Pushrod measuring tool

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SoulSurvivor

SoulSurvivor

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My machine shop let me use their pushrod measuring tool to determine which size push rod to buy. Is there a write up or experience here that I could gleen from you guys? Thanks, Doug
 
If you have a hydraulic cam you need to make sure you have the correct lifter preload. If a mechanical cam you need to make sure you have the correct amount of lash. I measured mine then took the push rod tool to the local engine shop and they determine the length push rod I needed based on the length of the tool.

What type of rocker arms? If they are adjustable and oil the push rod out of the adjuster that also has to be taken into account because you don't want adjuster to rocker arm mis-alignment blocking the oil passage.
 
I have stainless adjustable rockers and a hydraulic cam. I just can remember how to do the measurement
 
So you'll be using a ball/ball style pushrod? Comp magnum style rockers by chance?

Set the adjuster to comps specs. put the head on using a few bolts, slide tool in place, put rocker and shaft on adjust tool to remove all lash.

Once you length, add in lifter preload (.020-.050) and head gasket thickness. That should be your effective length.
 
SoulSurvivor said:
I have stainless adjustable rockers and a hydraulic cam. I just can remember how to do the measurement
Click to expand...

Yeah, like crackedback said. You need to make sure your rocker adjuster oil hole is lined up inside the rocker and you have the correct pre load on the lifter. Other then that its mock it up and vary the length until the above criteria is met.

I went through the same thing and could not find instructions anywhere out there on the web.
 
It is the ball to ball pushrod type. The pushrods are loo long. The shaft still floats above the 5 shaft mounts by about 1/4 inch with the adjustment screws turned all the way out on the rockers. Preload..is that the lifter pushed in .50? That would be one full turn on my pushrod measuring tool.
And that is measure on with the pushrod setting on the flat side of the cam?
And you are right...not much out there as far as guidance..except you guys.
Thanks
 
Yes preload is the ammount the lifter is compressed when the cam lobe is on the bottom.

But it's not .50 as you stated. .50 is a half an inch. Maybe you just left out a zero?

It would be on the order of .020~.050 as Crackedback said.

In other words it should be between one half to one turn on the adjuster.
 
The tool is too long?

Take a picture of you set up and post it.

Don't worry about preload or anything else at this point. All you care about is getting a static measurement of what will fill the gap between lifter and rocker..
 
I have two of the Comp Cams checking kits and I modified some for cup type pushrods. I use one on intake and exhaust, and I set the valvetrain up and measure them.
 
crackedback said:
The tool is too long?

Take a picture of you set up and post it.

Don't worry about preload or anything else at this point. All you care about is getting a static measurement of what will fill the gap between lifter and rocker..
Click to expand...
No. The stock pushrods are too long. And yes..that is what I am trying to do..just get what fits between the lifter and rocker. I am going from the stock rocker assembly to a roller rocker assembly. With the stock pushrods installed the roller rocker assembly 'floated' above the mounting valleys by 1/4 inch. 2 of the pushrods were preventing me from tightening the shaft down secure. Even when the adjusters were backed out as far as they would go. I just have to get the right pushrods. Make sure they fit. And make sure the length is right for the roller to travel across the valve tip properly.
 
If your engine is assembled already you need to remove all the pushrods (if they are in) and both sets of rockers (obviously) and the spark plugs should be removed.

If you only have one adjustable push-rod length checker, do the intake and then the exhaust (or exhaust then intake, does not matter).

Make sure the cam is on the base circle on the cylinder you are checking and put the adjustable pushrod(s) in place (adjusted shorter than needed) and install your rockers. You only need two on at this time, but you can leave them all on, no matter. Adjust the adjuster screws so they show about 2-3 threads protruding out the bottom of the rocker and lock them in place. If the thread count that the rocker manufacturer suggests is different than what I suggested, go with theirs.

The first thing to look at is the roller tip to valve alignment. The tip should be just inboard of center on the valve at zero lift.( see Valvetrain Geometry sheet below)

If that looks good, you can move on to adjusting the pushrod(s).

Adjust the pushrod(s) to take out all lash. Do not preload the lifter(s).

Have a helper slowly rotate the engine by hand 2 full revs and watch the roller(s) on the valve(s) closely. It should start at just slightly IB of center on the base circle of the cam, roll out to just OB of center at half lift, and end up at just IB of center at full lift.

If this all works out, add .040" to the actual pushrod length. This is the correct length.

If your roller tip is not in the right spot, you either have to shim the rocker shafts up or possibly use lash caps on the valves to get the required geometry. I have never used the lash caps so maybe some of the guys that have could tell you about those, if you require them.

Final adjustment procedure after new pushrod install:
When the intake just starts to open, adjust the exhaust
When the exhaust closes, adjust the intake

also, a quicker method:
valveadjustmentchart.jpg


This sheet really helps, too:
TDrollertipalignment001.jpg


I hope this helps. It is very important that everything is right on this. Once you have your new pushrods installed and adjusted, take a close look at all the valves for roller tip alignment while a helper slowly turns the engine to make sure you don't have any issues.
Good luck, Dave
 
You have to pull ALL the pushrods out on the side you are going to check.

All you need installed is the pushrod checker, one rocker shaft and two rocker arms. You can check multiple locations.
 
crackedback said:
You have to pull ALL the pushrods out on the side you are going to check.

All you need installed is the pushrod checker, one rocker shaft and two rocker arms. You can check multiple locations.
Click to expand...

I generally will trust the measurement on just one cylinder (or one on each bank of cylinders) if the valves all have the same installed height.
If you want to be really assured that you are good, you can check them all. It will only cost you a little extra time and might save you some, for sure!
If the valves installed height varies, you should address this issue at this time also....new valves and good valve job.

What brand are the rockers?
 
crackedback said:
You have to pull ALL the pushrods out on the side you are going to check.

All you need installed is the pushrod checker, one rocker shaft and two rocker arms. You can check multiple locations.
Click to expand...

mopar340dave said:
I generally will trust the measurement on just one cylinder (or one on each bank of cylinders) if the valves all have the same installed height.
If you want to be really assured that you are good, you can check them all. It will only cost you a little extra time and might save you some, for sure!
If the valves installed height varies, you should address this issue at this time also....new valves and good valve job.

What brand are the rockers?
Click to expand...

I agree that one spot is all that is needed.

Some people are a little more anal about thing. Needn't measure more than one spot, especially with adjustable rockers.
 
crackedback said:
I agree that one spot is all that is needed.

Some people are a little more anal about thing. Needn't measure more than one spot, especially with adjustable rockers.
Click to expand...

The only reason I mentioned that is that if the valves have different installed heights, it will affect your pushrod choice AND the roller tip alignment. It's something that gets overlooked and will bite you if it happens. Guess how I know? LOL
 
I did the pushrod measuring with just 2 rockers installed. The adjustable rockers are stainless 1.5 PRWs. I rotated the engine and the roller moved ever so slightly from the engine side of the the valve tip center to just past the exhaust side of the valve tip. I think I got the pushrod measured now. It came to 7.3xx(I still need to measure it accurately). It looks as if the pushrod will need to be about 1/4" shorter than stock. Does the pushrod length have to be exact?
 
Yes. I would take it to a store that sells dial claipers big enough to measure it and then add the .050" to the measurement. Your machine shop will have a set to measure them with. I have an extra set of ball and cup pushrods sitting here because I didn't do it right years ago. I guess I can call them brand new wrong old stock! LOL

P.S. Did it make the sweep back at full lift?
 
mopar340dave said:
Yes. I would take it to a store that sells dial claipers big enough to measure it and then add the .050" to the measurement. Your machine shop will have a set to measure them with. I have an extra set of ball and cup pushrods sitting here because I didn't do it right years ago. I guess I can call them brand new wrong old stock! LOL

P.S. Did it make the sweep back at full lift?
Click to expand...

Yes. I will add .050. Too bad all that cam lube is spread all over the place now. I sure am using a lot of that stuff.
 
Get a bottle of STP Oil Treatment. That stuff is the best for a flat tappet cam. It is mostly ZDDP and is what the EPA removed from motor oils. Typical motor oils contain about 1/4 of what they used to. They removed it because it is not good for cat converters. http://en.wikipedia.org/wiki/ZDDP
Flat tappet cams need it to live a long healthy life. I use it as assembly lube. It's cheap and it works. It also does not drip off. It stays on the parts you put it on and mixes with the engine oil to coat everything.
 
I'm a little late to this discussion, but I thought I'd add this: it's a page from the Comp cams catalog, a checking pushrod.

249.jpg
 
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