[blown 68]

so, i am just trying to get this straight. if my valve springs are installed at the recommended height of 1.650, and the stated coil bind for the spring is at .950, does that mean i truly have .700 of room for valve lift?(minus any margin for safety, this is of course assuming valve/piston contact is not an issue). my valve lift, after being rated with 1.65's will be .589 with this new cam, minus lash .025, (solid flat tappet), so, is my math assuming correctly that i have no problem with coil bind? i guess i would be wondering, on a pontiac engine being run to 6000rpm, what is the 'safety margin' that people use for the clearance up to the coil bind number? any and all info much appreciated, and thank you in advance folks, as usual, you all are a great help........

davey

[screamingchief]

The saftey margin your looking for is usually accepted to be appx. .050"-.060" clearance before coil bind.

So do the math 1.650"-.060" (clearance)= 1.590".

Thus 1.590"-.950"(cb) = .640" max lift w/.060" clearance.

So yes at .589" (-lash) lift you should be ok with a healthy bit of room to spare provided there is enough clearance between the retainer and valve stem seal/guide.

It's also a good idea to have this checked and verified on a spring tester as well.

HTH.
Bret.

[BVR421]

Originally Posted by screamingchief

/snip/ provided there is enough clearance between the retainer and valve stem seal/guide. Bret.

I think a lot of the "mystery" bent pushrods might be due to failure to check that interference point.

[Geoff]

You should also verify the rocker ratio. Some brands measure higher than than the designated ratio.

[Cliff R]

Just because the springs have the running room for the intended lift, doesn't necessarily mean they will have the correct pressure(s) for the rpm range. Always check any springs before placing them in service. We use coil bind plus .080" here, as a margin of safety. Some springs, due to their design, wire diameter, number of coils, etc, will show spikes in pressure(s) up near the coil bind specifications. Never assume that the manufacturer's supplied information with the springs is correct. In addition, the inner step on the retainers being used can alter the specifications considerably.

If assembling the heads yourself, obtain a spring tester, or take the springs/retainers to a machine shop, and verify the spring pressures at all points in the lift range they are going to be used in.

This is one area of engine assembly that often gets overlooked, or neglected....and....is probably why we see so many cam lobe failures these days, or at least a contributing factor?......Cliff

[blown 68]

thank you for the extra insight cliff, the spring pressures are in my range, but i had not thought about checking them throughout the range. will make sure to have my machinist check all parameters, retainers, pressures, etc........