Pushrod length - In the middle of Spring swap.
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Pushrod length - In the middle of Spring swap. Doing a valve spring swap on my car and converting from Harland Sharp rockers back to stockers on my 383ci car. Car has Patriot stage 2 heads and Comp R lifters. Stock size head gaskets as well. Noticed that the previous owner/builder also had 7.475" pushrods. This seemed a little long to me. I would think if anything the heads would be stock or milled some.
Anyone know if there is a possibility a motor would need these or did the builder just spec it wrong?
Motor ran fine and quiet but it was hard to tell if it was lacking on power due to inadequet bolt ons which are being corrected now as well.
Any input as to if I should change length pushrod would be appreciate.
Anyone know if there is a possibility a motor would need these or did the builder just spec it wrong?
Motor ran fine and quiet but it was hard to tell if it was lacking on power due to inadequet bolt ons which are being corrected now as well.
Any input as to if I should change length pushrod would be appreciate.
Doing a valve spring swap on my car and converting from Harland Sharp rockers back to stockers on my 383ci car. Car has Patriot stage 2 heads and Comp R lifters. Stock size head gaskets as well. Noticed that the previous owner/builder also had 7.475" pushrods. This seemed a little long to me. I would think if anything the heads would be stock or milled some.
Anyone know if there is a possibility a motor would need these or did the builder just spec it wrong?
Motor ran fine and quiet but it was hard to tell if it was lacking on power due to inadequet bolt ons which are being corrected now as well.
Any input as to if I should change length pushrod would be appreciate.
Anyone know if there is a possibility a motor would need these or did the builder just spec it wrong?
Motor ran fine and quiet but it was hard to tell if it was lacking on power due to inadequet bolt ons which are being corrected now as well.
Any input as to if I should change length pushrod would be appreciate.
Maybe the HS rockers were farther away from the lifters (possible) than the oem ones? Or, maybe the comp R lifters are shorter by a a few thousandths (doubtful) than the oem ones....or maybe the "preload" needed to be more on the comp r lifters? Maybe the heads were decked a bit (but then the pushrods would need to be shorter than oem, not longer)?
I guess that the only real way to know, would be to cc the heads, and measure everything else as well. I would think that .080 would be correct preload for the lifters, and 1.8 installed spring height as well.
Check it all, just to be sure.
Last edited by salemetro; Aug 18, 2009 at 07:35 PM.
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Thanks for the help. Whether or not there is a difference in the HS rockers compared to stockers is part of my question for sure. Preload on the Comp Rs is another part of my question too. Wouldn't a cut head need a shorter pushrod though?
If you check Comp's web site, you will find the Comp R's require 0.002"-0.004" and adjustable rockers. Not sure if the Harlands you are removing are adjustable, but if they are that my have been the reason for their original installation.
Some do but some have had the clips come out due to improper setup. Just be careful on your setup. That is a very narrow range of preload and Comp doesn't state whether it is "lifter" preload or bolt movement preload (which will be different). Do some searches and talk to Comp. Just don't want to see you run into a problem down the road.
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Looking like it'll never matter because I can't get the old valve springs off to swap em and put the thing back together. 135psi of air won't hold the valves closed when I compress the springs and I guess the pistons are fly cut enough where they can't hold the valves closed either. Whew. This is giving me a headache! Any suggestions on keeping valves closed?
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Finally got one cylinder's springs off and now I'm finding the Comp 921's spring seats won't fit my head's valve guides. Ok, not a big deal, going to use the old spring seats (only .003 thicker). I get down to putting the keepers back in the new 921's titanium retainers and yep, they're the wrong size. Way too big to fit the new spring retainers. What's going on here? Thought these complete spring kits were ready to go. Do Patriot Gold springs use a larger diameter retainer and keeper?
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The valvetrain probably wasn't setup right. Causing the valve float they were talking about in this thread https://ls1tech.com/forums/generatio...wap-power.html .
Looking like it'll never matter because I can't get the old valve springs off to swap em and put the thing back together. 135psi of air won't hold the valves closed when I compress the springs and I guess the pistons are fly cut enough where they can't hold the valves closed either. Whew. This is giving me a headache! Any suggestions on keeping valves closed?
Finally got one cylinder's springs off and now I'm finding the Comp 921's spring seats won't fit my head's valve guides. Ok, not a big deal, going to use the old spring seats (only .003 thicker). I get down to putting the keepers back in the new 921's titanium retainers and yep, they're the wrong size. Way too big to fit the new spring retainers. What's going on here? Thought these complete spring kits were ready to go. Do Patriot Gold springs use a larger diameter retainer and keeper?
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Trying to figure out pushrod length. Got new springs on and have the stock rockers ready to go on as well, just having problems figuring out which pushrods. Just talked to the guy that built the motor originally with the 7.475s and he said that's what he measure it needing when he built it. He confirmed it has '04 Ls6 block, Unmilled Ls6 Patriot Stage 2 heads, Comp R lifters, GM head gaskets. Seems odd to need that length.
Here is what I'm finding. With the 7.475s, when the exhaust valve starts down, I check the intake preload and 3/4's of a turn BEFORE it tightens down, the intake valve opens (compressing the spring without compressing the lifter). Turning the motor over by hand, it doesn't appear that the intake valve ever closes.
With the 7.4s, the rocker arm bolt tightens down before it takes up all the slack, leaving my rocker arm loose.
Car hasn't been cranked in 3 days.
Shouldn't the lifters be compressing before the valve springs?
Here is what I'm finding. With the 7.475s, when the exhaust valve starts down, I check the intake preload and 3/4's of a turn BEFORE it tightens down, the intake valve opens (compressing the spring without compressing the lifter). Turning the motor over by hand, it doesn't appear that the intake valve ever closes.
With the 7.4s, the rocker arm bolt tightens down before it takes up all the slack, leaving my rocker arm loose.
Car hasn't been cranked in 3 days.
Shouldn't the lifters be compressing before the valve springs?
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But will be calling tomorrow if I can't figure it out tonight. Thanks!
Trying to figure out pushrod length. Got new springs on and have the stock rockers ready to go on as well, just having problems figuring out which pushrods. Just talked to the guy that built the motor originally with the 7.475s and he said that's what he measure it needing when he built it. He confirmed it has '04 Ls6 block, Unmilled Ls6 Patriot Stage 2 heads, Comp R lifters, GM head gaskets. Seems odd to need that length.
Here is what I'm finding. With the 7.475s, when the exhaust valve starts down, I check the intake preload and 3/4's of a turn BEFORE it tightens down, the intake valve opens (compressing the spring without compressing the lifter). Turning the motor over by hand, it doesn't appear that the intake valve ever closes.
With the 7.4s, the rocker arm bolt tightens down before it takes up all the slack, leaving my rocker arm loose.
Car hasn't been cranked in 3 days.
Shouldn't the lifters be compressing before the valve springs?
Here is what I'm finding. With the 7.475s, when the exhaust valve starts down, I check the intake preload and 3/4's of a turn BEFORE it tightens down, the intake valve opens (compressing the spring without compressing the lifter). Turning the motor over by hand, it doesn't appear that the intake valve ever closes.
With the 7.4s, the rocker arm bolt tightens down before it takes up all the slack, leaving my rocker arm loose.
Car hasn't been cranked in 3 days.
Shouldn't the lifters be compressing before the valve springs?
3/4 turn is a lot of preload for the Comp R lifter. I am coming up with 0.058" preload so the fact that the 7.400" pushrods leave the rockers loose makes sense.
The real issue is that with the Comp R's, if you try to stay within the Comp recommended preload, will likely require 16 individual pushrods of exact length. My guess is the tolerance on a standard off the shelf pushrod won't even be accurate enough to set them up let alone the rest of the parts (valve stem height, etc.).
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How was this motor even running with the long pushrods? Is it likely something got damaged running them that long? And what should a guy do at this point to get this thing back together in good form?
personally I would pull the comp r lifters and sell them. Then replace them with a good set of ls7 lifters. Then it will be a sinch to finish everything up. For what it's worth I went from crane variable lift rockers back to stock for the same reason and gained almost 15rwhp across the board and the valve float was gone.
You should talk to Comp on the preload and see what they say. I would also do a search and see what preload people are running and what problems have occurred. I know several had issues with the upper clip failing the lifter grenading as a result but don't remember the details of the cause. Just look into things real well before making a decision on what to do.
The Harland Sharp rockers would normally require a longer pushrod. Going back to stock, however will require much shorter with Comp R lifters. See my response here:
https://ls1tech.com/forums/generatio...l#post12107909
Shane
https://ls1tech.com/forums/generatio...l#post12107909
Shane