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Aloha from Maui,

I have a 2002 Caravan Automatic with the 2.4L 4cyl with low compression after a rebuild...
Bought it with low compression and excessive blow by, pulled the head and found a popped head gasket between 1 and 2, with damaged #1 piston + rings.
I sent the head to the machine shop, and I swapped out the #1 piston and rings.
I also swapped the timing belt, timing tensioner, and water pump because, hey, it's the right thing to do.
Put it all back together and now I have low compression across all four cylinders...
Previous counts were 0, 40, 120, 150 and it ran!
Current counts are 40, 60, 60, 90, crank no start.
The timing marks are lined up.
The only thing that went wrong in my book was that the machine shop allowed the little rollers that rub against the camshaft to get all swapped around... I didn't realize I should have taken them out before handing it over. Are those specific to each valve?
Shop mentioned that I needed to prime the hydraulic lifters, but when I squeezed one it still had some dirty oil in there, so I just put them all in, assuming it would work itself out over time with oil changes. Maybe I was wrong, but wouldn't these fill with oil while I'm cranking?

Thoughts on why I have low compression??
Thanks in advance, I'll go surfing while you all chime in ;)
 

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The cam followers will be worn to specific cam lobes over the life of the engine which makes them mated to their originally installed positions. Moving them around might accelerate some new wear into parts as they break in all over again. I have no idea if that's a small problem or a catastrophic problem. Considering the engine hasn't ran since repair, I doubt it's not catastrophic yet. Priming the lifters should have been as simple as drowning them in a quart oil for a few minutes. You could pull the valve cover back off and see if your cams look like they're opening up your valves all the way. Use some Sesame Street logic and see if one of those things isn't like the others. If your lifters aren't primed, I'd suspect you can watch them collapse when a cam lobe should be lifting a valve instead. That aside, I'd want to move on to a leak down test. Compression testing checks engine breathing. Leak down testing checks the combustion chambers ability to seal at TDC on the compression stroke. I can just about guarantee a leak down will narrow down what's wrong with that engine.
 
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