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post #1 of (permalink) Old 08-08-2000, 05:44 PM
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chevy 307 heads

I have a 307 c.i. wondering what heads will work on it? tried 350 heads but had cooling prob's seems to get hot at highway speeds and sometimes in town with the 350 heads on it? the 307 heads don't have the accessory holes drilled for the a/c etc.

If it has tits or tires it will give you trouble.
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post #2 of (permalink) Old 08-08-2000, 06:23 PM
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Re: chevy 307 heads

I would have thought that 350 heads on a 307 would work fine. I'm not positive, but usually the 307 head requires the use of 1.72" intake valves, and 1.50" exhaust valves due to the 3.875" bore. It might be possible to oversize the 1.72" intake to a 1.84" intake valve, but I've never tried. Usually the 307 had flat top pistons and 76cc heads. If you go to a smaller head "cc" the compression ratio builds up fast! I'd install a heavy cast 76cc head that has 1.72" intake valves and 1.50 exhaust valves. The cars and pickups from 72-77 with 2 barrel intake manifolds will usually have these types of heads. Usually the heads after 72 will use the peanut spark plug and have flame hardened exhaust seats for use with unleaded fuels.

It could be possible the overheating is caused by a small vacuum leak. A vacuum leak will lean the fuel air mixture and very often a lean fuel air mixture will cause the engine to overheat. It's possible the end gaskets of the intake manifold are the cause of the leak. I do not install the SBC intake manifold with the rubber end gaskets, I use a 3/8" bead of High Temp silcione RTV adheasive.

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post #3 of (permalink) Old 08-08-2000, 06:57 PM
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Re: chevy 307 heads

Put 305 heads on there, it will increase your compression and give you some horsepower!!![img]/wwwthreads_images/icons/smile.gif[/img]
I don't know why the 350 head would make it run hot, but maybe they were warped or something?
Put the 305 heads on, and you will thank me later! [img]/wwwthreads_images/icons/wink.gif[/img]
Dave is right, throw away those rubber intake ends and use silicon! Even if you do get them on right and all sealed up, sometimes they still get sucked in later![img]/wwwthreads_images/icons/mad.gif[/img]
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