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Builds and Journals This is where the magic happens. Photograph & document your GMC build progress for posterity.
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  #1  
Old February 20th, 2013, 03:04 PM
AHarman AHarman is offline
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Default 478M head porting.

I have gotten final numbers on port flow for my 478M project:

all numbers are at 28 inches stock valves final E/I E/I E/I
Lift intake intake intake stock valves final
0.1 86 83 85 0.698 0.843 0.882
0.2 142 157 183 0.810 1.025 0.863
0.3 189 205 220 0.825 0.893 0.868
0.4 227 244 254 0.789 0.832 0.886
0.5 257 265 283 0.770 0.819 0.859
0.6 279 271 318 0.753 0.845 0.805
0.7 290 316 336 0.772 0.750 0.818

exhaust exhaust exhaust
0.1 60 70 75
0.2 115 161 158
0.3 156 183 191
0.4 179 203 225
0.5 198 217 243
0.6 210 229 256
0.7 224 237 275

This is fair-to-middling results, about equivalent to a big-block Chevy 390 aluminum head with a 2.25" intake valve. Think it'll get to 500 HP?
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Old February 20th, 2013, 04:54 PM
AHarman AHarman is offline
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Default Re: 478M head porting.

Sorry about the eye chart appearance of all the numbers up there.
Here are what the columns are:
The upper table of numbers is intake flow, and ratio of exhaust to intake flow.
The lower table of numbers is exhaust flow.
First column is valve lift.
Second column is for a stock Magnum head with 2.25" intake, 1.88" exhaust.
Third column is for the Magnum head fitted with 2.35 intake, 2.00 exhaust valves, but without any porting or seat blending.
Fourth column is for the ported head with big valves.
Fifth column is ratio of E/I for stock head.
Sixth column is E/I for the head with big valves unported.
Seventh column is E/I for the ported big valve head.
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Old February 21st, 2013, 04:35 AM
Mtnative Mtnative is offline
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Default Re: 478M head porting.

Looks interesting, just a suggestion but you might put this on an excel spread sheet to simplify it so that it's easier to decipher.

Just put your descriptions in Row 1, the 0.1,0.2,etc down the first row and fill in the rest similar to how you listed them. Depending on how things transfer it may come over to the forum just fine or give you problems.

I know at just a glance it would give a great read out that way.

Thanks for posting them anyhow!
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Rich Foley, Bozeman, MT
66 3/4T 351V6 Fleet side, White, haulin/workin truck
88 Formula Fiero swapin to 4.9L Caddy motor
2004 KLR enduro
90 Mazda Protege (the runaround 240K)
1967 Jeepster Commando Buick 225V6 (3.7 L) (wife's)
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Old February 21st, 2013, 04:13 PM
AHarman AHarman is offline
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Default Re: 478M head porting.

Yeah, the data was pasted from an Excel spreadsheet, but the message board wrecked the formatting. Or maybe I didn't paste it using the right mode.
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