How To: Check For Proper Push Rod Length.

[Venom351R]

A lot of the time people can neglect the fact that you need different size push rods when you change the geometry of your valve train. You just cant throw on your same size push rods you had before when changing your cam/ heads exc... So here is a guide to check for the push rod length you will need. This is also for Stud Mount Roller Rockers.

What you will need.

- Push rod Length checker These can be found at summit racing and other sites.

- Ratchet and socket

- Black sharpie

- Solid or welded hydraulic lifter

1. Use your old gaskets even though you are not going to be torquing the head down. Put the bolts in the head but do not torque them down just snug is fine.

2. Take a Black Sharpie and color in the tip of the valve.

3. Place the lifter in the lifter valley. You have to use a solid lifter or a hydraulic lifter that has been welded. This is to prevent the "plunging" effect of the lifter when the push rod press's down on it so you will get a proper indication of where your mark is on the valve tip. I have read that you can use a hydraulic lifter if its been soaked in oil over night and is "fully Pumped up" I have never used this method but the other two are fail safe ways to do it.

4. The purpose of the sharpie is to see where the mark is made on the tip of the valve by the roller rocker. This is called the "Witness Mark". Install the adjustable push rod checker and roller rocker and tighten it down. Rotate the engine by hand for two revolutions. Remove the roller rocker and check to see what your line looks like on the tip of the valve. You will probably get something that looks like this....

Your probably thinking...YES Right dead nuts in the middle of the valve, Im good to go....Sorry not so much. Notice how fat that line is. That means the roller rocker is being pushed a long the top of the valve. You have to picture the roller rocker being pushed down on top of the valve from the push rod. You want direct contact directly straight down. With that mark above the roller rocker is rolling across the top of the valve which means the push rod is to short. This is where the trial and error comes in. You want to keep making small adjustments to the adjustable push rod checker until you have reached the acceptable mark across the valve. Now your asking how should my mark really look?

5. You will hear a lot of the time that you want the mark to be dead in the middle of the valve, while this is not entirely wrong it is also lacking information. You want the thinnest line possible, the thinner the line the more the roller rocker is coming down directly on top of the valve tip which is what you want. If the line is moved closer to the intake side, or closer to the exhaust side then that is fine as long as your not riding the outside of the valve. When you are checking for this a line that is to close to the intake ports means your push rod needs to be longer so make the proper adjustments on the checker, if its to close to the exhaust ports then it is to long and needs to be shorter. In summary you want the line to be as thin as possible and as close to the center of the valve as possible but the thinness of the line being more important. This is how you want it to look when you are all done. Take the measurement you have off the push rod length checker and order the correct push rods.

Edited July 16, 2012 by Venom351R

[95riosnake]

Great post. I see many posts on different forums where people ask what length they need for their combo, unfortunately the only proper way to know what length you need is to measure. Valvetrain is not the place for guesswork.

[Venom351R]

Great post. I see many posts on different forums where people ask what length they need for their combo, unfortunately the only proper way to know what length you need is to measure. Valvetrain is not the place for guesswork.

Yeah your right, you really cant just "guess" on this type of thing. I mean there are some combos where you know what the push rod length is, like with the trick flow top end kits, its the same cam, same heads same everything in every kit so they know what push rods to send you. You dont need to check in this type of situation. Taking a look at my pics you can see how damn fat that line is, that is ONLY from a head change. I still had the same cam as the previous set up and I'm sure it was not right then either b/c this was not checked, I had the same push rods used from what I had with the other cam. This was back before I decided to start saving money and doing more stuff on my own.

[95riosnake]

I would still check pushrod length even when it comes in a kit, just for peace of mind. I'd rather know for sure that someone didn't accidentally throw the wrong part bag in my kit and potentially cause me problems.

I've always had to measure because I've never had a common setup. I don't think I've ever just bolted something on my car, I always end up modding the s*** out of everything, lol.

[Venom351R]

Yeah I know what you mean, with having a custom cam and high port heads it really threw off my push rod length from what it was with the crower cam and AFR heads.

[Det_Riot]

Great write up man! Very, very important information! I'll throw this is in here to supplement it:

How to make your own solid lifter for valve train measurements:

What you need:

-Old Lifter

-Tweezer / Forceps

-Paper Towels

-Small Needlenose

(note: pictures borrowed from online but this is the process I used)

1. Locate the lifter you plan to disassemble and use. I went with trickflow replacements so I had 16 to choose from =D Find your suspect and clean the oil off of it.

2. Use your small flat head srcrewdriver or the forceps to pop the clip out of place that holds the lifter together. Make sure you use care with this step because you need to use the clip later on.

3. Take off the top part of the lifter that the pushrod sits in. We'll call this the pushrod cup. If it won't fall out on its own, use the screwdriver to give it some motivation.

4. Use the forceps to remove the plunger as well by expanding them within the hollow part of it if the lifter won't just drop out it's components.

5. Use the forceps to remove the spring from the lifter and lay the parts out in front of you. For ease of storage, I cleaned all the parts after I took them out.

6. Take the plunger and insert it in the lifter in the opposite orientation that it was originally. This means put it on so that the nipple is facing up towards the pushrod cup.

7. Next, insert the pushrod cup the way it looked when you took it out and push it down as far as possible.

8. Last, using the forceps, insert the original clip, tucking in the bottom "U" first. Then tuck in each side. This I found easiest to do using the small flathead and sliding the tabs into the cup. It will also be much tighter than before, This is because now there is no play in your lifters.

[Venom351R]

Nice addition! I knew there was a way to convert it over but I was not sure exactly how so I was not going to try and explain it. When I did mine I borrowed a welded hydraulic lifter from a forum member and sent it back when done.

PS: Id also like to add that when starting out this process of what length push rod you will need adjust the checker to the length of your current push rods. This will give you a base line of where to work from as far as adjustment.

Edited July 16, 2012 by Venom351R