MFI 101: 2.4 MFI on a 2.8

[rs911t]

So, I have a 2.4T converted to 2.8S years back. That is, 2.8 P&C, S cams, S heads (36mm intakes) with Weber 40s. I acquired a 2.4S MFI system with all the bits and pieces. My question is this:

Can the 2.4 pump be adjusted to run rich enough for the added displacement?

Love to hear all ya MFI experts chime in.

BTW, this is not a Weber-vs-MFI-vs-EFI thread.

[Tim Walsh]

hmm.. ~15% increase in displacement.. with an 2.4S pump.. you might be ok.. can't say for sure at least you've got the right injection timing so that your mixture will be fine across the board.

[tobluforu]

So you have a 2.8s motor and you just bought a 2.4 s pump? If so, it will work great.

[Neilk]

It won't work. I will be in McLean this weekend so I can pick it up and take it off your hands.

Just kidding. I just want to reinstall the MFI in my car. If I had more time in the area, I'd love to get a ride in your car. It sounds like a beast.

[304065]

Greg,

I don't know the answer but I can tell you how I would get the answer.

What are the fuel requirements of the 2.8 vs. the 2.4?

I think it's in the Frere book, where they give the BSFC or brake specific fuel consumption, for the engines. So you need to find out what the BSFC of the 2.8 is. Unfortunately, since the 2.8 is a racing "Rat" motor, it probably won't be published, but you might interpolate from what figures are listed in the Frere book to come up with a fuel flow in grams per hour. See if they list the 3.0 and the 2.7 RS. We KNOW the RS used the "S" space cam.

Then check the Blue Book to see if it gives the flow rate, and you're home.

Or you could put it on a dyno, richen it all the way up, and try a few pulls!

[rs911t]

We KNOW the RS used the "S" space cam.

Really? Are you saying there's no such thing as an RS space cam?

[Jim Richards]

I think there's an RS space cam. That would be best, but maybe you can get by with the the S space cam and run rich (relative to S specs). Best to ask the experts (leaves me out), Greg.

[Paul Thomas]

I would think that it would run BUT a friend of mine has a MFI 2.9 that we are getting ready to install in his 73. He said they put a 2.4S pump on an 2.7RS one time and it would not run.

If there wasnt an RS space cam, why were the pumps numbered differently?

I would slap it on there and see

[rs911t]

I would slap it on there and see

That's what I intend to do!

[Chuck Miller]

The 2.4-S and 2.7 RS space cams are DEFINITELY different...

Had this job done to my pump at Pacific Fuel Injection

Seeing my pump was rebuilt awhile back ago all that was done was an RS space cam replacement and pump recalibration...

..the turn around was about 7 weeks from May to June of last year and cost about $780.00

BTW - the result was GREAT... After install I ended up turnin the main rack a couple of clicks richer and that was it...

[obrut]

I couldn't get a 2.4 pump to work on my 2.7 ++ motor - when we wound the main rack out far enough to run it would foul on something internal and not move through its full range of movement.