I'd just like to verify that I've done the math correctly and selected the correct pushrods:

Note: I've edited this post since I measured incorrectly the first time

Intake:
6.800 + 11.125 * 0.050 = 7.35625

7.35625 + Preload = 0.0?? = 7.xxx

Exhaust:
6.800 + 11.25 * 0.050 = 7.3625

7.3625 + Preload = 0.0?? = 7.xxx


Question: What is the proper preload on Comp 850-16 lifters?

I am running TFS 215s and Harland Sharp Non Adjustable 1.7s.

 

math will get you close measuring will get you exact. We measure.

 

Sorry, I didn't specify.

I used the comp adjustable length checker. I made sure that I measured at the base circle of the camshaft. This is at zero lash. The rocker is still able to move, but ever so slightly - not enough to make a "tick" noise.

If that is what you mean by measuring.

 

Math is correct based on your measurement.

I don't know the preload on the lifters, have you contacted COMP?

I believe the newer TFS heads will run 3/8" pushrods. Have you considered those?

 

Are your valve stem heights 25 thousandths difference? Not sure why you would get a difference like that bewteen intake and exhuasts seems like a large margin to me. Maybe somebody can help with clearing that up.

 

It seemed strange to me as well. I do not know why there is such a large difference.

I read a post by Predator-Z that said these lifters run 0.060>0.100 preload. Keeping that in mind, would it be fine to run a set of 7.425 rods intake & exhaust? I'd end up with preloads of 0.0875 (intake) and 0.0625 (exhaust).

 

Or go larger diameter, two lengths and get them from Terry Manton.

 

If you're confident in your measurement then I'd go with the two different lengths. We typically stock both those lengths in 5/16" and can get you the 3/8" drop-shipped from the MFG in a matter of days for the same price. Let us know if we can help

 

Here is the proper preload for the 850-16 lifters directly off the instructions

Through various testing we have discovered that lifter preload should be set between .030” to
.040” or ½ to ¾ a turn of the wrench past zero for optimal performance.

.080 is way to much

Here is the link also
http://www.compcams.com/Technical/In.../COMP4-116.pdf

 

They are measuring at the rocker bolt, which I suspect is for an adjustable system. However, at the rocker bolt you need to correct for the pushrod location. I get 0.048" - 0.064" when corrected at the pushrod.

 

I gave Comp a call today, and the guy said to run between 0.030 > 0.045 preload. Absolutely no more than 0.060.

I'm at a loss of what to do now.

 

So you have come across setups needing 2 different length pushrods? I'm just wondering how common this is to have 25 thousandths difference.

 

I should have updated this a while ago. I went back and re-checked (numerous times) and got a different measurement for the intake. This puts them within 0.00625".

The measurements with zero lash are: 7.35625 & 7.3625.

Now all that is left is to determine the preload.

 

7.400 pushrods

 

That puts the intake at about .044" and the exhaust at about .038" (for those who don't want to grab a calculator).

 

Thank you for all the help.

I have 7.400" rods on the way. I'll see how these work out!