Valve train testing

[STDog]

Ok, I'm sure something is wrong.

Is there a way to check my cam / lifter / push-rod / rocker-arm setup?
I'd rather not have to replace any gaskets, except perhaps the valve covers (but I think mine are rubber).

It seams to have no bottom. Got the front tires in a shallow trench the other day and couldn't back out, but the rear didn't break free either.

The cam, rockers and push rods are used, like 95k miles on them. I put new lifters in.

Can I measure lift on the rockers, either the valve or the push rod, without pulling the intake and using a solid lifter?
I was thinking drive the oilpump/run the engine, and the lifters should hold to test this. Thoughts?

Maybe I'm not getting enough lift and duraton, and the open is late, and the close early, tush takingaway the torque below 2krpm.
Worn rocker amrs/pedestals, push rods, or cam would cause this?

Maybe attach something to the crank to get an idea on the duration and max lift points? And compare them to stock specs?

I'm disappointed now. I just didn't have the cash to replace the parts, so stuck with the old parts. (thinking of a roller set up later ?)
But it not much better than before the build ( required by a failed oil pump drive shaft, the hex rounded off ), and no where near what it should be.
But I need to find the real problem, without throwing cash at it. And of course it's my daily driver, so getting to work is a pain when it's down.

[curtis73]

Well, the good news is that your lack of torque could be one of a thousand reasons; 2.73 rear ratio, a tired tranny, a sick carb...

The bad news is that you put new lifters on a 95k cam. If you're getting valve chatter, you've wiped a cam lobe or seven flat. New flat tappets on an old cam just doesn't work. Flat tappet cams are cast, machined, then hardened on just the very surface. Think of the cam and lifters as two identical sheets of sandpaper. Rub them together for a while and they will wear evenly until they establish their final abrasiveness. But, you change out one of the pieces for a new piece and it will eat through the old one in a heartbeat.

Cam lobes are much like the eggs they resemble. hard on the outside, but soft on the inside. Changing flat lifters is (sorry to say) an absolute no-no.

You can test the valvetrain with a dial indicator and a magnetic base. They're available at a parts store, but cheaper at harborfreight.com. Place the zeroed plunger on a rocker above the pushrod. In general this method won't tell you much since lifter bleed-down would skew the results, but since your lifters are new it might lend some insight into the cam lob condition. A flashlight down the pushrod holes might also let you see the condition of the lobes. I also recommend installing a magnetic oil drain plug to see if you get anything indicating that lobes are being worn.

[STDog]

New flat tappets on an old cam just doesn't work.Changing flat lifters is (sorry to say) an absolute no-no.

That contrary to everything I've ever read. Old cam + new lifter is fin, just follow normal break-in. The lifters harden to match the cam.

New cam + old lifters = no.
old cam + old liftes = OJK if the lifters all go back to the same bore.

This is according to the cam manufacturers and every engine rebuilding article I've ever read.


Do lifters bleed down that fast? I hoped I could driver the oil-pumop and keep them up long enough to check the lift.

[Andy V]

ST Dog,
I too have put new lifters on a used cam, without any issues so I believe this is an acceptable practice (so I've read too).

You will have to pull the intake to do this, but you may be able to check the cam lobe lift with a dial and mag. indicator, but instead of putting the dial shaft on the center of the lifter, use the outside housing of the lifter (that way you eliminate the plunger all together). There is typically enough flat spot on the outside housing that you can get the dial shaft to rest on it. You need pretty good alignment between the shaft of the dial and the lifter bore so it stays on there.

I highly doubt the upper valvetrain (rockers/pushrods) can be worn enough to cause your problems. I'd check the cam as a first item.
If you can check cranking compression you can find out how well each cylinder is sealing. If your rings are shot you loose lots o power as well.

[bondsman]

stdog is telling you the truth, all though sometimes you can put old
and new together without consequence. but the reason for all new
is the wearing down of the two identically once a cam and lifter have
had their mating surfaces together for a period of time they will almost look like they were machined together because of wear.but if you get
a motor that was well taken care of then you might get away with it.

[bondsman]

im sory about the wrong name i was making a responce from curtis post
not stdog. sorry.

[STDog]

You will have to pull the intake to do this, but you may be able to check the cam lobe lift with a dial and mag. indicator...
I highly doubt the upper valvetrain (rockers/pushrods) can be worn enough to cause your problems.

OK. I guess it'll wait a while.I'm just not able to pulle the intake right now. Good to know the top is probably alright.

If you can check cranking compression you can find out how well each cylinder is sealing. If your rings are shot you loose lots o power as well.

I'll try to get a compression guage. The rings were replace at rebuiild, 1400 miles ago, so they shouldn't be shot. Then again, I might have screwd somthinge else up.

I played with the carbn som. It wasn't dropping to the correct Idle when warm. I think I got it working better, and running on the idle circuit now. I pobably need to get a better tuned carb though. I think its running very lean, but the mixture screws don't seam to have much affect. Reducing the air (closeing the choke) speed up the idle speed. Isn't that a sign of a lean mixture?