Stroker rod length with custom pistons

[ChuckNE]

All
I am collecting parts to do a stroker build on my ix m20. I have an "e" crank and rods as well as "i" rods. I plan to go with custom pistons so my question is does it matter which rods I use...130 or 135. One better than the other and why? Any input would be appreciated.

[peterman]

There are so many posts and discussions on this. You need to search and define what your goals for the engine are. Piston design is not a simple process. There are many variables and paths to go down.
Read, read, read.

[digger]

135mm is preferred IMO for the following reasons.

1) More rod choices both OEM and aftermarket (use a 24V rod from M52 or S52 etc.)

2) It allows slightly less angularity which will give slightly longer life, though you probably need to do 120,000miles to detect a difference as its pretty slight. A pommy guy I know who used to build multiple 2.7L using both 130 and 135 rod options said they used to make the same power within a couple hp.

3) At BDC the piston is further from the crank with a longer rod so the skirt doesn’t need to be hacked. this is issue is not usually an issue with eta crank but more apparent with the 84mm cranks as the stroke is longer and the crank counterweights are bigger diameter making fitment of stock pistons difficult.

4) Better compression height. A shorter compression is usually better and more stable despite the opposite being more intuitive. Obviously this is within reason as too short is not good as you cant physically fit rings amongst other things etc but you’re looking at ~30.5mm or thereabouts with eta crank and 135 mm rod in a m20 block i.e. ~206.0 mm – 135mm - 40.5mm = 30.5 mm so thats still heaps of room

[ChuckNE]

Thanks for the reply...appreciate your insight.