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305 Heads

Ol'Scratch

Active member
Joined
Jun 2, 2004
Messages
35
Location
Columbia City, Oregon
Corvette
1988 35th Anniversary Edition
Howdy Folks !!..:w
I recently sold my L81 to a co-worker. He's in the process of overhauling the engine and ran into this oddity. When he took the heads off and droped them off to be restored...the mechanic in formed him that they were "305" heads...:eek What in the Wide World of Sports !!... Shouldn't they be "350" heads?...;squint: And added to that...he says the the pistons have "60" stamped on them. When I had the car...it looked completely stock to me. All the original equipment was on the engine....everything. He also stated that the engine number had been shaved off the block.:nono Now my curiosity has been piqued. Why would a person overhaul an engine and bore it "60" over...then put "305" heads on it. Then put the engine back "stock". When I purchased the car...I had the washington State Police check the "numbers" for me and they saw nothing out of sorts (engine block number shaved off). The current owner is going to raise the HP to around 290 with the overhaul...so obviously he will replace the heads. But I guess it shows that there's no telling what strange things that people do.;shrug Can anyone shed some light on this ?.

Thanks for your time:pat
Drive On..:_rock

formally had a L81, currently have a Z28
 

craig32

Well-known member
Joined
Sep 30, 2004
Messages
482
Location
PA
Corvette
1981 repainted black coupe
Hey Scratch,
Did you get the casting numbers off of the heads? I looked through Mortec's listings, and some are a digit different between a 305 and 350. The main difference in heads is combustion chamber size. (that and newer heads being 'vortec') They all bolt up the same, and if you increase the bore and reduce the chamber size, you should increase the compression ratio. If the block was 'decked' it can remove the stamp numbers. If an engine had a blown head gasket, it would be a good reason to deck it. I've been looking at heads on ebay lately, and I've found some people have 2 different heads on the same engine. I've seen a couple with a 461 and a 291 together. In those days, the only thing people must have looked at was the shape on the ends of the heads.
If it had .060 over pistons, a decked block and smaller chambered heads, the new guy might be lowering the HP to around 290.
Just my opinion.

Craig
 

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