unusual top-end knock

[TCullen]

I'm running an 86' HO 5.0 in a 67. It was recently flooded, cleared out, and now starts and runs. When she started up, there was a pretty loud knock, though. So, assuming that gas leaked down into the pan i immediately changed the oil and filter.

The knock seems to be coming from the top end of the engine. You could hear a valve tap before, but this is like 10x louder. What is more strange is that the oil pressure is higher than usual. For this reason, I'm assuming that the problem is not in the bottom end (at least i'm hoping).

If anyone has any insight, it would be greatly appreciated. Thanks

 

[zookeeper]

Knocks are never good, but it may not be the end of your motor depending on where it's coming from. If it's a bottom end knock, like a crank bearing, rod knock or piston slap, it's terminal. But I've had such nasty sounds be minor things, like a dent in the pan touching the crank. The first thing to do is find out where it's coming from. Is the oil pressure fluctuating? If so, it's likely a rod. Check the plugs for damage or to see if they're all the same color. You should pop the valve covers off to check for loose rockers or even a bent pushrod. You need to isolate whether the noise is coming from inside the valve covers (easy fix) or inside the block (not good). What you did when you flooded the motor is washed all the oil off the cylinder walls, so even when you purged the gas from the cylinders, you had a dry start condition. Maybe it'll go away, maybe it won't. If the oiling system in your 5.0 is stock, they don't have a bunch of oil pressure to start with. They don't need much due to having a roller cam, and since high pressure causes power loss, they're not too high when new. Good luck.

 

[TCullen]

the strangest thing about this situation is that the oil pressure gague reads that it's maxed out when before it was pegged on the center. i took the valve covers off, and there aren't any bent rods. then i started it up (without the cover on) and can't tell which one is the problem.

this motor was upgraded with the screw-in rocker adjusters. as far as i know the best way to adjust them is to take each cylinder to TDC then tighten the nut for each to 1/4-1/2 of a turn past where you start to feel resistance and then tighten the allen screw.

if this doesn't work a compression test would probably be the next move, i think. like i said before, though, i can't seem to understand why the oil pressure reads as high as it does.

 

[TCullen]

after further inspection, i found something really strange. the left (drivers) side rockers are loose. i mean really loose. when the valves are closed, you can move the rod up and down, and the rocker side to side. the right side of the engine is a lot tighter. when closed, there is still some play but a fraction as much.

i just took the car in to get a tune up, and the mechanic who did the job said that the knock was likely a product of fuel in the oil due to flooding. am i getting shafted here, or is there a legitimate explaination?

also, when adjusting valve lash, should you be able to turn the rod with your fingers when its fully tightened at TDC?

 

[zookeeper]

I've never tried, but I think you probably should be able to turn the pushrod after adjusting. I use a bit more preload than most people. I turn the adjusting nut one full turn after zero lash. But don't 5.0 motors have non-adjustable rockers? Or do you have aftermarket heads? Anyway, glad you found the noise.

 

[Shakin66]

You very well may have bent a valve. I am taking mine down today for that same reason. You can measure the height of your valves and that will allow you to determine if one is lower if so its time to pull the heads.

 

[D.Hearne]

My guess is that you've had the lifter spider come loose and one or more lifters have turned sideways on the cam lobes. If this is the case, you've got a destroyed cam and lifters, possibly more damage in the bottom end. Pull the intake and look in the lifter valley. Do not run it more, hoping for it to go away.

 

[65ShelbyClone]

But don't 5.0 motors have non-adjustable rockers?

Yes they do, but TCullen said the heads had been modified for screw-in studs.

I'm with D.Hearne. Pull the intake and make sure that none of the lifters have spun in the bores. If they have, you'll need a new cam and lifters.

 

[headgrinder]

knock

I hope I am wrong but after a car is in a flood I would be really concerned that a rod is bent by water in combustion chamber(water does not compress).
I would check lifter spyder as D. Hearne suggests.If that is not it try pulling plug wires 1 by one on side with knock to see if noise changes if it changes or goes away it is almost always a piston/rod problem. the oil pressure is another curve ball but water in oil can do strange things. good luck

 

[TCullen]

you were dead on, D.Hearne. of the 8 retainers that hold the lifters in place, 4 were broken (all on the left side?). 2 of the lifters were ground practically flat. and all inside 5-10 min of running at idle. so now its on to replacing the cam, lifters etc.

i'm hoping that the pan full of metal shavings didn't do too much damage to the bottom end of the motor. the rod/main bearings appear to be ok, but i guess that i'm gonna have to pull the heads to get a proper look at the cylinder walls. bummer

 

[D.Hearne]

Sorry to hear that I was correct. The clue you gave as to all one side developing slack in the rockers was the one I based it on.The oil pressure spike was the other. Sounds like maybe your cam had too much lift for the retainers. What cam was it? I've run the Z303 with the stock retainers and spider without problems, but I've also got a set of Crane's replacement lifters too. The Ford rollers float at about 6500 rpms. The Crane's are good so far to 7500. They cost me around $180 seems like.

 

[TCullen]

the motor that i'm running is from an SCCA car. this is the first time that i've torn it down. i know that it has a ford motorsport cam, but i don't know which one. do you know where the identifying marks are located?

i'm not sure what setup i'm going to rebuild with, probably another motorsport cam, some better lifters and upgraded retainers. its tough cause i'm on a college budget, this is my daily driver, and performance isn't something i'd like to compromise either.

 

[D.Hearne]

The Motorsprt cams are stamped on one end what they are. (B303, etc)