Pushrod length - does this sound right?
Thread Starter
Joined: Nov 2009
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From: THORNTON, PA (NEAR PHILLY)
Pushrod length - does this sound right? I have a 5.3 here, and I installed a TF cam 216/220 and when everything was installed I noticed the rockers were not touching the valves when tightened down! There was gaps from the valve tip to rocker arm of about .040+/-.
I then installed a z06 (early) and noticed the rocker gap was smaller. I was like WTF as I just took this cam out of a LQ9 and didn't notice this installed in that engine. Still baffled, I then reinstalled the factory LM7 cam back in, and the rockers were nice and tight against the valves.
I measured the base circles and came up with this:
LM7....................1.552"
Z06 (early)..........1.52" (.032 smaller)
TF 216/220 560....1.478" (.074 smaller)
Factory pushrods measures 7.395 end to end.
So if my math is correct, I need a .037 longer pushrod. 7.395+.037 = 7.432 to maintain factory preload. Doesn't this sound long? Not sure how all these folks are running 7.4" pushrods. In this case 7.425 doesn't even seem long enough as it will not preload the lifter as much as the stock setup did. I think I'm looking at the 7.45 pushrods, but man that's longer than everybody else.
Of course I will get a pushrod checker, but 7.45 to start is already much longer than most folks runs.
Seem normal????
I then installed a z06 (early) and noticed the rocker gap was smaller. I was like WTF as I just took this cam out of a LQ9 and didn't notice this installed in that engine. Still baffled, I then reinstalled the factory LM7 cam back in, and the rockers were nice and tight against the valves.
I measured the base circles and came up with this:
LM7....................1.552"
Z06 (early)..........1.52" (.032 smaller)
TF 216/220 560....1.478" (.074 smaller)
Factory pushrods measures 7.395 end to end.
So if my math is correct, I need a .037 longer pushrod. 7.395+.037 = 7.432 to maintain factory preload. Doesn't this sound long? Not sure how all these folks are running 7.4" pushrods. In this case 7.425 doesn't even seem long enough as it will not preload the lifter as much as the stock setup did. I think I'm looking at the 7.45 pushrods, but man that's longer than everybody else.
Of course I will get a pushrod checker, but 7.45 to start is already much longer than most folks runs.
Seem normal????
What's the cam mfgr say? Any info come w/ the cam?
"I think I'm looking at the 7.45 pushrods, but man that's longer than everybody else."
May/may not be. Unless you know the base circle dims on the other cams...
"I think I'm looking at the 7.45 pushrods, but man that's longer than everybody else."
May/may not be. Unless you know the base circle dims on the other cams...
Or look at it another way. If you had a 0.040" gap, then you would need another 0.024" of pushrod to reach zero lash (0.04/1.7). If you add the 0.050" for preload, that results in a similar value that you obtained (0.075").
How accurately did you measure the 0.040" gap at the rocker?
Always best to measure with an adjustable pushrod though.
How accurately did you measure the 0.040" gap at the rocker?
Always best to measure with an adjustable pushrod though.
Or look at it another way. If you had a 0.040" gap, then you would need another 0.024" of pushrod to reach zero lash (0.04/1.7). If you add the 0.050" for preload, that results in a similar value that you obtained (0.075"). How accurately did you measure the 0.040" gap at the rocker? Always best to measure with an adjustable pushrod though.
Thread Starter
Joined: Nov 2009
Posts: 1,621
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From: THORNTON, PA (NEAR PHILLY)
Or look at it another way. If you had a 0.040" gap, then you would need another 0.024" of pushrod to reach zero lash (0.04/1.7). If you add the 0.050" for preload, that results in a similar value that you obtained (0.075").
How accurately did you measure the 0.040" gap at the rocker?
Always best to measure with an adjustable pushrod though.
How accurately did you measure the 0.040" gap at the rocker?
Always best to measure with an adjustable pushrod though.
But it just occurred to me, we can't really adjust for proper geometry here b/c our rockers are not adjustable correct? All we can do is size the pushrod for proper lifter preload...am I off here???
There's some variances between different valves, probably b/c the valves sunk different amounts is my guess. I measured .040 and some .050.
But it just occurred to me, we can't really adjust for proper geometry here b/c our rockers are not adjustable correct? All we can do is size the pushrod for proper lifter preload...am I off here???
But it just occurred to me, we can't really adjust for proper geometry here b/c our rockers are not adjustable correct? All we can do is size the pushrod for proper lifter preload...am I off here???
If you're using shorter travel lifters, you might have to order a couple of different lengths to compensate.
Thus were my instructions from Tony, and it worked out great.
Thread Starter
Joined: Nov 2009
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From: THORNTON, PA (NEAR PHILLY)
You're not wrong. If you have stock-ish lifters, I think you can find a happy medium, order the pushrods, and the natural variance between them will give you longer and shorter ones. Use them where you need to and you'll be fine. That's another reason calipers are helpful for this. When you go to install, if you kept track of your measurements, you can measure the new ones and use the length variability to your advantage.
If you're using shorter travel lifters, you might have to order a couple of different lengths to compensate.
Thus were my instructions from Tony, and it worked out great.
If you're using shorter travel lifters, you might have to order a couple of different lengths to compensate.
Thus were my instructions from Tony, and it worked out great.
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Thanks Darth. The only thing that complicates this is the way pushrods are measured. You cant really measure them end to end w/o some correction for the oiling hole. So, maybe the factory pushrods ARE 7.4" vs my calipers measurement of 7.395? If that's the case I need even longer pushrods.
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One trick I learned from Tony is to put a little teflon plumbing tape on the threads of the adjustable pushrod and it will hold it's length without changing as you pull it for a measurement. You'll get better measurements. Also, you'll need a set of 8 inch calipers to get them right - there is no other way to do it!
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Joined: Aug 2005
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From: Monroe,NY
Thanks Darth. The only thing that complicates this is the way pushrods are measured. You cant really measure them end to end w/o some correction for the oiling hole. So, maybe the factory pushrods ARE 7.4" vs my calipers measurement of 7.395? If that's the case I need even longer pushrods.
https://ls1tech.com/forums/generatio...od-length.html
Thread Starter
Joined: Nov 2009
Posts: 1,621
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From: THORNTON, PA (NEAR PHILLY)
Just so you know factory pushrods aren't 7.4 the are a little less.
https://ls1tech.com/forums/generatio...od-length.html
https://ls1tech.com/forums/generatio...od-length.html
You have gauge length, actual length and theoretical length.
Actual length that I measured was 7.395. From what I u/s, an avg of .017 is added to that to account for the lack of radius (oil hole/chamfer). So now your at 7.395 +.017 = 7.412 theoretical factory length.
This is just my opinion, so take it for what it's worth (less than $0.02). As long as you are consistent with how you measure the pushrods, I think you'll be OK. You can always tell whoever you're talking to "I measured them directly with a caliper, and here is what I'm getting". The person on the other end of the phone can make the necessary translations.
Then, when you get them back, you can duplicate your measurement practice.
Then, when you get them back, you can duplicate your measurement practice.
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Joined: Aug 2005
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From: Monroe,NY
yeah I know, but there so many variables and ones person pushrod length could be different than somebody else's just based upon what measuring technique there using.
You have gauge length, actual length and theoretical length.
Actual length that I measured was 7.395. From what I u/s, an avg of .017 is added to that to account for the lack of radius (oil hole/chamfer). So now your at 7.395 +.017 = 7.412 theoretical factory length.
You have gauge length, actual length and theoretical length.
Actual length that I measured was 7.395. From what I u/s, an avg of .017 is added to that to account for the lack of radius (oil hole/chamfer). So now your at 7.395 +.017 = 7.412 theoretical factory length.
Thread Starter
Joined: Nov 2009
Posts: 1,621
Likes: 31
From: THORNTON, PA (NEAR PHILLY)
Tried the adjustable pushrod checker - what a PIA! Can't get in there to turn the sucker. Anyway, tried the 7.425 pushrods and they gave a preload of apprx .055+/-, so I'll stick with these. Looks like 7.4 pushrods would of worked too but would of been a little light in terms of preload.
Thanks all for the tips!!!
Thanks all for the tips!!!
Tried the adjustable pushrod checker - what a PIA! Can't get in there to turn the sucker. Anyway, tried the 7.425 pushrods and they gave a preload of apprx .055+/-, so I'll stick with these. Looks like 7.4 pushrods would of worked too but would of been a little light in terms of preload.
Thanks all for the tips!!!
Thanks all for the tips!!!