Rough running

[NorCalChris]

Hey guys, I have a stock renix 4.0 XJ that I replaced the headgasket on. I used the mopar perormance gasket and also had the head milled to correct run out. I reinstalled everything and it runs like garbage. I hear springs "popping" when the engine is shut off. I assume its lifters either bleeding off due to high spring pressure. Im not sure what the issue is. It sounds like it has a whacky cam that is never consistant. lol I wish i remembered how much I milled off the head, but I dont. Im afraid my pushrods are too long. I did buy a pushrod tool to measure required length, but Im not sure how that will work with my hydraulic lifters. Any help is much appreciated.

[NorCalChris]

According to previous posts by me, I had the shop take off .008 from the head.

[SilverXJ]

.008" shouldn't be enough to mess up the preload. What springs and cam are you running? Did you do anything else when the head was off?

[NorCalChris]

Everything is stock. I milled .008 off the head and used the mopar performance HG. Which I think is another .008. So a total of .016 was removed.

[SilverXJ]

ahh.. 016", possible to cause an issue. IIRC the stock gasket is .055", MP gasket is .044", so its .011" difference. I would check your preload.

One way:
1)Bring the cylinder up to TDC on the compression stroke (both valves closed)
2) unscrew the rockers completely and let it sit for a few minutes to let the lifters pump up.
3) tighten the rockers down until you can no longer turn the push rod easily. And by easy I mean very easy.
4) Take a straight edge on the valve cover gasket surface and mark on the push rod.
5) fully tighten down the rocker and let it sit a bit to bleed down the lifter,
6) mark the pushrod again,
7) remove the rockers and push rods and measure between the marks. That is your preload.

Another way:
continue from step 3 above
4) insert a feeler gauge between the rocker trunnion and the head pedestal.
5) increase or decrease the feeler gauge until all slack is taken up in the area measured. The feeler gauges used is your approximate preload.

There is another way to do it using the TPI of the bolt to figure your preload, but I don't recall the measurements for turns on the bolt.

-Chris