Pushrod length help ls3
Thread Starter
Teching In
Joined: Dec 2014
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Pushrod length help ls3 Hi guys so I installed a comp cam 54-469-11 lsr 3 bolt cam, ls9 7 layer head gasket, ls7 style lifters, dual btr .660 valve springs, stock rockers with comp cam trunion upgrade
So the problem I'm running into is my intake pushrod measures 7.335 0 lash and exhaust is 7.354 0 lash I've measured all cylinder across the block and all measure roughly the same is that normal and also what pushrod should I run I ordered btr 7.400 but when I measured them there 7.420 🤦♂️. Should I run these on intake and do 80 preload and buy some btr 7.420 and hope there off by 20 to make 7.440 and run those on exhaust to be 80 preload aswell
Thanks...
So the problem I'm running into is my intake pushrod measures 7.335 0 lash and exhaust is 7.354 0 lash I've measured all cylinder across the block and all measure roughly the same is that normal and also what pushrod should I run I ordered btr 7.400 but when I measured them there 7.420 🤦♂️. Should I run these on intake and do 80 preload and buy some btr 7.420 and hope there off by 20 to make 7.440 and run those on exhaust to be 80 preload aswell
Thanks...
TECH Apprentice
Joined: Jan 2023
Posts: 340
Likes: 47
From: Corpus Christi, TX
Im running into the same exact thing with my ls7 cam i did not measure the lobes before installing but the variation is obviously there and wondering if i need to pull my heads or order another slightly shorter set of rods. I may have done damage in my situation from too long so dont jump the gun on it dig in deep into the preload/installation method im barely learning myself
Thread Starter
Teching In
Joined: Dec 2014
Posts: 20
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Im running into the same exact thing with my ls7 cam i did not measure the lobes before installing but the variation is obviously there and wondering if i need to pull my heads or order another slightly shorter set of rods. I may have done damage in my situation from too long so dont jump the gun on it dig in deep into the preload/installation method im barely learning myself
Yh it's so weird I've read somewhere that it's normal on ls3 but not sure ive ran it for a while on the 7.4 since its pretty much still in the ok preload range for the lifters but after a year I started getting a tick put new lifters in it but still has the tick so now I'm guessing it might be the pushrods its not supper loud like a rod bearing or anything crazy and it's driving me nuts 🤦♂️
TECH Apprentice
Joined: Jan 2023
Posts: 340
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From: Corpus Christi, TX
No it sounds like a valvetrain problem to me if a rod bearing goes bad you will hear alot more from a loose piston. You said miles and not how many is it possibly wear from 2 different valves doing 2 different jobs I would susoect the difference in the plunger but thats me asking a question hoping a pro will chime in for you. Also want to add i was slightly upset i had 2 sets of BTR pushrods show up and both sets were .020 long one set nearly all 7.338-7.340 and the other set 7.356-7.369 i knew they wouldnt be spot on but I was betting on the short side lol
Thread Starter
Teching In
Joined: Dec 2014
Posts: 20
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No it sounds like a valvetrain problem to me if a rod bearing goes bad you will hear alot more from a loose piston. You said miles and not how many is it possibly wear from 2 different valves doing 2 different jobs I would susoect the difference in the plunger but thats me asking a question hoping a pro will chime in for you. Also want to add i was slightly upset i had 2 sets of BTR pushrods show up and both sets were .020 long one set nearly all 7.338-7.340 and the other set 7.356-7.369 i knew they wouldnt be spot on but I was betting on the short side lol
TECH Apprentice
Joined: Jan 2023
Posts: 340
Likes: 47
From: Corpus Christi, TX
You ordered the other set and got it running?! It's normal to have different sizes
https://ls1tech.com/forums/generation-iii-internal-engine/1521230-2-different-pushrod-lengths.html
I'm going to be tearing mine apart
https://ls1tech.com/forums/generation-iii-internal-engine/1521230-2-different-pushrod-lengths.html
I'm going to be tearing mine apart
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Based on your measurements it sounds to me like the top of the intake valve is taller than the top of the exhaust valve by about 0.021. This should not be of concern with a hydraulic lifter preload range of 0.080 +/- 0.010.
The split of the two PR lengths between the intake and exhaust comes out to be 7.425 so I probably wouldn't be worried about running the 7.420 PR as it would fall into this +/- 0.010 range. My .02
The split of the two PR lengths between the intake and exhaust comes out to be 7.425 so I probably wouldn't be worried about running the 7.420 PR as it would fall into this +/- 0.010 range. My .02
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..... Reality is that its a hydraulic lifter ... it has to have some preload in order to keep the plunger from beating the retaining clip all to hell and littering up the inside of your engine ... on Gen 1 sbc's there was ALWAYS someone touting whether 1/4 turn was better than one full turn ... the argument usually mentioned lifter pump up , valve float , etc. ... The other reality is that with a 24 thread per inch rocker stud , one full turn is .0416" ... now on an all aluminum engine with aluminum-like expansion rates you need to factor in a bit more preload to ensure that the retaining rings stay happy ... .010-.050 difference in preload does not change a whole lot within the day to day operation of the valve train ... if you are hearing ticking noises and nothing is loose under the valve covers , please change your exhaust manifold gaskets ! ... And ... educate yourselves on the correct way to measure pushrod lengths .
..... Reality is that its a hydraulic lifter ... it has to have some preload in order to keep the plunger from beating the retaining clip all to hell and littering up the inside of your engine ... on Gen 1 sbc's there was ALWAYS someone touting whether 1/4 turn was better than one full turn ... the argument usually mentioned lifter pump up , valve float , etc. ... The other reality is that with a 24 thread per inch rocker stud , one full turn is .0416" ... now on an all aluminum engine with aluminum-like expansion rates you need to factor in a bit more preload to ensure that the retaining rings stay happy ... .010-.050 difference in preload does not change a whole lot within the day to day operation of the valve train ... if you are hearing ticking noises and nothing is loose under the valve covers , please change your exhaust manifold gaskets ! ... And ... educate yourselves on the correct way to measure pushrod lengths .