MR NICE

need some help on this i have a 10114182 gen v block just found out gen iv heads wont work?anyone know if i can use 990 or 188 rectangle heads on this motor?thanks for any help or advise,i have a gen 4 motor dont know if its a 4 bolt yet,would rather use newer 1 piece seal block if possible?

MelWff

arent the 990 and 188 GEN IV heads?

voidhead1

Have you seen this article yet: http://www.chevyhiperformance.com/te...ons/index.html

At a high level it talks about the differences of Mark IV Gen V and Gen VI BBC

427Hotrod

Most aftermarket heads work fine on GenV blocks. There are iron GM rectangular ports that fit them with the correct coolant passages that they used on the 454/425 and 502/450 versions.

*SOME* Mark IV heads will work on *SOME* Gen V blocks but it's a case by case deal. You have to look real close at those upper coolant passages. There were some gaskets made by Fel Pro that helped a lot that you can do a search on.

See if you can swing some aftermarket heads because that's what a 502 needs to wake up....or a REALLY nice set of professionally ported GM iron oval ports if you want to keep RPM under 6500.

JIM

Ben Lurkin

That's a 454 gen 5 block. If you have Mk4 heads and another Mk4 block why not use them together? There's nothing special about the gen 5 block. The gen 5 502's are thin cylinder wall castings (can't remember on the 454's). A two piece seal rear main works just fine as long as it's installed correctly.

MR NICE

going with a 445 block,gen 4,just picked up a set of 990 heads,forged crank,rods and pistons,from a 454 mag mercuriser,will go with crank and rods looking for different pistons, 12 to 1 forged,comp 294 solid flat tappet,1050carb, going to run e 85,guess my HP