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If I were to get some stock heads and ported and polished them, would i have to change the valves in them since i am going to go with a 220/224 cam with a .551 lift on the intake and exhaust? What would be the best combo and best thing to do? What valves would compliment the cam?
So stock valves, sounds good. I want to keep the torque up as much as possible. How much hp/tq gain could i possible see from a good porting and polishing?
At home, expect to see 10, maybe 15 HP if youve ported before. A professional port job with stock valves might get you past 20. You might see 30HP with a pro port and new valves.
If I were to get some stock heads and ported and polished them, would i have to change the valves in them since i am going to go with a 220/224 cam with a .551 lift on the intake and exhaust? What would be the best combo and best thing to do? What valves would compliment the cam?
B/Bird, Your stock valves are fine, I've not seen a failure yet with them and besides they flow really well and they're not nearly as heavy as an aftermarket stainless. I've tried a few differant stainless valves for flow and regardless of how I grind them they barely beat the stock valve, only if you go oversize to a 2.02 or a 2.05 will you see an acceptable gain but that also requires a matching valve job to your new valve O.D. Regardless of what head you have LS1 or LS6 the flow up to .450 is pretty close and that's the biggest area of concern with your cam anyways. There's a big differance in port size with the LS6 ( about 11 c.c.'s ) which gains big numbers over the LS1 above .500 lift. ( as much as 40 cfm at .600 lift because the LS1 goes drasticly turbulant and flow drops off somewhere around .470-.500 where the big bowl in the LS6 keeps climbing. That's great if your going to run a .650+ cam but with your combo I'll take the smaller port. As far as porting you don't need to do very much to make decent gains, the biggest area is next to the guide on the let side, dont remove all the step but about half as there's water down at the bottom if you try to make it look like the right side. remove all the roughness from the short turn but don't lower it or change the shape. the port doesn't really need any real opening up, straightening the big bumps on the wall and roof and makes it look sexy but only adds volume to the runner. One thing , do not roll the bottom angle under the seat, if you do you'll kill your low and mid numbers without gaining anything up top and all your work will be a waste. We've got an LS1 here with just a slighly bigger cam than what you proposed with the same work on the porting I just explained making 400 rwhp and an LS6 with a much bigger cam making about 420, most people would think with all that flow gain past .470 lift that it be a huge advantage coupled with the bigger cam but it wasn't, it also had a price to pay for that bigger runner. I've seen motors with less airflow than these making 650 h.p. I'm sure you'll be far away from that. That's the logic Tony has at AFR with a great flowing port and a smal 205 runner. Keep it simple, you'll be fine.
06-06-2005, 08:10 PM
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