6 cilinder head info

willem

i am looking for info about the 6 heads
a have bought a very good 86 head castnr 3933002
but i have a 84 in my cj8 with a burnt valve
this is al wath i have found on the net:
AMC
1981-85 258 4.2 3.75 L-6 7/16" Head Bolts 3235444 3933000
3224480
3241656 3235477
AMC
1986 258 4.2 3.75 L-6 1/2" Head Bolts 3235444 3933002 3235477
the block en the cranck casting numbers are the same,but the headbolt are not #-o

is it posible to put the 86 head on my 84 block??

thanks willem

ironman_gq

yes either drill and tap for 1/2 inch head bolts or have bushings made for the smaller bolts. the best option is the drill and tap as you will gain strength and reduce the possibility of a leaky head gasket with the larger bolts.

willem

thanks ill try to get the bolts too willem

junkyard jim

Bit late now, but the best option would've been to get a 4.0L head.

willem

bether late then uuuuuuuhhhhh :-| :roll: what is the advantige if i put on a 4.0 head? do i need other things bisides the head? intake etc etc will it fit right on ? thanks

ironman_gq

just a need to block a few water passages and get the right bolts or bushings if needed. there are writeups everywhere heres one http://jeep.off-road.com/jeep/article/articleDetail.jsp?id=277013 They say its worth close to 50hp!! and better mileage.

junkyard jim

The head bolts on and allows you to use the 4.0L factory (or an aftermarket) header. The intake needs minor dremeling (where the alignment pins sit) to match up to the head. Bonus is aluminum valve cover, raised intake ports for more power (breathes better) and should you decide to go EFI (like I am) the later 4.2L runs almost the identical cam to the 4.0L so it works with EFI (works even better if you do the timing chain with the 3 key set and adjust cam timing slightly retarded to get rid of ping) Later 4.2L blocks are wider and shouldn't even require blocking the water passages.