Bacman heads - installed valve spring height

Trying to find out what the correct installed height is on bacman heads, not having any luck searching so hopefully one of you guys can help

Thanks
Adam

 

Depends on valve length, cam lift, spring used. Not cylinder head

 

You're installed height is going to be based solely on the camshaft and the spring used. Make sure your valve isn't something ridiculously tall or short and you should be fine. You'll put the valve in the head (lube it up), put your spring locator on, put the height mic/retainer/keepers on, adjust the mic until you seat the valve and that's your unadjusted spring height. On most springs you can go .060 away from coil bind. To figure that add the coil bind figure, plus valve lift on the cam card, plus hot lash, plus .060; this is your "installed height". Take the number that you had earlier which told you unadjusted height and subtract the figure you came up with coil bind + lift + lash + .060 and this is the amount of valve shim you need to reach the correct/desired height. Then you'll take whatever that number is and take that amount in valve shims and put them under the locator. Before you put the spring on for good, double check it with the shims under there to make sure you didn't make a mistake. It also doesn't hurt to measure the actual lift on the rocker arm (with rocker/spring etc bolted on the car, generally you'll find you're a bit more or less lift than what your cam card states. Sometimes your cam card will say the lift was figured with "such and such" rocker arm ratios, check and see. If you're going to be doing your cylinder head work yourself I'd recommend a cylinder head stand and a spring compressor. In regards to the spring compressor and cylinder head stand; I'd go with an MTI Compressor and a Triple T Stand.

For numbers here's an example
PAC 1320-1
480lbs. @ 2.100"
Coil Bind @ 1.230

296/300 BAE Cam
.750 int. lift
.775 exh. lift

1.230 coil bind + .750 int. lift + .026 hot lash + .060 =2.066"
1.230 coil bind + .775 exh. lift + .026 hot lash + .060 = 2.091"

The above are just basic numbers, on a hemi anything over 450 lbs. at the seat should be good. You'll want to check what you'll have pressure wise at the seat and maybe adjust your height accordingly. You can get an idea by taking the spring rate, usually listed lbs. per in., and putting the spring at whatever height it takes to reach a desired seat pressure. The number above are just a "don't run them any closer than this" sort of deal....for that specific spring and cam.

Also if these heads are new to you and valve depth hasn't been measured and recorded; check all your heights on both heads. You'll take the lowest number and you know you cannot go less than that, it'll also help give you an idea of what kind of shimming is in order on the other valves/springs.
Hope this helps,
Brandon Booher
NHRA TAD #34