74 390 push rods
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No, with non-adjustable rockers and hydraulic lifters you use the different lengths to set the plunger pre-load. They are not intake or exhaust specific, but actual rocker arm specific.
If they are out of order, you'll need to collapse each lifter and measure the clearance at the valve ~ should be .100" with lifter collapsed and cylinder set at TDC for the respective set of valves.
If the valves/ valve seats have been reground at one time or another you'll definately need different length pushrods for each valve.
So when removing FE pushrods from the engine that's why you have to keep them in order. Some will say to make sure the wear patterns remain the same, which is partially true. But nothing to lose sleep over, but the FE is a unique beast.
Josh
If they are out of order, you'll need to collapse each lifter and measure the clearance at the valve ~ should be .100" with lifter collapsed and cylinder set at TDC for the respective set of valves.
If the valves/ valve seats have been reground at one time or another you'll definately need different length pushrods for each valve.
So when removing FE pushrods from the engine that's why you have to keep them in order. Some will say to make sure the wear patterns remain the same, which is partially true. But nothing to lose sleep over, but the FE is a unique beast.
Josh
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From: Florida
I have replaced the cam & lifters, cleaned rocker arm assembly and lost track of where each rocker arm and push rod went.
Do you need to change push rods when changing cams? I am chasing a miss problem, it not carb or ignition. I replaced the intake gaskets today and while i was putting the rocker arm assembly back on head i noticed both valves are opening but not as much as the other, this must be part of the plunger preload you mentioned. After i spun it over a couple of times and brought the cylinder to TDC for each cylinder i was able to spin the push rod with my fingers with a little force does this sound about right?
Do you need to change push rods when changing cams? I am chasing a miss problem, it not carb or ignition. I replaced the intake gaskets today and while i was putting the rocker arm assembly back on head i noticed both valves are opening but not as much as the other, this must be part of the plunger preload you mentioned. After i spun it over a couple of times and brought the cylinder to TDC for each cylinder i was able to spin the push rod with my fingers with a little force does this sound about right?
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Joe Kucinski
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When you installed the cam with dry lifters would have been the best time to check the clearances.
Fully pumped-up FE lifters are a b*tch to bleed down.
Best thing to do is remove all pushrods and start over.
If the engine was OEM to the truck the pushrods stock should be 9.59" tip to tip.
Most FE engines from 61-68 used 9.62"
Other sizes +60 ~ 9.68" and -60 ~ 9.56"
The 69+ rods are sometimes nicknamed -30 even though they were stock.
You could be having a miss using a 9.68 rod when a 9.56 is what is needed. For instance on an intake valve the valve may remain slightly open when it should be closed causing the miss.
Josh
Fully pumped-up FE lifters are a b*tch to bleed down.
Best thing to do is remove all pushrods and start over.
If the engine was OEM to the truck the pushrods stock should be 9.59" tip to tip.
Most FE engines from 61-68 used 9.62"
Other sizes +60 ~ 9.68" and -60 ~ 9.56"
The 69+ rods are sometimes nicknamed -30 even though they were stock.
You could be having a miss using a 9.68 rod when a 9.56 is what is needed. For instance on an intake valve the valve may remain slightly open when it should be closed causing the miss.
Josh
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This is now what i am thinking is my problem after seeing it yesterday. I will pull the rods again this morning and measure. How do you go about bleeding down the lifters? Yesterday while i had the intake off, i pulled all lifters to inspect for wear and looked at cam lobes through lifter holes to see if i had a break in failure. I could not see where anything went wrong with this process and there was no metal in the oil off the lifters. Note, i did keep track this time where everything goes back. Another note i might add is this engine ran fine before with the stock cam and two barrell set up. Josh i feel like i need a hotline setup to you so i can call and ask questions. Thank you for the help.
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I think since i had the lifters out on the bench for a while, put them back in and bumped the motor over without distributor in they have bleed down because i am able to open the rocker on most of them by hand. Two of the rods measured 9-1/2" with a tape measure. Something else i noticed on the push rods is a wear partern, one end is rounded while the other end is rounded also but with a small nipple so to speak which i think would be the rocker arm end. Is the measurement between top of valve and rocker arm .100 or .010? Thanks again.
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My bad for coming in on the back end of the conversation. I rebuilt my 360 with stock 390 gt heads, edelbrock performer intake with matching 600cfm carb, performer plus cam , hedman headers and 2.5 exhaust. My cnc mechanic said to get the same size push rods (9.56)as I took out. I got it back together and running , I was expecting clatter as the new lifters fill and the clatter to go away. After 40 miles on it every lifter is clacking to the beat of a band.
Will buying the next size up (9.62) the answer to my problem or would forking over $$$ for adjustable rockers be the fit?
I'm just a shade tree mechanic and have learned a lot on this build. Any help would be greatly appreciated!!
Will buying the next size up (9.62) the answer to my problem or would forking over $$$ for adjustable rockers be the fit?
I'm just a shade tree mechanic and have learned a lot on this build. Any help would be greatly appreciated!!
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Joined: Nov 2006
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From: Simi Valley, CA
My bad for coming in on the back end of the conversation. I rebuilt my 360 with stock 390 gt heads, edelbrock performer intake with matching 600cfm carb, performer plus cam , hedman headers and 2.5 exhaust. My cnc mechanic said to get the same size push rods (9.56)as I took out. I got it back together and running , I was expecting clatter as the new lifters fill and the clatter to go away. After 40 miles on it every lifter is clacking to the beat of a band.
Will buying the next size up (9.62) the answer to my problem or would forking over $$$ for adjustable rockers be the fit?
I'm just a shade tree mechanic and have learned a lot on this build. Any help would be greatly appreciated!!
Will buying the next size up (9.62) the answer to my problem or would forking over $$$ for adjustable rockers be the fit?
I'm just a shade tree mechanic and have learned a lot on this build. Any help would be greatly appreciated!!