Pushrod help?

LilCop2002

Registered User
After reading page after page after page of information, I'm still confused where I stand.

I had the engine in my '94 rebuilt along with using 1.73 Roller Rockers, a regrind cam from Comp Cams, new Comp Cams springs, and possibly factory pushrods.

I got the engine started up, it ticked loudly on the top end, and the car's gauge showed low oil pressure. I opened the oil cap and looked down into the valve cover with a friend's camera and oil was covering everything like it should. That's when I shut the car down and attached a manual gauge.

I got the car started up and it showed that the car was making ~70PSI at cold start up, ~37PSI at warm idle, and up to~70PSI at warm revving up to ~4200RPM. I felt good with these numbers, replaced the oil pressure sending unit to be sure, and called the problem fixed.

The problem that I want to solve now is my ticking noise coming from the valve train area. I have a suspicion that my pushrods are too short, Paul from Blue Tongue Motorsports thinks that the pushrods are too short and recommended a longer pushrod from the 94ish Z28 Camaro with the 5.7L V-8, but I don't want to throw money at a problem.

The car hasn't been run in about 3 weeks now so everything should be pretty much bled out. I have an adjustable pushrod in the trunk of the car, but not the intelligence to use it. Can anyone walk me through the process of checking the length of my pushrods?

Any suggestions would be very helpful at this time. BTW, please forgive the stupid questions. I am a :confused: newbie.

Julian
 
I appreciate it and I did look at that thread. Hell, I've even got it bookmarked. I guess I am needing a little bit more entry level info.
 
If your using a regrind cam, the stock push rods are too short. You'll need to get longer ones. Did you order up the cam yourself or did you go through someone?

Frit
 
I ordered the cam myself upon recommendation of Paul from Blue Tongue. I will have to look for the card, but I can give the specifications of the cam if it will help.

Like I said, I know that the pushrods are too short, but I'm :confused: as to how to actually check the length of the current ones and the length of the ones that I will need.
 
Do you know what it looks like when the pushrods are the correct length? I ask because it is not a silly question. If you get pushrods that are too long, you can have a non running condition where the vavles hang open. You can get a length checker and go from there. It is an adjustable rod that sits in the lifter and goes to the rocker. You adjust it to the correct length and then measure it and order your rods.

Chris
 
No, I don't know what it looks like. That's why I am asking you guys for help.I hate to bother you guys with it, but if I don't ask, I may never know as the repair manual isn't clear to me.

How does the adjustable pushrod tool work? I know that I need to remove the current pushrod and install the adjustable pushrod tool, but from there, what is the next step?

Was the lifter supposed to be bled out or recently run?
 
Here you go, read this.

http://www.sccoa.com/forums/showthread.php?t=92130&highlight=correct+pushrod

I had a good thread that explained how to use the pushrod tool but I can't find it.

Basically, you need to get this tool. You want to have the valve you are checking in its closed position. BTW, once you have checked 1 valve, all the others should be the same or very close, so no need to check all of them before buying, but do what you want.

You want to adjust your pushrod tool, so that it is Touching the rocker when bolted down and Touching the lifter. You don't want it to push down on the lifter at all, just to touch it.

To the next bit of information: Your lifters will push down at a maximum of 0.80". You goal is to buy a pushrod that rides in the middle of this. So obviously 0.40" is the middle and optimum.

So after you get your length set with your pushrod tool measure it up, then add 0.40" to this number and that is your desired pushrod length.

After you buy your new pushrods, there is a quick way when installing them to make sure you are directly within the boundries of where you want to be also. You arn't there yet though, so check back with me later!

Chris
 
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If the cam is a regrind, you will need to talk to who you got it from, or measure it. I used the Comp p/n 7702-1 length checker. You just unscrew it and count the turns.

If the cam is the standard base circle, you just have to run a 7.200" small block Chevy pushrod, Comp p/n 7608. I have one of mine right in front of me. Oh, that part number is for the Magnum series. You can use whatever you want, as long as it is the 7.200" length.

I got the 7.200" from Bill at SCP, that is what you have to run with the Scorpion rockers. That matched up with the 7.200 I measured.
 
So, what ever you get with the push rod length checking tool, you add .040" to this correct?? Thats fourty thousandths, correct?? Having some pushrod length problems with nickleman60's new engine. The 7.2 " pushrods Dave suggested appear to be way too long (Valves hang open when tightened down). Stock pushrods appear to be closer to correct. But we need to take a measurement to be sure. This is a new cam, by the way, not a regrind and Scorpion 1.73 roller rockers....
 
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Have you pulled the valve covers yet? Is there a ton of play in the rockers? If so, only some of them will have play as the other ones will be on the lobe (valve event of the cam). Pull one of the rockers that are loose. Put the pushrod checker next to the stocker and open/screw it out to that length. Stick it down on the lifter and start to open it. It should be turned until it touches and it showing resistance from the touch of the rocker. Then, add forty thousandths. You SHOULD be able to get it really close from there.

Chris
 
After 2 years, 1 month, and 12 days, my Thunderbird SC is finally back together. I still have a few things that need to be tweaked, but it is running strongly and she is pretty fast.
The only thing left to do is clean it up and enjoy riding her.


Thanks for the help folks and the 7.2" did work.

DSC01426.jpg

DSC01432.jpg
 
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What you are looking for is the proper rocker to valve stem tip contact pattern. The length of the pushrod does have an effect one this.

First thing you need is a lifter that is solid internally. You can disassemble a used lifter of the same brand that you will be using, pull the guts out and make a shim that goes inside under the pushrod cup to bring the pushrod cup up to the retaining clip. Or you can try to get fancy and have the pushrod cup down about .030-.040 from the bottom of the retainer to simulate where it would be in a hydraulic lifter in action.

It is important that the lifter be solid because a hydraulic lifter has give to it that you can't control, and too much give which will end you up with a pushrod that's too long. This could be avoided with the use of very light springs (correct way) on the valves but at this point it's probably easier to make a solid lifter

Once you get your solid lifter made, install it in the lifter bore of the valve you're going to check. BTW, check at least one cylinder on each side of the engine. Mark the valve tip with something that rubs off easily, a marker works well, and install the pushrod length checker (set to current pushrod length) and rocker, adjust for zero lash. Roll the engine over a couple of times pull the rocker off and measure the width of the area that was rubbed off the marking compound and also where the rubbed off area was. it should be near the center favoring the exhaust side a minor amount. Too short favors the exhaust and too long is toward the intake.

Once you're in the ball park, you just add .010 to your length checker and recheck repeatedly looking for the narrowest contact pattern you can get which will be something like 1/64's IIRC. And yes, it is a complete PITA.
 
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