2.4 crank for a 2.2

[Zeke]

I've read about putting the 2.4 crank in the 2.0 and I've read about putting the 2.2 pistons in a 2.4. Each for their unique advantages. But what about putting a 2.4 crank in a 2.2? Wouldn't that be about the same as putting the 2.2 pistons in a 2.4? Use the rods on the 2.4 crank as well, correct?

[jluetjen]

Wouldn't that be about the same as putting the 2.2 pistons in a 2.4?

Yup. The only difference is that putting 2.2 pistons on a 2.4 doesn't require cracking the case. Changing the crank will.

Use the rods on the 2.4 crank as well, correct?

If by this you mean use the 2.4 rods with the 2.4 crank -- yup. You don't want to mix and match the rods will the crank.

[Zeke]

Thanks for the reply. Yes, that's what I meant, get a 2.4 crank and rods together to install in the 2.2. So, what CR do I end up with?

[Tyson Schmidt]

The increased stroke length will give you a .55 point compression ratio increase over what it was as a 2.2 liter. But, since Porsche apparently overstates their compression ratios, it will work out to a number actually less than what the 2.2 claims to be.

Example: 2.2S is 9.8/1 CR. So, when these pistons are used with the 2.4 crank, it should work out to 10.35/1. But it doesn't. It measures out at 9.66/1.
What this means is that the 2.2S isn't really 9.8/1, but something less to start with.
This is from an excerpt from Bruce Andersen's 911 Performance handbook.

[jcbear]

In Wayne's Engine Rebuild - Top Engine Modification Picks (page 112), he also lists putting a 2.4/2.7 crank in a 2.2 case with E pistons & E cam with a CR of 10:1. He also confirms Tyron's figure above, that a 2.2S pistons and cams with a 2.4 results in a CR of 9.6:1.

[Wayne 962]

This might be an error - I consulted with Bruce on this, and he mentioned (after the book was published) that he wasn't too sure. I think it should be about 10.3:1 or so...

-Wayne

[Zeke]

Originally posted by Zeke
Thanks for the reply. Yes, that's what I meant, get a 2.4 crank and rods together to install in the 2.2. So, what CR do I end up with?

Sorry once again. The engine in question is a "T." No S pistons to use.

[Tyson Schmidt]

Milt, what cams are you using? Those T pistons won't allow andything other than T cams unless you cut the valve pockets deeper, and even then, only E cams will clear since there isn't sufficient dome thickness to cut them any deeper than 1.8mm.

If you use the 2.2T pistons with the 70.4mm stroke, you'll end up with a little over 9:1 CR. 2.2T had 8.6:1 plus .55 for a net of 9.15:1

[Zeke]

Wow! Interesting stuff. So, if the E cams get into the piston, how in the world did they get a high CR with S pistions and S cams?

BTW, I didn't buy the 2.2 motor I was looking at. So this whole thing might be moot. But, it's good to know these things. I'll get Wayne's 2nd book before I ask any more questions. I WILL BUILD A HOT ROD (someday).

[Tyson Schmidt]

Milt, the pistons match the cams. S pistons have relief pockets for S cams, so when you do this, you need to either get E or S pistons for E cams, and S pistons for S cams. Or machine the valve pockets if there is enough meat in the piston crown.

2.2S pistons will go right in a 2.4S motor because those pistons were designed to clear S cams already.

[Mukilteo911]

another clarification on this.
2.2T engine
add 2.4 crank
T cams
2.2 T pistons
2.2 rods

will this work. I wanted to bump up my commpression usinf the 2.4 crank, but I hoped I would not need to replace the rods too.

[Wayne 962]

The 2.2 rods have different sized jounals than the 2.4 crank -> won't work.

You can use the 2.4 crank and rods with this setup, and it should work okay. I have a used set of rods for $150 ($25 each) if you're interested...

-Wayne

[Mukilteo911]

I may do that wayne. i will call ya if I can't find some local.

[Wayne 962]

Drop me an email - I'm not at my phone these days. Wayne@pelicanparts.com

-Wayne