Jeep Strokers

good morning to all of you jeep dreamers
is the block deck height of the 4.2l and the 4.0l are the same?
if i take 4.0l crank and rods and std pistons and put it in a 4.2 block will the piston deck clearance be the same as on 4.0l block?
is there any difference in deck height between production years?
if i use 4.0l crank,rods and 0.30 4.2l pistons in 4.2 block will the piston deck clearance still be the same as 4.0l ?
don't ask me why do i want to do this because i know it's stupid but my brother said it can't be done and the math' say it can.
thanks in advance
feel good and have a nice day


lishay
israel

well... you and your brother can come pay me the visit that you promised and take a look at this magic book that i have

4.2L engine: Bore 3.750", stroke 3.895", deck height 9.487-9.493", rod length 5.875", piston compression height 1.601" ('71-'78) 1.653" ('79-'90), deck clearance 0.0665" ('71-'78) 0.0145" ('79-'90)
4.0L engine: Bore 3.875", stroke 3.411", deck height 9.450-9.456", rod length 6.125", piston compression height 1.601", deck clearance 0.0215"

To answer your questions:

is the block deck height of the 4.2l and the 4.0l are the same? No
if i take 4.0l crank and rods and std pistons and put it in a 4.2 block will the piston deck clearance be the same as on 4.0l block? A 4.0 crank, 4.0 rods, and standard 4.2 pistons ('79+) in a 4.2 block would work. Deck clearance would be just 0.006" and you'd end up with a destroker displacing 226ci or 3704cc (3.7L), though static compression ratio with the 4.2 heads would be a hopelessly low 7.2:1. The 4.0 heads would improve the CR to 7.9:1.
is there any difference in deck height between production years? It's the same for all '71-'90 4.2 blocks and for all '87-'06 4.0 blocks.
if i use 4.0l crank,rods and 0.30 4.2l pistons in 4.2 block will the piston deck clearance still be the same as 4.0l? Displacement would be 3764cc with such a set-up but deck clearance would depend on the compression height of the aftermarket 4.2 pistons.

thanks man
if i understand correct when you take 4.0l crank,rods and std pistons and put it in 4.2 block(here in israel we oversize the bore on 4.2l block to 4.0l std size) there is no way that the piston would be 4 millimeter(0.157) down the bore?
i know that it's not the way to go but for the sake of argument with my brother

OK, now I got you. You're talking about using standard 4.0 pistons in a 4.2 block. I didn't think you could overbore the 4.2 block that far but I guess it must be possible. I really can't see the point of using the 4.0L crank, rods, and pistons in the 4.2L block. Displacement will be the same as a standard 4.0 i.e. 3958cc but deck clearance will be 0.0585" instead of 0.0215" 'cause the 4.2L block is slightly taller.
With so many 4.0L blocks being available cheaply in the junkyards, using a 4.2L block as the basis for any engine build seems a waste of time unless you already have one for free.

Well in israel anything is possible even overbored 4.2 block to 4.0 size
by the way i won
so many many thanks for the great info
great forum, great people

just make sure that your brother is unarmed when you'll show him that you won

it's ok. i'm heavily armed as well plus i know were he keeps the clip

Hi!
How can I measure actual cylinder block height by myself? Only by dropping crank with bearings, rods and pistons? Or there might be another way?

darkcorp wrote:Hi!
How can I measure actual cylinder block height by myself? Only by dropping crank with bearings, rods and pistons? Or there might be another way?

I use a 8-9" micrometer with a .200 ball end attachment.