Knock Knock..

Sorry, couldn't resist the catchy subject title. I have a knocking sound ONLY AT ITLE that if you hear it, you would say it was a rod knock. Here is the back ground; purchased this 70 B from gentleman who had completely restored it including the engine. Receipts show major rebuild kit from Brit-Tek and machine work including crank grind. When I purchased it, PO owner suggested it was the new SS Exhaust bumping against frame. I suspected different but decided to purchase anyway and take my chances. The car had only been shown up to this point and total milage after restoration was under 300 miles, but 12-15 years old. The PO was an engineer and his restoration work appears accurate and solid if less than perfect.

Now after 3000 miles the noise remains, oil pressure is fine, temp is fine. Valve lash is correct, timing is correct, oil is clean and compression is strong across all cylinders. I just returned from a 300+ mile trip, running at 4000-5000 RPM without a miss. However, the knock at idle seems more pronounced. The exhaust now seems louder (Moss Motors SS System, perhaps baffles have lossened?). My fear is that this REALLY is a Rod Knock. If so, I could loose the crank and block if not corrected. However, I don't understand how it could be, without showing other symptons.

I have tried to cancel out any secondary noise potential (air pump, alternator, water pump) by the old, "screw driver stethoscope" technique and with the exception of an oil pump, I don't think its ancillary component knock. What am I missing? I suspect if I drop the pan, I will see nothing. Could it be piston slap? If so, wouldn't this show as low compression? Anybody have similar experience?
Thanks in advance for responses!
S

Can you provide a read on your oil pressures, hot; cold; idle; at speed...

Yes; Fast idle (1,800-2,000 RPM with choke)= 60-65/Lbs (no noise when choke is on) Slow idle (800+/- RPM) 60-65/Lbs. Running speeds always stays about 60-70/Lbs.
Thanks Michael.
S

If you had the noise 3000 miles ago and it hasn't changed, it isn't a rod knock. If it was, it would have exacerbated and come undone.

Check under car for exhaust system banging against something.

Is your idle a bit rough?
I suspect other than a rod knock from reading the post.
RS

On several occasions I have seen leaks between the head and manifolds that sounds somewhat similar.

Leak test with carb spray. Takes 60 seconds.

Loose bolts.

Idle is a bit rough at times, yes. I cannot find any evidence or see exhaust hitting chassis. This was obviously my hope..!
Keep those cards and letters coming! I agree, you would think if a rod knock, it would have grenaded already.

Start with the easy stuff. I'd check for an exhaust leak first, especially around where the downtubes connect to the cast exhaust manifold. A leak there can sound like a knock. If your stainless system is a Moss TT then one should use the "flat" triangular shaped exhaust gaskets. Trying to get them to seal up with the stock doughnuts won't work (ask me how I know...). Also, those nuts have a habit of working loose. Also check where the manifolds bolt to the head. You may not be able to "catch" the exhaust leak, but look for evidence of it being there, black sooty stuff around the sealing surfaces where it is blowing out. May be able to put your hand around the flanges and 'feel" it, but be careful! I agree, if it were a rod, it most likely would have let go by now. As far as the exhaust banging around, the most likely place is in the back against the spring hangers or side of the gas tank, again depending on the exhaust.

Thanks Larry, that is a new idea. Unfortunately, when I tested it out, no apparent deviation. Any one ever seen either a distributor or oil pump offer similar sounds?
S

Sparky plugs in tight? If the air injection rail has been removed, check the plugs or bolts that cap off the ports by the spark plugs. If they loosten up you'll get a noise.

Hey Steve, great to hear that you had a good time on your drive. Here's couple of things that eliminated "Knock-Knock" sounds from my engine before. When I first got my RB, I had a large selection of sounds, from worn out suspension rubber bushings, to loose parts parts inside the cockpit. The engine was not exception to that either. One of the Knocking sounds I was getting got fixed when I replaced the Rod Bearings. Then after that, there was always another knocking sound that noone could figure out what it was. I got so used to it that I almost forgot about it. just couple of weeks ago, I had to replace the head gasket. After the gasket was replaced, the knocking was gone. Someone on the board suggested that the knocking could have been chamber gases escaping from one compartment to the other due to the damaged head gasket. at the same time I had to replace the exhaust gasket as well (needless to say, someone else suggested that the knocking could have been caused by a damaged exhaust gasket).
I am not suggesting that you start replacing all the gaskets but if you are experiencing erratic idle and uneven compression, it would be a good idea to look in that direction.

Here's that thread http://www.mgexperience.net/phorum/read.php?1,1970586

I don't think there is enough heavy metal in either the dizzy or oil pump to cause a deep knocking noise without having already failed. Here is a longshot - exhaust to steering column clearance. Could the pipes be banging on it at idle? There were shims under the motor mounts to shove things over a bit if needed, assuming the mount just isn't shot....

All great suggestions. Air rail still attached and fittings tight, plugs have been replaced and are tight. Clearance between steering shaft and header is OK. I think any headgasket problems would show with compression readings. The sound is very metallic and I suspect coming from right hand side of engine.
S

Right side of engine --
reminds me of the one I had at idle. The hard line from gas tank was bumping up against the frame where it starts to bend upward into engine bay. A slit piece of fuel hose fixed the problem.
RS

start pulling plug wires,...see if noise or pitch changes

Hey..@%$! What about timing chain?? Would a weak or bad tensioner allow slack and hence at idle..noise? I may need to repost this as a timing chain question. Thoughts?

Timing chains and tensioners seem to last forever and seldom do weird things. However, there is a chance... can the noise be isolated to the front of the engine? Someone posted up a while back about a waterpump going out that made a knocking noise, but I'd think one could trace that to the front pretty easy. May be worth a check, as well as alternator and any belt driven stuff out front if that's the case.... Not much on the right (pass) side of the motor to make a knock :S

Another long shot is the harmonic balancer bolt comming loose. Again, someone posted up about a wierd knock and found out that's what it was...

Checked harmonic balancer, its tight with locking washer intact. So, even if the PO failed to unlock the new tensioner, I gather from researching previous discussions regarding the tensioners, my symptom would be unusual. I did also check the cover and balancer with my "back yard stethoscope". I cannot hear a distinct knock/tap from this area.
Mystery continues.

Try using a length of garden hose placed to your ear and try to localize the knock. Also, did PO retorque head after say 500 mi. after rebuild? Com. ck. would rule out head gasket. We all know diagnosing the culprit is usually harder than the fix.

Thanks Bruce, I torqued head when I set valves and did compression check. I have been using similar to your garden hose trick. The best I can pin point is the knock is most pronounced on right hand side of block, lower rear and at low idle only. Any revs and it is gone. I suspect it could even be a sticking lifter? I think a compression check would catch that as well. What other lifter maladies might be in play?
S

Might be a detonation problem of sorts, sticky/burnt valve. #2&3 share the same exhaust port,thus run hotter. The area you discribe would be spot on. Setting these two exhaust valves @ 17 rather than 15 allows for more heat dissipation.Did you ck.for a weak spring? Did you torque head 15,30,47# in sequence? Sorry if I'm asking "duh" questions,you may be a better mech.than me. Diagnosing a problem can be a:devil: Bitch.Anyway,let us know when you run the culprit down.Good luck.

wrist pin bushimg? easy to overlook when redoing the earlier 5 main engines. will the noise [coming, as you say, from right rear down low] go away when you pull the plug wire from cyl 3 or 4?

Have you checked for a possibly loose flywheel? With the power pulses coming every 180 degrees, it would have the flywheel speeding up and slowing down. Higher revs would keep the flywheel in one position, relatively.

Hey I appreciate all your replies. Interesting ideas; No change (in noise) with any spark plug lead removal. Have not checked for weak spring..not sure how to do that sans removal. Would that cause symptom at idle only..Hmm.

Wrist Pin has had my interest from get go. But could not get my head around why only at idle? The pistons came From Brit-Tek in their major rebuild kit (according to my file of receipts) and according to their literature, pistons and pins are included. I would assume this would include matching bushings, but I don't know for certain. Are you suggesting that the rod to piston bushings may have not been matched? If so, it could indeed cause similar symptoms.

The flywheel theory is also new twist. Has anyone ever had this happen? Speaking of Twist, I though one of John Twist U-Tube videos may have hit the problem spot on; harmonic balancer "woodruff key way" sloppy. But all is tight with the balancer. The flywheel however, I have no idea at this point. Another unknown..Hmm

Thanks everybody for your ideas, I appreciate them all.
S

wrist pin bushes would NOT come with pin fitted pistons.

So if we hypothesize that the bushing/s was/were left out (likely all would have been) that it would make quite a bit of racket and likely at higher revs as well as idle. Although candidly, I can't say I have ever heard of it happening before.
S

No kidding. And in 3000 miles you would have most likely launched a piston free of the rod.

Steve ... my friend and I are trying to find the source of a mystery knock in his motor as well. It's a 1977 18V motor. We've removed the plug wires one by one, changed the water pump, removed the alternator belt and ran motor, replaced intake/exhaust gasket, removed and reinstalled the exhaust system, removed the exhaust hanger on transmission, oil pump has been rebuilt, new rod bearings installed, etc... sound is coming from back of motor on the RH side as well.

Compression checks are good, engine did not idle well and thus the search over the winter months. We did discover a badly worn camshaft. The number 2, 6, and 7 lobes were worn so we replaced the cam, lifters, push rods and the rocker arm adjusting stems as well as new timing chain and gears Upon startup and break-in ... nice and quiet. After about 250-miles the sound is returning. Original theory was the push rods were worn into the spherical balls, sticking and hammering the lifter to the cam lobes. Don't know what to think now.

Tonight we ran the engine with the valve cover removed and listened to each rocker arm with a stethoscope. They all sound the same, no sticking valves, no hammering through the push rods.

Car has been knocking since he bought it 7-8 years now. I'm thinking wrist pins or connecting rod bushings as well since that's about all that's left to check. Car runs better then ever, tuned the weber carb in over the weekend and she starts up and idles's great. Run's like a top.

Any and all suggestions welcome.

Steve you didn't say you pulled one plug wire at a time?

Been there done that one of the wrist pin snap rings popped out which allowed the wrist pin to have some fun banging up against the cylinder wall. Removing a plug wire located the area quickly.

Good luck..I hope it is nothing serious.

I find it interesting that you say it goes away when you choke the carb. Did you try a higher octane gasoline?

You have the Weber, it is possible that your idle jets are too small, not enough gas in the mixture will have your car running so lean it will knock like a 1980 Ford 4 truck cylinder going up a hill.

Michael ... thanks for your reply. We did consider the fuel grade and just switched to Premium fuel. Neither of us are familiar with the Weber carb to know the size of the idle jet. We do have a book on the Weber Carbs and will have to research.

We did install a new cam, lifters and push rods in March and the knock seemed to go away when we first ran it but now seems to be coming back. Ignition timing set at 13-degress BTDC. Maybe we need to tweek the timing a bit and investigate the carb jets to fine tune the knock out.

1980 Ford 4-cyl going up a hill is right on for the description.

and so, when you dropped the pan, and replaced the rod bearings, did you by chance take the opportunity to at least check the 3 mains that are lookatable?

John ... rod bearing replacement was done at University Motors. Not sure if they inspected the main bearings or not. I presume they did. They also rebuilt the oil pump and changed the timing chain in search of the mystery knock.

Car currently runs great and has good oil pressure 60-70 lbs.

If you remember the sound of a heat riser rattle on an exhaust system ... that's kind of what this knock is only from in the motor. Think we'll look into those idle jets Michael suggested, maybe this is a fuel related ping at idle.

i'd call the 'ol heat riser sound more of a "rattle" unrelated to crank or cam rpm. i presume the sound your car is making is directly related to rpm? if not its likely not in the rotating bits in the engine. i think you said its coming from the right rear side of the lump, if so, theres nothing there to cause a noise other than a rattle in the starter, perhaps the starter pinion occasionally touching the ring gear?

John ... agree. My description of the heat riser was off track. It's a knock. University Motors could not come up with a solution either. Think we will investigate the jetting of the Weber next. Perhaps it's spark knock, pre-ignition of some sort.

Appreciate everyone's inpurt. The mystery sound remains at idle and not detectable when running down the road going through the gears. The car runs great, idles good, good oil pressure but still has a rattle, knock, ping whatever ... at idle we're determined to find and fix.

We will find the solution and post the results.

Thanks again everyone for sharing your thoughts.

Hey guys, sorry for my late reply but been on vacation. After most obvious diagnosing techniques I believe my noise most likely is timing chain. Not motivated enough to pull apart yet but once I do I will report. I suspect PO did not release tensioner when he replaced it. Again, once any load is experienced (choke or higher idle) it is gone.
Thanks appreciate all ideas and experience.

Steve,

While it's possible that your noise is related to your timing chain, it is extremely unlikely that the problem is caused by a tensioner that was not released during assembly. The steps holding the tensioner restrained are small and sensitive, and even if the builder had not released it, engine vibration surely would have shaken it loose right after start-up. If your gut tells you your noise is in that vicinity, I'd look very closely at the balancer to assure that it's not loose or separated...

Dick

Does the noise sound like this?

http://www.youtube.com/watch?v=qlRFQ0-ELRI