71 corvette heads
12-18-2001, 10:36 PM
#1
Racer
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71 corvette heads
I am a new member. I have a 71 ZQ4 270HP 350ci. vette with 59,000 miles. I am getting ready to do a frame repair on the car (stored in a dirt floor garage so it rusted the frame) and I would like to bump up the compression but I don't know what heads it has. They are double hump with accessory holes. Any input would be helpfull.
12-18-2001, 11:14 PM
#2
Burning Brakes
Re: 71 corvette heads (compuvette)
What casting #? I have the SBC #s manual. I'll check it out & let you know. They're definitely '69 or later (acc. holes) & probably 492 or 186s (dbl hump). Casing # is found on top surface of head in the valve spring/rocker galley.
Mark
Mark
12-18-2001, 11:24 PM
#3
Melting Slicks
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Re: 71 corvette heads (mdsmith)
according to my lil black book
you should have 3973487 heads with a 270 HP engine...
487" – 3973487, OR 3973487X. The regular casting was found on the 1971-1972 350 LT-1 engines, had 1.94/1.50" valves, 76CC combustion chambers, DO have accessory holes, intake port volume should be 161CC's, exhaust port volume should be 65CC's. The 487X had 2.02/1.60" valves.
so 76 cc chambers...
thatll give yah like 9.0 :1 ratio..(approximately) and thats on flat top pistons...
you should have 3973487 heads with a 270 HP engine...
487" – 3973487, OR 3973487X. The regular casting was found on the 1971-1972 350 LT-1 engines, had 1.94/1.50" valves, 76CC combustion chambers, DO have accessory holes, intake port volume should be 161CC's, exhaust port volume should be 65CC's. The 487X had 2.02/1.60" valves.
so 76 cc chambers...
thatll give yah like 9.0 :1 ratio..(approximately) and thats on flat top pistons...
12-19-2001, 09:36 AM
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Racer
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Re: 71 corvette heads
Thanks! I will be taking the engine out in about two weeks and want an idea of what I have now. I am planning on putting higher comp. pistons and a crane cam in the engine. I have a crane Energizer 260 and a crane Blue Racer 284H. I have not decided witch one I am going to put in. Desktop dyno gives me about 15 more horse over the 260 with the 284 and if you look at .050 duration the 284 (218) is still smaller than the 350HP 327 (222) cam and the LT1 (242/254) cam. I will probably go with the 284, it is a vette after all!
12-19-2001, 09:43 AM
#5
Team Owner
Re: 71 corvette heads (compuvette)
Thanks! I will be taking the engine out in about two weeks and want an idea of what I have now. I am planning on putting higher comp. pistons and a crane cam in the engine. I have a crane Energizer 260 and a crane Blue Racer 284H. I have not decided witch one I am going to put in. Desktop dyno gives me about 15 more horse over the 260 with the 284 and if you look at .050 duration the 284 (218) is still smaller than the 350HP 327 (222) cam and the LT1 (242/254) cam. I will probably go with the 284, it is a vette after all!
At the last minute we decided to go with the blue Racer 284 in my 74 to match the 041 heads that were put in(10.5:1) and MAN I am so glad that I did....The sound and lope are INCREDIBLE......It now just sounds mean and NASTY :reddevil :reddevil :D
12-19-2001, 09:59 AM
#7
Team Owner
Re: 71 corvette heads (compuvette)
So far I am having no problems whatsoever.....I think it is a great choice..I was a bit worried at first but so far it is perfect no problems with stall speed at all......100 miles and counting :smash: I am also running a turbo 400
12-19-2001, 10:19 AM
#10
Team Owner
Re: 71 corvette heads (daily_driver)
and is there a noticable lope at idle??
