ACL 200 rod 250 x flow pistons

[Anonymous]

There have been a couple posts in the last few months that talk about using 200 rods in a 250 crossflow. It would appear that a special ACL piston should be used for this setup. My question is: How exactly are these pistons different from the regular replacement ACL pistons? What would be the problem with using regular pistons in this setup?

I'm probably not going to do this.....Just wanna learn

 

[alloydave]

Piston for 250 with 200 rods(6.27"long) have a comp height of 29.70mm
or 1.169" .The 250 pistons with 250 rods have a comp height of 1.53" or
38.86mm .Both have same pin dia .912 or 23.17mm.

Dave

 

[Anonymous]

So they have a shorter deck height. I know US pistons are shorter, so how close are they to US pistons?

This is probably a stupid question but I will ask it any way.......

Can .30 be milled off the top of the stock pistons to duplicate the special 200/250 pistons?

Just got to thinking about all this when my machine shop told me that sometimes the pistons can crack when pressing off and on new rods. I sure hope this doesn't happen to my brand new pistons :roll:

I don't need any more major setbacks.

 

[addo]

You can mill a little if absolutely necessary (and in the process void most warranties). However, the difference between the two Dave mentions is more like 0.375 inches!

 

[Anonymous]

math never was my best subject

 

[xctasy]

Put it this way, its easy to mill 30 thou (0.030") off a piston. Even 60 thou is permiasble on most cast alloy pistons.

On a forged piston, you can rip off 100 thou or more in some cases.

The ACL cast alloy pistons for the 200 rod/250 piston are 375 thou (0.375") shallower than the stock Aussie and US 200 and 250 pistons.

In simple terms, the stock Aussie and US pistons only have about 160 thou of alloy, then you hit the casting void.

There is, alas, no way to machine them down that far becasue there is no metal left under the top of the piston crown.

Second thing is that all Aussie/US 200/250 pistons have a top compression ring only 275 thou (0.275") below the top of the piston. By the time you'd machinind off 375 thou, you'd have lost the whole top of the piston and the top compression ring as well.