I went to order A set of world products cly heads for my gen 6 502 and talked to world products and they said you cant use them on a gen 6 block due to coolant hole passages location.Has anyone ever heard this.I no there was probems useing older cly heads on the gen 5 blocks because of the coolant transfer passages but they changed the coolant holes on the gen 6 and made them smaller so you can use the older heads.
Dave

my understanding that you can use mark IV heads on gen VI block just not gen V.

I have had a set of Edelbrocks and Darts on two different gen VI blocks. Just have to make sure you use the correct head gasket. Call felpro to be sure of the number...

Razor ,thats what i thought to?Brad,How did you like the edelbrocks heads?
Dave

They were the oval port 110cc ones on a 454 (300hp shortblock) with a 226/236, 578/610 crane cam with headers and a RPM intake. It ran wonderful. The boat must have been making around 450 hp at the crank, because I was then able to slightly outpace 502 equiped identical boats. Ran up to about 5500 rpm in the cool months.

Thanks Brad,
I have been looking at other heads now since world told me I couldnt use?,AFR,Edelbrock,canfeild and brodix so far.I gess this engine wont be done for this season .
Dave

i would call again and talk to someone else. gen 6 blocks can use mark IV, gen 5, or gen 6 heads. merlin heads also need 8 extra long cylinder head bolts with hardened washers in the holes near the exhaust ports exits because the bolt bosses were moved up to increase flow. the bolt kit # from world is #7301. also, mark IV heads can be used on on gen 5 bowtie block due to increased thickness, just not the production gen 5 blocks.

They will work I just did it!If you get the heads and you get the eight bolts,let me know and I will send you the washers as I had to buy 32 in the package just to get eight!

Thanks guys,
I did'nt make sense to me either.Flordian son,How did you make out with your engine project.Anybody ever use canfeild heads.
Dave

Well if you must Know,It has come down to one hose,what bull merc. has it on back order,it's the one from therm. housing to curlating pump, with luck it should be in by this weekend and she is ready to fire.I will post with details as to how it goes.Thanks for asking