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Old 11-06-2008, 07:39 AM
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Double Hump head Question

I have a couple questions about my double hump heads. I have a set of 3917291 head. They have been cut for 2.02/1.60 valves. I know that they are 64cc. My question is what are they suppose to flow. I've been told around 170. I also was wanting to know what the benefit of angle plug heads over straight plug heads. Thanks for the help.

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Old 11-06-2008, 08:09 AM
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I don't think there is really any advantage of straight vs. angle plug... the only purpose I see they satisfy is easier changing of spark plugs with tubular headers

Flow... I've seen a flow chart- google stan weiss cylinder head flow- but I think it's around 210cfm- intake and 160cfm- exhaust... now that was a 1.94 valve.
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Old 11-06-2008, 08:35 AM
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Thanks for the help. That web site is loaded with info. What i'm running is a 388 stroker in my drag truck. I have the 291 heads on it now but I'm trying to upgrade to a better set of head to get more out of it. It has flat top pistons, and a .510/.510 hyd cam with 1.6 rockers. I'm going to change it over to a soild lift cam as soon as I make my head selection.
Thanks again.
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Old 11-06-2008, 09:13 AM
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I read an article that angle plug heads will produce 10 -15 horsepower over standard heads when using high compression dome pistons. It suppose to improve the flame travel. It does not affect any horsepower when using flat top pistons. You will get better flame travel in a flat top piston because of the flat surface in comparing a dome piston.
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Old 11-06-2008, 09:22 AM
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Ok Well thats good information to know. Thanks. I'm just trying to make the best choice of heads for my race engine.
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Old 11-06-2008, 10:36 AM
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Quote:
Originally Posted by Stonebrier 2
I have a couple questions about my double hump heads. I have a set of 3917291 head. They have been cut for 2.02/1.60 valves. I know that they are 64cc. My question is what are they suppose to flow. I've been told around 170. I also was wanting to know what the benefit of angle plug heads over straight plug heads. Thanks for the help.
For comparison here's 291s with 2.02 and 1.6 valves against L-31 Vortecs with 1.94 and 1.55 valves

Vortec Lift 291
70/50 .1 54/54
140/105 .2 120/95
190/140 .3 170/120
230/150 .4 200/140
240/160 .5 220/145

The answer for flow potential becomes apparent, the stock Vortec out flows the modified 291 by almost a consistent 20 CFM on the intake.

Moving the spark plug toward the exhaust valve has shown that the plug gets a better prime from the fresh charge which reduces miss-fires and incomplete burns. It also starts the highest heat point over the exhaust valve moving away from it rather than toward it which is actually reduces the valve's operating temps a few degrees. But the Vortec which is a move back to the complete Ricardo chamber rather than the simplified version of the older pre SMOG heads puts the spark plug much closer toward the center of the cylinder which reduces burn time. It's difficult to do anything to older heads that make them competitive with an out of the box Vortec. Test after test for years have shown that the Vortec head will produce 20 to 40 more horsepower than well prepared Camel Humps. When I use the term Vortec this not only covers the so named GM head but, also, there many brands of comparable aftermarket heads like the World SR and the Dart Iron Eagle to name a couple reputable head manufacturers.

Bogie
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