Hey all, My Buick 263 inline is making a strange noise, and I'm thinking about it at work, so any ideas would help. It's a very faint "knocking" under acceleration. Doesn't sound sharp like a valve or rod. Doesn't make the noise when brake torquing in gear. Doesn't make the noise much at idle, but it sounds like it's coming from the fuel pump. The weird part is, I only hear it accelerating in drive INSIDE the car. So, is it possible that because I have the vacuum wipers, my fuel pump noise is being telegraphed inside the car? I'm just theorizing because I can rev the engine and let off quickly and it doesn't make any noise like a rod bearing might. Oil pressure's good. It's tough to find an engine noise when it only makes it when driving! Thanks for any input!
OK, let me rephrase...is it possible for a mechanical fuel pump to make more noise when accelerating because it has to fill the fuel bowl more quickly? It's the only significant noise I can hear with my stethoscope...
263s have really odd oiling systems. If you hear anything ticking or knocking, it's not a bad idea to consider it might be an oiling issue. If you have the time, it'd be worth you while to clean out your pushrods. The oiling system pressurizes the rocker arm shaft first, and then the oil flows down the pushrods to the lifters. If anything slows this flow down, inadequate oiling will happen somewhere else. If you clean out the pushrods (and maybe even the rocker shaft if you're feeling up to it) nothing bad can happen. Just make sure you know how to put it all back together. If you're convinced it's the fuel pump, pull it out and grease the end of it. If the noise goes away- even temporarily, you'll know what's causing it. ~Scotch~
Might also be the beginning of spark knock...if this is part throttle accel, remove and block vac advance line as a diagnostic experiment...if this is at full throttle, mark base of distrib for reference and retard a degree or two to see if this is the problem area.
Hey again, Bruce, it doesn't sound like spark knock...it's definitely a rhythmic noise...Scotch, I put new lifters in it, and I didn't check the rocker shaft, but the pushrods looked pretty clean and there's a ton of oil getting to the end of the rocker shaft when it's running...that's not to say it couldn't be better, but I was running it with the rocker cover off and it was throwing oil all over the place. (What a mess). I can hear the valves lightly under the hood though, but it doesn't seem like an abnormal amount of noise at all...It's weird, I've heard tons of noises from motors and this one has me stumped because I can barely hear it...I may try the fuel pump thing since that's the thing under the hood that I can hear....thanks for all your input...I realize it's a tough diagnosis without hearing it and I've done a crappy job explaining it!!!
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