Ok I got a bone stock 91 rs 305 tbi wanting to do a cam swap and I know I'll have to get a chip made for it when I put in a cam but can I use the spiral heads and have them ported out and use them or do I need a different set of head ........ I'm wanting to use or find a cam 218/224 with a lift of .553/.547 is there something around that ball park to use I'm new to this and needing some help from the group ( ps I don't want to swap a 350 in it)

 

Hi Austin, Welcome to TGO. The cam you are considering should be a good fit for the small motor, although I don't know about the lift for the stock heads. Be sure to look at what lift the guides allow. You'll want to change springs to match the cam anyway, but be sure that the guides and retainers will allow the lift you're looking at.

The 305, without a complete redesign, won't make alot of power but the cam up grade should get you some torque improvement in the engine's power band. I would leave the heads alone. If you want to pull them and do some bowl and pocket work, maybe clean up the runner entries a little, but keep it minimal. You won't get a huge improvement from going crazy and you risk making things worse. Focus on smoothing behind the valve seat pockets, around the guide bosses, smooth the short turn radius in the exhaust ports. It doesn't hurt to smooth out the rough cast surfaces of the ports, just don't remove too much material. Or, just leave them be, you'll still get a pleasant boost in torque from the mild cam upgrade. As far as finding the cam you want, look at Comp Cams catalog online. You'll find something in the range you're looking for. There is also Crane or Howard's Cams. Think about a manifold upgrade to compliment the cam.

 

There is no real need to go above about .470" valve lift on a swirl port head. The ports stall is below 0.500". I would look into something that does not require massive head work like screw in studs. Just a mild spring upgrade.

 

That sounds like good advice.