AMC Eagle Den Forum
The Mighty 258 => The Engine => Topic started by: win32exe on April 13, 2024, 11:06:46 AM
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Hi Team, My SX/4 had been recently been making a slight tapping sound and i figured it was the lifters getting tired and had planned on swapping them out soon, then driving on the highway recently this happened, (see picture) she started popping\knocking out of the carb, the #6 exhaust valve was not opening anymore, limped it off the highway and towed her home, took it apart and found the one bad lifter.
so i have a few questions...
How does the lifter get worn like that? the pushrod isn't bent, the lifter came out as easy as the rest, it wasn't stuck in the block, could it be a stuck valve, the valve looks good to the eye, seats flat, no visual bending.
Does that mean the camshaft definitely needs to be replaced?
If so what else should i do, new timing chain and gears? pushrods? rocker arms? Are these used OE parts on the engine better than replacements?
why do all the parts needs to go back to the exact position, pushrods, rockers, lifters in relation to replacing all the lifters or pushrods and\or rockers etc, none of the parts will be in the original positions, lets say two pushrods are bent, would we replace the whole set? i understand if the old parts are going back in then put them in the original position.
Head and pistons don't look too bad, but should i just drop a reman 4.0 Liter in?
I feel like i am at a crossroads
Any input is appreciated.
Henry
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I’m actually in a similar boat with my car, but I haven’t had any failures yet. For what it’s worth, here is my plan: new cam, lifters, timing set, and a 4.0 head.
To see if a valve is stuck, you should be able to push on the valve end of the rocker arm or tap it with a rubber mallet. If it doesn’t move and sounds solid, it’s stuck. If it moves and sounds kind of hollow almost, the valve is still functioning as intended.
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thank you for the input, why the 4.0 head?
Henry
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thank you for the input, why the 4.0 head?
Henry
The 4.0 head flows better and I think it might have larger valves. I’ve read that it’s good for 35-40hp, but it can be tricky to get the intake manifold to work.
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Is that rust on the head of the lifter?
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The 4.0 head flows better and I think it might have larger valves. I’ve read that it’s good for 35-40hp, but it can be tricky to get the intake manifold to work.
I had a 4.0 head installed on my Kammback, along with a new cam and the Cherokee 4.0 header style exhaust manifold. From what I recall, mounting the intake manifold wasn't a big problem, but he had to kind of rig up something to mount the power steering pump. It does provide better performance.
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The more I look at that lifter and the one sitting on my desk as a paperweight, I think what happened was the engine sat for a period with humidity in the crankcase and rust developed on the lifters. They should normally rotate while in service and looking at the galling they stopped several times and finally stopped spinning entirely and just started wearing down the lifter until it wore straight through.
I'd be concerned about how much of the filter collected the metal debris.