Mahle forged bore taper clearances ?

[glenenglish]

HI
We are (intending) to use the Mahle forged piston +40' sold by precisionintl (SKU: PHO38006040MMS) in an engine that uses stock L27 ((1990-1995) commodore 3.8 engine pistons +40 thou.
***My question is : for using these Mahle pistons, in the water cooled engine that is +40 over, do builders taper or shape the cylinder bores (IE hourglass, bottleneck etc ) or no bore taper? These are air cooled cylinders, hot at the hot end, cooler at the crankcase...

With thanks, Glen.

 

[Immortality]

Sorry, I'm a little lost here. Our V6 engines are liquid cooled. Are you using the pistons in a different engine?

Normally you want straight bores, no taper but if you are using a different engine than I don't know the answer.

 

[glenenglish]

Sorry, I'm a little lost here. Our V6 engines are liquid cooled. Are you using the pistons in a different engine?

Normally you want straight bores, no taper but if you are using a different engine than I don't know the answer.

Hi, thanks for the reply. yes. (air)
I wondered if any taper was used.

What is the bore size used with these pistons when using the 40 thou over ?

It's not unusual to apply a taper- wider toward the bottom where life is cooler. These bores are 4130 cromo steel, so the expansion characteristics compared to the ally piston can be quite different... hence the need to get it right.
and air cooled the bores go over 200deg C.
IE 14 ppm/degC for 4130 and 19.4 ppm/degC for the 4032. there are many traps.
as a result, during sustained high power output, the whole piston heat soaks and the (normally largest diameter ) of the skirts grow until.....|

BTW these are the pistons listed in
https://motorsport.org.au/docs/default-source/manual/race/2021/ra27-group-3k.pdf?sfvrsn=6a61806a_7

 

[Immortality]

I suggest you ask people who are familiar with the engine type you are using.

On our engines there is no taper.

 

[glenenglish]

I suggest you ask people who are familiar with the engine type you are using.

On our engines there is no taper.

Thanks on the no taper.
Is the 40 thou overbore, when using these homoglated pistons, is this out to 96.52+ 40thou = 97.53 ? -glen.

 

[Immortality]

The piston manufacturer will recommend a piston to bore clearance for their pistons (depending on application/use) so it's best to consult them, same with piston rings, gaps as per the manufacturers recommendations based on use.

 

[glenenglish]

The piston manufacturer will recommend a piston to bore clearance for their pistons (depending on application/use) so it's best to consult them, same with piston rings, gaps as per the manufacturers recommendations based on use.

I will. writing to Mahle.

 

[lmoengnr]

I will. writing to Mahle.

Or try contacting places that overhaul Continental and Lycoming aircraft engines.