Comp XE-R lobe base circle vs. stock
Originally Posted by Patrick G
Pushrod checker is not the answer I'm looking for. I'm looking for the base circle cam dimensions of a Comp XE-R cam and how that compares to stock. Even more importantly, how that base circle dimension change affects pushrod selection, if at all compared to stock.
Originally Posted by SideStep
7.240??? 
What are your mods????
What are your mods????
Originally Posted by TAQuickness
mod's are in sig. It's what she needed, what she got, and the results are pleasing.
Current Mods:
1qt Blinker Fluid, 5 Muffler Bearings, resonance coupled plasma discharges, and a Flux Capacitor - 1.8 jiggawatts on the rear wheels
needs more jiggawatts
Current Mods:
1qt Blinker Fluid, 5 Muffler Bearings, resonance coupled plasma discharges, and a Flux Capacitor - 1.8 jiggawatts on the rear wheels
needs more jiggawatts
Originally Posted by GuitsBoy
Is this a bad joke? I cant see those muffler bearings requiring .160 shorter pushrods.
Originally Posted by Tony Mamo @ AFR
Jeeeeez Pat.....That looks like a "noob" question 
Assuming heads are in place with the proper headgasket (or the same thickness shims during mock-up), the following is a quick rundown to check and measure for proper pushrod length:
Install an adjustable PR initially set too small (makes sure cam is on the basecircle of the lobe you are checking)
Bolt down the factory rockers....
Set the adjustable pushrod to zero lash and remove
Measure pushrod, then add .050-.100 to that figure which now represents your pushrod preload into the lifter and the total length of the pushrod your engine requires. This is obviously quickie instructions for a factory rocker arm set-up (pedastal mount).
------------------------------------------------------------
Guys....pushrod length/valvetrain geometry is critical to power output and reliability. "Internet Tech" may or may not give you the proper information for an optimal combination, or one that even runs for that matter.
Sorry Pat....couldn't resist the "noob" comment.....LOL
Tony M.
Assuming heads are in place with the proper headgasket (or the same thickness shims during mock-up), the following is a quick rundown to check and measure for proper pushrod length:
Install an adjustable PR initially set too small (makes sure cam is on the basecircle of the lobe you are checking)
Bolt down the factory rockers....
Set the adjustable pushrod to zero lash and remove
Measure pushrod, then add .050-.100 to that figure which now represents your pushrod preload into the lifter and the total length of the pushrod your engine requires. This is obviously quickie instructions for a factory rocker arm set-up (pedastal mount).
------------------------------------------------------------
Guys....pushrod length/valvetrain geometry is critical to power output and reliability. "Internet Tech" may or may not give you the proper information for an optimal combination, or one that even runs for that matter.
Sorry Pat....couldn't resist the "noob" comment.....LOL
Tony M.
Aren't you forgetting one VERY important aspect? The wipe of the rocker on the valve! (from many 'searches', it seems most on here are ignoring this?!)
Just installing a shorter/longer PR given the new heads/cam being used will not automatically keep the valve-wipe in the center. The geometry is almost assuredly not correct. The rocker needs to be shimmed and PR length checked iteratively until the proper wipe is obtained...then you have your proper PR length.
Originally Posted by redtail2426
I didnt think the wipe test applied to the stock rocker arm setup,i thought you only needed it for adjustable rocker arms.
The wipe in a fixed "pedastal" or shaft rocker type valvetrain can ONLY be adjusted by changing the height of the stands either by milling the head (to drop them lower) or adding shims to raise the height. Assuming yuo are just bolting them on, your wipe pattern is fixed and the only matter of concern is the proper preload depth.
Tony
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Originally Posted by Tony Mamo @ AFR
You are correct...
The wipe in a fixed "pedastal" or shaft rocker type valvetrain can ONLY be adjusted by changing the height of the stands either by milling the head (to drop them lower) or adding shims to raise the height. Assuming yuo are just bolting them on, your wipe pattern is fixed and the only matter of concern is the proper preload depth.
Tony
The wipe in a fixed "pedastal" or shaft rocker type valvetrain can ONLY be adjusted by changing the height of the stands either by milling the head (to drop them lower) or adding shims to raise the height. Assuming yuo are just bolting them on, your wipe pattern is fixed and the only matter of concern is the proper preload depth.
Tony
He has milled heads (see previous postings), and is going with thinner head-gaskets. Both will throw-off valvetrain geometry, and even the stock rockers will then need to be shimmed for proper wipe.
Likewise, I am assuming that he's not using stock valves (presumably longer valve stems), which will also affect the geometry - this goes for milled or unmilled heads.
In addition, the lift of the camshaft will also throw it off. A higher lift cam will wipe differently than a low lift.
LOTS of factors here have affected his VT-geometry, and just adjusting the pushrod-length only is not the correct answer.
.
Last edited by 02RedHawk; Feb 19, 2006 at 05:49 PM.
Originally Posted by 02RedHawk
He has milled heads (see previous postings), and is going with thinner head-gaskets. Both will throw-off valvetrain geometry, and even the stock rockers will then need to be shimmed for proper wipe.
Likewise, I am assuming that he's not using stock valves (presumably longer valve stems), which will also adjust the geometry - this goes for milled or unmilled heads.
In addition, the lift of the camshaft will also throw it off. A higher lift cam will wipe differently than a low lift.
LOTS of factors here have affected his VT-geometry, and just adjusting the pushrod-length only is not the correct answer.
.
Likewise, I am assuming that he's not using stock valves (presumably longer valve stems), which will also adjust the geometry - this goes for milled or unmilled heads.
In addition, the lift of the camshaft will also throw it off. A higher lift cam will wipe differently than a low lift.
LOTS of factors here have affected his VT-geometry, and just adjusting the pushrod-length only is not the correct answer.
.
Guys....the only thing that effects the wipe pattern or geometry of that set-up is changing the height of the pedastal as I said earlier. Unless you are willing to shim or machine (for a lower height) the wipe pattern is FIXED....end of story. (Yes, it might wipe a little differently if you have more gross valve lift). Milling heads, thinner gaskets, etc., etc. will have ZERO effect on the wipe pattern of a stock LS1 set-up....that will only effect the proper pushrod length for that particular combination ONLY relating to how much lifter preload you choose (or simply end up with) running. Obviously a milled head with a thinner gasket would require a shorter pushrod if you were wanting to keep lifter preload the same.
You guys are getting the stock valvetrain confused with an adjustable stud mount where now the correct pushrod length also effects the height of the rocker in relationship with the height of the valvestem tip thus effecting geometry and wipe pattern.
Think about it....in a pedestal system the heights are fixed in relation to one another unless you machine the head or shim, once again.
Tony M.
Last edited by Tony Mamo @ AFR; Feb 19, 2006 at 05:58 PM.
I think I understand the confusion now:
"The wipe in a fixed "pedastal" or shaft rocker type valvetrain can ONLY be adjusted by changing the height of the stands either by milling the head (to drop them lower) or adding shims to raise the height. Assuming yuo are just bolting them on, your wipe pattern is fixed and the only matter of concern is the proper preload depth."
You mean milling INSIDE the head where the pedastal goes vs. milling the bottom of the head for more compression.
Sorry if I misled anyone.
But how does this work:
"Install an adjustable PR initially set too small (makes sure cam is on the basecircle of the lobe you are checking)
Bolt down the factory rockers....
Set the adjustable pushrod to zero lash and remove"
Once you bolt them down, you can't get your fingers in there to adjust it right?
"The wipe in a fixed "pedastal" or shaft rocker type valvetrain can ONLY be adjusted by changing the height of the stands either by milling the head (to drop them lower) or adding shims to raise the height. Assuming yuo are just bolting them on, your wipe pattern is fixed and the only matter of concern is the proper preload depth."
You mean milling INSIDE the head where the pedastal goes vs. milling the bottom of the head for more compression.
Sorry if I misled anyone.
But how does this work:
"Install an adjustable PR initially set too small (makes sure cam is on the basecircle of the lobe you are checking)
Bolt down the factory rockers....
Set the adjustable pushrod to zero lash and remove"
Once you bolt them down, you can't get your fingers in there to adjust it right?
Originally Posted by Tony Mamo @ AFR
NOT with a pedastal (or fixed shaftmount) set-up....
Guys....the only thing that effects the wipe pattern or geometry of that set-up is changing the height of the pedastal as I said earlier. Unless you are willing to shim or machine (for a lower height) the wipe pattern is FIXED....end of story. (Yes, it might wipe a little differently if you have more gross valve lift). Milling heads, thinner gaskets, etc., etc. will have ZERO effect on the wipe pattern of a stock LS1 set-up....that will only effect the proper pushrod length for that particular combination ONLY relating to how much lifter preload you choose (or simply end up with) running. Obviously a milled head with a thinner gasket would require a shorter pushrod if you were wanting to keep lifter preload the same.
You guys are getting the stock valvetrain confused with an adjustable stud mount where now the correct pushrod length also effects the height of the rocker in relationship with the height of the valvestem tip thus effecting geometry and wipe pattern.
Think about it....in a pedestal system the heights are fixed in relation to one another unless you machine the head or shim, once again.
Tony M.
Guys....the only thing that effects the wipe pattern or geometry of that set-up is changing the height of the pedastal as I said earlier. Unless you are willing to shim or machine (for a lower height) the wipe pattern is FIXED....end of story. (Yes, it might wipe a little differently if you have more gross valve lift). Milling heads, thinner gaskets, etc., etc. will have ZERO effect on the wipe pattern of a stock LS1 set-up....that will only effect the proper pushrod length for that particular combination ONLY relating to how much lifter preload you choose (or simply end up with) running. Obviously a milled head with a thinner gasket would require a shorter pushrod if you were wanting to keep lifter preload the same.
You guys are getting the stock valvetrain confused with an adjustable stud mount where now the correct pushrod length also effects the height of the rocker in relationship with the height of the valvestem tip thus effecting geometry and wipe pattern.
Think about it....in a pedestal system the heights are fixed in relation to one another unless you machine the head or shim, once again.
Tony M.
Hmmm... I think I'm almost with you.... But what about an assumption of longer valve stems? I've seen firsthand the difference on wipe with a larger cam and different-length valves versus a stock setup. Help me out here; I want to take that blue pill, but apparently I'm struggling with grasping it!
longer valve stems are far and few,the only ones i know of are the lightweight ls6 valves,if its a small amount like the ls6 valves then dont worry about it.But if the valves are longer and the valve seats have been cut(this would allow the valve to sit deeper in its seat,making the valve seem even longer)then shimming up the rockers the same amount would take care of this.But as i said,longer valves are rare.
What about setting a dial indicator on the rocker at the pushrod cup, then tightening the rocker and watching how much the dial indicator moves? It will eventually stop when the lifter stops compressing. Mine read 0.090" compression with 7.4" pushrods, so I changed to 7.35" pushrods and it now compresses about 0.035" (my measurements could be off as much as 0.010"). Any problems doing it this way?
Originally Posted by redtail2426
i would be suprised if most ported heads came with longer valves.That would mean a lot of people needing to shim there stock rocker arms,and i dont see that to often.
A longer valve is actually a good thing - as it does help bring the VT geometry back closer to stock when using higher lift cams.