Valve Spring Installed Height?

[axelbaker]

I am rebuilding my heads, and cannot locate a number in the manual for the correct valve spring installed height. I am getting approx. 36.2 - 36.3mm. Is there a factory spec?

Thanks.

-- Alex

[18Fiatsandcounting]

I've never seen a factory spec for this, but that doesn't mean that there isn't one. However, I'm curious why you would want to verify this particular measurement. The height of the springs would be determined by the placement of the valve seat in the cylinder head, the valve itself, and the top plate and collets. Assuming that these are all standard Fiat parts and correct for your engine, the spring height is what it is when the spring is installed and compressed.

Usually people are more concerned about the tappet bucket-to-camshaft clearance, and that would be 0.015-0.019" for the 4 intake valves, and 0.018 to 0.021" for the 4 exhaust valves, on a cold engine, and with the camshaft housing box bolts torqued to spec to the head with the appropriate gasket between the two. This spec is for an earlier DOHC engine, so you would need to verify for your 1981 engine.

-Bryan

[axelbaker]

It determines the preload on the spring and therefor pressure on the valve. It's a fairly normal measurement to check when building a head. It increases slightly every time you lap or grind the valves and seats. You shim (or re-cut) the spring seat to compensate and balance between springs. It's normally spec'ed when you buy valves or cams too. I found the spec for Iskenderian springs, it's should be the same.

Installed height: 1.417 inches (36mm)

Mostly I would just expect to see it listed somewhere, especially on a motor that people race.

[18Fiatsandcounting]

Thanks for the explanation. I did find this spec for the (uninstalled) spring deflection under a specified load, if that helps:

Outer spring: 36 mm with an applied force of 59.5 kg plus/minus 2.5 kg.
Inner spring: 31 mm with an applied force of 28.1 kg plus/minus 1.2 kg.

-Bryan

[axelbaker]

Cool your numbers match the ones I found.