2.7 going MFI

speedo · speedo's Garage

I built a 2.7 RS spec engine a few years ago with the correct Mahle P and Cs and used weber 40s which technically speaking...means that it was not an RS spec engine. Engine is great, but I want to replace it with a real RS spec engine. Plan is to build a separate engine and then do the swap. I have all the induction, and a good core 2.7 core which supposedly has the correct Mahle 8.5:1 pistons. Is there any reason NOT to go ahead and take the 90mm 2.7 heads and get them machined for the MFI injectors, vs finding 85mm 2.4 S heads and turning them into 2.7 heads? Is there anything else I need to do to the heads while I am "in there"? I had heard that the intakes were ok, but the exhaust ports need to be massaged.
I am thinking of using what I already have (good 2.7 core) than recreating the wheel and boring the 90mm cylinders to 2.8 and buying new pistons etc.
If someone has done this, feel free to post the good, the bad, and the ugly.

Speedo

speedo · speedo's Garage

Which is a 72-3 CIS case. My heads look like 72 stampings with plugged injection. I don't know if 73.5 induction used the same heads as 72-3 MFI. If they did I am fine.
Just want to assemble all my components before I start to tear down and rebuild.
Guide me...

Speedo

burtm5 · 06-25-2014, 11:33 AM

Why are you keeping 8.5 pistons? I know that's what an rs spec has but if your going to buy pistons if it were me and it kinda was, I'd get 9.5 or 9.8. best Henry

E Sully · E Sully's Garage

The injector mounts are not the same for the cis and mfi. The T ports are also a bit small.

speedo · speedo's Garage

Yeah I did a side by side comparison of MFI and CIS heads. Lot more material on the left side of the CIS hole, not so much on the MFI. My heads are tapped and plugged CIS heads which were ported 36I and 35E. My option now is to machine a sleeve for the tapped CIS holes that will mate with the MFI injectors, or replace the heads with MFI heads and re-machine the ports.

Why keep the 8.5 Mahles? Because they are original to the early 2.7 RS engine. Built correctly with MFI, this should be a 200+ hp engine. It is going into an 1800 lb R clone...and that is plenty.

Speedo

DaveA · 07-01-2014, 01:41 PM

Can't Ollie's Engineering 1080 Aviation Dr B100 Lake Havasu City, Arizona 86404
(928)855-6101 machine your heads for a MFI injector? Give them a call, and ask.

R/Dave

kenikh · 06:08 PM

^ yes they can. And since the heads are out, doing it with hand tools is not hard. Lars, if you have em, run em, but...8.5:1 was less than ideal. Consider decking the heads for a little CR bump to 9:1 then use a spacer between the heads and cam towers to get the chains in proper tension. Or for the ultimate:

Old school with a twist