edelbrock magnum head flow?
so what is it exactly about the shape that holds it back? im interested to learn. is it the sides, short side, roof needs raised etc? where is the big drawback in shape for this particuliar head? Also so removing the pinch may show no gain on bench...but how would it translate to the dyno? thanks for any info
You can’t get the cross section big enough to feed that valve size. You are probably better off with a 50 degree valve job and the size valve you have.
Look at the shape of a W2 port, and then go look at the shape of some of the best heads going today and you will see a similar shape. A rectangle port is what you use when you can’t get an oval shape big enough to feed the valve size/CID/RPM you are using.
Again, removing the pinch rarely shows up on a flow bench, if at all. BUT...I’ll say it again, you have to look at the shape of the port. Every time you have a change in cross section, you have a flow loss. In a steady state test you may not see it, but it’s there. When you consider the dynamic situation of a port you can see why any change in cross section is not good. You just have to live it unless you can get it out.
Look down your port from the intake port and look at how many cross section changes you have. At the pinch. Then on the valve side of the pinch you have a divergent port wall (it is divergent from the common wall) running right to the bowl.
Not much you can do about that. The W2 takes most of that out, plus the pinch. It’s about minimizing compromises.
I’m all for the tunnel ram if you can find one. They are damned hard to find and they are getting expensive. If you can get the Weiand it’s a real nice piece. Make sure you think it ALL the way through. Start at the fuel tank and work you way forward. I’d run an electric pump and a bypass system. So you need a pump and regulator. Then you need TWO carbs. At 408 inches I would use a 1.375 venturi and a 1.688 throttle bore. Maybe, maybe a 1.750 throttle bore. If you get bigger than that (ignore carb CFM ratings and select a carb based on the two above metrics) you will certainly need annular boosters and they may not be a bad idea anyway. You need to buy carbs that have replaceable brass for everything, not just the main jets. I would use a Holley clone. I hate Holley with a passion because of how they have mislead and kept ignorant the end user. So I don’t buy their stuff unless I absolutely have no other option. I’m not a fan of the Carterbrock carbs because you just can’t tune them as easily as a Holley carb. You can’t separate the main circuit from the power circuit like you can with a Holley. Remember the clones are the same.
Also, you need to think about the surface finish of the manifold. A cold intake with that much surface area will benefit from a burr finish. If you do a Holley clone, you need to order the correct floats for a TR. Those floats have a wedge shape to them. When you tune the carbs sideways with the standard floats, every time you drop the hammer the fuel moves to the back of the bowls and it will raise the float and shut off the fuel at the needle and seat. That’s not good.
You will certainly need to change some brass to correct the idle circuit. And probably the power valve channel restrictors. You may have to do some drilling and tapping to get it done but it’s easy.
If I think of something else I’ll post it. I’d think long and hard about increasing the valve size. And I’d think the TR all the way through. It’s not cheap to do it right, but done correctly you have more bottom and middle RPM power than you can with any other manifold. And don’t buy an off the shelf cam. Call someone and have them help you. And don’t let the nattering nay bobs and whiz bang in gym shorts types tell you the linkage for sideways mounted carbs is a problem. If you can operate a pop up toaster you can handle that linkage.
