high compression 2.4S

[Johan123m]

I know I should ask this q in the engine rebuilding forum, but I thought I would get more response over here...

One way to bump the compression of 2.4 engines is to use the pistons of the 2.2 engines. This I know by now,

but what kind of 2.2 pistons I should use on a 2.4S engine?
T,E or S?

Do I need to check valve-clearance anyway or is it gonna be 100% safe?
What method is there to check valve-clearances?
Thanks for any feedback guys
Johan

[Early_S_Man]

2.2S are the only ones with enough valve relief to clear the valves operated byan 'S' cam! Plus, they are the only forged pistons in the family.

[Grady Clay]

Johan,

Warren is right on. The 2.2S P&C are the only bolt-on option. A new set may be difficult to find?

There are also some other things you should consider.

First is your use and fuel availability. Higher CR means higher octane fuel is required. This can be mitigated slightly with twin plug ignition. What is your local access to high octane fuel? If your use involves cross-Europe drives, it may take serious effort to find appropriate fuel.

Needless to say you will want to do a complete overhaul to build in reliability, safety and longevity.

There are also some fun more extreme modifications. I like to use the 2.7RS Mahle Nikasil P&C and for stellar performance the 2.8RSR version. These are both popular (and expensive) options. This is the edge of the “slippery slope”.

If your MFI is in good condition, it takes nothing other than adjustment for any of these combinations. If your MFI needs work, the bill can be US$4K.

Tell us more about the current condition of the engine and car.

Best,
Grady

[Johan123m]

Hey Grady,

It's an old 2.4S engine I picked up a year ago in Germany (my car itself is a '73T with most of the s-options and some other goodies. It's getting a bare-metal-respray as we speak!

The engine was last used in the beginning of the 90's, so I'll check compression and the mfi-pump, but the odds are that the engine will need a complete overhaul.

I read that the 2.4S engine is a bit underpowered beneath 5000rpm, but that this fact could be countered by upping the compression. So, it's one of those...while I'm in there...hehehe!

So I guess I gotta start looking for some 2.2S pistons. Probably not easy to find?

Fuel is good over here 98 octane.

Here's a picture a the engine
(wenn I just bought it. right now it's only a long block and all the other stuff is cleaned up)

Johan

[Early_S_Man]

Johan,

Another option would be to use 9.5:1 JE forged pistons with valve relief pockets. The 9.5:1 compression ratio is a significant bump from the stock 2.4 ratio and yet will be easier to find high enough octane fuel for in the furure ...

[Johan123m]

Hey Warren,

Thanks for the info
How much would a set of forged JE's set me back?
What would be the CR compared to using 2.2 pistons?

Johan

[tangerine911S]

What CR do you get with the 2.2S pistons? What kind of hp increase can you expect to see from the higher CR?

[jstobo]

My set of JE 9.5:1 were $1000 four years ago. Do not know if prices have increased. Good Luck.

[Johan123m]

One more Q:

Do I only buy the pistons at JE or is it recommended to buy the whole P&C combo?
(even if my original cylinders are still ok)

What about expected CR (I probably can choose the CR if I buy new P&C's, not?)

Regards
Johan

[Johan123m]

I just checked JE's website and on the Porsche-page of the catalog, they only start at 3.0L...

I guess the smaller displacements are custom made or what?

What specifications do I have to give to JE to get a correct quote?

Thanks for all the help guys!
Johan

[jstobo]

yes mine J& E's were custom made. I had them made at 86MM to increase my displacement. Then bored out my cylinders. If your cylinders are stock spec. then order stock replacements. I would go one step oversize though. Then have your cylinders bored to match the pistons. You have biral cylinders. Iron lining with AL fins. You can bore them a little. I do not remember what spec the oversize pistons are but J&E would know. Have fun.

[rrcrawford70s]

I had my 2.4 S rebuilt using Mahle 2.2 S P and C's.

I had the engine dyno'd it showed 217 hp and 180 torque..

I have had cars with 2.2S MFI, 2.4 S MFI, 2.7 RS spec MFI and 2.9 twinplug MFI. This is the best way to go!! Smooth torque and lots of hp.

See the link:
http://scottsind.com/Navigation/WorkInProgress/RayC/WIP0474RayCFrame.htm

Follow the website on the dyno day and the rebuild.

[Johan123m]

Hey Ray,

I followed the link to scottsind.

You've one beautyful car and your engine was built with great care!
I've a very similar color on my '73, gold metallic.

What color is yours?

I can get some 2.2S pistons, but I like the option jstobo suggested. Buy some oversized J&E's and bore out the jugs a little!
A new set of Mahle 2.2's is quiet expensive...

See ya
Johan