MAHLE/ ANDIAL 2.7 L- 90 mm 10.5:1 PISTON SET

[Koichi Watanabe]

Hello.

I have purchased MAHLE/ ANDIAL 2.7 L- 90 mm 10.5:1 PISTON SET in ebay.

I received the set today and checked, I think the pistons are look like 8.5:1 for 2.7 carrera, not 10.5:1.
I am disappointed, because I am thinking to build 2.4 or 2.7 full race engine.

And the two of oil rings were missing.
Is it possible to buy only the two of oil rings for Hahle somewhere?

About the engine which I useF
A former owner had rebuilt 1973 CIS 2.4T engine on a 4R case with 70.4 stroke crankshaft.

I am thinking to order machining of the shuffle pins to my 4R crankcase.
Is strength short with a 4R case to build 2.7 race engine?

I would be happy if I could have answers.
Please forgive my poor English.

[JGalt]

This a picture of a high compression 90mm Mahle piston acquired from Andial.

[Cupcar]

I built an engine with the 2.7 High Compression Mahle piston and cylinder kit. Below are pictures comparing the two Mahle 90 mm pistons, note the 10.4:1 on left and the standard factory 2.7 RS 8.5:1 on right.

I think you have the 8.5:1 standard 2.7 RS pistons in the kit you picture. I would return if they were represented as the high compression parts.

I just noted the piston above, which looks different than my pistons which were in Mahle boxes and clearly were otherwise identical to the low compression RS pistons other than the piston top.

[Koichi Watanabe]

JGalt:

Thank you very much for photo.
This piston looks like very special one.

[Koichi Watanabe]

Cupcar:

Thank you very much for obvious photo and advices.
The high compression piston top looks very attractive beautiful for me.
How about your feeling of 2.7 high compression engine?

I am thinking to sell out only the standard pistons if it is possible.
And re-purchase high compression JE pistons with using Mahle cylinders.

I read about JE pistons have some problems around wrist pins.
Are the JE pistons not so good?

[Cupcar]

Koichi-

The engine I built used 2.7 heads drilled for twin plug. The compression came out at just a tick over 10:1, not the 10.4:1 that Mahle claims. It may have come out higher if the head volume were not increased by the twin plug drilling, but I have usually found that Mahle is conservative in their compression ratio claims.

Otherwise the 2.7 engine had Weber carbs, S cams and 38 mm head ports with custom exhaust headers to match heads.

Great throttle response and power. I would guess it made around 230 HP but I did not dyno it.

[Koichi Watanabe]

Cupcar-

Thank you very much for reply.

Great throttle response ... oh fantastic!!!

I have already purchased used 2.2 cylinder heads to modify into twin plug by Competition Engineering.
Maybe 2.2 cylinder heads have a little small combustion chambers than 2.4 heads.
MAHLE may have considered such circumstances.

Were the studs and rod bolts replaced with Raceware or ARP?

[Koichi Watanabe]

I measured the cylinders and pistons, using cylinder gauge and micro meter today.
The pistons were oversize 89.99mm, and the cylinders were standard 90mm.
( The piston size was marked on the top. )

There are very little clearance.
Therefore, these pistons and cylinders are not pairs.

Are these pistons(89.99mm) the parts for repair?

[Cupcar]

By the way, just to make clear. I used 2.4 heads but I meant with the 2.7 chamfer cut around the perimeter, which adds combustion chamber volume.

The piston in my picture above was from an engine I built with the 2.4 heads and NO 2.7 chamfer cut. Note on both pistons there is a perimeter ledge before the dome starts which allows the piston to clear a 2.4 head without the 2.7 style chamfer.

Bottom line is if I did it again I would not cut the 2.7 chamfer in order to raise the compression ratio- but I would check clearance anyway before I finished the engine!!!

[Koichi Watanabe]

Cupcar-

I have understood it.
When I build the 2.7 engine, I would check clearance carefully.
Thank you very much for excellent advice.