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Am I killing this thing by letting it rev up......?


ZondaC12
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Alright first of all I dont know why I did ask this oh maybe LAST YEAR or something but I guess it can't be too late if the barge is still goin alright!

As I think almost everyone knows by now, I have that tapping noise under load at low rpm's, that people have said is either piston pins or maybe valvetrain/lifters.

So what I do, is I rev it up to much higher rpms in 1st and 2nd gear. I shift into 2nd at maybe 15 mph, and into 3rd at 30 maybe 32 33 mph. So this puts the shifts at roughly 2800-3000 rpm I think. At all times with this car I open the throttle very little, or at least compared with the speed its currently moving. I dont accelerate hard, I dont "beat on the car". But I do this so that when the next gear comes, the car isn't under load at low rpm, making the tapping noise.

Which is worse for the car? If the piston pins are "bad" that means what? Do the pistons wear first or the pins? The pin is worn away? Just needs to be replaced? So more banging around would hog out the piston pin hole and ruin it?

How about the lifters? I've never really known WHAT a "bad lifter" is, never thought to ask I guess, though its a term thrown around like a hot potato. What has occurred in this case? Is the cam surface getting ruined? Quickly/slowly? I have had the oil pan down before, and the lobes I believe all looked nice and shiny, and felt smooth and slippery too.

My instincts just seem to tell me that when you're hearing that kind of a noise, that it's wearing on <span style="font-weight: bold">some</span>thing more than it should when you hear it. Is this the equivalent of "an old wive's tale" or am I correct?

It's funny. I'm very fastidious in being careful with this car, though I find I keep up with traffic better and get to cruising sooner if I use the method I described. The thing really does get up and go if allowed into the higher rpm range, and often you can get out into heavy fast traffic if you really need to in a pinch. I do try to avoid it as much as possible, and will even more, and pay them no attention and simply take all day to get to 40 mph if thats what any of you think it's what I need to do.

Is it hard to replace a piston pin? How much do they go for? Can I get em from Bob's/CARS/Kanters/elsewhere? Im gonna have the head off this winter to check on the headgasket, I'd consider it. Just need a piston ring compressor right?

It would just be nice not to have to worry about loading the engine. As I said, I let it wind up, but I keep throttle pressure VERY light, so as not to hear the noise. It's not that the noise bothers me, its what the noise <span style="font-weight: bold">means</span> that bothers me.

Just to make it clear (though I think I have beaten this dead horse many a time too!) I would like to run this engine as long as possible, un-torn into. I just think that would be really neat. It has 86000 miles on it now. Could it make it to 100k alive and kickin'? 110? 120? The second I get a bearing knock, shows OVER. Yanked and sent to a rebuilder, or if thats while Im still a poor college student or something, it simply won't see the road anymore until. But if it's still good to go I want it to stay that way.

Thanks as always

Paul aka "the sponge" (though sometimes an excessively drippy one, we ALL forget stuff!)

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Some Buicks had a reputation of wrist pin noise. However you only get that noise when you take your foot off the accelerator and let the engine slow you down. You probably have tappet (solid lifter noise). With a little tappet noise your valves will probably last forever. If you adjust them right the will last many many thousands of miles. If they are too tight and/or you carb is set too lean you will probably burn out your 1 and 8 exhaust valve. Setting the tappets is easy. Just follow the directions in your shop manual.

My 53 had wrist pin noise from 39,000 miles to nearly 100,000 miles. I overhauled it (pistons, pins, rings, bearings and valves) and 20,000 miles later the wrist pin noise was back.

Interestingly enough I always started in second gear (as the owners manual suggested) and usually up shifted about 10 mph. The exhaust note when I did this was the most melodious moan you ever hears. If I was in a hurry (turning onto a highway or showing off to my friends with F***s) I would start in second and shift to high about 80 or 85 mph. After I overhauled the enging it was nearly 15,000 miles before the engine loosened up enough to hit 80 mph in high.

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This may be a dumb question but here goes. Is it possible that you have a carbon buildup in the cylinders that is actually making a higher compression ratio and as a result you are hearing a knock on load or a "ping". Have you tried using a higher octane gas? I too am very hesitant on taking down an original engine. My 65 has 70,000 on it and has never been down. Hope this helps.

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Yes it is possible, but I don't know if it holds true for your engine. If ya change a variable (higher octane) and the noise goes away you know to look for things that cause a "ping" rather than internal engine parts. Timing, defective advance, etc. can all cause a ping and are a heck of a lot cheaper than ripping down an engine.

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If you can cause it at a given RPM (particularly lower RPMs) by getting on the throttle, then it may be preignition "rattle" or "ping". As the names imply, these are sorta hi pitch sounds, not really like a "tick" or "click". Pretty easy to tell if you know what your listening for, but hard to describe unfortunately. Do you hear it at idle or just under load? Does it get louder or quieter when you increase RPMs without load?

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I think im gonna need to make a video. Youre right it is tough to describe. It seems like a lifter or something tapping to me because (shoulda mentioned this) at a cold start at idle it does it intermittently, like maybe youll hear one tap every 1 or 2 seconds. Revving it up slowly sitting still makes it tap once or twice, wack it real fast it comes up to speed without any noise. Warmed up no matter how you rev it it doesnt tap. Then its just under load at lower rpms. Sounds to me like the typical oil-not-there-yet deal. I think I'll make a video this weekend, post it up on youtube or something and that will tell the tale the best, especially as to the tone of the sound. It is metallic sounding, not like marbles. Like hitting a hammer against a solid thick block of steel I guess....I dont know let me put the video up I could be describing it totally wrong. It even changes too.....when its cold at idle its more hollow-sounding (like hitting the same hammer against a frame member maybe), warmed up its more like the first description. crazy.gif

Also I dont know if this is usually the case with these kinds of noises or if I incorrectly assumed that, but it occurs "with" the pulsing of the exhaust. As in, mainly with 8 cylinder engines you hear em idling there is that one pulse, much louder than the beats from the other cylinders, "buh-buh-buh-buh-buh" say that out loud, Im sure you all know what I mean if you've ever heard a loud v8-powered car before, it happens right in step with that.

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I wonder if you are describing two different sounds? A pronounced "out of beat" note in the exhaust is often a miss, exhaust valve, or weak cylinder. I assume you've adjusted the valves and done a compression check? I don't have much experience with straight eights, but the one I did play with had chronic exhaust leak problems. That can make a sharp sound, particularly under load, and can change from cold to hot.

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Ugh yeah I guess it came across like that. I mean a normal, perfect-running engine. Theres obviously way more pulses that what I described, its 8 cylinders, the whole thing turning somewhere between 500 and 100 rpm, but theres a pulsing you notice thats much slower. maybe its cause I'm a kid and my hearing is superhuman or something but it's unmistakable. It's slowest with v8s, significantly faster with v6's, and with a 4 banger...well theres like none haha grin.gif

The engine does not miss or run rough it is very smooth. Perhaps this isn't significant, just an observation. Anything like that I go nuts, I guess I'm OCD or something but I notice that kind of stuff QUICK haha.

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Sure, they all have a rhythm to them. When you said it was synchonized, made me wonder. My advice, fo what it's worth, would be drive and get accustomed to it. Don't worry about every little click and rattle it makes. It's a 70 year old motor, unless it's really making some noise, it's probably nothing to worry about. If it changes or starts making a new noise, then you should pay attention. Nice car by the way, we've got a '37 bus coupe.

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Tapping under load can also be an exhaust leak. It sounds just like a tapping valve train and occurs under many of the same conditions. These long Buick straight eight manifolds are prone to warpage and leaking, so I'd also be sure to check there. While it's running, move your fingers CAREFULLY around all the exhaust ports to see if you can feel exhaust gas leaking out.

Just a thought. Hope it helps.

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Oh theres an exhaust leak alright, on one of the "pairs" of tubes on the exhaust manifold. The one thats second-to-furthest-back actually. I know what that sounds like. This is different.

And as an addition...Im convinced its a lifter. I had it outside last night for a couple hours while I worked on ym other car in the garage (26 degrees out!!!) So when I went to move it in, the tapping was significantly louder and much more frequent. Just needed to move the car in, but I just felt that running it for only a few seconds like that wouldnt be good, probably get condensation in the exhaust, oil too, wouldnt warm up enough to burn it off, so I let it warm up a couple minutes then took a short drive around town, just like 10 minutes. And in comparison once it warmed up the noise was very quiet and even under a little bit of load wasn't always there, at least not prominently.

Next thing on the list...gotta unbolt the manifold, and get some gasket paper to fill in the gap at that one pair of ports. I think some exhaust fumes tend to come into the interior through the toeboard, where the holes for the pedals are, so I always crack the cowl vent and a window a little.

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