Posted By: Badge
Need Help with matching camshaft and valve springs - 03/14/13 09:11 PM
I have a 360 small block. I am going to install a purple shaft camshaft P 4120233 AC hydraulic flat tappet .508/.508 @ 292/292.
I have a new set of Manley dual valves springs. Seat 115 lbs @ 1.80,
Open 310 lbs @ 1.25. Are they to much spring for this cam? Thanks.
Posted By: dogdays
Re: Need Help with matching camshaft and valve springs - 03/14/13 10:30 PM
Important question: What is your spring installed height? I'd be surprised if you had all of 1.80" on a stock smallblock head. I've measured between 1.6 and 1.625 on mine.
So 1.625 - 0.060 for coil bind -0.508 lift equals 1.057 maximum spring solid or coil bound height. Anything more than that and you're breaking things.
Another thing, your spring has a rate of 355 lb/in, the reduction of height puts the seat pressure at 177 lb. That's quite a bit.
I'm not as experienced as many others, but IMHO going high-lift on an LA motor takes some careful juggling of spring parameters.
R.
Posted By: Badge
Re: Need Help with matching camshaft and valve springs - 03/14/13 11:34 PM
Good point. I have not measured the existing springs for installed height.