so I think I've figured out what my issue is with my car.

I did 243 heads (used and unknown if had previous work), lifters, btr stage 3 cam, and 7.4 pushrods (and all the other fun upgrades)

Anyway. I've been chasing this nasty... not a tap. Not a knock. I thought I had a clutch issue. Anyway. Removed the inspection plate and I swear this noise is coming from the collectors on the long tubes.

So after consulting the almighty c5 pages. i pulled the valve covers. And remeasured my push rod lengths.

Ok so here's my lifters

https://www.lgmrnd.com/Performance-LS-842-Dia-Hyd-Roller-p/mrl-5206.htm

They had 500 miles on them in my buddys gto. I soaked them in oil overnight and installed and measured with the push rod length and this is where I ended up



So with a 7.4" I should be good right?

Well tonight I remeasure since I'm running out of ideas on wtf is going on and I get 8.5 turns. Not 10.5. Then as a check. I try the old zero lash to 22 lbs on the rocker bolt and I'm at 1 3/8 turns roughly.

So when I do the math. And do .100 preload (as btr recommends and I didnt know) I'm getting that need a 7.325 pushrods.

so here's my question. When I initially measured the lifters had been sitting for a year or two. Today the car had been run a few hours prior.

Where does that internal piston need to be for the measurement? These are .120 travel pistons in these lifters. So it makes sense that im getting a different reading by about 2 turns if they were collapsed completely or close to completely at setup and now they are pumped up.

I should be setting preload off their fully pumped up position right?

 

Yes you measure the length with a fully pumped up lifter, get the correct pushrod length tool and you won’t have this issue checking the length.

 

You really need an 8 inch caliper to measure properly. Find zero lash with the pushrod checker, pull it out and measure it with a caliper. Counting turns on a checker is fraught with errors. Wrap the threads of the pushrod checker with white plumber's tape so that it doesn't turn too easily and change your settings while removing it from the engine. One can be had for $35.00 online.

 

I have a pushrod length checking tool.

what I ended up doing was letting the lifters drain off. Then used a push rod to make sure the piston was totally collapsed.

Then I measured to zero lash. That gave me the length of 100% preloaded pushrod.

So I know these lifters have a .120 piston travel.

also they call for .035-.060 preload.

so I measured 7.335 with a collapsed lifter. I ordered a 7.275 set of push rods to get me to .060 preload. Guys say closer to .060 will be quieter at start up. And 7.275 was the shortest btr offered other than 7.2.

This isnt an ideal way to measure but im working my way through this. I definitely learned something too haha. Next time flip the parts in the lifters to make a solid lifter to measure with. 7.4s were way too long.

 

Wouldn't an excessively long pushrod prevent valves from closing completely?

 

BTR pushrods are owned by Summit. I bought two sets from them and both sets were too long. I bought a set from Smith Brothers in Bend, OR and they were within .0015 of correct. I wouldn't trust that the BTR's are the length they say they are or were sold as. Just an FYI...

 

that’s because there’s 2 different ways of measuring pushrod lengths, you have to see how the companies advertise their lengths compared to how you’re checking them.

it’s stupid I know.

 

I asked Summit how they were measuring them; I also asked Brian Tooley Racing. I also asked Smith Bros. In all cases I was measuring them per their measurement methods for advertising (actual end to end,, including the ball or chamfer. Anyway, now I know where not to get pushrods...