Spd-Kilz

iTrader: (35)

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.

99blancoSS

iTrader: (115)

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

Spd-Kilz

iTrader: (35)

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.

vettenuts

iTrader: (4)

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?

JFM-jr

iTrader: (23)

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.

Spd-Kilz

iTrader: (35)

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).

vettenuts

iTrader: (4)

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

Sales2@Texas-speed

iTrader: (5)

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

EDS01SS

iTrader: (30)

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

vettenuts

iTrader: (4)

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.

Spd-Kilz

iTrader: (35)

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.

JFM-jr

iTrader: (23)

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

Spd-Kilz

iTrader: (35)

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.

PREDATOR-Z

7.400 pushrods

Sales2@Texas-speed

iTrader: (5)

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

Spd-Kilz

iTrader: (35)

Thank you for all the help.

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