SBC Heads 993, 882, 0r 624?
 

1976-77 350/275 ihra /287nhra

1976 is allowed 993, 882, 624

1977 is allowed 882, 624

There are others listed, but i know these are the common ones. I've always heard that 882 and 624 are virtually identical, but that 993 were a better head. Anyone know for sure?

Re: SBC Heads 993, 882, 0r 624?
 

I always liked the 993 head but you've got to give them a good looking over because they were made for years and installed on everything from Vettes to crate motors. 624s are OK and easy to find. 882s are probably the worst head that was ever put on a 350.

Re: SBC Heads 993, 882, 0r 624?
 

993 heads were also used on the original Chevy (I understand we're not supposed to call it Chevy any more. Ya, sure) crate motor built in the late '80's. It was called the 'TARGET MASTER' engine. They were cast in Mexico (identified under the valve cover). Engine builders claim these are very sturdy heads as opposted to the other legal light weight castings (882's and 624's).

I have a virgin pair with a 1988 casting date that I found at the Charlotte Swap Meet. I'm planning on having them done and using them on my '73.

Re: SBC Heads 993, 882, 0r 624?
 

I found the runner volumes on the NHRA site and noticed that the 493 has the same volumes as the 993. Any known differences in these heads? They seem to be a bit more common up here, but i've only seen them on 400's.

Re: SBC Heads 993, 882, 0r 624?
 

Small block heads varied a lot in casting hardness and quality. Some old castings like early 461's were sometimes pretty soft and often had cracked or broken head bolt bosses.

Later heads were somewhat harder and usually better....

993's were much better than 882's for casting quality and the 882's were very often cracked and went in the scrap pile. I would have to really check over an 882 before I'd use it for anything....

I always thought the Heco in Mexico heads were better castings than a lot of the GM castings from the US......The '70's was when GM produced a lot of real junk.....cars and engines..........

Re: SBC Heads 993, 882, 0r 624?
 

Most SBC heads of the '71-77 era had a hard life because of the excessive exhaust gas temperatures they ran under, and excessive exhaust seat wear and guide wear due to the low lead and unleaded gas that came out about then. Good cores always were harder to find. The GM Target Master crate engine( I've personally installed about a hundred of them) was a low compression one size fits all replacement smog motor, and not all, but most of the later ones were cast in a Mexico foundary. They evidently dodn't employ the thin wall casting techniques that the domestic and Canadian engine plants used on both their heads and blocks. Domestic heads used to crack across the center exhaust seat, or around head bolt holes, even the outer wall of the head. Someone we knew got a Mexican block, was skeptical of it, sonic tested it, and that block was very thick.They went on to build it into a Super Stock motor, and that thing was one of the fastest 350 SS motors he ever built. In the old days, the Tonawanda engines seemed to be the best,as the thin wall casting techniques came later. Small blocks, big blocks, and all the 348 and 409's were built there. Nothing thin anywhere on those. Good luck inn your search for cores. At least, SBC cores aren't exactly rare.

Re: SBC Heads 993, 882, 0r 624?
 

my expierience has been that almost every sbc to come thru the rebuild shop that had a 624 at least one of the heads were trashed. cracked, warped beyoned belief. the 882's seem the be the replacement of choice at least in stock to semi decent performance builds up here.