What Pushrod length?
Re: What Pushrod length? I have heads milled .30 and 224/224 563/563 114 with 7.400 pushrods. are my pushrods too long and my valves arent closing all the way...stock rockers and lifters. Thanks ALOT!
Tony
Tony
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Joined: Nov 2001
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From: SW Florida
Re: What Pushrod length? I would say that 7.40" rods are the ones you need.
Your cam's smaller base circle requires a longer pushrod
Milling the heads, requires a shorter pushrod.
In your case, they both cancel each other out. Kind of like "Tit for Tat", if ya know what I mean.
If your pushrods were so long as to keep the valves from fully closing, the motor would have no compression and would run very poorly, if at all.
Your cam's smaller base circle requires a longer pushrod
Milling the heads, requires a shorter pushrod.
In your case, they both cancel each other out. Kind of like "Tit for Tat", if ya know what I mean.
If your pushrods were so long as to keep the valves from fully closing, the motor would have no compression and would run very poorly, if at all.
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Joined: Apr 2002
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From: Honoulu, Hawaii
Re: What Pushrod length? Quiz time:
6.0L heads milled .030"
03 LS6 hollow valves .6mm longer than stock LS1
YT rockers
Comp Cam 222/222 .566/.566 112 (help w/ base circle)
918 springs & 772 retainers
What can I do to compensate for the longer LS6 valves?
Can I get shorter pushrods?
Would putting in Comp R Lifters w/ their different pre-load help or hurt the geometry?
Am I going to have problems w/ my valve train geometry because of the LS6 valves?
6.0L heads milled .030"
03 LS6 hollow valves .6mm longer than stock LS1
YT rockers
Comp Cam 222/222 .566/.566 112 (help w/ base circle)
918 springs & 772 retainers
What can I do to compensate for the longer LS6 valves?
Can I get shorter pushrods?
Would putting in Comp R Lifters w/ their different pre-load help or hurt the geometry?
Am I going to have problems w/ my valve train geometry because of the LS6 valves?
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Joined: Nov 2001
Posts: 1,975
Likes: 2
From: SW Florida
Re: What Pushrod length? IslandTahoe ....
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Stock GM pushrods are 7.385" long. This 7.385" rod gives the correct GM spec lifter preload on a stock cam and head engine.
With that info in mind, lets see how you have changed things:
Your stock LS1 cam had a cam centerline to lobe heal distance of .775"
Your Comp Cam has a cam centerline to lobe heal distance of approx .751" (at least that's what a TR220 is) (your cam will be very close to this)
This means the Comp Cam has a .024" smaller cam centerline to lobe heal distance which would require a pushrod that is exactly .024" longer than the stock 7.385" It would need a new rod that is in fact 7.409" long.
Now, you milled .030" off the head. That will now require a reduced rod length of .030"
The rod length now becomes 7.379" (7.409 minus .030)
Last, but not least, you now have LS6 sodium valves which are .6mm (.024") longer than the stock valves. That, in itself would require a .024" shorter pushrod. So, the required rod length now becomes 7.355" (7.379" minus .024")
You would actually need a set of Thunder Racing 7.350" hardened pushrods.
That newly required 7.355" rod is only .005" (5 thousands) in difference from a set of 7.350" Thunder hardened rods.
You will actually have .005" less lifter preload than you had when the motor was bone stock. And that 5 thousands is nothing to worry about. In fact, slightly less preload actually has an advantage. Your geometry will by fine.
99-PR7350 Thunder Racing Heat Treated Chrome-Moly Pushrods, 7.350" $109.99
http://www.thunderracing.com/index.c...yid=1114#T1554
Hope this helps,
Ron
__________________________________
Stock GM pushrods are 7.385" long. This 7.385" rod gives the correct GM spec lifter preload on a stock cam and head engine.
With that info in mind, lets see how you have changed things:
Your stock LS1 cam had a cam centerline to lobe heal distance of .775"
Your Comp Cam has a cam centerline to lobe heal distance of approx .751" (at least that's what a TR220 is) (your cam will be very close to this)
This means the Comp Cam has a .024" smaller cam centerline to lobe heal distance which would require a pushrod that is exactly .024" longer than the stock 7.385" It would need a new rod that is in fact 7.409" long.
Now, you milled .030" off the head. That will now require a reduced rod length of .030"
The rod length now becomes 7.379" (7.409 minus .030)
Last, but not least, you now have LS6 sodium valves which are .6mm (.024") longer than the stock valves. That, in itself would require a .024" shorter pushrod. So, the required rod length now becomes 7.355" (7.379" minus .024")
You would actually need a set of Thunder Racing 7.350" hardened pushrods.
That newly required 7.355" rod is only .005" (5 thousands) in difference from a set of 7.350" Thunder hardened rods.
You will actually have .005" less lifter preload than you had when the motor was bone stock. And that 5 thousands is nothing to worry about. In fact, slightly less preload actually has an advantage. Your geometry will by fine.
99-PR7350 Thunder Racing Heat Treated Chrome-Moly Pushrods, 7.350" $109.99
http://www.thunderracing.com/index.c...yid=1114#T1554
Hope this helps,
Ron
TECH Apprentice
Joined: Apr 2002
Posts: 369
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From: Honoulu, Hawaii
Re: What Pushrod length? Ron -
Perfect, I appreciate your help. This valve length issue caught me by surprise. My fault for not fully searching past posts, but I really didn't understand the geometry (impact) anyway.
Thanks,
Gregg
PS - would love to visit Thailand too!!!
Perfect, I appreciate your help. This valve length issue caught me by surprise. My fault for not fully searching past posts, but I really didn't understand the geometry (impact) anyway.
Thanks,
Gregg
PS - would love to visit Thailand too!!!
