67 911s Engine: Carbs to MFI
 

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

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

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.

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.

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

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.

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.

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.

Good point Jon, missed that one.

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

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.

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

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

carb it
 

Run 46mm Webers with 36 mm venturi.

ty faapgar

EFI/ITBs a consideration?

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.

carbs are cool too!

Love how the OP talks about wanting MFI, and everyone brings up carbs.....http://forums.pelicanparts.com/suppo...s/a_frusty.gifhttp://forums.pelicanparts.com/suppo...eys/spankA.gifhttp://forums.pelicanparts.com/suppo...leys/smash.gif

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

At the end of the day its a classic case of cost vs benefits. But I still daydream of MFI on that car. I have time to make a final decision. I'm just getting opinions from diff folks. Who knows? Maybe I'll just strap on JATO packs to give it that EFI/MFI feel coming out of a corner.

Your 100% right Al. Boy sometimes I wish I could just plug in a laptop to the MFI pump!

Mark.....I might have something for you in a year or so.

regards,
al

Carbs vs MFI

Today I'm thinking MFI.

It can be lots of fun..........

http://forums.pelicanparts.com/uploa...1515868212.jpg

wow...looking good, mark.

High throttle body injectors, yea!http://forums.pelicanparts.com/support/smileys/clap.gif

Mark, how did you mount the pump, one would typically weld studs to the case.

Well I forgot about the early case's not having the MFI mount studs. That makes it a little more money to have the case modified. I've never had it done and it seems it would be $$$$. Maybe not worth the hassle.
The engine in my photo is a 76 turbo case so has the mount.

Ruh Roh, Mark.... approx how much to have a MFI perch installed on my 67s case? More or less than a thousand bucks?

@Mark, if that's an early turbo case... is that a 2.8 liter special engine (faapgar special) w the 66mm crank, the engine Porsche never made?

Are your heads drilled for MFI injectors? You can run ITB EFI with MFI stacks. This utilizes your existing parts stash. Provides the best of both worlds and you don't have to modify the case to add injection pump mount.

Thus it begins.

Ollie's can do the MFI perch mod. I don't remember what the cost is.

The Turbo case engine I posted is a 66mm X 100mm, so a 3.1 liter short stroke.

decisions, decisions

Do the MFI or you will just regret not doing it in the future. SmileWavy

Can always be pulled and sold if you don't like it.

@ eastbay, so I'm told. Hmmmmm.

Question for the team: beyond the modifications and costs the OP would require, is it accurate to portray MFI as being difficult to live with once installed? My frame of reference is all Alfa Romeo based, having had a GTV equipped with their SPICA system for over 30 years. Very similar system, right...developed originally from diesel pump technology, IIRC.

Full disclosure: I think it's very cool, especially on a good looking motor...think MB 300 Gullwing.

The SPICA system is dead reliable, and maybe more so today than when it was new due to the clever people (here in the US) who took the time to understand it and provide information/service to owners. If it's set-up by the book (pump calibrated; linkage adjusted right; timed right with its drive belt; mixture set; healthy electric fuel supply pump, clean filters and good ignition system) then, at least for the Alfa, it's something you can just leave alone. The two common failures are a rack spring in the pump breaks (has happened to me once) and a thermostatic bulb that provides rich to lean modulation for cold starts which can lose it's mojo (mine has thus far been fine). Since the "map" is essentially the shape of the internal space cam, there's not much to futz with.

Is the Bosch/Kugelfischer system less reliable? I do remember reading that 911E's had good driveability but not the best MPG's. Is the system disparaged, like SU carbs were by Chebby mechanics, simply due to lack of understanding, or does it, as installed on a 911 engine, have real reliability issues?

Thanks in advance for some education...John in CT

I too have had Sipca injected Alfa's, The Bosch is just as reliable, arguably maybe even more so than the Spica.
As with both systems there seems to be more support and parts now than 25 years ago.
Rochester FI was what the Chevy guys hated then and love now just like the Porsche guys with the Bosch MFI amd Alfa guys with the Spica, Lucas MFI for the British and Can AM guys. unfamiliarity, tune ability and part cost were their down falls in the day. Now it is cool and appreciated for the better performance than Carbs.
The one real down fall for those that drive a lot, these systems relied on the lead in the gas to lubricate the pistons of the high pressure pump. I do not know the rate of failure, but over time the cars still run great but they start "making oil" as the gas leaks around the pump and gets into the common lubrication oil of the pump and engine. A lot of people's cars handily leak oil at the same rate so no one is the wiser:)

Update: I went with the 40 IDS carbs. Paul Abbot refurbished to like new. They are artwork. Thanks Paul! I still have the MFI equipment and it's for sale. I just reposted at a lower price, complete system for $7000 obo