I Just got my heads back from the the machine shop. How much variation is acceptable in seat depth. A few of my valves stems are up 0.03" - 0.05" when compared to the others. Will this be a problem when I install the rocker assembly. I don't have adjustable push rods so was wondering if the the deeper valves will fully close? Any advice would be much appreciated. 1961 364 (stock)
The 57 manual states that any stems .075" above the normal stem height need to be ground down or new parts added to reduce height. The 60 and 66 manuals state any stem .050" higher than the normal stem height need to be ground down or have new parts added to reduce height. The 364, 401 and 425 all used the same head in these manuals. The normal height of the valve stem above the valve rocker arm cover gasket surface is stated at 1.540". It looks like Buick determined that the maximum height above normal was less over time. I have seen a figure of .030" as acceptable in the Rebuilders Handbook. I would personally want no more than .015" because I want preload very similar at the lifter. Cheryl
I agree Mike, i just pulled out 2 old freeze plugs from the water jacket too I brought a laundry list of specs, had to argue to not have hardened seats installed... i guess i left out “remove old freeze plugs when knocked out”... sheesh
.050" is a lot of veriation boy, and it sure means that there is going to be big differences in the valve job along with the end result of big differences in flow numbers!!! Where new valves used, I am betting not? GM Hydro lifters have a .120" plunger travel range and most times the factories set up the valve train / push rod lenght to run in about the middle of that .120" range, so a valve height change of .050" does not leave much room for the motor to deal with expansion and contraction rates and worn parts. And yes very sloppy work!!
Remember .050" in valve travel is only .031" in lifter travel because of the 1.6:1 rocker ratio. Cheryl
All parts used were new. Valves, springs, guides, locks, seals on in intake valves... It appears the stem height variation is the least of my worries. I bolted one head on and did a leak down test and 80% of the pressure is leaking out of the valves. Time to find another machine shop
