Maximum safe lift on valve springs

[Rob B]

I have a 400 WT Motor with #12 heads. It originally came with the "067" which I believe the gross valve lift is around .407"
The motor has been rebuild but never fired. It now has a cam with a similar profile to the "068" grind except the gross valve lift is .444" not .407" I plan on pulling this motor apart and check everything before it is installed and fired in the car later next spring. Assuming that the heads have stock height replacement springs, will this new camshaft be okay to use with a non adjustable valvetrain? Memory serves me right, I thought you can safely go up to around .460-.470 on stock springs without any issues.

[PONTIAC DUDE]

.450 and a similar profile is not a problem with stock springs.

[Rob B]

.450 and a similar profile is not a problem with stock springs.

Thanks Ken!
I just don't want to get this car done next spring and have a problem or have a turd of a motor. It's basically a resto with a factory 4spd with air. doesn't have to be quick, I've got the other one for that.;)

[Mr. P-Body]

Rob,

We routinely use replacement springs with Comp XE262H, which has .470" lift on the exhaust. No issues.

FWIW

Jim

[Rob B]

Rob,

We routinely use replacement springs with Comp XE262H, which has .470" lift on the exhaust. No issues.

FWIW

Jim

Do you switch over to an adjustable valve train with that cam/lift or do you leave it "as is", torque 'em 20 and go?

[PONTIAC DUDE]

If it has replaceable screw in studs, I always talk the customer into replacing them with the BBC 7/16" studs. Can get them anywhere.

[Rob B]

If it has replaceable screw in studs, I always talk the customer into replacing them with the BBC 7/16" studs. Can get them anywhere.

That's generally what I've done in the past but I haven't pulled the covers yet to see if the studs are pressed or screw ins. There 1970 #12 heads.

[Mr. P-Body]

Rob,

For mild builds, we try to stick with the non-adjustable system. It's maintainence and worry "free". Yes, the XE262H has a stock base circle and works fine with the stock rockers. For cams with lift above .500" or with a smaller-than-stock base circle, we convert to "adjustable".

12s are all screw-in studs.

Jim

[Rob B]

Thanks Jim.