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Discussion Starter · #1 ·
I recently picked up a set of these heads redy to bolt on for 200 bucks.My question is do i really need the special headers or are there ways around the plug issue.

Also right now i have D8OE's on this 302 what kind of improvement will these GT40's be?Will it be very noticeable?

And one more thing does anyone have the specs on these heads like combustion chamber sizes and so on?

<font size=-1>[ This Message was edited by: Fiveoh on 5/5/06 11:54am ]</font>
 

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Discussion Starter · #2 ·
With a 80' 302 sixty over,Performer intake,1406 carb.BBk shorties,crane z cam Basic Operating RPM Range: 1,800-5,600 RPM
Intake Duration at 050 inch Lift: 218
Exhaust Duration at 050 inch Lift: 224
Duration at 050 inch Lift: 218 int./224 exh.
Advertised Intake Duration: 268
Advertised Exhaust Duration: 274
Advertised Duration:

what kind of gains can i see and power will this make over the stock D8OE's?
 

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check out
http://www.stangpro.com/
They do flow good, don't bother with a huge cam as these or any other stock head don't flow too good after 0.500" lift without a little porting.
If it doesn't go straight to the article about the heads go under "articles" then look for the GT-40P section, it's a good one. Peak flow isn't all you should be concerned about, check out the 'area under the curve'.
The headers will be a problem, some shorty headers work like MAC & BBK as long as they go straight away from the heads a couple inches before turning down, the problem is that the plug sticks almost straight out and most headers are going to hit the plug. You can modify headers pretty easily just be sure to only do one at a time. Usually the passenger side is not a problem.

Intake Flow @ 28" H20

.100" .200" .300" .400" .500"
GT-40P 61 128 169 195 196
GT-40 54 107 157 183 192
E7TE 59 114 144 156 156
'69 351W 52 103 149 174 183
289 50 97 127 156 165
GT-40 (Y303) 64 114 167 199 213
GT-40 (X303) 53 114 170 207 226


Exhaust Flow @ 28" H20

.100" .200" .300" .400" .500"
GT-40P 52 90 123 135 139
GT-40 47 94 119 128 128
E7TE 42 78 105 115 116
'69 351W 48 77 100 113 118
289 37 71 93 104 107
GT-40 (Y303) 52 98 128 137 134
GT-40 (X303) 50 106 139 153 161

Intake A.U.C. Exhaust A.U.C.
GT-40P 65.1 46.95
GT-40 59.7 45.2
E7TE 55.1 39.8
'69 351W 56.95 39.7
289 51.45 35.85
GT-40 Al. 65.1 48.26
GT-40X Al. 65.7 52.9
Twisted Wedge 76.65 57.3
"Power heads" 67.05 57.9
 

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And equal length shorty headers won't fit at all.

Most people use a 90 degree plug boot to gain some clearance, and Accel makes a special short spark plug but they're about $12 each.
 

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Forgot about the combustion chamber.
They're listed as being 60cc's, that will bump your compression up some over the heads you've got now.
I measured the combustion chambers on mine and they were about 59 to 60+ on one head, and 60 to 61 on the other.
 
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