Inliners International Forums General Discussion Engines My engine knocks

After revving my '54 235 higher than intended, it now has a knock. The noise sounds like something hitting thin metal , like the oil pan. It still runs on all 6 cylinders and still has good oil pressure. I have no dust cover over the flywheel/clutch, so the oil pan , side cover, timing cover and valve cover are the thin metal parts on the engine. I will remove it for teardown and repair this week.Thanks.

Is it a constant sound or one that goes away when the engine is under load? Can you tell where on the engine it is coming from?

Your flywheel May??? have come lose.?

I agree, check the flywheel.

Same thing happened on my 64 GMC 305 V6. Engine started knocking when the engine was idling. Turned out to be either a sticky lifter or a piece of carbon wedged in the valve. Does yours sound similar?

https://www.youtube.com/watch?v=HyhgUvL-2wU

I started the engine today with the trans in neutral then pushed the clutch pedal and listened for a change in the sound. No change. I feel pretty sure the sound would change if the flywheel was loose. The sticking lifter or carbon under the valve sounds like a possibility because the engine is now running very rich and the tailpipe is very black. I will pursue that next. Thanks.

Don't run it anymore. Might cause further damage. Open side cover and check all lifters. Remove plugs and check them for impact damage (from any foreign debris bouncing around inside the cylinder) Turn engine by hand and observe valves moving. Try to back off all rockers to make sure you can get valve clearance, see if anything feels weird. Check springs.
Look and feel oil pan with your hand for bumps from rod bolt or something hitting it from the inside. Might want to drop the oil pan to check rod end caps and bolts.

Just some thoughts that came to mind

Trust me the sound will not change if the flywheel is lose. BUT
One thing for sure it will have a rattle after you shut it off as well if it is lose.

I do intend to remove the valve cover before I pull the engine. My engine has solid lifters , so that decreases the chance of a sticking lifter.I will pry on the flywheel to check for "play". I will not be able to remove the oil pan with the engine in the car. I have Mustang II ifs, using the factory Mustang crossmember and there is not enough clearance for pan removal. Thanks.

My 305V6 has solid lifters.

Actually, I just remembered that I didn't mention it before ,a few miles before the knock began , I put about a pint of alcohol in the tank because I thought I might have bought gas with water in it. The tank had about 12-13 gallons in it at the time.I have done the same before without any problems.

You're engine is drunk.

Stop wasting the booze on your ride.

That's for drinking


MBHD .

What did ya use? Bud Light? That'll cause a hiccup or two.

I removed the bolts and screws holding my oil pan on. It will drop quite a bit at the rear but won't quite come out from between the engine and the Mustang II crossmember. I did not have time to jack the engine up to get the pan out. I didn't think to turn the engine and see if that would allow it to drop out. The pan will drop enough that I could get my hand in the sump. There are no loose pieces in the pan. I could check the back four rods for excessive play. There is none.I can move the pan around enough to see up into the back cylinders. The piston skirts that I can see appear to be intact and I can see no cracks. How does a 235 type piston crack , usually. Should I be able to see the bad one from underneath once I get the pan down?Thanks.

I raised the engine and got the oil pan off. I checked all the rod bearings and they all look like new.I looked at all the pistons with each at the bottom of their travel and they all look fine. The engine was a reman engine when I got it. It must not have many miles since the reman because it looks very good and clean inside. I am now trying to decide what to do next. Off with the head , I suppose.

Is there still a possibility of a loose flywheel? Jay6155

Possible , I guess. The way I checked the flywheel was with a pry-bar and could not fell or hear any movement. I believe I'll check the harmonic balancer the same way.Thanks.

Mine did that after a long trip two weekends ago. I tried the cheap route thinking it might be crud in the lifters: Seafoam in the oil. Seems to have gone away.

I'll change the oil in a week or two. I don't drive the car often so it's not a huge rush.

I had Vthingie I rebuilt back before I got myself inline . . . It would tap at idle and lift throttle (even at high speeds like the freeway) . . . I rolled down the window and drove close to the Jersey barriers @60 - the tap echoed off the concrete when coasting. Press the accelerator and it would go quiet.

But a pry-bar wouldn't find the issue - the movement was much too subtle . . . and turned out to be a single fly wheel bolt that had backed out a half turn. I cranked the engine to check each of them. The loose one spun freely by hand (nut locked on the bolt both spinning). The resulting small space in between the fly wheel and torque converter was the source of the tap . . . we're talking feeler gauge here . . . not pry bar . . .

I'm still trying to find the knock in my engine. Since everything in the bottom end looked fine,I removed the head.Everything good there too. I now have the pistons and rods out. They are very clean, as is the rest of the engine. I can see no cracks or any other problems there. There was NO ridge at the top of the cylinders, another sign that the engine has low miles since being remanufactured. I have another set of pistons,rods, and rings that I might use when I reassemble the engine. I'm not sure what I will do next.

Lifters ok? Any crowing on them? Could have been a sticky lifter the cam was hitting. No pushrods bent?

Makes me wonder if the cam gear is walking off the end of cam and hitting the cover?

If you could not PIN point the knock Or it sounded as if it was at the front Or then at the rear IT IS THE CAM walking back and fourth.

This tool works great for finding where a noise is coming from.

It is very sensitive, 100X better than a long screw driver trick.

http://www.amazon.com/Lisle-52750-Stetho...cope+automotive

MBHD

OK, I found that the crankshaft has .013 endplay/ clearance. The manuals say .003-.009. I can move the crank back and forth and see the movement and hear a "clunk". The main bearings are still torqued. The rods are removed. Would .013 (.004 more than suggested) cause my noise, you think? I'm trying to decide the right way to remove the main bearing cap. It has the oil pick up tube & screen attached.Thanks.

Still looking for the problem. It seems that the clutch pedal, up or down, would have made a difference in the noise if the crank end-play was the cause, doesn't it? It didn't.

I have now removed the engine from the car and removed the transmission from the bellhousing. With the clutch removed , it seems that the flywheel bolts are all still tight. They have the locks still in place. The locks are the ones with tabs that are bent against the bolt heads. I have been told ,by guys who know more about engines than I do, that the .004 "extra" crank endplay is not uncommon, and would not cause noise. I have no idea what to do next. thanks.

If the dampener is not Lose and neither is the flywheel. I still say your cam is walking in the block front to back. And did you check the flywheel for wobble? Or rotational play. meaning clock
to counter clock wise?

Check all your timing gear teeth very closely for defects

There is no extra play in the camshaft and the timing gears look perfect. They are new.That's why it is frustrating that I can't find a fix for the problem.The engine is like new inside.It ran great with plenty of power. It had fantastic oil pressure.I intend to check every piece from the block up and reassemble it. Thanks and keep the suggestions coming please.

I have realized that just because the flywheel bolts were/are still locked does not mean that the bolts were tight enough when someone locked them last.I suppose that the engine has so few miles on it since the remanufacture the movement/knock could have taken until now to occur? I will unlock them and see if they will tighten more. There appears to be some loose, very fine red rust coming from between the crank and flywheel.After checking the tightness or lack of tightness I will remove the flywheel and look for any sign of movement.I intend to reassemble this engine checking and measuring all the parts as I go. Everything will be mic'ed and plastigaged. However for now I believe that I will use another engine I have. It is a '62 model 261 with 40,000 miles on it. It came out of a school bus. It has never been rebuilt and has very very little ridge in the cylinders,possibly only some carbon build up ridge. I have the head off and one piston out. I believe the piston came out with no ridge reaming.I will have to find one rod bolt for it as I have lost one. I've had it for over 15 years, saving it for a "special occasion". I will save the 235 for a spare, or another project.

Is the floating oil pump a noise possibility?
I've never built a stovebolt, but when I looked in Motors just now, it looks a lot like the Model A Ford in there. And when I read "floating oil pump", I remembered when I fixed a noisy Model A engine once like that - the oil system parts were banging around in there. Some jiggling fixed it - no more noise.

Same scenario - this "A" engine had just been rebuilt (not overrevved though). It purred like a kitten but made this clunking noise - it was down there in the oil system.

Just a thought, wish I could offer more. I hate mystery noises!

Oil pump doesn't appear to be the problem. Neither is the flywheel. Still searching.
How does this plan sound?
step 1- with bare block- check condition and position of cam bearings, hone cylinders(all expansion plugs will be replaced with brass plugs)
step 2- install crank, with new rear main seal,put existing main bearing shims back in place, check clearances with plasti-gage, install cam
step 3-install pistons and rods, checking clearances as with main bearings
step 4-install cyl head,lifters- back in the hole they came from,push rods,back where the came from, and rocker arm assemblies,side cover.
step 5-install flywheel and clutch
step 6-add externals, distributor, fuel pump, manifolds, water pump, balancer and alternator etc.
EVERY part will be cleaned and examined under bright lights, with at least on more pair of eyes and hands on.
Anything I'm missing? Thanks.

Just one more idea, happened to me on a big Ford -
Clanking noise, I thought it was crank hitting the oil pump shaft, or timing chain hitting something, loose rod, rods hitting oil pan, etc. Tore half the motor apart looking.

Turns out, a high spot on the damper was banging on the timing tab. Oh so slight but very scary noise, sounded internal. Simple fix. DUH. But no harm done except a couple wasted gaskets.

Thanks, There is no timing tab on these engines. The pointer is in the bellhousing with a "bb" in the flywheel.My problem may be something simple , but if so I have overlooked it, so far. I would love to find something , anything.

I've heard knocking sounds coming from valvetrain on big block chevies. Knock comes and goes as the pushrod spins so I'm sure it was valvetrain in my case.

May not apply to your engine.