304 with valve problem

304 with valve problem
J

jay47

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Location
Cedarville
Vehicle(s)
'74 CJ5, 304, T15, D20, D30 front, D44 rear
My 304 is running on 7 cylinders, #1 plug is firing, but not cooking the mix. I pulled the cover off, and fired it up, and lo..... the tappets not moving on #1 hole. No noise ever when running. Engine has less than 1000 miles on the rebuild. I let it sit in storage for long periods of time. Could it be bad lifters, or just need to adjust the nuts on tappets holding them in place. I rolled the push rods in place, and they don't feel bent. Tappets are really loose, and the others are tight. Any help is welcome. Thanks.
 
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Well, sounds like you have a case of some stuck lifters. There is no adjustment procedure for the rocker arms. The bolts just tighten down to 19 ft.lbs.
The cam could have gone flat, but two lobes on the same cylinder is almost unheard of.
Are the rocker arms loose, as in have a lot of movement without engine running?


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I had a similar issue with 'Black Betty' and it turned out to be a stuck valve, due to carbon buildup on this older 360.
 
:agree:

Check for stuck valves, before doing anything else.
LG
 
A stuck valve should create a dead miss. Check the compression on the hole with the loose valves. If it has decent/good compression a stuck valve is not your problem. If it is low, then it’s a good bet the rocker arm that is loose is the valve that’s stuck.


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A stuck valve normally ends up with a bent push rod.
 
True, sometimes, if the valve hangs open far enough, it won’t bend it.


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How often due you see a valve stick open?
 
Kinda common on long term stored vehicles.
LG
 
Valve(s) stuck it could be. I'll check it. The push rods seem to be ok as I twirled them around, and seem true, although the rockers are both loose, as I tried to tighten them up while engine was running, just didn't really throw a lot of weight behind em when I did. I thought they may have come loose. Oil is flowing through the push rods. I put finger tension on the rockers to the push rods when engine was running, and they were pushing back with rhythm, so the cam is good. I guess I'll try a compression test on that hole. If it is stuck valves, what next? Seafoam treatment? Thanks for the reply's
 
The AMC V8's don't have an adjustable rocker/valve train like Chevy's. On the AMC's they're just run down to the correct torque. Do you have the Bridge pivots in place? Insure that they're straight, mine were a little bent but I fixed them in a vise VERY carefully as these bridges can be brittle.
Their torque is 19 ft./lbs.
 
I would pull all the valve train components for that hole and inspect them. Pull a working rocker and push rod for comparison. If all looks good resinstall them with new lock nuts and torque to specs. The rockers could have been installed without lube and started dry which destroyed them. Or just go to the parts store and buy all new parts for the dead hole and R&R them, don't forget to lube them before install.
 
Unfortunately, just because the rockers are moving up and down under finger pressure does not mean the cam is "good". It must have the proper lift on the cam lobes to be considered good, as well and little to no wear.
Cams are only surface-hardened. Meaning once that hardened surface is worn away, the cam looses it's lobe fairly quickly, even with proper oiling. Once the hardened surface wears away, this usually ends up gaulding the bottom of the lifter, causing further damage and wear to the cam shaft.
Often, the surface of the lifter will wear out, or get rough, then that takes out the camshaft. I've seen many failed cams, for a variety of reasons.
Checking the camshaft with your finger will find a "flat" cam pretty easy. But a "flat" cam will cause a dead hole, or dead miss. Depending on which lobe wears out, it may show "good" compression (exhaust lobe gone) or it may show no compression (intake lobe worn out).
Let us know what you find and we will help more.
It might be your lifters are just stuck in the collapsed position.
 
Talked with a tech friend, and he said same thing. With as few miles on complete overhaul, and storing it without cranking it over to lube, it sounded a lot like collapsed lifters. I don't have a heckuva lot of experience with this stuff, so how do I get them taken care of? I bought 2 new lifters, so I guess I'll pull them out, and replace. I suspect that without proper lube due to inactivity, they froze, and perhaps rusted in a collapsed state. Anyway thank you for the help.
 
Sounds like you have a good plan. Be sure and soak the lifters in oil before installing them. Lay them flat, completely submerged. In the groove in the center of the lifter there is an oil hole. Point the oil hole up, so trapped air inside the lifters can escape. Give them a shake every once in a while to help release the air. Then install them while dripping oil.


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Once you pull the lifters, the bottom of the lifters will tell the tale of the cam. If all galled up, grooved or completely flat, the cam is usually done. Use a flashlight to inspect the cam, check the lobes for pits, uneven surfaces and shape. If the cam is good, I would buy bottle of Lucas engine breakin and dump it on the cam, lifters during install and also the rockers. Don't let it idle for the first 10 minuters or so to breakin the new lifters, keep it up over 1500 rpms.
 
So fast forward 6 years, after pulling both lifters from #1 hole, I find them both in a concave state. After contemplating what the heck to do, and consulting various shops, and "experts", all say pull engine, and have a do over getting all the real small particles out of engine. Man, it cost me grand last time I did that, now 35 years later probably triple that, so maybe its time for a SBC swap. Hate to do it, as its a stock '74. What to do?
 
The only thing that comes to mind is oil starvation at that specific valvetrain component. There might be a way to augment the the oil flow and address the issue.
 
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