From what you posted, you did not degree the cam. There is a chance things got messed up on install and a chance the cam gear was out some.
Did you also use a aftermarket timing pointer without establishing ture TDC on the balancer? They are famous for being pretty but inaccurate. The last one I installed was a full 4deg out.
Any and all of these oversights or a combo of, can and will cause you to get a good bit less power than what you would expect from the parts.
My old, simple, throw together 350 vortec head motor with rpm manifold and generic 214-224 .442-.465-112 cam wanted 36deg timing and ran 13 flat @105 all day every day. Picked up a full 1 sec in 1/4 mi et and 4.5 mph drag test compared to #882 heads/performer manifold on the same motor
It made a true 374 Brake Horsepower, exactly as it should. The true cr was 10.05:1 measured.
Something is definatly up. Unless the 487's were big valve and expertly ported, you should have seen a good increase in both torque and power.
What is the casting number of your vortec heads? (under the valve cover)
New, recent GM Parts heads or the origional '96 to 2000 GM OEM L-31 truck heads, or aftermarket copy?
Apparently the new/recent GM service heads are from Mexico and do not flow the same as the old OEM L-31 heads or make as much power. (typically down 20hp according to some engine builders dyno results)
Your true cr with a .041" gasket and a .045" piston deck clearance (typical rebuilder 1.54" CH flat top pistons) can be a as low as 9.3:1 If this is the true specs of your motor, swapping to a .015" shim gasket would get you up to just a hair under 10:1 true cr.
I put my bet on a cam timing/ignition timing accuracy issue.
What vehicle is this motor in? what rear gear ratio? what transmission, converter stall speed.
Last edited by F-BIRD'88; 07-06-2009 at 10:47 AM.