2.2S pistons in 2.4E MFI or 2.4T CIS

[TangerineT]

Hey Wayne-

I read your book and am intrigued by your recommendation to rebuild a 2.4S using 2.2S pistons. What type of power does this make vs. a stock 2.4S and at what RPM? Can I make this conversion using either a 2.4E MFI or a 2.4T CIS? What would I have to do? Where do you recommend buying the parts? In one of your posts you mention that it won't work in a 2.4T CIS - what if I convert to MFI? I've also read a few posts that suggest that the compression ratio of 2.2S pistons in a 2.4S is higher than the 9.6:1 you mention in your book. Is this true? If so, what sorts of problems would this cause, and what are the solutions?

Money isn't really an issue. I know I can buy a nicely rebuilt 3.2 for $12K, but that isn't what this car is about. I somehow felt compelled to buy and rebuild a 90 year old friend's '72T - I've already put $25K into the car and interior, exterior, and suspension rebuild - I'm kind of fascinated with the notion of keeping displacement 2.4L.

TangerineT

[Tim Walsh]

I'm not sure about the 2.4 CIS (The cams should clear but they have a swirl pattern on them that the 2.2S pistons don't.

The 2.4E engine with 2.2S pistons would make a fun motor. I'm currently doing the samething except I'm using 2.2E pistons instead.

DO a seach there is LOTS of informationj on the 2.4L engine combinations.

[TangerineT]

Tim-

I've done a lot of searching...still don't have all the answers.

I've never rebuilt a Porsche engine, just some Pontiacs. My current project is my fifth Porsche, all the other have had the benefit of previous owners putting lots of dollars into the engines. Probably won't do the work myself but wanted enough info to direct my mechanic. He has a good and long standing reputation, but he seems to do things unconventionally.

Tell me about your project. Are you using the 2.2E pistons with your existing 2.4E cylinders? What else are you changing? What kind of power do you expect to gain vs. your stock engine?

[Wayne 962]

What are your specific questions? I can't glean exactly what you're looking for...

-Wayne

[TangerineT]

Sorry Wayne, I'll itemize:

1. I'm not clear from your book whether a stock 2.4S with 2.2S pistons provides "...10 more horsepower, and a boost in torque at the lower end." over a stock 2.4S or the 2.2L S-Spec Engine you mention just above on the same page. Specifically, what power can be expected from a stock 2.4S with 2.2S pistons?

2. I have a 2.4T MFI engine with E pistons, cylinders, cams, stacks, and recalibrated pump. I also have a stock 2.4T CIS engine. Can I convert to a 2.4S with 2.2S pistons from either of these engines?

3. If yes to #2, what would be the best engine to use?

4. If yes to #2, do I need to get S cylinders, cams, stacks, heads, and recalibrated pump?

5. If yes to #2, do I need anything else?

6. If yes to #2, where would be the best place to find parts in #4 and #5?

7. You mention in other posts that the compression ratio of a stock 2.4S with 2.2S pistons might give a compression ratio higher than the 9.6:1 listed in your book. Does this mean that the conversion wouldn't work for a street car running pump gas?

[Wayne 962]

1. HP estimates are all approximate, I would guess 10-20 HP depending upon other things, but that is just a guess (haven't dyno'ed them). The 2.2S pistons give you a nice increase in compression. You may have to cut deeper pockets into the pistons to accomodate their closeness to the cam.

2. Your 2.4T MFI is essentially an 'E' engine. You could run the 'E' cams with the 2.2S pistons - that should give you a nice bump in compression and a boost in HP, without sacrificing the low-end.

3. The CIS engine has CIS cams, - I would want to use the 'E' cams with the 'E' pump. Changing the compression ratio shouldn't make that much of a difference to the point where your pump won't be able to handle it.

4. No, no, no, no, and probably not. The only thing you might have to change is the space cam in the pump, if the final engine doesn't run to your liking.

5. Not that I can think of, although I'm really hungry and tired, so I might have missed something...

6. Not applicable.

7. This is a big, huge question up for debate that I have not been able to figure out a definitive answer to. The experts disagree on this one, although the math seems to generate a different answer than some of the experts. In general, the answer you're looking for is "it should work fine on pump gas. The people who have done this upgrade have found it to work well."

Hope this helps...

-Wayne

[murbanowski]

Hi Wayne:

I'm in similar situation (though I have not yet acquired the engine as of yet). I have the opportunity to pick up a 73 2.4 TV-E and was considering your suggesion on putting in S cams and 2.2l P&C's. I've read your book (excellent resource BTW) as well as Bruce Anderson's and haven't completely decided on my approach

I'm building for street and auto-X.

Any issues or concerns about going this route for this application? Your thoughts and comments are appreciated.