Lifter preload delema
distance from top of lifter to base of rocker rocker is 7.4 (lets ignore pushrod for now and refer to distance)
block gets hot and expands .015, heads get hot but not quite as hot as the block and they expand .010. so since the block is hot and expanded the distance to rockers has shrunk from 7.4 to 7.385. now we add in the fact that the heads expanded away from the block .010., so add .010 to the 7.385 and we now have 7.395. we are now .005 shorter after expansion, but the pushrod length doesn't change much, so if it doesn't increase by at least .005, you will be increasing load. feel free to post me a link of a RELIABLE and technical source to better explain to me if im not right
Valve lash (lifter preload) increases as engine gets to temp. On my solid roller setup, I’m at .003 cold lash. At temp, it grows approx. .010 to .013. Aluminum will “grow” more than steel or iron, so your heads are the biggest mover in this scenario.
i believe all you guys about it growing, but i just cant make sense of it........so basically if the pushrods were made of aluminum (lol) they would expand the same thus keeping preload or lash the same weather motor is hot or cold correct?
Last edited by Floorman279; Aug 3, 2018 at 06:33 PM. Reason: balls
i know they are both similar aluminums, but i just thought that since all the explosions are occurring in the block, and the heads have only a small part touching the fire and a good chunk of the head is away from all that i just thought the block would expand a little more
i believe all you guys about it growing, but i just cant make sense of it........so basically if the pushrods were made of aluminum (lol) they would expand the same thus keeping preload or lash the same weather motor is hot or cold correct?
i believe all you guys about it growing, but i just cant make sense of it........so basically if the pushrods were made of aluminum (lol) they would expand the same thus keeping preload or lash the same weather motor is hot or cold correct?
You can take two identical engines, one with aluminum heads, and the other with the exact same head, only made out of cast iron, and all things bring equal, the cast iron headed engine will make more power, due to the iron headed engine holding heat in the chamber longer.
forgot about hot exhaust gasses lol so that makes sense. in theory if the pushrods expanded the same as the rest of the block preload would be unchanged when hot correct? so basically this saying if true makes sense to me , "since the entire motor expands, and the pushrods dont expand as much, your preload changes"
forgot about hot exhaust gasses lol so that makes sense. in theory if the pushrods expanded the same as the rest of the block preload would be unchanged when hot correct? so basically this saying if true makes sense to me , "since the entire motor expands, and the pushrods dont expand as much, your preload changes"
i understand that, but do aluminum heads expand almost exactly as the block does? id imagine that the block expands more than the heads, so it will minimally tighten......just a random numbers example of what im thinking, not saying im right or wrong just how i would imagine it.......no idea what expansion numbers are.
distance from top of lifter to base of rocker rocker is 7.4 (lets ignore pushrod for now and refer to distance)
block gets hot and expands .015, heads get hot but not quite as hot as the block and they expand .010. so since the block is hot and expanded the distance to rockers has shrunk from 7.4 to 7.385. now we add in the fact that the heads expanded away from the block .010., so add .010 to the 7.385 and we now have 7.395. we are now .005 shorter after expansion, but the pushrod length doesn't change much, so if it doesn't increase by at least .005, you will be increasing load. feel free to post me a link of a RELIABLE and technical source to better explain to me if im not right
distance from top of lifter to base of rocker rocker is 7.4 (lets ignore pushrod for now and refer to distance)
block gets hot and expands .015, heads get hot but not quite as hot as the block and they expand .010. so since the block is hot and expanded the distance to rockers has shrunk from 7.4 to 7.385. now we add in the fact that the heads expanded away from the block .010., so add .010 to the 7.385 and we now have 7.395. we are now .005 shorter after expansion, but the pushrod length doesn't change much, so if it doesn't increase by at least .005, you will be increasing load. feel free to post me a link of a RELIABLE and technical source to better explain to me if im not right
yea i did see that when i bought the drop in 5315 or whatever......i got .75 preload so when it loosens im at a real comfy .63 give or take
On The Tree
Joined: Sep 2016
Posts: 103
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Linear thermal expansion of anything is "per inch/per degree". Heads and blocks (both being aluminum) may expand at the same rate, but won't expand the same amount. A 4" tall head will grow less that a 15" tall block. Per INCH/per degree. Pushrods don't see anywhere near the heat seen by the block or heads, per inch/per DEGREE. And I wouldn't sweat the .0045 difference in deck heights. That could be accounted for in the offset piston pin alone, bank to bank. The preload will take care of it. Not a big deal unless you're building a ragged edge type engine.
Thread Starter
Teching In
Joined: Jul 2018
Posts: 31
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.080 is ALWAYS my target preload on LS7 lifters. I've never had an engine tick or sound like a sewing machine at this preload. Trust me, that sound is annoying.
Also,
What about your different sized banks? I may have read your original post wrong, you're not running two different head gaskets are you? Don't
You should be just fine running a 11/32" PR with a preload near or at .080" IMO. Again, IMO. Also, it's always a good idea to measure each and all 16 valves for the proper preload.
I've found many rebuilt engines with severe differences in between valves. Especially if the heads/valves have been worked on. It only takes one value with minimal preload to make noise.
Good Luck with your build!
Also,
What about your different sized banks? I may have read your original post wrong, you're not running two different head gaskets are you? Don't
You should be just fine running a 11/32" PR with a preload near or at .080" IMO. Again, IMO. Also, it's always a good idea to measure each and all 16 valves for the proper preload.
I've found many rebuilt engines with severe differences in between valves. Especially if the heads/valves have been worked on. It only takes one value with minimal preload to make noise.
Good Luck with your build!
Thread Starter
Teching In
Joined: Jul 2018
Posts: 31
Likes: 0
So, after installing those pushrods, i ended up with just over a full turn, about .050- .055 preload. I called summit and had them send me out the next size up, and now i am just shy of 1 3/4 turns, about .080- .082 preload. Not sure how I was off that far measuring with the comp checker tool, but Im happy with that. Will let you know how it goes.
First, the torque procedure results in some bolt rotation where no lifter preload results (rocker is bottomed). I measured 1/3 turn on my motor. So you can't simply ratio the 0.048" preload for one turn, that actually results from using the amount of bolt movement and the rocker ratio.
How much longer are the new pushrods than the originals you installed?
Do you have a dial indicator? That is the most accurate way of measuring, counting turns is highly inaccurate.
How much longer are the new pushrods than the originals you installed?
Do you have a dial indicator? That is the most accurate way of measuring, counting turns is highly inaccurate.