I've never checked pushrod length, and my engine is fully assembled right now. I've been having valve-train problems, and looking at how my rockers sit, my pushrods may be too long and causing my problems. What's the best way to check for the correct pushrod length with the engine fully assembled and what parts will I need to buy (other than new pushrods)?

I've seen the ones that use the really weak springs, but I'd REALLY prefer to not take the springs off because I don't have a spring compressor to take springs off while the head is mounted on an engine. I've seen ones that look like they are a plastic rocker arm, how do these work? Looking for easiest way to do this.

Thanks

 

I bought an adjustable pushrod from Summit that Comp makes and put it in on the #1 cylinder. Turned the moter over by hand and watched and adjusted it until I had the correct geometry. Like you the moter was in the car and assembled so I'm sure that the lifter wasn't pumped up and I think I kinda guessed in the differance with the lifter pumped up. A test spring would probably be much better, but no problems after a few thousand miles. The adjustable pushrod has a base length and then you call Comp and tell them which length checker you have and how many turns you adjusted it. Only problem is that you get to pay $100 for Comp's pushrods because you never have an actual number for the length. If I do it again I am going to buy a set of calipers that go up to 8" or 12" and know what length pushrod I need. Save $50. I think it was Vader that posted some great sketches on here somewhere about obtaining the right geometry. They were very usefull and I saved them at the time but then lost them on the computer.

 

okay, I found a place called PowerHousePerformance and bought an adjustable pushrod length checker from them. It's in the mail fedex 2day. It's cheaper than the comp cams one, and is etched with the exact size, so you don't need to use calipers to tell the correct size and you don't HAVE to buy the comp cams pushrods.

I was thinking of unplugging the fuel injectors and having my wife crank the engine with the adjustable pushrod in a rocker that I can see well. I was under the impression that this would break the adjustable pushrod. I'm running a .500" lift cam and the springs are good upto .600" (came with the heads). It's really hard to turn my engine over by hand. Would really prefer not snapping the adjustable pushrod in half inside my lifter valley

Thanks for the reply

 

Does anyone know if doing it that way will break the pushrod length checker?

 

This is a pretty grassroots approach but has worked for me. Find TDC on number one piston. Loosen one of the rockers on number one cylinder enough to place a piece of paper underneath the rocker. I gently run a screwdriver or something hard around the valve tip to make a good impression on the paper. Readjust that rocker and turn the engine two full revolutions until it's back to TDC on number one. Loosen the rocker again and remove the paper. The rocker will leave an impression of it's path on the paper. If the path is generally in the center of the circle left by the valve tip, you're good. If not, you need a geometry adjustment. Now it's time to get out the adjustable pushrod and work it until you do get a favorable impression within the circle.

 

The way that I used to check my geometry was to bring number 1 to TDC then take the rocker off, clean all the oil off the roller tip and then take a marker and cover maybe half or so of the tip with marker. Then reinstall and wiggle the rocker back and for a couple times and then take the rocker back off. The tip should leave a "witness mark" and if you have correct geometry, it should be right on the inner 3rd of the valve tip, not in the middle and not on the very inner edge.

Tom

 

So if the rocker is on the inner third of the valve stem with the lifter on the base circle of the cam, then you will be fine once the lifter if pumped up and everything?

 

AS I understand it proper valvetrain geometry is obtained when the center of the tip of the rocker is on the center of the valve stem, at 50% max lift. And while this is happening the push rod should be adjusted so that the rocker arm is at 90 degrees to the valve.

This is how I was shown by some salty dogs in the race club I belong to. THe checker they had was designed for use this way. Im sure the checker you are getting willl tell you how it should be used.

 

This will help.


http://compcams.com/Technical/Products/Pushrods/