ive got a 68 polara 500 with a 225(original),at idle it has a bit of a bottom end knock,oil pressure has gotten a little lower since i started driving it last summer.but if i give it a bit of rpm it runs quieter.a friend of mine runs these motors in his farm equiptment,he told me that i should change the spring in the oil pump to boost pressure,this should make it run quiter at idle.(he has experienced the same problem)does this sound right?the motor is still strong with about 80000miles on it.

If it was running fine before, but knocking now, increasing oil pressure with the spring or by using thicker oil may help but its a bandaid to help you limp along not a fix. I know the valve can get gummed up / stuck and cleaning it restores pressure if thats the case -
http://www.slantsix.org/forum/viewtopic.php?t=21641
http://www.slantsix.org/forum/viewtopic.php?t=11468

How much is "a little lower" oil pressure and are you measuring with an electric or manual gauge?

What clues do you have that it is bottom end as opposed to anything else?

You have to be careful here. 80k is nothing for a slant in proper working order. If the bearings are on their way out and you keep running it you may of just turned your rebuildable core into an unrebuildable core.

It might be piston slap....and not much can be done (aside from a rebuild)....but not much needs to be done either.....

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Yeah....Im the one who destroyed this rare, vintage automobile.....

its a mechanical oil gauge and i think its the bottom end because there is a fair bit of smoke coming out of the pcv hose when i disconnect it.the top end was just changed with a recent rebuild. i ran 15w40 in it and i think it kind of made it quieter.i definitly know its the bottom end,its got that dead knock sound,but why does it go away with rpm?

The smoke doesn't mean bottom end. Like Sandy said might be piston slap and the smoke could be coming from the loose piston(s) Dose this motor get run regularly to boil the moister out of it? Maybe smoke is really steam.

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

I've got the same knock. I only have the oil idiot light but it's not flickering at idle. I rebuilt the engine only replacing rings, bearings, and gaskets. I'm thinking it's piston slap (you get what you pay for). I took the 3.23 geared Valiant, top down, up to 90 mph on the level interstate and it stayed together. I'm not worrying about it.

Oh, and that's about the top speed. Like hitting a brick wall. 75, 80 ,85, 90, 90, 90. That's enough for the old BBS 1 barrel.

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'63 Valiant V200 Convertible
225 Aluminum Block

Before we start talking about solutions, we need to figure out what the actual problem is. Could be as simple as a knocking fuel pump!

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

i just replaced everything in the fuel system(pump,carb,lines)still knocks.the car is a daily driver so the smoke is actual oil burning.i mean its not blinding but i know its there.would a compression check tell anything about piston slap and why doesnt it do it at higher rpm.come to think of it i did hear some rattling when i go up the one hill intown at 80km into the throttle 1/2-3/4 .whats a remedy.....cheap remedy.i can teardown motors no problem but am limited when it comes to machine work.what causes piston slap and can i just replace those parts without a major rebuild?