ZL1modified

I have an install height of 1.80 on my crane 99893 springs and i have 150# closed and 370# open...

Is 150# too much seat pressure for stock valves?

and if you could please tell what maximum seat pressure is for stock valves... i did search and could not find my answer...

R/
Mike

BUBBA

your cam card gives recommended spring pressures, however having more pressure on the seat is a good thing. Extreme open pressures might compromise the longevitly of the cam and lifters, however more than recommended pressures ensure better control. There probably is some point where too much is bad, however I doubt that you have reached that point. If your cam card recommends the pressures and installed hts that you have, I certainly wouldn't worry about it. Just curious why you would install them at different than recommmended hts to begin with---not that it will make any difference as long as you have the required .060 margin for coil bind. JMHO

ZL1modified

i installed at this height because i used the .060 comp spring seats instead of the shims that crane gives you... and they took my install height from 1.85 to 1.805... But i am .173" away from coil bind and i also got the new ls7 lifters and cloyes double roller... i just want to make sure i will be fine... i get paranoid...
i did the mid lift check on my push rods too and it looks like i will be within .009 if i change from 7.200 to 7.250... i was .041 away from exact mid lift but they don't make 7.241 rods...
But i'm going to triple check it tonight to be SURE...
paranoid and obsesive compulsive!

BUBBA

Suggest using a checker for correct PR length. If it happens that you need .7250s, I just happen to have a set of Crower 4130 Chromoly =.050 PRs. I thought I needed that length, however they seemed too long so I went back to stock. They were spendy, but maybe see can work something out--buy, trade, etc.

truedualws6

What I have been told regarding spring pressure is 140# closed is the max you want for a stock lifter. Other than hearing this from a few different sources I'm not sure what it's based on, but probably the roller material. Springs will also lose some % of their pressure after the first few heat cycles. The only way to know is to check a spring new and then after break in.

I would have done it the same way you did and use a good spring locator instead of the .015" shims in the Crane kit. What I did was use a different Crane spring (96872) that has a lower rate but has the same closed pressure. I don't think a 391#/inch rate is necessary for smallish cams with non-agressive lobes. My car ran fine with the 26918 beehives for 5,000 miles and they are only 313#/inch rate.

There are probably 100's of LT1s running the 10308 kit and/or the 99893 springs so you should be just fine. I just did not want to have all that unnecessary spring pressure. The 96872 springs are 326#/inch rate, 140 closed and 325 open for my setup. And probably more like 130# closed after initial losses.

Both the 99893 and 96872 springs are shown in the chart in my sig.

ZL1modified

i'm not sure i understand why the closed seat pressure would break the lifter when that lifter is going to feel the most pressure when the valves is open... will the lifter not feel the open spring pressure? i would assume that the pressure would be throught out every component from the timing chain to the locks and retainers...

truedualws6

Closed to open pressure is relative (i.e., a straight line graph) and the higher the closed pressure the higer the open pressure will be. Open pressure will depend on your net lift and spring rate. I would imagine that 140/400 closed/open is the upper limit for reliability with a stock lifter. The cam lobe design and RPM is key in determining pressue necessary to avoid float. For a stockish cam (GM Hot, GM 845, LPE 211/219, TPIS ZZ9, CC 305, etc.) running up to 6,200 RPM you don't need 140/400 spring pressure. Look at the LT4 springs, look at the 26918s, Comp 987s, Isky 235-D. These are all low 300s rate springs with closed pressures in the low 100s, and they all work.

The 99893 spring is sort of a one size fits all. You can run just about anything up to the GM 847 (Crane 109841) with them. It's a very good spring and has lots of installs and I have not heard any negatives. I look at this like the mid-lift discussion. If you want it the best it can be then you want the spring pressure adequate (with some safety factor) for your application. The more pressue you have above this point is creating unnecessary friction and wear. No need to install a thumb tack with a sledge hammer.