[mgarblik]

I have had some time to evaluate what I have for valve springs on these heads. The installed heights without shims varied quite a bit unfortunately. 1.840" was the shortest and 1.870" was the tallest. This was of course due to the valves and seats being ground at least once or possibly twice in the life of the engine. The valves have usable but pretty thin margins, but not overly concerning. The seat work looks OK but I haven't had a chance to run a pattern yet. Setting the springs back to factory height of 1.810" yields a seat pressure of 90-109 lbs through the set. Open pressures of 245-270 lbs at full lift. By reducing the installed height to 1.750" and using a pile of shims to equalize the installed heights I can get to 125 lbs. seat pressure. This would require a set of billet 7 degree keepers @ -.050. I have decided against this set-up. Although it would work, the cost of the new special keepers is 75% the cost of nice new springs that would give me the desired stock installed height and they are a known spring I have had good luck with. Decided to go with Howards Cams 98447 spring. This spring is a dual without damper, micro polished wire. 145 lbs. @ 1.750 and a spring rate of 283 lbs. Setting these springs up at the stock 1.810" installed height should give me 125-130 lbs. on the seat. Other Howards springs I have used lose 5-10% of their seat pressure after the first heat cycle and then settle in. The springs have the right dimensions and don't require any guide machining. Other sets of Howards springs have been pretty consistent pressure wise. I think these springs will be pretty gentle and close to stock SD specs. Only drawback to these springs is the wide distance from coil bind when fully open. But with the RPM limits of a 455, not overly concerned with spring surge. The OE SD springs were a very sophisticated spring design with inactive coils at the bottom. Way ahead of their time.