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Old 01-04-2011, 11:48 AM
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Putting larger valves in a set of heads questions.

I just picked up a set of 305 heads, casting number 376450, ready to run for $50.00. They have new Z/28 springs installed, valve job, planed, hot tanked, and cracked checked. The guy I got them from also pocket ported the heads, and It looks like he did a really nice job on them. I have seen some pretty trashed home ported heads before in the past. He basically gave them away because friends of his said all 305 heads are junk. However, being the junk collector I am couldn't pass up a fresh set of heads for $50.00, especially with port work done to them.

I know they are not performance heads, but I am thinking of putting them on my old 4x4 chevy truck that the engine needs redone in. The truck has a 350 in it. I think they will work well since it wont probably see over 5K rpms in its life, and the added low end grunt to get its heavy butt moving. The heads have 60cc chambers in them.

They have the standard 1.72 intake and 1.50 exhaust valves in them. I have a set of new 1.84 intake valves sitting in my garage(again me and my collecting). I know the later 305 HO heads had 1.84 intake valves in them. It is possible to get these cut for 1.84 valves? I would disassemble the heads before I would take them in, and I can put the valves back in. I am wondering what kind of cost I would be looking at for a machine shop to do this if possible?

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Old 01-04-2011, 12:49 PM
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To just cut the seats for the intakes I'd guess about $100. Its probably possible but will only know for sure after you try it. it will help but its like putting lipstick on a pig.
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Old 01-04-2011, 01:07 PM
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Unless you are lucky, chances are that the larger valves will also require additional porting on the backside to accommodate them. It may be cheaper to just have the original heads done.
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