Reply to "Valve spring selection"

Cleveland valve springs are usually sourced from BBC applications. Keep in mind the Cleveland valve train is identical to the valve train of other "big block" engines in terms of valve size and weight, rocker arm ratio, etc. The installed height of BBC valve springs is 1.88 inch, whereas the installed height of Cleveland valve springs is 1.82 inch. With the flat tappet springs I find you can get away with installing the BBC springs at the Cleveland height while keeping the seated force in the desired range, and while providing enough maximum lift. This is not the case with roller tappet springs. Those springs must be installed at the BBC height (1.88 or 1.90 inch) which requires cutting the spring pedestals, longer valves, or both.

As per Harvey Crane modern flat tappet cams need springs rated 115 to 130 lbs on the seat, and 300 to 330 lbs over the nose.

One possible valve spring for flat tappet cams is Crane 99839, it is a single valve spring plus damper, 1.50 diameter, 354 pounds per inch spring rate. When installing this valve spring please ignore the factory specs, and adhere to these: 1.82 installed height, 114 lbs. seated force, 0.590” maximum lift. This spring provides a range of over the nose forces from 284 lbs (0.480 lift) to 323 lbs (0.590 lift).

Another possible valve spring for flat tappet cams is PAC Racing 1900, it is a single valve spring plus damper, 1.50 diameter, 376 pounds per inch spring rate. When installing this valve spring please ignore the factory specs, and adhere to these: 1.82 installed height, 120 lbs. seated force, 0.605” maximum lift. This spring provides a range of over the nose forces from 300 lbs (0.480 lift) to 348 lbs (0.605 lift).

Both springs allow more lift than you'll likely need, even when installed at 1.82 inch. My preference lately has been the PAC Racing spring.

Roller cams require a bit more spring force than flat tappet cams because the tappets are heavier, and potentially open the valves a bit faster (higher flank rate). I shoot for 150 to 160 lbs seated force, and 370 to 400 lbs over the nose. A valve spring for roller cams is Manley Nextek 221432, it is a dual valve spring plus damper, 1.53 diameter, 435 pounds per inch spring rate. When installing this valve spring please adhere to the manufacturer's specifications: 1.90 installed height, 150 lbs. seated force, 0.630” maximum lift. This spring provides a range of over the nose forces from 368 lbs (0.500 lift) to 424 lbs (0.630 lift).

Beware, if the Manley spring is installed at a height of 1.82 (the standard 351C height) then its maximum lift should be limited to 0.550, and the seated force increases to 185 lbs.

Accompanying any valve spring upgrade my preference is to install valve spring cups and to use titanium retainers. The spring manufacturers should have the tools for cutting the spring pedestals for the spring cups. I know Manley does for sure, I haven't checked on PAC racing yet.