Pushrod Length Oddity! (long)
05-29-2014, 07:40 PM
#1
Pushrod Length Oddity! (long) Here's something I hadn't come across before.
To confirm that my existing set of TR 7.4 pushrods are the correct length for me, I purchased a Jegs 80681 length checker. It has no graduations or instructions. The 7.4s were recommended by TR, given my components.
On the base circle of #1, it takes 5 turns to snug up the checker with the rocker on both Intake & Exhaust.
Every thread I've seen describing this procedure, shows 1 turn of the checker = .050.
Not with this one.
Starting out, the checker, retracted, is (by sight, bec I don't have a caliper) 7.1875 inches, end to end. This = 7 3/16". 7 1/4" = .250" >>from this, 3/16 =.1875
Now, the interesting part...when the initial 5 turns (@ 1 turn = .050) was not adding up (coming up short), combined with the length of the checker, I then opened up
the checker 1/2 inch (.500), to verify the turns.
1/2" = 13 turns = .500 divided by 13 = .0385.
So, we have the checker @7.1875, + 5 turns (.0385 x 5 =.1925) = 7.1875 + .1925 = 7.380
7.380 + .062 preload =7.4"
I've seen several preload recommendations, @ Ls1Tech....anywhere from .065 to .080.
This engine has not been run for awhile, therefore the lifters are drained.
How can I duplicate a pumped-up lifter, for accurate measurement, if the engine is together? Maybe I can crank it till oil pressure, then repeat these measurements?
Can someone please chime in with some feedback? Thanks.
To confirm that my existing set of TR 7.4 pushrods are the correct length for me, I purchased a Jegs 80681 length checker. It has no graduations or instructions. The 7.4s were recommended by TR, given my components.
On the base circle of #1, it takes 5 turns to snug up the checker with the rocker on both Intake & Exhaust.
Every thread I've seen describing this procedure, shows 1 turn of the checker = .050.
Not with this one.
Starting out, the checker, retracted, is (by sight, bec I don't have a caliper) 7.1875 inches, end to end. This = 7 3/16". 7 1/4" = .250" >>from this, 3/16 =.1875
Now, the interesting part...when the initial 5 turns (@ 1 turn = .050) was not adding up (coming up short), combined with the length of the checker, I then opened up
the checker 1/2 inch (.500), to verify the turns.
1/2" = 13 turns = .500 divided by 13 = .0385.
So, we have the checker @7.1875, + 5 turns (.0385 x 5 =.1925) = 7.1875 + .1925 = 7.380
7.380 + .062 preload =7.4"
I've seen several preload recommendations, @ Ls1Tech....anywhere from .065 to .080.
This engine has not been run for awhile, therefore the lifters are drained.
How can I duplicate a pumped-up lifter, for accurate measurement, if the engine is together? Maybe I can crank it till oil pressure, then repeat these measurements?
Can someone please chime in with some feedback? Thanks.
05-30-2014, 06:40 AM
#3
Chuck, I agree.
I verified the measurement with a caliper, and the total length comes out to within 3 thousandths of the initial guess...both of the contracted length of the checker, and of the thousandths per turn.
My focus is on the lack of oil in the lifters..how it should be remedied, and how the pumped up lifter affects the true measurement.
I verified the measurement with a caliper, and the total length comes out to within 3 thousandths of the initial guess...both of the contracted length of the checker, and of the thousandths per turn.
My focus is on the lack of oil in the lifters..how it should be remedied, and how the pumped up lifter affects the true measurement.
05-31-2014, 06:04 AM
#6
Glenn, Darkman's comment is what I found to be true on my engine. I could push the rocker down, the lifter spring would collapse, and then snap back up when pressure was removed.
At first, I was concerned that the lifter plunger may stick down... Didn't happen. [Lifters had been lubed prior to install.]
At first, I was concerned that the lifter plunger may stick down... Didn't happen. [Lifters had been lubed prior to install.]
