First off, the previous owner (PO) may have installed a custom ground camshaft in your multi-fuel engine. The camshaft could have different lifts for the intakes and exhaust or the same lifts. It doesn't matter. We will be checking ALL the camshaft intake-lobes and then comparing them to one another. Then we will be checking ALL the camshaft exhaust-lobes and then comparing them to one another. Also, be aware that some of the camshaft lobes can be worn, and some of the lifters can be worn/broken, and possibly the pushrods are worn or of different lengths. This will cause reduced power.
Likewise, if all the camshaft lobes are OK, the camshaft STILL needs to be "timed/degreed" to the crankshaft (i.e. crankshaft piston location relative to camshaft valve openings/closings). If it's not timed/degreed properly, then the power will be down.
So , let's get started with some basics;
1. Jeep 4.0L engines typically have non-adjustable lifters. The lifters are "pre-loaded" 0.020"- 0.060" by placing spacer washers under the valve pedestals on the head.
2. Hand rotate the engine CW until both intake & exhaust, for one cylinder, are closed, i.e. lifters setting on the camshaft lobe "base circle".
3. Loosen/remove rocker arms from pedestal. If there is a spacer washer on the pedestal remove/mike the thickness and save. That spacer washer is your "pre-load" for the lifter.
4. Give the lifter a few minutes to "bleed-down". As the lifter bleeds down, an internal spring, in the lifter, will push an internal cylinder in the lifter up to the "neutral position" where it is stopped. The spring-backed cylinder inside the hydraulic lifter will now support the pushrod.
5. Place a plunger type dial indicator, with a plunger range of about 0.5"-1", on the plunger on top of the intake valve pushrod and zero it.
6. Slowly manually rotate the crankshaft CW and write-down the maximum camshaft lobe lift for that intake valve.
7. Now switch the dial indicator to the exhaust valve pushrod. Rezero the dial indicator on the lobe base-circle, manually rotate the crankshaft again and write down the exhaust valve maximum camshaft lobe lift.
8. Repeat this for all camshaft lobes in EACH cylinder.
The trick here is to place the hydraulic lifter in the "neutral-position", so its internal spring-backed cylinder supports the pushrod as the lifter rides on the camshaft lobe. This technique is similar to determining the proper washer thickness to set the lifter preload. Essentially, the neutral-positioned hydraulic lifter is made to act as a solid lifter. If done carefully, all the camshaft lobe lifts can be checked with only the pushrod riding on the lifter. Likewise, the dial indicator plunger force is negligible. Repeat each lobe measurement to insure repeatability. Replace the "preload washers" on top of the pedestal when you re-install the rocker arms. If pushrod weight become a problem when measuring lobe lift, replace the heavy pushrod with lighter straight aluminium tubing, of the same length as the pushrod to do the lobe lift measurement. When done measuring the lobe lift, replace the aluminium tubing with the original pushrod.
When you're done measuring the lobe lifts, show us what you have.
Best regards,
CJR