# 46 Heads question



## rustorod (May 8, 2011)

Hello,
doing some research into a future build for my GTO. I have a 400 short block thats needs some machine work, but before I do that. I had a question regarding Pontiac 46 heads. I have a set of 46 heads, I was wondering what would be a set of good pistons to get. I want the car to be streatable, and to keep the compression reasonable.

Thanks.
Mike


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## Thumpin455 (Feb 17, 2010)

Those are 350 heads, small valves but with screw in studs. On a 455 they make a nice pump gas engine with flat tops. You can have larger valves installed and porting them doesnt hurt either. With new larger valves they flow about the same as any other big valve D port head.

You wont have any problems with compression or octane using those on a 400 unless you do lots of milling or run domes.


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## rustorod (May 8, 2011)

Thumpin,
thanks for the response. Can I just measure the base of the valve to see what size they are? I've been reading the Batman thread and saw he has similar heads that I have. I guess I plan on using flat top pistons and maybe porting them (budget providing). Just want to double check to see if its worth investing int hese heads or keep a look out for 400 heads.

Thanks.
Mike


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## geeteeohguy (Feb 2, 2008)

No need to measure the base of the valves. Thumpin is telling it like it is. The big valve heads have almost no space between the valves...you can just get your fingernail in there. The "small" valve heads have about 1/8-3/16" gap between valves. Depending on cam choice and rear gear, small valve heads can run just fine as is.


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## rustorod (May 8, 2011)

Thanks for the pointers. I'll check the space. Got these heads a few years back and don't remember if they were modified or not.


Thanks.
Mike


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