Compression height of Black top pistons

[racermr2]

Does any forum members know the Compression height of Black top pistons? I've looked everywhere I know and can't find it . I know the compression height of stock 4AGE pistons is 30.50mm to 30.68mm. I'm not sure about the black top!! Help!!

[101gze]

Its the same. Why would it be any different?

[racermr2]

All things being equal(bore, stroke, rod length, block height, etc.) something had to change! Are you absolutely certain that the compression height is the same(you have measured 20v black top versus 4AGE)?

[101gze]

I'm not sure why this engine has you so mystified? there's nothing magical about it. All "later" rods and pistons with 20mm small end are interchangeable. Same deck heights, same piston to head clearance same stroke.

Therefore, nothing had to change.

20V blacktop v's 4age? I think this is where your confusion begins. The 20v IS a 4age.

If you were to explain to forum users what it is your attempting to achieve, some may be able to cut though the mud for you.

So...what is it your trying to achieve?

[knightrous]

All things being equal(bore, stroke, rod length, block height, etc.) something had to change! Are you absolutely certain that the compression height is the same(you have measured 20v black top versus 4AGE)?

The thing that changed across all variants was combustion chamber volume and piston dish/dome to allow the change of compression ratio.
Silvertop has less combustion chamber volume then a blacktop, hence if you drop blacktop pistons into a silvertop motor, you get a higher compression ratio (11.x:1) then if they were installed into a blacktop

[racermr2]

Guys, thx for the info. It has been invaluable.