3400 piston height

[treeZ24]

do the 3400 pistons stick out of the block like the 3100 pistons? i always assumed they were about .020" above the deck but since i dont have an engine i cant verify that.

any

[bszopi]

http://60degreev6.com/test.php?do=start

Select a 3400 and pick "Calculate with Defaults", and it'll give you all the numbers...

[treeZ24]

yes i realize that, and the number used for the piston height in the bore seems incorrect to me. i have some 29cc wiseco forged pistons ( spec sheet says 30cc ) and the compression ratio is supposed to be 9.0:1

kenton (89jyturbo) pm'd me back with, " Well my block was decked .003" and I came up with the pistons out .024"

but if you do that, and use the other stock numbers, the compression comes up a bit past 10:1.

so there's something else here not adding up

[bszopi]

Here is the thread where the CR Calc numbers were based on:

http://60degreev6.com/showthread.php?t=27898&highlight=compression

[Guest]

if you do the math then the piston comes out .007 if memory serves correctly. That is if everything is within specs like gm says. Basically blueprinted.

[treeZ24]

found it.

the compression height on the stock 3400 piston is 1.4600"

the supposedly lower compression wiseco forged pistons are 1.4800" (with a 30cc dish) which i measured at 29cc and the compression height checks out close enough i'm happy with the stated length. (over bore by .020" as well)

this concerns be since these are "supposed" to be lower compression pistons, however i run the numbers through the calc on the site using the piston sticking out .020" from the block, with 30cc dish, and i get a 9.98:1 scr. from a piston thats supposed to be 9.0:1 compression, for boost obviously.

thanks for all your help guys.

[Guest]

you have yet to measure your deck height from teh crank centerline. Or have you done that? If the block has a higher deck height then factory specs, then the CR will be lower.

This is why you have to measure everything to get a accurate reading.

[treeZ24]

i just asked kenton to do a little more measuring so i'll have to wait on this since i dont have a 3400..

however i figured there were enough people with torn apart 3400's the information would be reasonably easy to get. i was looking for the 3400 deck height and piston compression height, i found the deck height when i was looking though in the specs and it came up as 8.818 in .

assuming everything the same as a stock 3400, and assuming gm's clearances are close enough to be the same from block to block my conclusion should be valid.. no?

before i put together the engine i will re-measure everything of course, it just struck me as weird when i cc'd the piston dish (because i could lol), threw in the calcs and the scr didnt turn out to be what i expected.

[Guest]

No you can not assume that every block is the same. That is why there are blueprint specs. Some could have a bit less deck height, and some could have more, and some could be perfect.

That is why you have to measure YOUR block. Not have someone else measure theirs. You need to measure the exact one you plan to use to get the exact CR for your specific engine.

[sharkey]

yes you always measure your own stuff when building a motor, but as bad said, he doesnt have a 3400 block or crank yet. measurments will varry from block to block, but they should be withing a few thousands. right now, close is good enough for rough calculations before building the engine.