Pushrods too long? Picture inside........
07-23-2006, 03:59 PM
#1
Pushrods too long? Picture inside........ Trying to determine if my pushrods are the correct length.
I have Thunder Racing chromoly 7.200" push rods. These rods appear to be about .020 longer than bone stock pushrods.
I am using Comp Cams 1.6 ratio Pro-mags on stock valved heads with LT4 valve springs.
I did the sharpy marker test with 1/4 turn past zero lash and this is what I get.
The pattern that I see clearly is not in the center. It is shifted down toward the exhaust side of the valve stem.
It appears that I need 7.150" or shorter push rods.
Any suggestions?
I have Thunder Racing chromoly 7.200" push rods. These rods appear to be about .020 longer than bone stock pushrods.
I am using Comp Cams 1.6 ratio Pro-mags on stock valved heads with LT4 valve springs.
I did the sharpy marker test with 1/4 turn past zero lash and this is what I get.
The pattern that I see clearly is not in the center. It is shifted down toward the exhaust side of the valve stem.
It appears that I need 7.150" or shorter push rods.
Any suggestions?
Last edited by wrd1972; 07-23-2006 at 08:57 PM.
07-23-2006, 04:38 PM
#2
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They are a tad too long. Do you have an adjustable pushrod to find the correct length? Most cam companies sell them (comp, crane, etc) and will make finding the exact length a piece of cake.
07-23-2006, 04:51 PM
#3
Originally Posted by Strokinit383
They are a tad too long. Do you have an adjustable pushrod to find the correct length? Most cam companies sell them (comp, crane, etc) and will make finding the exact length a piece of cake.
I know there are a lot of people who have installed the exact same very popular roller rockers, I have yet to read that anyone had to install slightly shorter pushrods to correct bad geometry. Myabe they have the same bad geometry too.
Last edited by wrd1972; 07-23-2006 at 04:59 PM.
07-24-2006, 10:32 AM
#6
What can be said about this:
http://www.carcraft.com/techarticles/116_0401_push/
The way I understand it all you do is hold the rocker down and spin the roller tip several times and read the marking at base circle. This apparently does not depress the lifter at least it did not when I tried it last night. The one marking was dead center of the valve stem which is still indicating a long rod.
Again I am scared to take the lifter apart, however I am trying to find a used OEM one
http://www.carcraft.com/techarticles/116_0401_push/
The way I understand it all you do is hold the rocker down and spin the roller tip several times and read the marking at base circle. This apparently does not depress the lifter at least it did not when I tried it last night. The one marking was dead center of the valve stem which is still indicating a long rod.
Again I am scared to take the lifter apart, however I am trying to find a used OEM one
07-24-2006, 07:52 PM
#7
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This is the article i used as a reference when i did mine:
http://www.carcraft.com/techarticles/116_0401_push/
I took all my plugs out to make the motor easier to rotate.
http://www.carcraft.com/techarticles/116_0401_push/
I took all my plugs out to make the motor easier to rotate.
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07-24-2006, 08:03 PM
#8
Get the adjustable pushrod from Comp. It will let you set your witness mark with the Sharpie so it is dead on, then measure and order the pushrods from Summit. They have all the common sizes in stock and you should have no delay with the new length. Why mess around with lash caps? Then you have to change locks. Stick with using as much of your stock stuff as possible. I did the pushrod thing and was up and running with perfect valvestem sweep in like 2 days.
Jim
Jim
07-25-2006, 07:01 AM
#9
Originally Posted by DeltaT
Get the adjustable pushrod from Comp. It will let you set your witness mark with the Sharpie so it is dead on, then measure and order the pushrods from Summit. They have all the common sizes in stock and you should have no delay with the new length. Why mess around with lash caps? Then you have to change locks. Stick with using as much of your stock stuff as possible. I did the pushrod thing and was up and running with perfect valvestem sweep in like 2 days.
Jim
Jim
Did you do the check like it is shown in the carcraft page?
07-25-2006, 05:46 PM
#10
Update.
I got the adjustable pushrod.
The pattern has moved more to the center. The sweep is tad larger.
This is for comparison purposes only to see what size looks best. I will be using the same size PR's for all valves.
Left valve- 7.100"
Right valve- 7.150"
Both valves- 7.200"
I think according to this I am real close.
http://www.pontiacstreetperformance....traingeom.html
Any comments?
I got the adjustable pushrod.
The pattern has moved more to the center. The sweep is tad larger.
This is for comparison purposes only to see what size looks best. I will be using the same size PR's for all valves.
Left valve- 7.100"
Right valve- 7.150"
Both valves- 7.200"
I think according to this I am real close.
http://www.pontiacstreetperformance....traingeom.html
Any comments?
Last edited by wrd1972; 07-25-2006 at 06:07 PM.
07-25-2006, 07:15 PM
#11
Okay this is the last picture
Left valve- 7.100" PR with .85" of sweep. Slightly below stem centerline.
Right valve- 7.050" PR" with .105" sweep. Perfectly centered on stem
So its down to what is higher priority, more centered up or lesser sweep.
I can only assume that the CC Pro-mags are necessitating this .150" shorter pushrods.
Does this sound right?
Left valve- 7.100" PR with .85" of sweep. Slightly below stem centerline.
Right valve- 7.050" PR" with .105" sweep. Perfectly centered on stem
So its down to what is higher priority, more centered up or lesser sweep.
I can only assume that the CC Pro-mags are necessitating this .150" shorter pushrods.
Does this sound right?
Last edited by wrd1972; 07-25-2006 at 09:01 PM.
07-26-2006, 09:21 AM
#13
I am still using the hydraulic lifter. I have heard many so you can while others say you cant so I dont know what to believe right now. I have used the Carcraft method and the final outome is to use a 7.150" PR instead of the 7.200" PR.
I understand that removing the intake and installing a solid lifter is best but I cant do that right now.
I am finding it very hard to believe that my Pro-mags are requiring a much shorter PR than stock.
I think I have to rely on the carcraft method for now. The way I see it this method does not care about whether the lifter is solid or hydraulic, maybe I am wrong. When I am at base circle and I mark the stem on lightly mount the rocker to make the mark I get just under dead center with 7.200" and I get dead center with the 7.150" PR.
I am aware that the photos that show the dead center mark with the hydraulic lifter are likely to move upward when the engine is running, I guess this is all part of the learning process.
I understand that removing the intake and installing a solid lifter is best but I cant do that right now.
I am finding it very hard to believe that my Pro-mags are requiring a much shorter PR than stock.
I think I have to rely on the carcraft method for now. The way I see it this method does not care about whether the lifter is solid or hydraulic, maybe I am wrong. When I am at base circle and I mark the stem on lightly mount the rocker to make the mark I get just under dead center with 7.200" and I get dead center with the 7.150" PR.
I am aware that the photos that show the dead center mark with the hydraulic lifter are likely to move upward when the engine is running, I guess this is all part of the learning process.
