[66sprint6]

Since I'm unable able to get the parts I need to install our Round Port engine in our '67 LeMans, I've been trying to improve on the overall performance of the engine that is in the car now. It's a 400 engine from a '74 vehicle.
It ran poorly when we got it, but I changed the plugs and wires, switched to HEI, made sure that there were no vacuum leaks, etc. It runs much better now, but it's not quite there as far as the idle and power are concerned.
It's got good compression and it seems equal across all cylinders. It also has decent vacuum. The timing is good. So I'm kind of stumped as to how it feels like it's got less power on one cylinder or something. When it idles theres a bit of a shake to the car.
I'm wondering if the problem may be the camshaft. But before I go and tear the engine apart, I thought that I should check the intake and exhaust valve lift on each cylinder, to see if they are equal. I'm thinking that this would also tell me what cam is in the car with some calculations.
At first I thought that a simple dial indicator, mounted to each individual rocker would indicate the lift. But I then realized that with hydraulic lifters, the valve spring would overtake the lifter and keep the rocker from coming up. In this case, is it possible to undo the rocker, push it aside, and put the dial indicator on the end of the pushrod? What do you think? Is there another way to check if a lobe on the cam has been diminished?

[leeklm]

Putting a dial indicator on the pushrod will certainly work, and will also tell you what the total lobe lift is. Tech officials used to check our lobe lift using that method in circle track racing..

I see no reason why it would also not work to determine if you have a rounded lobe. However if you do have a bad lobe it will likely be immediately noticeable due to a loose rocker arm on the corresponding lifter.

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[steve25]

When cam lobe’s are good as far as ware on the base circle of the cam and ware to the face of the lifter, then each time the lifter passes over the base circle area the lifter will spin.

This means so will the push rod.

What you can then do is pull a valve cover, wipe off the oil at the top of the push rods( with brake cleaner or paint thinner )and then paint a white mark on them.

Next cut a tall section of cardboard off ( that’s taller then the rocker’s ) that’s also long enough to span the width of the head.

Stuff this down in between the valve springs and the side of the head above the exh ports.

This is needed to deflect oil from getting kicked out and all over everything.

Then start the motor.
It should already be warmed up enough to idle.
Then watch for the push rods spinning.

They should all rotate at the same rate if all is well,
Any that spin slower or with less of a rotation to them have warm lobe’s with lifters riding on them that are on the way out also!

[steve25]

You have posted a lot about how this motor runs, have you ever checked the condition of the timing chain?
This check/ test takes all of 1/2 hour and can tell you a lot about why the motor may not be running as good as it could.

Also you have posted that you swapped over to a HEI set up.
These need a full 12 volts, not 9 volts like the old point set up does.
This can make for poor performance also!

[steve25]

Also you can get a pretty good idea of how much lift the Cam has by looking at the ware pattern on the push rods where they pass thru the guide plate.

[67Fbird]

travel indicator on top of push rod is plenty good for what you are looking for. Two things to be aware of 1st that indicator travel is parallel with pushrod travel (the closer the better) . The push rod will not try to spin as the only thing applying pressure to is the plunger of the indidcator.

Might also check backlash of timing chain WHILE you have an indicator on one of them...

[66sprint6]

Thanks, guys. I really appreciate the suggestions. I never gave any thought to the condition of the timing chain. I did ensure that I have a 12v supply to the new HEI. So this should keep me busy for a while checking this other stuff out.

[steve25]

Also confirm that the balancer is good by checking that at TDC the mark lines up with zero on the timing cover.

The outer ring on the balancer which has the mark on it has been known to slip out of place.

You can pull all the plugs and check this with a dial indicator also if you have a long enough extension to add to it.

If not having a helper to bar the motor over while you hold a long screw driver in the number one plug hole perpendicular to the piston top can get the job done also.

Note that the piston will dwell a bit around TDC so your looking for point where the piston just stops moving,

[77 TRASHCAN]

A flat cam lobe can show up, doing a compression test. THe questionable cylinder could have higher or lower pressure depending upon how far the lobe is knocked down...

You might be able to see the difference in rocker movement by just spinning the engine over with the starter motor.

If the engine pops at higher RPM's and still runs fair at lower RPM's this can be a sign of a flat cam lobe...