Pushrod length- seem right?
05-02-2011, 03:10 PM
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Pushrod length- seem right? So I got to measuring pushrod length today. I used the comp pushrod length checker (6.800 closed length). I got cylinder 1 on TDC and checked like 5 times.
I have- LS7 lifters, TFS 215's (not milled), GM MLS gaskets, YT 1.7's, cam (don't have specs handy).
Anyway, I came up with 7.58 (intake) & 7.605 (exhaust) with .080 preload added in. Does this sound a little long? I think I'm just second guessing, but it seems a good bit longer than what I see most folks running. If it doesn't look way off I'll go with a 7.600 pushrod and double check when they come in.
I have- LS7 lifters, TFS 215's (not milled), GM MLS gaskets, YT 1.7's, cam (don't have specs handy).
Anyway, I came up with 7.58 (intake) & 7.605 (exhaust) with .080 preload added in. Does this sound a little long? I think I'm just second guessing, but it seems a good bit longer than what I see most folks running. If it doesn't look way off I'll go with a 7.600 pushrod and double check when they come in.
05-02-2011, 09:11 PM
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This is gonna look familiar-
This is assuming you have the Comp Cams adjustable pushrod, which at its shortest length is 6.800".
Each turn of the adjustable pushrod is 0.050". When fully closed, it is 6.800". This is pushrod "gauge length" so you can't measure it directly as the pushrod length is actually based on the length between the ball ends where the ball end measures 0.140" in diameter. Assuming you are using stock rockers or a non-adjustable rocker.
1. Open the adjustable pushrod to the same length as your stock pushrods
2. Close it down two turns
3. Put your rocker rail on the head
4. Make sure you cylinder (typically #1) is at top dead center on the firing stroke so both valves would be closed
5. Put the pushrod in place on the intake valve and make sure it is in the lifter cup
6. Install the rocker and snug down the bolt (don't need to torque, just make sure it is snug)
7. Lift rocker tip up and down, if it "ticks" the pushrod is too short. If you can't easily move the rocker the pushrod is too long.
8. You can try and adjust the pushrod in place but my fingers are too fat so I end up pulling the rocker and adjusting the pushrod length. Go either shorter or longer 1/2 turn and try again.
9. You are trying to get to the point where the lifter doesn't "tick tick" with the pushrod in place nor is the rocker snug. When you get the pushrod length such that you just barely get rid of the "tick tick", you have found "zero lash".
10. When you have found zero lash, carefully remove the rocker and pushrod without rotating the pushrod.
11. Tighten the pushrod until it is fully closed counting the turns as you go.
To figure out your pushrod length you do the following. Let’s assume it took 10-1/2 turns to close the pushrod down to its shortest length after you reached zero lash. Each turn is 0.050".
Your length is then: 6.800" (fully closed length) + 10.5 X 0.050" (number of turns times the length change per turn) = pushrod length minus preload. So for this case:
6.800 +10.5 X 0.050 = 7.325"
This is the length you measured to zero lash without any lifter preload. Now let’s say you want to have 0.075" lifter preload, you add that to the measured number and you end up with 7.400" pushrods.
Now repeat for the exhaust valve to verify the length. If you have something like Yella Terra's, it is the same procedure but you must snug down the rocker pair rather than the single rocker.
I came up with 14 turns on the intake side and 14.5 turns on the exhaust side. Once I got the measurement, I then tried to back the tool down some to ensure I had the fewest turns possible. These were the measurements that got me to what I feel is zero lash with the fewest turns possible. I then added in .080 preload to come up with my final numbers.
I tried the method Shane posted, but I think that my old pushrods were too short (7.400) as I couldn't get zero lash no matter how tight I got the rockers. I am planning on trying that method as a backup to verify the new pushrod length during the install.
This is assuming you have the Comp Cams adjustable pushrod, which at its shortest length is 6.800".
Each turn of the adjustable pushrod is 0.050". When fully closed, it is 6.800". This is pushrod "gauge length" so you can't measure it directly as the pushrod length is actually based on the length between the ball ends where the ball end measures 0.140" in diameter. Assuming you are using stock rockers or a non-adjustable rocker.
1. Open the adjustable pushrod to the same length as your stock pushrods
2. Close it down two turns
3. Put your rocker rail on the head
4. Make sure you cylinder (typically #1) is at top dead center on the firing stroke so both valves would be closed
5. Put the pushrod in place on the intake valve and make sure it is in the lifter cup
6. Install the rocker and snug down the bolt (don't need to torque, just make sure it is snug)
7. Lift rocker tip up and down, if it "ticks" the pushrod is too short. If you can't easily move the rocker the pushrod is too long.
8. You can try and adjust the pushrod in place but my fingers are too fat so I end up pulling the rocker and adjusting the pushrod length. Go either shorter or longer 1/2 turn and try again.
9. You are trying to get to the point where the lifter doesn't "tick tick" with the pushrod in place nor is the rocker snug. When you get the pushrod length such that you just barely get rid of the "tick tick", you have found "zero lash".
10. When you have found zero lash, carefully remove the rocker and pushrod without rotating the pushrod.
11. Tighten the pushrod until it is fully closed counting the turns as you go.
To figure out your pushrod length you do the following. Let’s assume it took 10-1/2 turns to close the pushrod down to its shortest length after you reached zero lash. Each turn is 0.050".
Your length is then: 6.800" (fully closed length) + 10.5 X 0.050" (number of turns times the length change per turn) = pushrod length minus preload. So for this case:
6.800 +10.5 X 0.050 = 7.325"
This is the length you measured to zero lash without any lifter preload. Now let’s say you want to have 0.075" lifter preload, you add that to the measured number and you end up with 7.400" pushrods.
Now repeat for the exhaust valve to verify the length. If you have something like Yella Terra's, it is the same procedure but you must snug down the rocker pair rather than the single rocker.
I came up with 14 turns on the intake side and 14.5 turns on the exhaust side. Once I got the measurement, I then tried to back the tool down some to ensure I had the fewest turns possible. These were the measurements that got me to what I feel is zero lash with the fewest turns possible. I then added in .080 preload to come up with my final numbers.
I tried the method Shane posted, but I think that my old pushrods were too short (7.400) as I couldn't get zero lash no matter how tight I got the rockers. I am planning on trying that method as a backup to verify the new pushrod length during the install.
05-03-2011, 09:45 PM
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Yea, I didn't. I was thinking that came after the pushrod length.... How can I properly verify the wipe pattern without the proper length pushrod? Is the only way with a checking spring and dial indicator? I have no dial indicator.....
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05-04-2011, 10:49 AM
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No I don't really have anything to measure the lift with. Also, with my limited knowledge of camshafts once upon a time I had a shop custom grind one and install it a few years ago. When the install was done, they refused to give me the cam specs and to this day I don't have them (don't particularly wanna go thru pulling the cam to figure it out either...yet). Lesson learned.
There has to be a way to set these up properly though, I can't imagine I'm the only person to ever find themselves in this situation.
That said, without having a solid lifter to use the pushrod length checker with I'm at a complete loss as to what options I have.
There has to be a way to set these up properly though, I can't imagine I'm the only person to ever find themselves in this situation.
That said, without having a solid lifter to use the pushrod length checker with I'm at a complete loss as to what options I have.
05-04-2011, 10:54 AM
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Googled some more and found this- thoughts?
When I am setting up hydraulic lifters I bottom the lifter out. I keep adjusting the pushrod length until I get the desired pattern on the valve. At this point I lock the adjuster on the rocker. Then, I shorten the pushrod to get zero lash. Then, I remove the adjustable pushrod and measure the length. Then add your desired lifter pre-load to that, which will be your actuall pushrod length. Hope this helps. Adjustable pushrod is a must.
Could this be used in some fashion with a non-adjustable rocker like mine?
When I am setting up hydraulic lifters I bottom the lifter out. I keep adjusting the pushrod length until I get the desired pattern on the valve. At this point I lock the adjuster on the rocker. Then, I shorten the pushrod to get zero lash. Then, I remove the adjustable pushrod and measure the length. Then add your desired lifter pre-load to that, which will be your actuall pushrod length. Hope this helps. Adjustable pushrod is a must.
Could this be used in some fashion with a non-adjustable rocker like mine?
05-04-2011, 11:07 AM
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Here is another from Thirdgen.org- seems like it involves some speculating though, not sure I like that.
Start off with adjustable pushrod adjusted to the stock length. You then mark the valve stem tip with a Magic Marker. Install the adjustable rod.
Now it's trial and error time.
Install the rocker and poly lock and just tighten down the poly lock while watching the tip of the roller. When the rocker makes contact with the rod and is solid, stop.
Wiggle the rocker tip side to side to make a witness mark. Remove the rocker and look at the mark you made when you rubbed away the marker color.
The CLEAN area, with the lifter on the base circle of the cam's lobe, SHOULD BE ON the INBOARD THIRD of the valve stem tip, CLOSEST TO THE INTAKE MANIFOLD. If it's not, remark the tip, re-adjust the pushrod, wiggle and re-check.
Visually divide the valve stem tip into thirds;
INNER MOST THIRD IS WITH THE LIFTER ON THE BASE CIRCLE
MIDDLE THIRD IS WITH THE VALVE AT ITS MID-POINT OF LIFT
OUTBOARD THIRD IS WHEN THR VALVE IS FULLY OPEN
Once you nail the INBOARD position, the rest will be correct too.
Since aftermarket rods generally come in .050" increments, select ones closest to what you measure once the roller tip is correctly placed. You then add to that measurement the amount of preload you're going to run. The actual amount of preload should be the recommendation made by the lifter manufacturer.
You DON'T want the mark in the middle of the stem WITH THE LIFTER ON THE BASE CIRCLE OF THE CAM LOBE. That spot's for MID-VALVE LIFT.
This is the quickest and easiest way and doesn't involve buying or making a solid lifter or removing the stock spring to install a low tension spring. None of that is required.
Start off with adjustable pushrod adjusted to the stock length. You then mark the valve stem tip with a Magic Marker. Install the adjustable rod.
Now it's trial and error time.
Install the rocker and poly lock and just tighten down the poly lock while watching the tip of the roller. When the rocker makes contact with the rod and is solid, stop.
Wiggle the rocker tip side to side to make a witness mark. Remove the rocker and look at the mark you made when you rubbed away the marker color.
The CLEAN area, with the lifter on the base circle of the cam's lobe, SHOULD BE ON the INBOARD THIRD of the valve stem tip, CLOSEST TO THE INTAKE MANIFOLD. If it's not, remark the tip, re-adjust the pushrod, wiggle and re-check.
Visually divide the valve stem tip into thirds;
INNER MOST THIRD IS WITH THE LIFTER ON THE BASE CIRCLE
MIDDLE THIRD IS WITH THE VALVE AT ITS MID-POINT OF LIFT
OUTBOARD THIRD IS WHEN THR VALVE IS FULLY OPEN
Once you nail the INBOARD position, the rest will be correct too.
Since aftermarket rods generally come in .050" increments, select ones closest to what you measure once the roller tip is correctly placed. You then add to that measurement the amount of preload you're going to run. The actual amount of preload should be the recommendation made by the lifter manufacturer.
You DON'T want the mark in the middle of the stem WITH THE LIFTER ON THE BASE CIRCLE OF THE CAM LOBE. That spot's for MID-VALVE LIFT.
This is the quickest and easiest way and doesn't involve buying or making a solid lifter or removing the stock spring to install a low tension spring. None of that is required.
05-05-2011, 10:27 AM
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Not exactly sure how you are doing this, but there are a couple of ways. I prefer to check pushrod length by using the soft springs that come with most timing degree wheel kits for the intake and exhaust valves. This reduces any negligable lifter pressure. Mark the complete valve tip with magic marker and carefully install the roller rockers and adjust them to suit 0 or the desired lash. You should get a good finger feel for the adjustment since normally the valve spring will start to compress before the lifter does but look at the lifter plunger in the process to make sure it isn't compressing too. I usual run about 1/2 turn lash on stock roller lifters in operation.(Your choice). I then crank the engine over about 5 or 10 seconds with no plugs in the engine to allow maximum freewheel of the crank (about 180 rpm's) and reduce battery load. This should give you enough cranking oil pressure to insure lifter is extended. Remove the rocker and inspect contact pattern for an acceptable narrow width and center location. Make pushrod length adjustments as necessary and repeat. Wipe off old marks and remark for next attempt. I normally do this on the engine stand using a spare starter and battery setup which makes it easier to do than in the car.Hope this helps.
Good luck.
Rick
I think this sounds like the way to go. Check springs and adjustable pushrod, get the lifters pumped and check the wipe pattern. Then measure pushrod length at zero lash w/ lifter on base circle of cam. Right?
Good luck.
Rick
I think this sounds like the way to go. Check springs and adjustable pushrod, get the lifters pumped and check the wipe pattern. Then measure pushrod length at zero lash w/ lifter on base circle of cam. Right?
05-06-2011, 12:43 AM
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I am going to pick up a dial indicator and magnetic base. I should be able to use that setup to measure the lift and then set up the wipe pattern at midlift. Picked up checking springs today, so we'll see how it goes this weekend.
05-06-2011, 07:14 PM
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I was fortunate that the shaft that would normally screw into the magnetic base was 8mm thread and screws right into the head. You might was to see if you can adapt it to do the same. With Yella Terra you can use the rocker pad for the #3 cylinder. Other option would be to get some 8mm screws and a piece of steel and bolt that to the #3 rocker pad for a base.
