Mark v heads on Mark IV block?

[Rannos]

Am building a 496 and was going to use a set of 049 GM oval port heads. I came across a set of 088 rect. ports off a 502 mercruiser for a reasonable price. I have heard you can run the newer heads on an older block but not the other way around and I have heard you can use older heads on the newer block but not the other way around. Both versions I have heard you have to use a special heads gasket. Has anyone done this? If ya have do you have the part number for head gaskets the later model heads to mark IV block?

[hotrod 80]

I have run the older style heads on the newer style block . This was a 468 . It required a special head gasket due to the water jacket/coolent ports . I will see if i can find the info tommorow .

[WAAF]

the 502 heads are non adj valvetrain.. you are going to need to change all the valve gear to get adj valvetrain

[Rannos]

I would just have to buy studs and guiide plates they are already machined. I also found an article in Chevy High Performance where they used the 088 heads on a Mark IV 505 build that's very similar to the build I am doing and they listed the head gasket number I need. Thanks for the infomations guys.
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[69trk]

Those are the heads that i'm running... They flow pretty dang good for an iron head!!!

[Rannos]

Yeah they are actually a little on the big side for what I'm doing but for the price I couldn't pass them up. I am doing a 10.2 to 1 496 with a mild street solid roller. Would like 550-600 horse and close to that intorque. Truck is rather light... about 2800Lbs with the small block in it. So if I get close to those numbers I can try to run the 6.5 index at HMP here in Houston.
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[Rannos]

Well plans changed. No more local index racing. Sold my BBC stuff, except the heads and doing a little SBC for the truck and will do more street driving and a little bracket racing. I am thinking should I use this virgin 509 400 block and do a little 406 with a decent set of heads and hope I dont go to far for the block or use one of my 010 350 blocks and do a 383 or 396 and just not worry so much about it? Seeing as I am also trying to restore my boys camaro at the same time I can't budget a block in so its what I have or nothing.

[hotrod 80]

What body is this going in and what weight ?

[Rannos]

Truck weighed a little over 3300 with me in it with the aluminum headed SBC in it. I have built a few 400's and never hurt one but I was going to do 6" rod dart 230 heads with 10.5 to 1 compression. Do a street solid roller. That should be close to if not 500hp so if I spray it at all I am worried I would be getting close to the limits of the GM block even if I Hardbloked it and used a girdle.

[dinnut]

If you need the part number for the head gaskets your best option is to goto your local parts house ( I went to Oreilly). Have them break out the felpro catalog there is a whole section in the catalog for BBC head gasket interchange. Different bores...different thickness.... really useful for me. I'm putting together a .70 over 454 right now with 088 heads and the gaskets They said to use were like a hundred bucks a pair!! Hopefully they work for that cost!
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