Pushrod length/preload discrepancy?
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Pushrod length/preload discrepancy? I have the Comp pushrod length checker and proceeded to measure Cyl. 1. It took 9.5 turns to get where I was comfortable with zero lash. The intake valve I couldn't really move at this length, but the exhaust valve would lift very little (without a tick, tick sound). So, at that many turns, I got 7.275" + what ever preload I choose. I think I want to shoot for 0.05".
I wanted to double check so I moved to Cyl. 6. On these two, I got 10.5 turns to zero lash. That game me a length of 7.325" + desired preload.
I had no real way of measuring TDC other than my eyeball, so I'm guessing that's why the pushrod measurements are equal lengths apart, in different directions? Am I correct in assuming that?
I know the Comp tool is measured in gauge length, so how would I equate that into my measurements?
Right now, It looks like I'll have to order some 7.350" pushrods with my 0.05" preload. I read that this is a great preload for a quiet valvetrain, but it doesn't seem to be well understood on the interwebz. I have a set of Texas-Speed 7.400 pushrods, but I'm afraid they will be too long.
I wanted to double check so I moved to Cyl. 6. On these two, I got 10.5 turns to zero lash. That game me a length of 7.325" + desired preload.
I had no real way of measuring TDC other than my eyeball, so I'm guessing that's why the pushrod measurements are equal lengths apart, in different directions? Am I correct in assuming that?
I know the Comp tool is measured in gauge length, so how would I equate that into my measurements?
Right now, It looks like I'll have to order some 7.350" pushrods with my 0.05" preload. I read that this is a great preload for a quiet valvetrain, but it doesn't seem to be well understood on the interwebz. I have a set of Texas-Speed 7.400 pushrods, but I'm afraid they will be too long.
Gauge length is 0.017 inch shorter than actual measured length. Comp and Trend pushrods are, of course, gauge length. (A 7.300" gauge length would actually be 7.317" overall length.) If you order pushrods from aother supplier such as Manton, for example, they use measured overall length.
Your math appears to be correct.
Your math appears to be correct.
Last edited by Darkman; Feb 20, 2012 at 06:09 PM.
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Thanks for the reply.
What do you think is the deal with cylinder 1 being 9.5 turns to close up the adjustable pushrod and cylinder 6 taking 10.5 to close it up?
What do you think is the deal with cylinder 1 being 9.5 turns to close up the adjustable pushrod and cylinder 6 taking 10.5 to close it up?
https://ls1tech.com/forums/7957678-post2.html
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The first thing to check is to make sure that piston/valve position is correct on both 1 and 6. Are you using the same method to establish position on both?
https://ls1tech.com/forums/7957678-post2.html
https://ls1tech.com/forums/7957678-post2.html
This may be where there is an error on my part....
I know that #1 is at TDC and I looked back at my pictures and #6 is also at TDC (visually). I can tighten down the rocker at both valves on #1 and #6 without turning the motor over to reposition and the valves do not move, so I assumed both are at TDC, yet I'm getting different measurements.
The Service Manual says:
6. Rotate the crankshaft until the number one piston is at top dead center (TDC) of the compression stroke. In this position, cylinder number one rocker arms will be off lobe lift, and the crankshaft sprocket key will be at the 1:30 position. The engine firing order is 1,8,7,2,6,5,4,3. Cylinders 1,3,5, and 7 are left bank. Cylinders 2,4,6, and 8 are right bank. Notice: Refer to Fastener Notice in Service Precautions.
7. With the engine in the number one firing position, tighten the following valve rocker arm bolts:
•Tighten the exhaust valve rocker arm bolts 1,2,7, and 8 to 30 Nm (22 ft. lbs.).
•Tighten the intake valve rocker arm bolts 1,3,4, and 5 to 30 Nm (22 ft. lbs.).
8. Rotate the crankshaft 360 degrees .
9. Tighten the following valve rocker arm bolts:
•Tighten the exhaust valve rocker arm bolts 3,4,5, and 6 to 30 Nm (22 ft. lbs.).
•Tighten the intake valve rocker arm bolts 2,6,7, and 8 to 30 Nm (22 ft. lbs.).
10. Install the valve rocker arm covers.
If I am reading this correctly, cylinders 1 & 6 are not in sync.
6. Rotate the crankshaft until the number one piston is at top dead center (TDC) of the compression stroke. In this position, cylinder number one rocker arms will be off lobe lift, and the crankshaft sprocket key will be at the 1:30 position. The engine firing order is 1,8,7,2,6,5,4,3. Cylinders 1,3,5, and 7 are left bank. Cylinders 2,4,6, and 8 are right bank. Notice: Refer to Fastener Notice in Service Precautions.
7. With the engine in the number one firing position, tighten the following valve rocker arm bolts:
•Tighten the exhaust valve rocker arm bolts 1,2,7, and 8 to 30 Nm (22 ft. lbs.).
•Tighten the intake valve rocker arm bolts 1,3,4, and 5 to 30 Nm (22 ft. lbs.).
8. Rotate the crankshaft 360 degrees .
9. Tighten the following valve rocker arm bolts:
•Tighten the exhaust valve rocker arm bolts 3,4,5, and 6 to 30 Nm (22 ft. lbs.).
•Tighten the intake valve rocker arm bolts 2,6,7, and 8 to 30 Nm (22 ft. lbs.).
10. Install the valve rocker arm covers.
If I am reading this correctly, cylinders 1 & 6 are not in sync.
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The Service Manual says:
6. Rotate the crankshaft until the number one piston is at top dead center (TDC) of the compression stroke. In this position, cylinder number one rocker arms will be off lobe lift, and the crankshaft sprocket key will be at the 1:30 position. The engine firing order is 1,8,7,2,6,5,4,3. Cylinders 1,3,5, and 7 are left bank. Cylinders 2,4,6, and 8 are right bank. Notice: Refer to Fastener Notice in Service Precautions.
7. With the engine in the number one firing position, tighten the following valve rocker arm bolts:
•Tighten the exhaust valve rocker arm bolts 1,2,7, and 8 to 30 Nm (22 ft. lbs.).
•Tighten the intake valve rocker arm bolts 1,3,4, and 5 to 30 Nm (22 ft. lbs.).
8. Rotate the crankshaft 360 degrees .
9. Tighten the following valve rocker arm bolts:
•Tighten the exhaust valve rocker arm bolts 3,4,5, and 6 to 30 Nm (22 ft. lbs.).
•Tighten the intake valve rocker arm bolts 2,6,7, and 8 to 30 Nm (22 ft. lbs.).
10. Install the valve rocker arm covers.
If I am reading this correctly, cylinders 1 & 6 are not in sync.
6. Rotate the crankshaft until the number one piston is at top dead center (TDC) of the compression stroke. In this position, cylinder number one rocker arms will be off lobe lift, and the crankshaft sprocket key will be at the 1:30 position. The engine firing order is 1,8,7,2,6,5,4,3. Cylinders 1,3,5, and 7 are left bank. Cylinders 2,4,6, and 8 are right bank. Notice: Refer to Fastener Notice in Service Precautions.
7. With the engine in the number one firing position, tighten the following valve rocker arm bolts:
•Tighten the exhaust valve rocker arm bolts 1,2,7, and 8 to 30 Nm (22 ft. lbs.).
•Tighten the intake valve rocker arm bolts 1,3,4, and 5 to 30 Nm (22 ft. lbs.).
8. Rotate the crankshaft 360 degrees .
9. Tighten the following valve rocker arm bolts:
•Tighten the exhaust valve rocker arm bolts 3,4,5, and 6 to 30 Nm (22 ft. lbs.).
•Tighten the intake valve rocker arm bolts 2,6,7, and 8 to 30 Nm (22 ft. lbs.).
10. Install the valve rocker arm covers.
If I am reading this correctly, cylinders 1 & 6 are not in sync.
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They both can't be at TDC on the compression stroke at the same time.
Last edited by ZeeOSix; Feb 20, 2012 at 07:48 PM.
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If Cyl #1 is on TDC on the compression stoke, then Cyl #6 is on TDC on the beginning of the intake stroke (and cam lobes are in over-lap in this position). Therefore, a 360 rev of the crank would put Cyl #6 at TDC on the compression stroke.
They both can't be at TDC on the compression stroke at the same time.
They both can't be at TDC on the compression stroke at the same time.
I can now feel confident in measuring a second hole to validate the first.
