i was gonna use this small compcam in my 86 tpi 305 and wanted to know if anybody knew how much lift the stock springs could handle? isnt it like .475 lift or am i wrong?

 

A stock spring is good for nothing, at best, as far as controlling a valve is concerned. They are weak. They are rated, from the factory at a measily 85 lbs on the seat (or something very close to that number). They get weaker from there. I have seen valve springs off of my old LG4 get rimac'd at about 50-55 lbs of seat pressure.

Anyway, the factory springs themselves are good to about .510" of lift before they come accros any bounds themselves (coil bind). The biggest factor is the clearance between the guide boss and the bottom of the retainer. Thanks to the micacle known as casting imperfections and variations between castings, the generally accepted value is about .460" to .480" of valve lift. If you have a valve spring micrometer, that is the best way to tell for sure what maximum lift you can use.

 

ok, so i should be ok if the cam i am gonna use is 460 or so lift?

 

stock valve springs are good for whatever scrap iron price is. no matter what replace them.

 

ok, so ill get the comp replacements

 

You'll probably be just fine.

Stock valve springs won't.

There's ALOT more to evaluating whether a valve spring is suitable, than just the peak lift rating.