Which heads are better 1970 Mustang 302 heads or gt40 - Ford Mustang Forum
 
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post #1 of 8 (permalink) Old 08-24-2011 Thread Starter
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Which heads are better 1970 Mustang 302 heads or gt40

I have a 1970 Coupe with a 302.It was a daily driver until some valves started pinging. So i pulled the original motor out and i had a '76 302 that fairy new so i stuck it in. I also added a performer intake, 500 cfm carb, and headers. But my car seems slower now than before. so i would like to do a head swap because i understand that '76 heads are extremely weak ( goverment emisions) Would i be better off to get my original '70 heads redone, with a hotdip, pressure check, ect ect, or would a good set of gt40 or gt40p heads be better (i understand my headers may not work with gt40p)????




1970 coupe 302 C4
2007 V-6 5-speed, shaker 500, premium wheels ECT ECT
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post #2 of 8 (permalink) Old 08-25-2011
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gt40 heads any day over those. The gt40p's flow a little better but you won't get the header issues with the normal gt40's.
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post #3 of 8 (permalink) Old 09-06-2011 Thread Starter
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all right thanks a bunch. Im new at the car game and im self taught so any imput is great. thanks
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post #4 of 8 (permalink) Old 09-07-2011
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Well, the '73-76' motors are some of the worse. Down to 8/1 compression from 9/1 you had before. Think the crank timing is retarted also. Going to the GT-40, which do flow a lot better, is going to further drop your compression ratio. I'm guessing down to about 7.5/1. Could mill the GT-40's heads to get some of that back, not sure how much.
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post #5 of 8 (permalink) Old 09-07-2011
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worse heads were the 255(4.2) v-8 heads.
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post #6 of 8 (permalink) Old 09-07-2011
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Quote:
Originally Posted by Dave View Post
Well, the '73-76' motors are some of the worse. Down to 8/1 compression from 9/1 you had before. Think the crank timing is retarted also. Going to the GT-40, which do flow a lot better, is going to further drop your compression ratio. I'm guessing down to about 7.5/1. Could mill the GT-40's heads to get some of that back, not sure how much.
Dave
why would gt-40's reduce the compression ratio? The gt40's are 61cc what are the stock 302 cc volume?

1968, 302 .030 / Comp Cams Magnum 270h #31-414-3 501 lift @ .050 dur 224/224
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post #7 of 8 (permalink) Old 09-07-2011
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I think the 76 302 where 58.2cc. If that is the case, seems like using the 76's it would have higher CR, even though slight. I'd still choose the GT40's and mill them to your desired CR. Although before you go sinking money into rebuilding heads - there are some good cast iron aftermarkets for 1000$.

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post #8 of 8 (permalink) Old 09-07-2011
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theres also brand new edelbrock aluminum e-streets for $900ish from CJ Pony Parts (cjponyparts.com). when they have a sale they go down to $836

talk about breathing better... aluminum cnc heads >>>> cast iron 302 heads from any year ever
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