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Old 01-05-2009, 11:08 AM
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has anyone heard of these heads??

the casting number on the heads is 3878487 and they're stamped march of 71 i was interested in the valve size and combustion chamber cc's

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Old 01-05-2009, 11:42 AM
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I don't come up with that number, are you sure it's not 389***? Sometimes the casting of 9 will look like a 7.

Vince
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Old 01-05-2009, 11:50 AM
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re: has anyone heard of these heads??

i cleaned up the numbers a little more and came up with these numbers
3973487
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Old 01-05-2009, 11:53 AM
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3973487....71-72...350..........1.94/1.5 or 2.02/1.6 valves, was also used on '71 350/330hp LT1, 75cc chamber

3973487X...71-72...350..........1.94/1.5 or 2.02/1.6 valves, 75cc chamber


from mortec.com
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Old 01-05-2009, 12:07 PM
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Intake port volume should be 161CC's, exhaust port volume should be 65CC's. Depending on where you look for info, the heads are listed at 75 or 76 cc's, but are probably larger than that if you pour them with a cc burette and alcohol, unless they have been milled in the past. In that case (and you don't really know what's been done to these heads in the past 38 years), pouring them will be mandatory.
http://store.summitracing.com/partde...5&autoview=sku

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Old 01-05-2009, 01:00 PM
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or buy a digital scale. 1cc water weighs 1 gm.

Use a squirt bottle to fill the chamber then do a before and after weight measurement of the bottle. An old cd works well for a chamber cover.

http://store.summitracing.com/partde...5&autoview=sku
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Old 01-06-2009, 08:20 PM
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re: has anyone heard of these heads??

they are competely stock heads that came off the original 1971 245 hp 350 stock gm bearings stamped 3 71 no numbers on rods showing that it was rebuilt it even had the original gm oil pump
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Old 01-06-2009, 11:20 PM
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These are a decent large chambered head. They aren't anything special or rare. These particular heads and their siblings (487x) heads are preffered by some dirt track racers for classes where stock heads with large chambers are required.

They are worth a couple hundred bucks on ebay only for that reason. If they have not been ported.

Have them cleaned and crack checked for sure. Anything that old should be anyways even if it came off of a "running motor" which is something people like to say....then you have to wonder how long it would have been running for.

I don't buy used heads without a money back agreement in case they are cracked. I would rather spend 20-30 bucks checking a set of heads then getting stuck with a junk set for 200-300.
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Old 03-18-2009, 04:35 PM
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whats the best hp rating i could make if i milled ported to a 1207 gasket and polished them
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Old 03-23-2009, 09:26 AM
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About as much HP as you would make with any other Stock head. "Not alot" Like I said these are the best heads for restricted classes. Which means that they are not a "performance" head. You would be better off with a set of vortecs or something aftermarket.
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Old 03-23-2009, 03:03 PM
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487 X heads.

Last week, in the transmission forum, I posted about a trans and rebuild kit I bought for CHEAP. I also wound up buying a bunch of other parts and pieces very CHEAP also. Saturday I went back and bought a set of 487X heads for $40.00, that look virtually unused. I'm going back for another set of heads he has, also CHEAP, they are small valve heads, by todays standards, but they are a bit on the rare side. Now, if I can just find the F.I. or dual quad setup, to go with these heads for the same "CHEAP". The recession is having an effect on this hobby.
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