m20 stroker confusion....

[decay]

Pistons are different.

ok, but what you were speaking of was removing a super-eta head from a super-eta bottom end, and then putting on an i head.

so the pistons aren't what's changing.

and the heads are the same casting.

so how is the CR not still 8.5:1?

[Sean]

Pistons are different.

ok, but what you were speaking of was removing a super-eta head from a super-eta bottom end, and then putting on an i head.

so the pistons aren't what's changing.

and the heads are the same casting.

so how is the CR not still 8.5:1?

Ohh, got confused there. I thought he meant something else lol

And...wow, you're right! :shock:

[Switch]

so, the only way to get a little higher compression is to use "i" rods....


u take eta (88 super), throw "i" rods in it, and I head... then u have a 2.7, with "ok" compression..... b/c the thing that gives it the 8:1:1 compression is the eta rods .. (right)

[decay]

so, the only way to get a little higher compression is to use "i" rods....

u take eta (88 super), throw "i" rods in it, and I head... then u have a 2.7, with "ok" compression..... b/c the thing that gives it the 8:1:1 compression is the eta rods .. (right)

NO.

eta crank + i rods + any stock pistons = pistons banging into cylinder head.

think about it. you're adding 3mm of height at TDC, and there really is not that much room.

again, if you have a super-eta bottom end already, you don't need to do anything to it to fit an i head (or as stated, you can just do the valvetrain swap instead; but that involves pulling the head anyway, which pretty much makes it a wash as to which is easier, IMO).

if you want to use i pistons with an eta crank, you need custom rods that are 3mm shorter than the i rods are. there is simply no way around that.

the ONLY way to do a high-compression stroker with factory parts is with an eta bottom end and a 731-casting head. and even then you need to big-valve the head up to "i spec" if you want it to be a worthwhile effort (again, IMO).

sorry if i sound overly emphatic, i just don't want someone to waste time putting together an engine that will self-destruct on the first crank.

[Switch]

thanks, sry i thought i heard somewhere u can use super eta pistons with i head and it will not conflict.. oh well..


so.. how much better is a 2.7 w/ 8:1 compression (super eta plus i head.. done) , then a stock "i" lol

[decay]

thanks, sry i thought i heard somewhere u can use super eta pistons with i head and it will not conflict.. oh well..

you can. but you have to use the entire super-eta bottom end in factory config, nothing changed.

so.. how much better is a 2.7 w/ 8:1 compression (super eta plus i head.. done) , then a stock "i" lol

go back and read the thread again. super eta plus i head is exactly the same compression ratio as a complete super eta motor- 8.5:1. the only thing that changes in that scenario is the valvetrain.

i'm thinking the lower-compression motor Jordan was referring to is what you get when you slap an i head on a regular eta bottom end.

and yes:
2692cc @ 8.5:1
will make slightly more power than
2494cc @ 8.8:1
with more area under the torque curve.

which is not to say there aren't better alternatives out there- but if what you want to do is bolt together a bunch of parts you can easily find in junkyards, it's about the best you're going to do.

[Switch]

your right, sry, should have just re read thread, it was like 5:15 when i posted (yawn) thanks alot for the info i appreciate it.

[Sean]

If someone were putting an I top end on a Super Eta bottom end, they could deck the block a little to raise compression, couldn't they?

Or, would custom pistons just be the way to go?

[modifiede30]

You guys are thinking about this whole thing wrong with the super eta. The super eta head is the same exact casting as an i, so what's the point in changing heads, just change the springs and cam and you're done. Since you'll have the head off, shave it to spec to increase compression.

[modifiede30]

If someone were putting an I top end on a Super Eta bottom end, they could deck the block a little to raise compression, couldn't they?

And you can do this as well as shave the head to further increase compression. Just be careful how far you go or the timing will be off and you'll run the risk of valve slap very quickly.

[Jordan]

I made a typo guys, chill.

8.5:1 is still weak.

metric mechanics sell a offset dowel pin for the cam gear to correct for decking the head and block. Either way I don't recommmend doing this to increase compression.

[decay]

8.5:1 is still weak.

*nod* the only config i see really taking good advantage of a super-eta bottom end is a turbo setup... for that, more displacement + slightly less compression is a good thing.

otherwise, either custom pistons, custom rods, or some cross-pond parts hunting is on the menu.

[Switch]

i'm really just looking for a little more low end torque, since i figure thats the weak point of the 2.5.

would simply super eta, w/ i head (cam whatever) be the ticket to same power of 2.5 + a little more low end torque?

[ultima]

Its not that much, you gain about 15 ft/lbs at most. But like in the previous post, if you're going turbo, then just slapping the "i" head on the super eta bottom end is a decent candidate for a low compression engine.

[Switch]

yeh, if only i had 2 to 3 grand to toss into it... i'd have a nice shiny blow off and everything *dreaming* *VROOOOM... PSSSHH*
yes.. that would be nice... i guess the best thing i can do right now is chip it, intake and exhaust,,,