63super88

It appears the #1 cylinder has mysteriously gone dead all of the sudden, started running rough all of the sudden and found #1 misfiring. Did compression test, #1 hardly puts out 20psi while the rest on that side are 115-120 psi. there arent any obvious valvetrain noises or anything, just no compression from #1. Plugs looked ok, tanish/white and #1 didnt really look any different from the others so i think it was running fine up until this. Im going to try a leakdown test with it at tdc on #1 with the valve cover off and see if i find any obvious leaks, im praying its just a valve not seating fully for some silly reason, and that nothings actually bent/burned. (It did ping here and there under heavy load from todays crappy fuels, i fear a valve may have finally kicked the bucket). Just figured id share with you guys my plight, maybe you guys have a trick for diagnosing loss of compression. Thanks!

442Harv

I would think broken valve spring, bent push rod, or lifter came apart.

63super88

I looked under the valve cover and the springs look to be ok. There isnt any real tapping or knocking or smoke from the tailpipe. A valve either has to be stuck in the open position or isn't seating and letting practically all the compression out. Either way its looking more like the head has to come off unfortunately for me. Just unsure of what parts i would need until i do, i dont want to start ordering a heap if parts in advance unless i just atart replacing it all.

m371961

If a valve is stuck open you would notice excessive valve clearance. Did you observe it while cranking to insure Intake is opening fully? If air don't get in, it can't compress.

63super88

No i didnt crank it while the cover was off. Im only hoping that its a valve stuck or lifter not lifting. The lack of noise or even any real stumbling is strange. Just praying the cam is ok, i think the rings and piston are fine because theres no smoke or knocking. im leaning more towards a bad lifter as 442harv suggested. Disassembly will tell for sure and the compression test made that obvious so im going to try a leakdown test with the cover off at tdc on #1 to see f i can pinpoint what the issue could be, then ill pull the head. Ill need manifold gaskets, head gaskets, and then see what is failing at that point. My machine shop guy can prob get the valves/lifters, and do the work. I just want good replacement parts to do it. Im not going to touch the other side if i dont have to, it was a really healthy motor up to this point. I guess this is typical of a 100,000 mile 5" yr old high compression engine though. Not that complicated, its not rocket science after all! Or is it? 😂

Sugar Bear

Using a spark plug adapter, put air in the cylinder with the rocker arms on the cylinder being tested in the closed position and see where it leaks. It will leak from any of these:
tailpipe (exhaust valve),
carb (intake valve),
crankcase/breather (ring/piston), and or
cooling system (head gasket/cracked head/block).

Don't get concerned about a cracked block or head, that is the least likely.

Good luck and keep us posted!!!

Tedd Thompson

Does it have the typical burnt valve swoosh sound at the tail pipe? Before I would tear it down I would do all the test as described above and try and narrow it down.... Tedd

63super88

its hard to tell with it running roughly and misfiring, but i guess you could say that. I have a leak-down tester, and ill set it to tdc (which for cylinder 1 should be the timing mark), take the cover off and see if a valve has an obvious leak. really hoping i only have to just replace the lifters for #1 and put it back together. Only trying to replace whats actually failing.

Sugar Bear

You can use the balancer to set number 1 close to TDC but remember the balancer may have slipped some and the timing chain is stretched. There is a 50/50 chance #1 will be at TDC on the compression stroke. Confirm #1 is on the compression stroke and your test result will be reliable. You don't want the cylinder being tested possibly on the exhaust stroke.

Good luck!!!

63super88

So the results if the leakdown test are as follows, I tested the #1 and #2 cylinders at tdc, and got some ok results. #2 cyl is the one with the lower reading, but both were right around the 25-30% area in green. No air from out of the valves or carb/exhaust, i tried to listen with the cover off. This tells me that the valves and compression are ok, and leads me to believe what i had previously thought, a lifter just isnt lifting the intake valve to let air in. Its hard to tell if they are opening/closing cranking the engine by hand, but im pretty sure now its a bad intake lifter collapsed. Right?

Don R.

Have you cranked it over with the valve cover off? It should be obvious if a valve is not being actuated.

63super88

Not sure how to get a video on here, but after observing the valves while cranking it actually appears as though both are opening up. I'm sort of lost at what i should do, the compression is gone and im now unsure why. They both seem to function fine, and hold up to a leakdown test. Its as if the valve timing was off for just #1 valves

Sugar Bear

I'd redo the compression test. It is possible that a valve was sticking open or had carbon on the seat. If the compression is still low, try replacing the valve springs.

The chance of it being lifter related is low especially if you don't hear ticking etc.

Keep diagnosing until you find the problem before pulling it apart.

Good luck!!!

63super88

well i re-did compression test, and still only 20 psi from #1 The neighboring cylinders all put out a healthy 115-125 psi. Still unsure whats going on exactly, tried some marvel mystery oil and spirited drivig to see if i could free it up and nothing. Any further driving is probably putting alot of stress on the dead cylinder

oldcutlass

Did you try adding a couple of squirts of oil to that cylinder through the spark plug hole and redo the compression test? If it goes up its rings.

63super88

Ill try it again tomorrow, see if that gets a response. It held up well to the leakdown test, didnt seem to leak air into the crankcase any more than the others and read about the same on the tester. Im beginning to think maybe its not mechanically related at all, maybe theres a leak in the head gasket, it had a habit of pinging under a load and i think possibly pre-detonation may have caused the gasket to fail somehow. I'll probably try the leakdown test again as well, and this time closely check the coolant for air bubbles.

Sugar Bear

Ran into this once that turned out to be a bad valve spring, I hope you are that lucky!!!
Can you put compressed air directly into the cylinder without any testers to try to detect a leak? I'm wondering if the tester is limiting the air flow too much for the leak to be heard.
Try the oil in the cylinder too as suggested for a wet test, it will go up a little every time e.g., 20 lbs or so but if you get a big jump 50 lbs or more that indicates rings.
Keep us posted!

63super88

So in doing the compression test with a bit of oil in the cylinder, it shot up to 100 psi and gradually fell back down to 20 again. I can hook the air compressor up to it through the adapter for the leakdown tool and try to put a bit more air into it to try and see where it blows from, but im getting pretty worried where this is all leading.

oldcutlass

You have either stuck or broken ring/s.

63super88

This cylinder was prone to 'ping'. I guess that could have cause the rings to fail in that cylinder, probably more broken and less stuck. Which would spell disaster for my poor 394 if thats the case. Im not ready for bottom end work on this car.

Don R.

Don't give up on the engine too soon, the 394 can take a lot of abuse and still be repairable.

oldcutlass

Pinging may cause the piston ring grooves to crack. Fill a 16oz container with tap water and run the engine to temp. Raise the engine idle by hand high enough to slowly dribble the water into the carb until the container is empty. Pour some wait for the idle to recover then pour a little more. Do not pour so fast as to hydrolock or stall.

oldcutlass

Remove 2 qts of oil and add 2 qts of Rislone engine treatment concentrate. See if you can drive it for about 100 miles and then change your oil.
https://smedia3.webcollage.net/956aa...pplication/pdf

https://smedia3.webcollage.net/956aa...pplication/pdf

63super88

These olds engines are pretty tough. If icould get it on a stand, pulled the head off and oil pan off, i could probably get that piston to replace the rings, and just reassemble. Long as theres not a deep ridge in the bore, but my 62 f85 has 150,000 on its 215 those cylinders didnt even have a ridge you could feel. I can only hope this engine is the same.

Even if an additive did manage to free the sticky rings, it still needs mechanical attention. So it looks like im doomed to pulling that piston 😥

oldcutlass

Not necessarily, if the ring gets unstuck it could run for years. Try doing the Cadillac Cure with the water and ad the Rislone.

Charlie Jones

I bought a "running engine" from a 63 Starfire .
I considered it a "core" because I wanted to re-build it anyway . It is going into a " full on " restoration.
As I was tearing it down I noticed that it seemed to have two "Ridges" , one below the other in many cylinders .
When I removed the pistons I discovered why . All eight top rings were broken in half .
It appeared that the engine was probably ran in this condition for thousands of miles , because the second rings had worn their own "ridge".
Not only that , but some of the top ring grooves were worn so badly , that the ends of the broken ring pieces actually overlapped each other.
I can only speculate as to the cause . But , I suspect that someone attempted to run regular gas in the car . It probably "pinged" like he!! until it broke all eight top rings .
After that , there probably wasn't enough compression to cause detonation.
Yes, these 394 engines are "tough" .

63super88

Well as with any older engine there is always the luck of the draw. But i understand what you mean, if theres are cracked up rings in there then you know it will cause irregular types of wear. My engine was pretty healthy before this, and the other cylinders ive tested seemed strong so hopefully i luck out on the 88 like i did my cutlass. Good luck with your build on your 394. Where are you sourcing the parts?

Sugar Bear

If a ring(s) is stuck due to carbon and it gets freed up then a mechanical fix is not needed.

If a ring is broken then yes a mechanical repair is needed. If the cylinder wall is in decent shape it could be deglazed, the piston replaced if necessary, a new set of rings on the one cylinder. An advantage to reusing the piston if it is good is the wall clearance is good, the weight is the same, the compression ratio is the same and well...you don't have to source a piston for an engine over fifty years old.

If the old piston is ok and you don't want to do an overhaul now, reuse the piston.

If you try the water/steam cleaning be very careful, it works but can damage the motor. Don't exceed a dribble of water as old cutlass advised. Another way is to put a solvent in that cylinder through the spark plug hole let it sit for a few days, crank it over to blow the solvent out (disconnect the coil wire), put the plug back in it and run it then retest.

Good luck!!!

Charlie Jones

Ross Racing Engines for the major parts ; Pistons , rings , cam , lifters , valve springs , timing chain , and sprockets .
NOS valves , guides , cam bearings , rocker arms , and shafts , courtesy of E-Bay .
Gaskets , rod bearings , oil pump , and shaft , from O'Reilly's
Frost plugs from Fusick Automotive .
Main bearings from Falcon Global.
I went with the forged Ross pistons . Because i could "hammer on it " , and not worry about breaking cheap , off-shore cast pistons .
In fact , my whole goal here was to find as many "Made in USA." parts as possible .