I have a set of PAC1518, recommended install height is 1.75".
Coil bind for these springs is 1.08", then add the extra 0.05 that makes it 1.13"
Max lift on my cam is .561"
With stock valves, the install height without +.050 locks will be 1.70"

That means 1.70" - .561" lift = 1.139" which should be plenty of room.

My question is, is it ok to install these springs at a lower install height as long as there's no coil bind?

The reason I don't jst go with the +.050 locks is because they do not make them for use with lash caps and the current setup has lash caps on it, otherwise I'll need to get new length pushrods too.

 

Rumor control has it that they should be installed as close to coil bind plus the safety margin as you can.

 

So actually using the shorter install height is recommended in this case from what you are saying as long as the max lift does not reach coil bind?

 

Any other insight on this anyone?

 

I've always heard you need at least .060 clearance before coil bind.

 

You can install them @ .060" to coil bind no problem, but if running them that close - you need to measure each and every installed height and spring to make sure that none of them fall below .050". Generally cam companies will recommend .120" to coil bind so that tolerance stack does not allow them to fall below the true minimum rating for the spring due to variances in installed heights and spring coil bind heights. .065" - .085 is where I try and end up.

 

My factory PAC spec sheet says 1.80" installed height for PAC-1518s. So, that gives you another .050" to consider.

WD

 

There is no logic to thinking of "reccomended" installed height. Install them where they need to be. Just avoid coil bind. I like to select springs so that I get the desired seat and open pressure with ~0.060" clearance. You need to be careful if you go this close as it is just about the minimum. By doing this you increase the damaping effect at full lift because some of the coils will be in contact.

Rich

 

Good point. Checking with the cam supplier for his recommendation would also be a good idea and may ease you mind.

Jon

 

ok, thanks for the input. If Il go with the +.050 locks and ditch the lash caps and get some new shorter pushrods then, this would give me an install height of 1.75". Therfore 1.75 - .561 = 1.189 which is a 0.109 buffer from reaching coil bind.
But I guess I'll just measure each one, I think these heads have had a valve job, so the stem height may be slightly higher than stock..thus allowing me to keep the current combination...guess I'll find out when I get in there.
Thanks for all the help.

 

Make sure your spring mic is dead nuts reading and do all of your install carefully and you will be fine at 1.700"

WHY DO YOU NEED LASH CAPS ON STOCK VALVES?

WHY DOES THE PUSHROD LENGTH HAVE ANYTHING TO DO WITH INSTALLED HEIGHT?

 

If he uses a +.050 keeper he can't use lash caps he said.....

But I have + .050 and they are cut for lash caps.....either from manley or isky

 

Yeah MY POINT is WHY DOES HE NEED THEM?

HE DOESN'T! And if he gets a .050" shorter pushrod too boot, that's a GOOD THING!

 

I don't have to have them, but the builder that put these together used them due to the type of retainers used they were needed.
If I keep them on there I don't need new length pushrods. I realize there's some gain to be had by reducing the weight here too but this isn't s race application, this is on my truck. I'm installing new springs with different retainers so the caps can go if I must go that route.
This is also something that needs to be together for years to come so having lash caps is just a safty mechanism to keep the valve tips nice in case something starts to wear wrong etc....like the guide plates that are all worn in there now from a previous post.