2.2 Pistons in a 2.4

WadeO · 04-15-2005, 11:27 AM

I took my cylinders & pistons to the machine shop and he suggested that I go to 2.2 pistons as the cylinders needed machining. I have a 2.4 - '72 911 T and am confused after reading several posts. Can I use 2.2 S pistons on my T cam or do I have to machine this too? Or should I order 2.2 E pistons and leave the cam as is?
Thanks for your help? Wade

dtw · 04-15-2005, 06:07 PM

What do switching pistons have to do with machining your jugs? Either 2.2 or 2.4, they're all 84mm and if your cylinders are out of spec, switching to 2.2 ain't gonna help. It's just a nice "while you're in there" upgrade.

To realize the full benefit of any increased compression from upgraded pistons, you're advised to move to a hotter cam. Late E, early E/Solex, S, mod S, there's lots of options.

JohnnyT · 04-15-2005, 11:36 PM

Wade, 2.2S pistons give you a nice bump in compression ratio. 2.2S was 9.8:1, where the 2.4T was dropped to 7.5:1 for emisions???
When you put the 2.2 psitons in the longer stroke 2.4 you get even a little more compression. Your T cams will clear the S piston just fine, a better cam is the E cam with 2.2S pistons, get your pump recalibrated to 2.4 E specs and you have a torquey little motor! Been there done that, and it is GOOD!
But is your cylinders are oversize the 2.2 wont do you any good.
No point in going to E-Pistons in my opinion.
John

WadeO · 04-16-2005, 02:47 PM

Thanks guys, after reading your responses, I know I am confused. I was under the impression that a 2.2 piston was slightly larger than the 2.4 in diameter and you could machine the cylinder to fit the 2.2. Maybe what my machinist was saying was that I could custom order JE pistons to fit my cylinders after they had been honed? Sorry if I am asking dumb questions, but I really wasn't looking forward to buying new cylinders also $$$$$.
Still confused, Wade

Jeff Alton · 04-16-2005, 05:08 PM

The 2.2 pistons should be the same diameter as the 2.4 ones...

Jeff

Mukilteo911 · 05-27-2005, 09:14 PM

so to clarify, you can use 2.2 S and E pistons in a 2.4 T motor with S, E and Solex cams, correct?

Shuie · 05-28-2005, 06:44 AM

Quote:

Originally posted by Mukilteo911
so to clarify, you can use 2.2 S and E pistons in a 2.4 T motor with S, E and Solex cams, correct?

Sure. You could also use an S+ to take better advantage of the high comrpession. PM camgrinder for a recommendation. Make sure you have access to good fuel. Your compression ratio is going to be in the neighborhood of 10:1.

Im confused about the first post. Are your cylinders out of spec?

Fperotti · 05-28-2005, 11:49 PM

Wade,

You can use either 2.2 or 2.4 pistons in a 2.4 engine. The point here is if your cylinders are out of specs, you will have to hone them. You can hone them to 84.25mm, 84.50mm or 85mm as far as I know. Then you can choose among several options. One wich seem to be good -as Wayne recommends in his book- is JE pistons (84,5mm or 85,mm).

Fernando.

Ian Donkin · 06-02-2005, 10:23 AM

Quote:

Originally posted by JohnnyT
Wade, 2.2S pistons give you a nice bump in compression ratio. 2.2S was 9.8:1, where the 2.4T was dropped to 7.5:1 for emisions???
When you put the 2.2 psitons in the longer stroke 2.4 you get even a little more compression. Your T cams will clear the S piston just fine, a better cam is the E cam with 2.2S pistons, get your pump recalibrated to 2.4 E specs and you have a torquey little motor! Been there done that, and it is GOOD!
But is your cylinders are oversize the 2.2 wont do you any good.
No point in going to E-Pistons in my opinion.
John

John

Can the 2.2S pistons / E cam upgrade combination work successfully with the CIS from a 73.5 2.4T?

I like the low end torque and would like to keep this when upgrading my setup.

Thanks
Ian

JohnnyT · 06-02-2005, 02:09 PM

Ian,
The 2.2 S pistons may work with the CIS but not the E-cams!
You will get the higher compression ratio benefit from the pistons, The E-cams are too radical for the CIS, too much overlap and will result in poor drive quality. The CIS cams have much less overlap to prevent pulsation in the intake system which would upset the Air flow measuring system of the CIS.
The "low end torque" you so much enjoy is due to the CIS cams!
I don't think that the CIS cams will be a problem with interferance, but you should be sure to check the valve clearance on assembly, as this is a pretty unusual combination of components.
The only other caveat would be that the compression ratio may be too high especially with the milder cams. Race gas anyone?
Anyone else care to comment? What experience does anyone have with this combo? I bet few!

John

Fperotti · 06-02-2005, 02:35 PM

Ian,

2.2s pistons in 2.4 engines will take you near the 9:8 CR if I am not wrong. As far as I know high CR's with mild cams will produce even higher dynamic CR's wich doesn't seem to be good for the engine life. In addition the CIS doesn't work properly with very overlapping cams.

A friend of mine has a 2.7CIS carrera with 964 cams and original P/C's. I guess the CR he has is 8.5:1. Perhaps you can find out the similarities between the 964 camshaft and the 2.2/ 2.4 series ones. I really don't know if you'll find similarities between these two cams and if you can use 964 cams in 2.4s, I gues you cannot. One thing I can tell you my friends car pull like a train.

What I'd do is keep the CIS, and use 2.2T psitons. You will have 8:8 CR aprox., nice low-end torque and perhaps a little bit of extra power.

Fernando.

WadeO · 06-02-2005, 06:51 PM

Well my Nickies have arrived!!! I ordered my 85 mm cylinders from Charles at LN Engineering and he also set me up with 2.2 S JE pistons. Thanks Charles. I also sent my T cams to Camgrinder and he is sending them back with the E cam profile, can’t wait. Thanks guys for all your help, Wade.

Fperotti · 06-02-2005, 06:55 PM

Wade,

May I ask you how much did you pay for the set of nickies and pistons?

Thanks,
Fernando.

JohnnyT · 06-02-2005, 07:22 PM

Way to GO, WadeO!!
I can't wait to hear the results!
Are you going with Mechanical Fuel Inj or carbs?

John

Fperotti · 06-02-2005, 08:29 PM

Wade,

Congrats!!. They are a beauty. Let us know how they perform. (Nice surely)

Fernando.

WadeO · 06-03-2005, 07:34 AM

Hi John,
The main reason I started this project was my Porsche couldn't pass the emissions testings here. Oil was leaking from the engine on to the exhaust system and it was pushing blue out the pipe. Anyways I thought I was going to just do a basic rebuild and leave everything stock. I seem to have caught a bug "while you are in there", I think it is terminal and I can't control it. I am not sure if my MFI system is worn out and needs rebuilding or I am looking into PMO's? Anyways that is farther down the road. Wade

JohnnyT · 06-03-2005, 09:30 AM

Wade,
Stick with the MFI, spend the money on the rebuild for the pump and throtle bodies if needed instead of on carburators and manifolds.
You will not regret it.
Upgrade to E or S specs, the product is incredible!

John

Ian Donkin · 06-03-2005, 10:07 AM

Wade - those P & C's look good! And sorry for piggybacking on your post.

John / Fernando - thanks for your input; my thoughts were to move along in stages and I hoped the E cam would be mild enough for CIS reversion issues - now I guess I need to rethink.

Suppose d-day will be when I pull it down and see what's already inside...