Just a quick question..

[Dezertxj88]

When installing the 232 crank how much further are the pistons up in the holes? The 232 crank is a 3.500" stroke compared to stock 3.413"..so thats .087 difference, give or take a little..so the pistons are now .043 closer to the deck correct?

I'm basically trying to find out if a 1.592" compression height piston can be used? I don't want opinion or hear say, I need factual proof. From my math the 1.592" compression height would give 0 deck..but Dino said I can only use a 1.581" compression height piston and that they'd be protruding .005 above deck? Is my math coming up wrong?
Dino can you help me here..I'm just trying to figure it out!

This is assuming a 100% untouched, normal deck block.
3.500, 1.592" compression height pistons and 6.125" con. rods. I've decided that I'll be keeping the 4.2L turbo stroker in action after all!

Oh and I should have pictures by this weekend, safc II, wideband, egt, valve train and crank are all here..I canceled my previous order of pistons until I can get the math done.

[Dezertxj88]

I'll be honest and post up my math if anyone can correct me please.

3.935 bore
3.500 stroke
61.8cc (tripple checked)

.Now heres where I get confused.
stock deck clearence is .0215, now with the bigger stroke, .043 doesn't this put the pistons .017 above deck? And with a 1.592 compression height piston that would give me a -.01 deck clearence?
The 1.581 compression height pistons would give me basically 0 deck...


God dang it I just answered my own question..Sorry guys. I wasn't subract the difference in compression height to get the final deck clearence!
Guess I just needed to write it out and not do it in my head

[Cheromaniac]

In case anyone else is confused by the maths, I'll try to clarify it.

Deck height = Rod length + stroke/2 + piston pin height + deck clearance

If we rearrange that equation we get:

Deck clearance = Deck height - rod length - stroke/2 - piston pin height

Now let's add some numbers. The 4.0 block deck height is 9.453", 4.0 rod length is 6.125", 4.0 crank stroke is 3.411" so half of that is 1.7055", and stock 4.0 piston pin height is 1.601". The result is:

Deck clearance = 9.453" - 6.125" - 1.7055" - 1.601" = 0.215" (give or take a smidgeon depending on production tolerances)

If we replace the 4.0 crank and pistons with the 232 crank (3.500" stroke) and Silvolite 2229 pistons (1.581" pin height):

Deck clearance = 9.453" - 6.125" - 1.750" - 1.581" = -0.003" (give or take a smidgeon depending on production tolerances)

If you use taller pistons than 1.581" with the 232 crank, they'll be higher above the deck at TDC.
The Speed Pro 525 pistons for the AMC 2.5 I4 have a 1.580" pin height and would also be suitable for a mini-stroker build, while the Speed Pro 677 pistons with a pin height of 1.585" would be marginal.

[herbiehind]

In case anyone else is confused by the maths, I'll try to clarify it.

Deck height = Rod length + stroke/2 + piston pin height + deck clearance

If we rearrange that equation we get:

Deck clearance = Deck height - rod length - stroke/2 - piston pin height

Now let's add some numbers. The 4.0 block deck height is 9.453", 4.0 rod length is 6.125", 4.0 crank stroke is 3.411" so half of that is 1.7055", and stock 4.0 piston pin height is 1.601". The result is:

Deck clearance = 9.453" - 6.125" - 1.7055" - 1.601" = 0.215" (give or take a smidgeon depending on production tolerances)

If we replace the 4.0 crank and pistons with the 232 crank (3.500" stroke) and Silvolite 2229 pistons (1.581" pin height):

Deck clearance = 9.453" - 6.125" - 1.750" - 1.581" = -0.003" (give or take a smidgeon depending on production tolerances)

If you use taller pistons than 1.581" with the 232 crank, they'll be higher above the deck at TDC.
The Speed Pro 525 pistons for the AMC 2.5 I4 have a 1.580" pin height and would also be suitable for a mini-stroker build, while the Speed Pro 677 pistons with a pin height of 1.585" would be marginal.

man you really do your home work !!!

[Dezertxj88]

In case anyone else is confused by the maths, I'll try to clarify it.

Deck height = Rod length + stroke/2 + piston pin height + deck clearance

If we rearrange that equation we get:

Deck clearance = Deck height - rod length - stroke/2 - piston pin height

Now let's add some numbers. The 4.0 block deck height is 9.453", 4.0 rod length is 6.125", 4.0 crank stroke is 3.411" so half of that is 1.7055", and stock 4.0 piston pin height is 1.601". The result is:

Deck clearance = 9.453" - 6.125" - 1.7055" - 1.601" = 0.215" (give or take a smidgeon depending on production tolerances)

If we replace the 4.0 crank and pistons with the 232 crank (3.500" stroke) and Silvolite 2229 pistons (1.581" pin height):

Deck clearance = 9.453" - 6.125" - 1.750" - 1.581" = -0.003" (give or take a smidgeon depending on production tolerances)

If you use taller pistons than 1.581" with the 232 crank, they'll be higher above the deck at TDC.
The Speed Pro 525 pistons for the AMC 2.5 I4 have a 1.580" pin height and would also be suitable for a mini-stroker build, while the Speed Pro 677 pistons with a pin height of 1.585" would be marginal.

Ya Dino you really cleared it up for me, alway there to help out lol. I just kept forgeting to subract the difference in pin height. I was looking at jeep I4 KB pistons, I want to say 3238's..1.592 pin height, but after seeing what I was doing wrong with the math I understand why a 1.58x pin height would be the best! Thank you Dino.

[ghetdjc320]

Wait a minute. Your only talking about a .011 compression height difference between. With a .043 gasket the quench would be .029 but with a .051 gasket it puts quench back to .037 which is only .003 difference. That should be fine! In addition the 1.592 hypereutectics have a 15.1 cc dish.

[amcinstaller]

seems to me hes long gone now, probly wont see your post?

[ghetdjc320]

Yeah your probably rite but this thread has some realy good info! All well

[Cheromaniac]

Wait a minute. Your only talking about a .011 compression height difference between. With a .043 gasket the quench would be .029 but with a .051 gasket it puts quench back to .037 which is only .003 difference. That should be fine! In addition the 1.592 hypereutectics have a 15.1 cc dish.

Indeed that's correct. If you use pistons with a compression height of 1.592", the deck clearance will be ~-0.014 but adding a thicker 0.051" head gasket will put the quench at ~0.037" (provided the block deck isn't milled).