Hi all, I was wondering what the safe lift limit is for my 305 engine. It's a 1991 camaro z28 with the F code. It has the dual cat option if it makes a difference. I want to put a cam in it and I wanted to know what kind of limits I have with stock heads and stock valves before i have to change valves or anything. Also, just out of curiosity, is it possible to remove all the roller components and switch it out for a non roller cam and lifters?

 

Why would you even consider a flat tappet cam vs a roller... to save from buying a Roller
you really need to measure your springs on every application.. you would be safe if you stayed under .500.. install 1.6 rockers... you would benefit.. if you did more mods with a cam

 

.480" is the commonly quoted value, but production tolerances vary considerably on stock heads. If you're getting close, you should measure.

 

The benefits of a roller cam FAR outweight the higher price tag, especially if you're already starting with a roller-cam block. Yes you can use a flat-tappet cam in a roller-cam block, but its not worth it once you consider the hassle of swapping.

Any cam less than .460" will work with the stock heads, and that includes the rockers. Using 1.6 rockers with a .460" cam will not work as that makes the lift .491". You can put 1.6 rockers on your stock cam, that's ok.

However, I hardly feel its worth the hassle to pull the intake manifold, front cover, and go thru the hassle to swap the cam on an engine with stock heads and intake. Dont forget the stock springs and valve seals that are on there are 20 years old and should be replaced when you change the cam.

 

I work with stock heads a lot, and I see much variance in clearances.

IMO anything over 0.450" lift, and breaking out the measuring tools is a MUST.

Some heads will clear a little over 0.480" with no modification, but you have to measure everything carefully.

If you plan to run without valve-seals, then you can go over 0.500" lift without modification, and though some racers do it, it isn't advisable to run without seals on the street.