Had a strange hollow rap that seemed to come from the #1 or #3 cylinder at idle. Sound stopped when I pulled #3 spark plug wire... thought valves,rebuilt heads... rapping ping still there. replaced cam, lifters,timing set...sound still there... removed pan to check bearings and wrist pins nothing wrong found.I kept looking and saw a wear mark on the rear counter balance where it was hitting the oil pump at the driven gear shaft...looked like the oil pump pin had worked up and was hitting the counterbalance...Ah ha problem found... I thought. long story, I rebuilt the entire motor and replaced the oil pump, only to have the same hollow rapping at idle as before... No way could the crank move to hit the oil pump,must be oil pump moving to hit crank checked the bolt holes on the old pump they were 18 to 20 thou. oblong! could a new pump holes be oblong too? I'm thinking the bolts must be worn too, allowing the pump to turn into the crank. I guess I'll find out tomorrow. Anybody hear of this kind of problem before? I'm thinking of making a spacer to move the pump down and away. Good idea?
Well... I pulled the new oil pump today no sign of interference with the crank, so I ground 1/8th off the high spot and doubled the gasket. put back together, started her up "her" being a '29 ford hiboy, dag nab it, same ping, rap, whistle as before... still goes away when I pull#3 plug wire or rev up the motor. I thought the hack job my buddy did on the lakester pipes might be the source of the sound, pulled them off and started her up same crappy sound. I can change the timing to get the sound to go away kinda but it's so retarded that it barely runs. The motor was a junk yard pull and was untouched when I put it in ,only change was new plugs, wires and a new Eldebrock carb.It still runs fantastic just this damn hollow rap sound. Oh yea I'm using a stethoscope to pin point the noise I cannot find any place on the motor that would be the source of this racket. I'm thinking wrist pin again... how could my builder miss a bad wrist pin after reconing the rods? I don't honestly know what to do next... Any Idea's
Thanx for the reply. No marks on pistons that would raise concern... but then I chose not to replace them when It was reringed, When the builder checked the bores there was no measureable wear or taper, so we decided to rering and not go 30 over. Before it started this noise, before it was rebuilt, we did do quite a few huge burn-offs just to get the feel of the car, it ran fantastic for a 44 yr old motor, still does.. but the noise is too embarassing at the stop light to take out on the street. I'll pull the pan again and look up at skirt, could I check skirt with feeler gauge? any thanx again for replying
The 401 core I'm building right now had the same problem with the oil pump gear pin. It also had a bent pushrod so I tour it down to find the pin had came up and hit the last crank counter balance as yours. Looks like it just nicked the crank and looks like motor was shut down fairly quick. Didn’t seem to do any other damage other than the pump. I will be sure to mention this to my machinist to watch for problems. Keep use informed.
thanx again for the interest and replies... no dents in the pan. the piston slap or bad wrist pin is about my last hope... I'm not looking forward to another tear down but the snow is still deep here and I've got nothing but time. but would like to get the interior finished, I'd post a pic some time, oh and no that is not my car at the Spokane show, I'm gonna stay in gray primer,'60s Ansen wheels, 33's in the back, lakesters w/ 60's Thrush side pipes, boat steering wheel, it sits up high enough to crawl under and I grin ear to ear when it's on the road.
I had a similar problem on a 67 Mustang a few years ago. Did everything. A different torque converter cured the problem. I don't know anything about Buicks, but it may be worth changing out. Ron
no luck with my 401 rapping noise..this winter hoping it was piston slap I pulled #3 piston and had my builder knurl the piston that added 6 thou. to skirt, dropped the piston back in... same racket as before, so I pulled the engine and had it bored .040 over. now the entire engine has been gone thru, I also rebuilt the rocker arms with new tips and shafts. same pinging rap at idle and now the noise is there at while I'm tooling around at street speeds. found no place on the engine to track the noise except on the #3 exhaust header, I'm gonna track down another set of heads and try them maybe mine are cracked internally I don't know. Anyone had a problem like this or care to guess?
Rap, ping, whistle. What does it closely resemble? And where does the sound seem to be the loudest, head area or lower block? Maybe you can make a video with audio and put up on youtube, then post the link so that we can listen to the sound.
Well I'm kinda embarassed after 10 months and about 1700 bucks I finally found the source of the god awful noise I've been chasing thanks to d2 willys Rap, ping, WHISTLE comment. The sound always kinda sounded like a metallic whistle so I was thinking the head might be cracked inside... got looking at the heads which are the california smog heads, the ones with the plugs in the exhaust ports, when I got the motor it had a 1 1/2" regular bolt in a plug hole that I changed with a regular allen head plug just to clean it up a little and never thought to pull one of the other plugs to see what it looked like (big,expensive,mistake) the other plugs have a 3/4" long pin/plug about 1/4" around beyond the threads. anyway about a half hour with a 1/2" bolt and a grinder I made a pin/plug to match the original and it works and sounds beautiful!!!! Thanks to those on this forum for their input and that one word (Whistle) I was finally able to sort this mystery out. Thanx
Good deal! Too bad you put all that money into it. But sometimes it comes down to that. Glad to hear all is well now.
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