Hi-Comp 2.4 E Rebuild Options

jsm911E · 03-03-2004, 01:30 PM

I am considering options for rebuilding my now stock '72 2.4 E motor with working MFI.

My plan was to try to get as close to 200 HP as I could by using either 2.2 E or S P&C's with the existing E cams and MFI.

This motor will see 90% street use with perhaps the occasional DE and/or Autocross.

If I keep the MFI, what piston and cylinder mods can I make without adverse running conditions, ie. flat spots, too rich, etc.? Will the E-cammed MFI run well with 9.5 - 10.3:1 compression?

Has anyone done this with E MFI?

I want to focus this post on P&C sets that are proven to work with MFI, aside from re-building the pump to S or RS specs and using the S cam.

I have considered building a 2.4 with new 2.2 S P&C's with Webers or a 2.7 with either the RS or new 9.5:1 Mahle 90mm P&C's and Webers with either Solex, E or S cams, but I really want to re-use my working MFI, if possible.

In addition, I've read Bruce Anderson's book and I know that 9.5:1 seems to be a wide consensus for the hi end of compression for single-plug motors running non-race gas (I can get 92-93 unleaded here), but I've also found lots of early S owners and folks running 2.8's who haven't had problems at 10+:1 compression, everything else being equal.

I apologize in advance to Wayne if this very topic is handled in his book but I haven't read it yet.

Shuie · 04:29 PM

Grady Clay posted a thread recently about a single plug 2.8 built on a spec E motor keeping the MFI and going to Mahle 92mm RSR P&Cs. I'll link the thread if I can find it, great info. This really sounds like a great motor, especially if you have access to the good fuel.

I think that Dave (dtw) and Tim (l33t9eek) have both rebuilt 2.4 MFI motors to either E or S spec, you may want to search for some of their old posts for some good input. Oh, and read Wayne's book

edit:

heres the link for the info on Grady's 2.8

reading about this engine made me wish I still had my 7R case

Tim Walsh · Tim Walsh's Garage

I'm in the middle of doing just that... 10.0:1 JE's adn early E cams. i'll let you know in a few weeks how it runs. I'm hoping for between 180 and 190 horsepower. Do a search for my name and "dog" and you'll have a nice long thread about it or just search for 2.4 and my name and you'll get LOTS of stuff.

btw dtw's motor is almost broken in and I can say that I'm really suprised it's quite a fun motor. It has shaved heads and 2.2T pistons for 9.8:1 and some hotrod crane cams (between an early E and S cam..quite hot but very streetable)

dtw · 03-04-2004, 05:25 AM

Do a search. I've recently built a motor similar to what you describe, I have disclosed all details on several threads.

Mr Beau · 03-04-2004, 11:57 AM

If the factory used 9.5:1 on the earlier 2.2's, you should be able to push that a bit if you're "mindful" of mechanical things, especially with 93 octane. If you put it more aggressive cams, you'll be even safer as they'll bleed off some of the pressure at lower speeds, which is where detonation tends to be more of a problem. Oh, and make sure your ignition timing is accurate.

If the cams aren't changed, the MFI should need no adjustments as the volumetric efficiency is unchanged by the compression ratio--the engine is just more efficient with what makes it into the chamber.

Finally I would steer towards some new oversize pistons for your current jugs. As there is an iron sleeve, you can have them machined to size by any competant machine shop. No need to deal with worn out 2.2 stuff that probably won't end up being any cheaper in the long run.

Good luck!

jsm911E · 03-04-2004, 12:30 PM

Thanks guys for all of your responses. They have been very helpful.

Most likely, I am going to build the following:

* late 2.7 7R case with all the mods
* SC oil pump
* new RS pistons and cylinders
* my E cams and MFI
* my single-plug 2.4 heads perhaps ported to 34 or 35 mm
* front oil cooler

This will best meet my power, torque and reliability goals and most importantly, the budget. In addition, octane will not be an issue.

Bobboloo · Bobboloo's Garage

I liked your initial plan myself. It's cost effective, a great motor and stays true to the car from an originallity standpoint.

If you do go the 2.7 route leave the ports alone unless you plan to ditch the E cams and MFI. Induction, ports and cams are designed together. You'll probably end up loosing rather than gaining power in this scenerio. Porting is an art form that is best left to people with mega bucks and lots of experience. Porsche already did the work for you.