Preston129

iTrader: (3)

I'm going to be installing PAC1518 in stock (for now) 243 truck heads, using stock rockers and most likely stock retainers and locks.

I just want to get my head around some issues with measuring and shimming (if necessary) so this is how I understand the process:

Measure all valves with micrometer;
If measurement >1.800, then shim just that one valve
If measurement <1.800, then shim all 16 valves

e.g. If one valve measures 1.830, then shim that valve .030;
if one valve measures 1.770, then that is the new “installed height” and all 16 valves get shimmed .030, then coil bind occurs sooner and max lift is reduced.

And the PAC1518 have an OD of 1.290”, so would I use 1.250” shims? And would these ones from Comp be the right kind? http://www.compperformancegroupstore...Code=VALVESHIM

Is doing the wipe test on the valve tip necessary for stock rocker arms?

Preston129

iTrader: (3)

Just felt like bumping this to the top in case anyone has some input, if not i'll let it die..

99ssleeper

iTrader: (98)

correct.

but no wiper test necessary, there is no adjustment but check your pushrod length for 0 preload and add (if i remember correctly) .060"

vettenuts

iTrader: (4)

You don't mention cam, stock? If all stock then you may not need to check wipe, I would anyhow if it were me. Adjustments are made by shimming the aluminum rocker support or removing material from it as necessary.

I also think you will find none of the springs are currently at 1.800 but rather closer to 1.765" to 1.770" based on my prior measurements stock. Unless you have messed with the stock setup they should all be close to the same. If you are using the stock one piece seals, the Comp shims will work and they sit on top of the base of the seal that is the seat of the valve spring unlike duals where the shim goes under the seat. You are correct, shimming may reduce the total lift. Run the numbers after you find your installed height and see what your final installed clearance is.

Preston129

iTrader: (3)

I'm going with an aftermarket cam, and changing lifters and pushrods. I'm hoping getting the right pre-load won't affect the rocker arm geometry but I guess I'll check it anyways to be on the safe side.

I haven't touched the heads so the spring pockets should all be stock and I'm hoping all measure close to one another. I wasn't too sure if shimming was uncommon with all 16 valves, but I guess I should order more shims since you found they all measure to the smaller side.

Paint_It_Black

iTrader: (1)

Depending on your cam, you may want to measure coil bind and shim all the way up to within .050 thou of it.

Preston129

iTrader: (3)

Ok, now this doesn't make sense to me, could you elaborate please? Lobe lift is going to be just under .600 I and E. Pac specs the coil bind at 1.080, so what I figured was if I found the smallest installed height to be 1.770, and if I added 0.060" to be safe, max lift would .630" (1.770-1.080-0.060).

Are you suggesting I measure what the actual coil bind of each spring is? So for example, say I measured coil bind and it showed 1.080, and the intake lift was .598, are you suggesting to install the springs at 1.728" height (1.080+.598+.050)?

Paint_It_Black

iTrader: (1)

Yeah basically. Outside of .050 within coilbind is accepted to be safe and not too tough on spring life. It will also increase your seat pressure and be more stable at high rpms. Google it if you like or do a search here. I wouldn't want you to take advice as gospel from just 1 person, even if they are right.

Preston129

iTrader: (3)

I'll look into that today, thanks for your input