS's Garage

Quote:

Originally Posted by Jon B

4: Figure out how to mount an MFI pump on a crankcase not designed to support one.

Good point Jon, missed that one.

ficke · ficke's Garage

15 years ago, two set of carbs with manufacturing defects in the machining for jet.

JackMan · 01-09-2018, 04:36 PM

So while I have your ears, whats the value of a 1970-71 911s mfi pump and matching stacks/runners and throttle bodies, fuel lines, linkage, air intake shroud, factory mfi manual, and other odds and ends.

I'm thinking carbs would be a better setup.

Matt Monson · 01-09-2018, 05:03 PM

You can buy 3-4 sets of carbs with your mfi Parts.

JackMan · 01-10-2018, 04:10 AM

@Matt, uh.... how many Bitcoins is that? lol, thanks for your input

faapgar · 01-10-2018, 04:27 AM

Run 46mm Webers with 36 mm venturi.

JackMan · 01-10-2018, 04:28 AM

ty faapgar

al lkosmal · 01-10-2018, 08:25 AM

EFI/ITBs a consideration?

JackMan · 01-12-2018, 05:18 AM

I thought about EFI/ITB... but I already have the MFI equipment. I could sell the MFI stuff and get EFI/ITB or Carbs. Carbs are the easiest route, I just bolt them on and away I go. MFI and EFI/ITB just get complicated. I already have hotrods with more HP than sense. I'd love to go with mfi or efi/itb bcs of the throttle response and the sound, plus mfi has a really great cool factor. But for this one I'm just going to go carbs. I can get a complete PMO set up installed for under 5k. Plus, I can adjust carbs myself. MFI and EFI/ITB are black magic.

al lkosmal · 01-12-2018, 08:05 AM

carbs are cool too!

Tippy · 01-12-2018, 09:18 AM

Love how the OP talks about wanting MFI, and everyone brings up carbs.....

al lkosmal · 01-12-2018, 09:44 AM

People, in general, are way more comfortable with carbs, than MFI or the voodoo EFI. Most DIYs or mechanics can work with carbs, but not so much with MFI or EFI.

I like em all, but I personally find it easier to dial in a set of EFI/ITBs with my laptop, than dialing in a set of Webers/PMOs. Much easier to make changes on the fly than changing jets, etc.

That's just me, i could be wrong...........

regards,
al