1991 RS 305

1985 TPI 305, mods in sig. I'm porting & installing a TPIS base. Cam is non-peanut .403/.415 lift. To enhance the effect of the ported TPIS base, would it pay to go Comp Cam 1.6 roller tips? These would yield .430/443 lift. Or would 1.52 roller tips work as well, or just stay stock? Some say 1.6 will increase guide wear, some say the total lift is within reality, and its a non-factor. How much HP gain can I REALISTICALLY expect from this combo, separetely and combined? Comments?

Morley

TPIS bigmouth base? You'd need larger runners to go along with that and the plenum. Not to mention you'd need headers to expell all of that burned air/fuel mixture.
The gutted cat may actually be hurting your performance (this has been explained here before) and I don't now if the lil ole 305 can really make use of all that extra flow (but an increase over stock will help)

D Stroy H8

Go with the 1.6s

On an offshoot, I wouldn't siamese the bigmouth base, as it should be great out of the box for a 305. You could lose more torque than the hp gained.

1991 RS 305

I'm not siamesing the base, just removing the "step" at the runner entries, and generally cleaning up any flash and smoothing things out. The runners are the least restrictive component of the TPI system, especially for a 305. The base is the bottleneck, since the stock heads will outflow the base. The plenuum is ported. The T-Body is the stock 48mm with airfoil, which is fine. As for exhaust, I want to keep stock appearence, and have opened it up as much as possible short of headers. As for gutted cats, it "might" not flow as well as a straight pipe, but it flows at least as well as any cat, and would pass a "visual" inspection if need be. Plus it sounds better. When its all said & done, I'll again scanner-tune the A/F for 13.1 at WOT, like I have it now. FWIW, my fuel pressure is down to 38 lbs from 43 lbs stock. So much for adding more fuel pressure to go faster, not always the ticket. My concern for the 1.6's is valve guide wear vs the 1.52's, although I'd go 1.6's if safely possible. What are others experience with this?

8Mike9

Assuming trading stamped rockers for stamped, the increase (if any) in wear would be minimal.

Going to a roller tip or full roller, should be less wear, as the "tip" would then roll across the valve, instead of slide.

All that said, isn't the increased "load" on the rocker on the pushrod side anyway? So then the only real difference in that the valve will go "down" further in the guide.