Engine measurements?

[GSGoinFast]

Ok guys im really curious to know what those engine measurements mean when you purchase pistons and rods and stuff. like the bore size, main bearing size, and rod bearing size? what does it do if you increase it? thanks
sorry if its been beaten to death but i searched and found nothing

 

[Defiant]

A pretty good question.

Bigger pistons are larger diameter- the distance across the top. Which is more area and more displacement, although only in tiny amounts on a 4-cylinder, since you're only doing it four times. V-8s and V-10s, etc., will get more displacement increase from overboring. The limits on boring is the thickness of the iron that makes up the cylinder wall. Too thin and it'll either flex or break under running conditions. General max I've heard for DSMs is .040", so it's a scratch-repair method rather than a performance booster.

Now, on rod and main bearings, it's kind of the opposite because to use bigger bearings you have to make the journals smaller. Which takes away strength from the crank. The reason you find different sizes for DSMs is manufacturing tolerances to start with, then polishing cleanup. I don't think you're supposed to grind a DSM crank. However, in the muscle car world, they even do things like offset grinding where you change the center of the old crank journal in order to increase stroke.

Congratulations, you've noticed the iceberg that is the world of automotive dimensions. It goes on just forever.

 

[GSGoinFast]

Well thank you, i have only been in this buiseness for about 9 months but i think ive learned a lot. and that was one thing that i couldnt figure out on my own or by reading other threads. but thanks for clearing that up

I think your title should not be "Moderator" but changed to "DSM God"

Thanks!
-Chris

 

[Defiant]

I think your title should not be "Moderator" but changed to "DSM God"

We need urine tests in here.




:laugh: