LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

checking pushrod lenght

Old May 18, 2010 | 10:37 PM
  #1  
z28beast's Avatar
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checking pushrod lenght

ok so can someone give a yes or no answer.....can i measure for pr length with a stock 94 lt1 lifter? if not what do i need to do?
Old May 19, 2010 | 07:18 AM
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i got this from lloyd on pr length checking

PR length is something that you need to check to get the EXACT length. Use an adjustable PR checker and start at 7.100" and adjust the length until you get the wear pattern most centered in the valve. Go .050" shorter and watch the wear pattern move. If it gets worse, go .050 longer. It could be anywhere from 7.00 to 7.250 depending on everything done but a 7.100" (Trik Flow 21407100) is what I suggest for people that do not know how (or do not wanna take the time) to do this.

The following is a method of verifying proper valve train geometry. After you have estimated the required pushrod length using a Pushrod Length Checker, use this method to verify that the valve train geometry is correct (using the rockers you are using in your engine):


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1
The first step is to install a solid lifter and an adjustable pushrod. Mark the tip of the valve with a marker


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Install your rocker arm and set it up with zero lash.


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Rotate the crankshaft clockwise several times. Remove the rocker arm. The contact pattern of the rocker tip will be where the marker has been wiped away from the valve tip. The pattern should be centered on the valve tip, and as narrow as possible. If it is not, experiment with varying the pushrod length to yield the best pattern.


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Pushrod Too Long: Notice how the pattern is wide, and shifted to the exhaust side of the valve tip.


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Pushrod Too Short: Notice how the pattern is wide, and shifted to the intake side of the valve tip.


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Pushrod Length Correct: Notice how the pattern is narrow and is centered on the valve tip.
Old May 19, 2010 | 09:55 AM
  #3  
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Don't forget to use a weak/checking spring. The pushrod tools will bend with high spring pressures. ( my cheap one anyways)
Old May 19, 2010 | 08:23 PM
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i used compcams length checker 7702-1 on the elliotts gold springs with no problems.
Old May 19, 2010 | 08:34 PM
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I bought a cheap one and found out that my springs(little over 400lbs) Bent it. I have a good one now and i doubt i can bend this one. Most people that are doing this once normally do what i did and buy cheap. The comp cam one is a good one
Old May 19, 2010 | 09:32 PM
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I used the 7702 and it worked fine - much higher quality than the cheap knock-offs.
Old May 19, 2010 | 09:40 PM
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Originally Posted by craby
i used compcams length checker 7702-1 on the elliotts gold springs with no problems.
ok so heres what i did....i started at top dead center ....i took a stock lt1 lifter and put a tack weld on the plunger so it wouldnt depress.....i then put marker on the valve stem and installed my roller rocker to zero lash...i then rotated the crank until i was back a tdc... i then removed the roller rocker and checked the line it left on the valve stem...i did this many times until i finally found that 7inches is perfect......is it odd to have such a short pushrod? btw im using a comp cams pushrod checker....
Old May 19, 2010 | 11:57 PM
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i dont know if it matters but did u take into acount the 1/4 to 1/2 turn on the rocker/lifter? after all the measuring and marking mine came out to 7.1 so i could have went with the easy way lloyd mentioned. tpis is were i got my lifters and i asked what soiid lifter would match there hydro ones so they sent me one to use. cant find my mic here so its back at the gear shed. i aint going out there tonight, blowin 50 and rain.
Old May 20, 2010 | 09:31 AM
  #9  
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Originally Posted by craby
i dont know if it matters but did u take into acount the 1/4 to 1/2 turn on the rocker/lifter? after all the measuring and marking mine came out to 7.1 so i could have went with the easy way lloyd mentioned. tpis is were i got my lifters and i asked what soiid lifter would match there hydro ones so they sent me one to use. cant find my mic here so its back at the gear shed. i aint going out there tonight, blowin 50 and rain.
1/4 to 1/2 turn for what preload? i was at 7inches and i had it set to zero lash so i guess i didnt measure for the preload... but anywas i ordered 7inch hardened 1 piece trick flow pushrods......im going to do the test with them in just to make sure....does 7 seem small though?
Old May 20, 2010 | 10:27 AM
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yes the hydro lifters will be holding the pushrods in a little different spot once the motor is running. i think ull be ok. ill see what if any difference there is. i have a set of old hyro lifters and a solid.
Old May 20, 2010 | 10:47 AM
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cant find the dang hydro lifters. the solid i have is right on 2 and 6/10s in. from the roller to the top of the lifter. the pushrod seat looks the same as a hydro one.
Old May 20, 2010 | 11:11 AM
  #12  
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Originally Posted by craby
cant find the dang hydro lifters. the solid i have is right on 2 and 6/10s in. from the roller to the top of the lifter. the pushrod seat looks the same as a hydro one.
well i tested it a couple more times and i think im going to go with 7.050.....is this a more common lenght?
Old May 20, 2010 | 11:33 AM
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lloyd says the 7.1 is the most common. not sure u can get a 7.05 and in any case i dont think its common.
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