Piston Sizes

[420a16g]

Well i searched the forums but couldnt seem to find a thread that really answered this question for me. unless i just overlooked it.

anyways heres my question. im ordering the long rod bottom end rebuild kit from Howell Automotive. under the piston drop down box (ordering on the internet) it gives me these options. 10.5, 12.5, 8.6. Im guessing these are piston sizes or the compression ratios for the pistons, it doesnt really specify. I was wondering if anyone could tell me what the differece is and what would be a better choice.

this is for a Hahn 16g turbo setup btw, doesnt know if that makes a difference or not.

someone please educate me.

thanx

 

[420a16g]

Anyone?!?!?

i need to order this kit by tomm so please anyone help me out

 

[selmerguy]

to awnser your ? those numbers are the compression ratio. which is the difference of volume in the combustion chamber between the top and the bottom of the stroke. the rule of thumb as far as i know is that if you want to run high boost you will want lower compression pistons. 8.6:1

you might want to check: with that long rod motor i think you need a bigger head gasket to make up for that long stroke. good luck

 

[420a16g]

Thanx that answers my ?. i thought it was 8.6 but just wanted to make sure.

thanx for the recomendation. i didnt think about the head gasket.

 

[Kirby]

You will NOT need a bigger Head Gasket. Use the stock HG and everything will be fine. A long rod kit does not cause the piston to raise out of the bore, if it did your rings would hit the gasket. All the long rod does is keep the piston at TDC for a milisecond longer....

 

[420a16g]

well i ordered the kit today. got 8.6 compression pistons bored .20 over. the tech at Howell said that same thing about the HG, but i plan on using a Cometik HG cuase i heard they are real good for cars running high boost. the kit should be here within the next week. ill post some pics and info on the kit when i get it if anyone is interested.

 

[DSM Loki]

make sure you use ARP head studs, the stockers can stretch under higher boost, and as far as i know, stretching headstuds, and therefore risking the head, or at very least the hg, usually isnt good

 

[420a16g]

yea i was planning on using ARP headstuds. im not sparing any expense to make sure this engine is done right the first time.

but thanx for the look out

 

[420a16g]

yea i was planning on using ARP headstuds. im not sparing any expense to make sure this engine is done right the first time.

but thanx for the look out

 

[Kirby]

yea i was planning on using ARP headstuds. im not sparing any expense to make sure this engine is done right the first time.

but thanx for the look out

If I were you I would just use the stock gasket.. The stock MLS is a great HG and I doubt you'll get any better performance from the other one. Plus I have not heard any issues using the stocker, but I have not ever heard of this other one and it's results...