bosworth Posted February 6, 2018 Report Share Posted February 6, 2018 (edited) Hi All; I thought I was finally finished with my 51 B3B, got it on the road, exterior and interior finished. Now that I am able to put some miles on it, I think that I am hearing a serious engine noise. I know very little about the engine, the only things that I have done involve the cooling system, rebuild of the ignition system and carburetor. At idle and when the engine is cold it sounds great! As quiet and smooth as any one of my new cars. When the engine is hot, 190 on the meter and running for at least 3 miles, it starts making a rapid clacking noise. I at first thought I had something loose vibrating on the engine or exhaust system. This noise goes away under load like acceleration or going up a grade, is most prominent when cruising along at 35 to 50 mph on level ground. I can cause the noise when parked by accelerating and then letting off of the throttle. I tried shorting out the plugs one at a time and the noise is reduced or eliminated when no. 1 is shorted out. My guess is a bad rod bearing on no. 1. I would appreciate your input and suggestions for further tests. It's kind of ironic, when I first got the truck it had a blown engine, the rod bearing had spun on no.1 and the piston skirt was cracked. I got a different donor engine that seemed to be perfect, quiet, no leaks, runs clean.... Is no.1 a standard problem? Thanks Bill Edited February 6, 2018 by bosworth Quote Link to comment Share on other sites More sharing options...
motterso Posted February 6, 2018 Report Share Posted February 6, 2018 Might just be valve noise. Try adjusting the valves and see what happens. Take the passenger side wheel off (safety stands please) and remove the inner fender panel and you'll be able to get in there pretty easily. While you're in there check for any broken springs, etc. Quote Link to comment Share on other sites More sharing options...
NiftyFifty Posted February 6, 2018 Report Share Posted February 6, 2018 Are you 100% that it’s engine noise and not drive line? Engine noise typically doesn’t go away, although I had a Massey tractor that the main bearings were shot in, and under load it actually quited. Could it be as easy as your timing is too far advanced and your hearing “pinging” which sounds really like a rapid knock Quote Link to comment Share on other sites More sharing options...
PT81Jan Posted February 6, 2018 Report Share Posted February 6, 2018 (edited) My engine had a clacking noise some month ago pretty similar to your description. Smooth / absolutely no noise while idling. I could cause this while accelerating and letting off the throttle, too. According to the noise I first was thinking of a bad piston pin bearing. But I noticed a low oil pressure while idling when the engine was hot at he same time. Before the noise I had a pretty good oil pressure at any rpm. A bad piston pin bearing would barely have an effect on the oil pressure in my opinion. A bad connecting rod bearing will for sure. Both the pin and conrod bearings can be checked when removing the oil pan. In my case it turned out to be damaged camshaft bearings which meant to completely disassemble the engine ... Did you notice any changes on the oil pressure of your engine ? If not, you maybe will be lucky in misfortune. Just my thoughts - Good luck ! Edited February 6, 2018 by PT81Jan Quote Link to comment Share on other sites More sharing options...
bosworth Posted February 7, 2018 Author Report Share Posted February 7, 2018 All good thoughts, I'll try to do some more testing and get some more experienced ears involved. I am not real crazy about the oil pressure. It runs about 40 lbs cold and drops down to 30 lbs at 30 or 40 mph when hot. Hot Idle pressure down to about 15 lbs.or a little less. The engine in my 48 Plymouth runs closer to 50 lbs, idle at about 30 lbs. According to the Plymouth service manual low oil pressure at idle is ok as long as the pressure increases with engine speed. it says that at 30 mph that the pressure should be 30 to 50 lbs. How did you determine that your engine had a bad cam bearing? I'm pretty sure that we can change the main and rod bearings without pulling the engine, but cam bearings would be a different matter. Thanks Bill Quote Link to comment Share on other sites More sharing options...
PT81Jan Posted February 7, 2018 Report Share Posted February 7, 2018 2 hours ago, bosworth said: ... How did you determine that your engine had a bad cam bearing? I'm pretty sure that we can change the main and rod bearings without pulling the engine, but cam bearings would be a different matter. Thanks Bill Since I could not determine the main, piston pin and connecting rod bearings as a source (from underneath with the oilpan removed) the only bearing(s) which could be the source were the cam bearings. Did pull and disassemble the engine then. I do not know another proper way to check them while the engine is installed. Quote Link to comment Share on other sites More sharing options...
wallytoo Posted February 7, 2018 Report Share Posted February 7, 2018 21 hours ago, bosworth said: I can cause the noise when parked by accelerating and then letting off of the throttle. I tried shorting out the plugs one at a time and the noise is reduced or eliminated when no. 1 is shorted out. My guess is a bad rod bearing on no. 1. 19 hours ago, 4mula-dlx said: Are you 100% that it’s engine noise and not drive line? i infer from the OP's post that he's fairly certain it isn't driveline noise. r-i-f. to the OP, the #1 rod bearing isn't the most common failure; seems to be the #2 that more commonly fails. but your symptoms do at least hint at rod bearing noise. Quote Link to comment Share on other sites More sharing options...
NiftyFifty Posted February 7, 2018 Report Share Posted February 7, 2018 2 hours ago, wallytoo said: i infer from the OP's post that he's fairly certain it isn't driveline noise. r-i-f. to the OP, the #1 rod bearing isn't the most common failure; seems to be the #2 that more commonly fails. but your symptoms do at least hint at rod bearing noise. Never make any assumptions when it comes to noises, they come from many spots and we don’t always have all of the information to diagnose from a quick post. I’m giving all ideas not denying it could be as simple as a bad bearing. Quote Link to comment Share on other sites More sharing options...
wallytoo Posted February 7, 2018 Report Share Posted February 7, 2018 rod bearing noise most certainly does go away. not audible at idle, increasingly audible with higher revs under light acceleration or cruising, almost disappears under heavy throttle application. Quote Link to comment Share on other sites More sharing options...
NiftyFifty Posted February 7, 2018 Report Share Posted February 7, 2018 1 hour ago, wallytoo said: rod bearing noise most certainly does go away. not audible at idle, increasingly audible with higher revs under light acceleration or cruising, almost disappears under heavy throttle application. Tell that to the three stooges impression my Massey gas engine was doing on my tractor...lots of knock knocking at idle, only went somewhat away under load, but once "hot" it came back with a force. Once the OP drops the oil pan, the guessing can most likely cease Quote Link to comment Share on other sites More sharing options...
bosworth Posted February 8, 2018 Author Report Share Posted February 8, 2018 I'm picking up a pan gasket at napa this morning and will get some plasti-gauge. I'll do a compression test and a combustion gas test first just to cover the bases. I'll post my findings once the pan is off. Thanks for your thoughts! Bill Quote Link to comment Share on other sites More sharing options...
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