Going to measure the seat pressure on some old 430 springs, and I thought they might be good to use for cam break in. I supposedly have stage 1 TA springs on my old 455 heads, but haven't checked nor have torn them down to verify. Was either going to swap the stage 1 springs in after break in, or just call it a day with the old ones. Also, when the valve job was done they sunk the valves about .020. Should I really worry about shimming them to stock height @ 1.86? Bad decision on my part, because the shop got the valve stem heights varied, ranging in the largest difference about .015. I do have adjustable pushrods so I'll deal with it that way. I'm just trying to get the car running before winter sets in, as this was just a "stand in" engine for a year or two while I build another 455.
I would just break it in with the new springs they don't have no where near enough psi to cause concern imo, nor is .015 stem variation that's extremely minor from the ones I've had and seen anyway
I break cams in with the weakest single springs I have or remove the inner spring if dual springs are used. Less spring pressure during break in means less pressure and wear on the lifter and lobe therefore less potential for lifter & lobe failure. The engine is running at 2000 - 3000 rpm for a minimum of 20 minutes therefore minimal valve control issues. After the initial break in I replace the springs or inner spring as needed and move on. I have done this with 30 engines over the last 6 years with no issues.
In days gone by the factory (GM) was able to break in Cams with over 120 psi on the seat and 320 psi open with just mineral based oil and break in additive and with today's assy lubes, break in oils and that same additive you should have no issue doing the same ! Old springs with 100 psi or less is even better , but don't be looking to top 5300 rpm when you put your foot in it for long!
Will the crappy old springs coil-bind when used with the new cam? Spring pressure is one thing. Actually having clearance is another. If there's clearance, YES I would shim to proper installed height. Why would you need adjustable pushrods if you have hydraulic lifters with reasonable plunger travel?
I had the heads milled to straighten up the surface, and I think the deck was milled on the first rebuild before I bought this engine. After checking valve stem height, they are all in range but they are not the same which kinda rubbed me the wrong way with the machine shop I use. Anyway I figured adjustables I could make up any of the stem top heights. I doubt it's 100% nessecary for the heights to be perfect but I would assume when you do a valve job you try to match them. I guess if it's not a "race" engine these things get overlooked sometimes. That being said I just need it running asap and don't want to deal with the machine shop again and see the snow fall before I drive my car once this year. I'll be checking pressures and cool bond this weekend...
So a rough check with a bathroom scale and a drill press tonight showed a very consistent 60 lbs at as close as I could eye 1.89 and about 180 lbs at an eyed 1.39. Looked like I had another .3 to coil bind. Goes along with slightly worn stock specs. Max lift on my cam should be .470.
looks like I have at least .250" from seal to retainer. I should have checked when the springs were off, but I just took my retainer to seal measurement when the spring was installed, and subtracted my max lift.
