1.25" SBC max valve lift possible?

[CAPTAIN COMMANDO]

I have DART 165cc heads with 1.25" springs rated to supposedly .510" lift. Truely what is the safe limit on choosing lift for cam with my heads and spring combo? Is .502 lift with my 1.5's gonna hurt anything? Current cam is a .224/.234@.050 114lsa and .465"/.488" lift with 1.5's. I wanna install a cam with .488/.502 lift and duration is definately bigger. Hope to make a difference in Hp with my cam swap but If I'll push the limit on the springs too much I won't do it. What do you think?

[Corvette Kid]

When I read your thread title, I thought you were wanting to achieve 1.25" of valve lift! If your springs are rated to .510" and lift with the new cam will be .502" you should be fine. Make sure installed height is correct and check the springs for proper tension if they've been in use for very long.

[C4Techie]

Originally Posted by Corvette Kid

When I read your thread title, I thought you were wanting to achieve 1.25" of valve lift!

That IS what it says.

Your 1.5's have nothing to do with anything. It is the distance of valve traval that counts. A valve travel of .502" is cutting it close with a spring rated for .510". Besides the above good advice, check the clearance between the coils for the posibility of coil bind.

[CAPTAIN COMMANDO]

I did it to get the attention of you guys! LOL! Thanks for the info.

[TimAT]

Originally Posted by C4Techie

That IS what it says.

Your 1.5's have nothing to do with anything. It is the distance of valve traval that counts. A valve travel of .502" is cutting it close with a spring rated for .510". Besides the above good advice, check the clearance between the coils for the posibility of coil bind.

You'll get ONE chance at coil bind. When the valve spring coils stack, it is no longer a SPRING- IT'S A SPACER. And something's gonna' give. I tend to use the cam builder's springs spec'd for that cam.