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Push rod help we are putting a 383 in a buddies 85 but today while assembling the motor we have come to the conclusion that the push rods are too long. The ones in the motor now are 7.75" and when we adjust them the valves don't close. Can someone tell me what size pushrods we need? The came is 440 lift on the Intake and 454 lift on the exhaust. It has 1.5 RR. Advertised duration is 270* intake and 276* exhaust. Flat tappet. The heads are summit castings and it has 1.5 full roller rockers also summit brand Hopefully that is all the info needed. Any ideas? |
Re: Push rod help You can get a push rod measuring tool from Compcams, basically it is an adjustable pushrod you adjust to perfect length and then measure. |
Re: Push rod help The engine being a stroker has no bearing on the push rod length. you should use stock rods for that set up. flat tapped, 1.5 ratio, this is all stock stuff. you may need guide plates might wanna recheck your installation procedures and make sure your hydraulic lifters are good and that you have the proper valve springs for your cam. |
Re: Push rod help
Originally Posted by jjlabinski
(Post 4326791)
The engine being a stroker has no bearing on the push rod length. you should use stock rods for that set up. flat tapped, 1.5 ratio, this is all stock stuff. you may need guide plates might wanna recheck your installation procedures and make sure your hydraulic lifters are good and that you have the proper valve springs for your cam. Hmmmm I guess checking the valve springs is next. The pushrods are stock length. Thanks we'll do some more measuring. |
Re: Push rod help Aftermarket heads and/or cam always require a pushrod length check. They often move things around in subtle ways vs. stock. 7.80" is stock length for a small block Chevy with a flat tappet cam, BTW. |
Re: Push rod help Would it matter if we did this with the engine on a stand with no oil in it? Would the lifters not being pumped up matter? |
Re: Push rod help
Originally Posted by raidmagic
(Post 4327820)
Would it matter if we did this with the engine on a stand with no oil in it? Would the lifters not being pumped up matter? No, many people have built motors on stands including myself. The only thing is that the lifters need to be primed with oil (soak in oil overnight before installing) Now if I am correct, when you put the pushrod in and place the rocker on the stud, you are tightening the stud bolt all the way down, so that the valve is open and never closes? If so that is not the right way to do it. The proper way to do a valve lash is to make sure that the cylinder is on the compression stroke and bring the piston TDC. Once it is there, place the rocker on the stud and slowly tighten the nut while spinning the pushrod with your thumb and index finger. Once you feel a slight resistance/drag stop. At that point tighten the nut 1/2 turn. that should give you zero lash. Now, at the same time, if you let that sit for a while the pushrod will feel like there is no resistance again. Don't worry, this is becuase the pressure of the valve spring is forcing the lifter to become preloaded. Once the oil pressue raises it will be good. If you are not sure, take the rocker off and do it all again. The easiest way is to do the firing order of the motor, and do both intake and exhaust at the same time for each cylinder. |
Re: Push rod help
Originally Posted by hrspwr
(Post 4327826)
No, many people have built motors on stands including myself. The only thing is that the lifters need to be primed with oil (soak in oil overnight before installing) Now if I am correct, when you put the pushrod in and place the rocker on the stud, you are tightening the stud bolt all the way down, so that the valve is open and never closes? If so that is not the right way to do it. The proper way to do a valve lash is to make sure that the cylinder is on the compression stroke and bring the piston TDC. Once it is there, place the rocker on the stud and slowly tighten the nut while spinning the pushrod with your thumb and index finger. Once you feel a slight resistance/drag stop. At that point tighten the nut 1/2 turn. that should give you zero lash. Now, at the same time, if you let that sit for a while the pushrod will feel like there is no resistance again. Don't worry, this is becuase the pressure of the valve spring is forcing the lifter to become preloaded. Once the oil pressue raises it will be good. If you are not sure, take the rocker off and do it all again. The easiest way is to do the firing order of the motor, and do both intake and exhaust at the same time for each cylinder. Below is the procedure we used to set the valves, the lifters were not soaked in anything and put in the motor dry. Rotate the engine until the mark on the timing tab by the damper lines up with the ZERO position in the number one firing order. You will want to pull the #1 spark plug (driver side front) with your finger in it while turning. When it pushes out air hard as the line comes to ZERO - you are there. In this position - you can adjust Exhaust - 1, 3, 4, 8 Intake - 1, 2, 5, 7 You will want to run the nut on the rocker down while spinning the push rod in your fingers. When you can't easily spin it - are at zero lash. From there go one full turn. Now, rotate the engine one full revloltion Exhaust 2, 5, 6, 7 Intake 3, 4, 6, 8 Repeat... |
Re: Push rod help Yes that is also the correct way of doing it. It saves time as you do not have to rotate the motor. Now the trick with this one as well is that the motor has to be with the number 1 piston TDC on the compression stroke and not the exhaust stroke. The easiest way to find that is if you have the timing cover off, line the two dots on the gears up. when that is done adjust these valves Exhaust - 1, 3, 4, 8 Intake - 1, 2, 5, 7 Once those are done, spin the crank 360* and then adjust these valves Exhaust 2, 5, 6, 7 Intake 3, 4, 6, 8 like I said to adjust them do what I said. Spin the pushrod until there is a resistance and then 1/2 turn on the nut. make sure that the socket is not pushing the rocker down as well as it will give a false reading when spinning the pushrod. If the cover is on the motor, then you can tell as soon as you try to tighten the number 1 exhaust valve, it will tighten sooner than the intake and will look like it wants to open the valve. If that is the case adjust the second set if rockers first, or turn the crank 360* |
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