Thread: .450 lift, stock valve springs?

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The heads are rebuilt by machine shop with 3 angle valve job. This is a 283 .060 over. Installing 218/218-.450/.450. 106 lsa. I realize it is good practice to change out the valve springs but I would rather not if not necessary with this lift. BTW- hyd/ flat tappet. Thanks guys

While not stated, I will assume that your heads are “period correct” for a 283:

The stock GM SBC valve spring from the mid 50’s to mid 60’ was installed at 1.70" and had a physical limit of about .490". Hot rodders routinely modified the installed height upwards to 1.75" so the spring would take more lift, but there as typically not enough pressure for high rpm.

A factory “stock” (single) spring in good condition is good for 5,000 or so rpm with a cam that has slow opening and closing ramps, i.e., the “stock” factory cam. This is where the engineering for cam geometry was performed and while it’s one of the fist places we want to modify, it’s the place most susceptible to failure because more lift and faster profile cams are beyond what the components were designed for. A lot of the “performance cams” have steeper opening and closing ramps and cam lobe lift acceleration rates thus they require a spring with greater seat and open pressure than a factory "stock” spring provides. The stock spring will not be able to control the valve at high rpm, causing float and bounce. These conditions, if occurring even rarely, are very bad for the valve train and almost always lead to broken parts.

Your cam specs seem reasonable for a mild performance, “streetable” engine and you’ll have a noticeable “lopy” idle. Perhaps Tech (an others) will add more precise data for you if asked.

Have Fun!
Glenn

buy the 1.700 lt1 Z28 springs part number 98214 $30. put them in at 1.700 or buying a +050 valve locks and a hi set up retainers if your thinking of going up to 1.800 or buy the kit www.competitionproducts.com sells

Thanks for the info guys. You all have helped me out present and past. I wish i was more familiar w/chevrolet so that i could offer more info to people with questions. I'm more familiar with bb chev than sb. I'll get those springs.

Thanks again

I concur w/Pat. The Z28 springs are the way to go. They're good to .510" and a great value.

Regards,
Glenn