Received my High Compression RS pistons

[Peterfrans]

the postman brought a nice packet today, a set of high compression mahle RS pistons. After a lot of thinking about aftermarket like woesner or JE I came across a company that is able to deliver custom mahle piston only sets, very nice. For reference on the left the original 8.5 compression RS piston that came out of the engine.

[gestalt1]

what company is selling the pistons? i need a set also.
-matt

[Peterfrans]

wahl in germany, they are located in the same town as Mahle. Very small operation, but they were able to deliver these in matter of days.

[Geronimo '74]

What's the price on those, Peter? Are they expensive? Stijn told me already about these, they use Mahle, so that's perfect
Does this guy have a website? Email?


I'm doing a rebuild and going to 3.4. FVD sells a set 98mm jugs and pistons but they are CR 10.3/1. This might be on the high side since I am not twin plugging. Custom pistons would be great for me because then I can go for 10/1 CR.
Although there is a guy on this board (Sirish, in the UK) who has a CR of 10.3/1 on a single-plug engine and has had no problems yet. (only 98oct of course)
I just want to be on the safe side though.

[Peterfrans]

240 a piece (ex sales tax). Still have to receive the bill though

[JFairman]

Wahl Pistons
Every piston you want, new made, improved, restored Helmut Wahl

Gartenstr. 57A
70734 Fellbach/Stuttgart
Germany

+49-711-589660

Helmut Wahl is well know all over the world as "the" man for all possible and "impossible" piston works (Walter)

[Peterfrans]

That is indeed the address I got them from.

[Henry Schmidt]

We used a set of these to build the 2.7 twin plug engine for Jerry Murray's 67 "S" soft window coupe.
The engine produces 235 rear wheel horse power in a very drivable street car.

[Peterfrans]

Originally Posted by Henry Schmidt

We used a set of these to build the 2.7 twin plug engine for Jerry Murray's 67 "S" soft window coupe.
The engine produces 235 rear wheel horse power in a very drivable street car.

Nice engine Henry, I would be very happy with 235 rear wheel HP. I will also twinplug but use MFI in stead of carbs.

[Peterfrans]

Henry, I saw that you used a modified heater duct on the left side. Is this mandatory for a twinplug distributor or will that also clear a standard duct?

[Henry Schmidt]

You need to modify a stock air duct or use a 3.3 Turbo air duct for distributor clearance.
I'm not certain if that duct is modified stock or turbo but either way will work.

[Will 1967]

Looks great!
What compression these will be?

(very interested to get set as well)

[Peterfrans]

nominally 10.3:1 (similar to the sets Andial sells, but those are p's and c's), but i need to do some measurements to see where the real cr will end up given resurfaced engine case, heads etc. Several parts are ondergoing machining, so I will only be able to do this in a few weeks time.

[Will 1967]

Originally Posted by Peterfrans

nominally 10.3:1 (similar to the sets Andial sells, but those are p's and c's), but i need to do some measurements to see where the real cr will end up given resurfaced engine case, heads etc. Several parts are ondergoing machining, so I will only be able to do this in a few weeks time.

Thanks!
I'm aiming to get similar compression but with 66mm crank so I need to check what they (or Andial) can offer.

[Cupcar]

Originally Posted by Peterfrans

nominally 10.3:1 (similar to the sets Andial sells, but those are p's and c's), but i need to do some measurements to see where the real cr will end up given resurfaced engine case, heads etc. Several parts are ondergoing machining, so I will only be able to do this in a few weeks time.

With a twin plug drilling and the 2.7's 90mm radial bevel cut performed at the edge of the combustion chamber on new, unsurfaced 2.4 heads my 2.7 built with these pistons came out at 10:1.

I think you can get away without cutting the radial bevel since the ledge on the piston I think would clear the head anyway and you will get a higher CR.

Peterfrans a Dumb Question for you: Cylinders came with those pistons too, right?

[Henry Schmidt]

Originally Posted by Will 1967

Thanks!
I'm aiming to get similar compression but with 66mm crank so I need to check what they (or Andial) can offer.

If you want to make good compression with the 66mm crank you may be forced to use the 89mm 2.5 ss pistons.

[Cupcar]

Originally Posted by Henry Schmidt

If you want to make good compression with the 66mm crank you may be forced to use the 89mm 2.5 ss pistons.

Engine we did with these 89s on 66 came out at 10.2 with single plug.

Would be cool to do an engine with the short stroke 2.5 89s and the long stroke crank which would come out at around 11:1.

If I had my choice for an ~2.7 liter engine on a long stroke crank, I think I would give up 65 cc and go for the higher compression of the 89s rather than the "high compression" 90 mm piston.

[Henry Schmidt]

If the actual compression ratio of a piston is 10.2 on a 66mm crank, the compression ratio on a 70.4 crank would be 10.8.
Still a very nice CR for a twin plug engine. As a general rule, .5 change in the compression between 66 and 70.4 is expected.

[Cupcar]

Originally Posted by Henry Schmidt

If the actual compression ratio of a piston is 10.2 on a 66mm crank, the compression ratio on a 70.4 crank would be 10.8.
Still a very nice CR for a twin plug engine. As a general rule, .5 change in the compression between 66 and 70.4 is expected.

Jeez Yoda, I did say approximately 11:1.

Given the same combustion chamber volume, the CR would increase by the ratio of the cylinder volumes.

Assuming the 89 X 66 2.5 liter has a CR = 10.2:1

The 89 X 66 2.5 liter has a 410.38 cc volume and the 89 X 70.4 2.6 liter has a 436.76 cc cylinder volume.

CR of the 89 X 70.4 = 436.76/410.38 X 10.2 = 10.8556752278

[Henry Schmidt]

That shows you what happens when I get bored.
Cheers