302 & 351w E7 Heads

[StangaTang]

Hey got a couple questions about some heads i've got. Ok here goes both sets come off roller motors and i'm going to a flat tappet cam & lifter in my new motor I was wondering how big off lift can I run with valve springs that are already on the heads the valve springs are the stock roller ones nothing done to them? And which ones should I run the 302 or the 351's the 351's has little bit bigger valves in them, but I know also that I have buy some bolt spacer for the 302 headbolts to work because the 351's use bigger head bolts. Would the difference in the valve size make it worth it or should I use the 302's. And how big of a cam can I run before I run into any ptv problems? My pistons has the valve reliefs. Thanks for your help and advice!

[SHONUF816]

i do know that the stock e-7 head springs will support the stock roller cam which comes in @ .444 inch lift. running anything bigger than that will cause your valves to float at high rpm's. i would just upgrade to the right springs for the cam you are running and save yourself the headache in the long run. i run a trickflow stage1 cam w/1.72 roller rockers which raises the lift of the cam even more and i have not ran into any piston to valve clearance problems but i'm also running edelbrock heads. jmo.

[StangaTang]

The cam I'll be running will only be 448/472 lift.It won't be seeing alot of high RPM's mostly just a driver may take to the dragstrip everyonce in a while.

[lone sailor]

You really should upgrade your valve springs regardless, but .500 and over is generally the rule of thumb.

[Black90gt]

Why flat tappet verses roller just out of curiousity

[StangaTang]

Because the flat tappet is free and the roller cam that was in the motor was a wasn't a H.O. cam i've heard they have really small lifts. I have a used H.O. cam but I don't have the roller lifters for it. If the roller lifters out of the Non H.O. will work I'd use it.Just worries me a little about using those used lifters on a different used cam. If they 'll work i'd use it.

[Black90gt]

I've reused roller lifters before especially if you are sticking with a stock or close to stock cam....don't worry about using used roller lifters with a different used roller cam. It's not like a flat tappet cam where the lifters and cam wear into each other they are roller tips....

[StangaTang]

Thanks for all the help guy's