I was wondering how much lift could be run on stock style valve springs?

Thanks

Ben

 

.49 is pushing it.

 

There is a lot of variance in "stock" springs, and a lot of variables that determine what is safe. Aside from the simple mechanical binding point of the coils at a given lift, there are other factors to consider. Just because the coils don't bind at 0.480" lifts doesn't necessarily mean that stock springs are adequate for a particular engine.

Typical stock valve springs have a closed seat pressure under 85 lbs. This might be enough for smaller diameter valves at low RPMs with a relatively mild cam profile. Increase the valve mass, engine RPM, acceleration rate (lobe ramp), lifter mass, rocker design, and the low pressure stock springs can start to lose control of the valve train. This can mean anything from power loss due to valve float at higher RPMs to valve spring failure with catastrophic damage as a result.

It's all a necessary part of selecting the appropriate camshaft and components to suit the engine and its intended use. Stock springs at 0.480" lifts in a stroked truck-pulling engine might be adequate. A higher RPM, large valve street/racing engine might not fare too well with them, however.

 

.46 is my limit, actually i most always change springs when i change a cam, even if the springs are a stock type replacement.