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ok.... so in hopes of building 475 horsepower on a 1970 460, I have started to play with valve sizes on my desktop dyno. Since I am looking for low range torque, I am toying with the idea of putting Manley SS 2.08 or 2.19 Intake and 1.83 Exhaust valves in my Dove-C heads. My desktop dyno shows the 2.08 gives me 435 ft-lbs of torque at 4000 rpm. A question for you? As long as I do a nice job on my port job, what else do I have to worry about with increasing the valve sizing? More airflow means more compression right? So with bigger valves would I have to be concerned with cylinder pressure?
 

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Changing the valve diameters should do nothing to change the compression ratio, provided you do not open up,or increase the chamber size. Increasing the chamber size would lower the ratio slightly. These heads usually are listed as 72cc chambers but are actually closer to 75cc (at least mine were 75cc).
 

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By all means upgrade to 2.190 intake and 1.77(or thereabouts) exhaust. I've used Milodon, Manley,and a couple of others, all worked fine.DO NOT use a "BOWL HOG" to open the pockets. There is water between the bowls. You hit it and the head is junk. Unfortunately, the water is right where the intake port wants to be opened up. Don't touch the floor of either port, just get the "berries" out and blend things with a hard roll. If there are thermactor bumps in the exhaust ports, grind 'em out.
 

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If you want 475 horse out of a 460, leave the heads stock and just give them a 3 angle valve job. A Comp Cam 290H Magnum cam(or smaller), Rhoads lifters(for added low end torque), 10.5 to 1 compression, Torker II/Stealth/Performer RPM intake, 1 7/8" headers, & electronic ignition should easily get you there with over 500ft/lbs torque too.
 

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you go with a bigger intake valve and your RPM's go up.If you want to keep it a 5000 rpm keep the stock intake.I'd take 89coupe's advice.On my V3.0 my 460 is at [email protected] and 499tq at 4000 and thats runnin 8.5 comp,stock D3VE heads,RPM intake,735 holley,lunati BMII cam,early T-chain and gears,2in prim.headers
 
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