I have read that you need .050 clearance before coil bind on valve springs. Would .041 be acceptable?? This would be my clearance after subtracting net lift from the installed height and then subtracting the coil bind from that number. (1.85-0.539=1.311 1.311-1.270 coil bind=0.041 clearance) Will this work or do I need to loose a few pounds of seat pressure to get the other .010 clearance?
Thanks
Caleb

depends on the other parts you are using.......kinda sounds like these numbers are just from the book or stated given specs from the manufacturer.

the recommended intalled height of the spring is ussually just that a recommendation. the actual installed height is usually more then that if you are working with a rebuilt head because the valves can be sunken some making the installed height higher. so shimming under the spring comes into play to correct the valves spring seat pressure for a given height.so at this point you can take some shim out to gain some clearence.

to me most cam companies spring pressure recommendations for a given cam are slightly over kill and loosing a few lbs of seat and open pressure wont hurt nothing at all.(think of it this way you put in say spring that was new with 120# of seat pressure and it ran great to 7000 rpms for 5 years....then you pull the motor down and check the springs again ,and even thou you didnt have no problems they read 100# lbs now)

most lifts of the cam are really lesser then stated, so you are gaining clearence there.and if your running stock rocker arms you might as well forget that you are getting the full 1.7 ratio. because stockers are hardly ever that.

chances are that you will have more clearence then you think.....

your best bet here is to put the engine together with the given parts you have and measure the actual clearence with a feeler gage. you will be surprised with how much room you got.

just make sure you measure the clearence of the retainer to valve guide with what ever oil control seal you will be using. the unbrella seals are pretty thick and you might run into spliting those if you dont have enough room.

just make sure you use a solid type lifter when making your checks........most hydraulic lifters have .060" of travel between the retainer lock and bottoming out the plunger.so if you was to use the hydraulic lifter you would have to make sure the plunger was fully seated and then you would subtract .060 off the given clearence you have before coil bind.

These are the actual numbers measured off the heads that were just built. They are set up at 1.85" and the guides were cut down to install the teflon type valve seals. After subtracting valve lash for my solid cam, I get an actual .539" of lift. I am using some 1.7 roller rockers also. The coil bind was the manufacturers number though. Assuming the springs coil bind at the given number and all my numbers are right on the money, is .041" enough clearance? It would be no problem at this point to take .010 shim out of the heads to be at 1.86" installed height, but if it will work I will leave it alone. Sorry for beating this to death but this is finishing off of a 396 that ate a cam last year, so I am being kind of anal.
Caleb

Originally posted by dukejoh:
These are the actual numbers measured off the heads that were just built. They are set up at 1.85" and the guides were cut down to install the teflon type valve seals. After subtracting valve lash for my solid cam, I get an actual .539" of lift. I am using some 1.7 roller rockers also. The coil bind was the manufacturers number though. Assuming the springs coil bind at the given number and all my numbers are right on the money, is .041" enough clearance? It would be no problem at this point to take .010 shim out of the heads to be at 1.86" installed height, but if it will work I will leave it alone. Sorry for beating this to death but this is finishing off of a 396 that ate a cam last year, so I am being kind of anal.
Caleb Caleb,
Never take the published numbers as gospel. Check them yourself or have them checked.
You can check the springs actuall coil bind in a vise if you don't have access to a spring compressor.
You will find on a Rat that you will probably not have .539 lift because of the angle of the pushrods. It will always be less than the lobe lift times the rocker ratio by a small amount.
If you end up with .041 I would fix it. I do not run any spring at less than .060 from coil bind.
That is the minimum I will run period.
Also if it is close to coil bind I will check every spring not just one or two.
Now this is probably what would be called "anal" :D

I would agree with the others,but I would check them all just because i'm paranoid when it comes to someone else putting something together,it would only take one to wipe a cam! graemlins/waving.gif