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.

Thanks George!

Is there a way to change the springs without removing the heads? Would that be a bad idea?

Its always more difficult working on the heads installed on the engine rather than working on them on a bench, but it is possible. I don't recommend doing any spring pedestal machining however because of the iron filings it creates. So limitations in what work you can do, and increased difficulty are the two drawbacks.

There are tools for compressing the springs from the top-side, making it possible to remove & install them. The trick to preventing the valves from falling into the engine once the springs are removed is to place the cylinder you're working on at top dead center.

Would installing the new springs with the heads on the car change your recommendation for the springs being installed?

Can any spring be installed if I do not pull the head?

Also if the rockers have different lift ratios 1.8 & 1.9 does that effect the spring selection?

quote:

Originally posted by tajon:
Would installing the new springs with the heads on the car change your recommendation for the springs being installed?

I would limit it to the Crane or PAC Racing springs, i.e springs with 1.82 inch installed height.

quote:

Originally posted by tajon:
Can any spring be installed if I do not pull the head?

Since machining the spring pedestals creates iron filings, I don't recommend machining the pedestals while the heads are mounted on the engine. Therefore your spring selection should be limited to springs with 1.82 inch installed height. This in turn limits your camshaft selection to flat tappet cams.

quote:

Originally posted by tajon:
Also if the rockers have different lift ratios 1.8 & 1.9 does that effect the spring selection?

The springs are limited to a specific amount of valve lift, regardless of the rocker arm ratio. The Crane spring is limited to 0.590 inch, the PAC Racing spring is limited to 0.605 inch lift.

The intake port airflow performance of unported 2V heads hits a brick wall at 0.400 inch lift, nothing to be gained with high ratio rocker arms.

being that the heads are not virgin, you have to find out if the spring seats have been altered from factory before doing anything

also, assuming they've had a valve job and the installed heights are not necessarily 1.82" or even within factory spec, you should measure each (all 16) installed heights from spring seat to retainer w/o shims for a baseline

from this baseline you can figure things out on paper before ordering parts that aren't optimized to what you're really working with. + and - retainers can be used to gain or tighten installed height, even shims can be calculated on paper before ordering parts