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busting valve springs

PostPosted: June 13th, 2011, 1:37 pm
by grumpyvette
Ib was chased my "backfiring out the exhaust issue" to a broken valve spring yesterday. This is the second spring I've broken on these 2.02 fuelie heads in about 10 years. The springs are single coil, "racer brown" springs that were part of the head rebuild in 1988. Heads maybe have 3000 miles on them. Cam is a healthy lunati-00012, int/exh lift 0.515 in.
Question is, do valve springs break with these newer camshaft profiles? Is this set due to be replaced? Again only 3000 miles, tops. Revs are kept under 6000.
Any suggestions for a replacement set?"

keep in mind that weak link in the chain idea, in many engines with upgraded valve springs the rocker studs benefit a great deal from a stud girdle as it significantly reduces rocker stud deflection, certainly by the time your looking at using more than 160 lbs of valve spring pressure use of a rocker stud girdle and quality roller rockers, and the correct geometry, clearances and checking for significant oil flow over the valve springs becomes almost mandatory to maintain durability

when valve train parts fail, 99% of the time its a symptom of a clearance or lubrication issue.
a great deal has to do with the CLEARANCES and the springs installed height, if your breaking springs at only 3000 miles theres a very good chance the installed valve spring height and spring bind, or retainer to valve guide clearance was not carefully measured
or the rockers bind on the rocker studs at max lift
guys frequently take the springs that cam with a cam kit out of the package and install them with the stock retainers and never give it a second thought!, the truth is that in 90% of the cases I see where parts break,they never measured clearances, on the springs, retainer to valve guide or rocker to rocker stud
when a cam manufacturer suggests a certain valve spring be used he also suggests the installed height and minimal clearances, you can,t install the springs without verifying clearances and installed height, and if they suggest new springs its generally because the stock valve train and components and clearances and springs won,t work







BTW if your thinking about getting those stamped steel, roller tip rockers , DON,T!!, they have a tendency to fail, and they don,t handle high spring pressures well, and they don,t reduce friction much so they are basically a (FEEL AND LOOK GOOD" part that doesn,t do much constructively[/color]


Because, easily 90% PLUS of the friction in the valve train is NOT on the contact between rocker arm tip and the valve stem, so swapping to a roller tip on a rocker provides negligible benefits in friction reduction.
you can buy decent quality full roller rockers, for well under $250-$300
and roller tip rockers commonly cost 1/2 or more of that making the full rollers a much better option