Engine Knock

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joe
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Engine Knock

#1

Post by joe »

Hello List.

I bought a 1948 Pan a few weeks ago and the engine knocking sound has been driving me nuts. When you start it up it is noisy (it has solid lifters but I think its noisier than that) but what is really annoying is it gets louder when warmed up. It just takes a few minutes to reach this point. At first I thought it was piston slap but I think I read that piston slap gets quiter as the engine warms. It does not get a lot louder with engine RPM like I think a lower end would. I believe it's coming mostly from the front Cylinder.

Before I take the front cylinder down does anyone have a guess as to what the offender is? Maybe wrist pin slop??

Thanks Joe



1951 adam
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Re: Engine Knock

#2

Post by 1951 adam »

Joe ,
If it was me I would at least pull the cylinders and check it out, if it's that loud , you should be able to see the problem . Verify bottom end at that time. And pistons , cylinders ,, ect.
Adam

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Re: Engine Knock

#3

Post by blewcrab »

could it possibly be the rocker arms hitting the pans ?

tomfiii
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Re: Engine Knock

#4

Post by tomfiii »

Hope it's not a noisy head.

joe
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Re: Engine Knock

#5

Post by joe »

The vales are not hittng the pans (anymore). I took care of that already. But since they were hitting at one point it couldn't done the valve guides any favors.

Noisy heads? I wish! that would be a realatively easy fix. If its the wrist pin bushing its going to be a bear to fix without removing and splitting the flywheels. If I can't find anything in the front cylinder I will pull the can cover off, perhaps something in lower valve train.

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Re: Engine Knock

#6

Post by 1951 adam »

Joe if it's the wrist pin bushing they can be pressed out without splitting the cases.
Adam

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Re: Engine Knock

#7

Post by tomfiii »

A noisy head was on a bike with bottom end reassembled twice and heads reassembled and noise coming from intake valve area and not hitting pan,it has had several people look at and listen to. Noticed different sound when manually rotating rockers to this intake. Ended up removing and selling off.

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Re: Engine Knock

#8

Post by VPH-D »

You could pop the primary cover to check for too much endplay on the flywheels. Use a rubber mallet, or a block of wood to knock the motor sprocket in, then carefully try to pry the sprocket out away from the cases. Anything more than a few thousands of an inch [don't know the number offhand] endplay is bad news.
VPH-D

joe
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Re: Engine Knock

#9

Post by joe »

Thanks for all the replies guys, it will be interesting to figure this out and I look forward to your comments as I tear into it.

My point about the lower valve gear train was suggesting a loose gear mesh of the pinion and cam gears. It of course would not explain the knocking but may account for the overall noisy valve train.

Joe

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Re: Engine Knock

#10

Post by 58flh »

-Joe---All I run are solids.I find poping the tubes & checking adj. as often as oil changes.What takes the punishing is the rollers!--I have had ones start loud & if it dont go away when hot & if it follows the engine rpms--Its always been a roller!--Your doing the right thing by pulling everything off & look it over as you know nothing about the newly aquired toy!---Any number of things can be at risk.Running it will olny prove in more cash & work to fix.Taking it apart as you said is best!--good-luck----Richie

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Re: Engine Knock

#11

Post by Hogboy5-Too »

Before taking the motor apart I would suggest taking a length of heater hose and listen while moving it around the motor. It's a quite accurate way to isolate a noise. I once spent a considerable time fussing about with what I thought was valve train noise until I tried this trick and quickly found it was coming from the generator. The drive gear had a tooth broken off.

Good luck.

3711
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Re: Engine Knock

#12

Post by 3711 »

joe,
I had a piston cracked near the pin hole in it (was noisy for quite a while but I had NO idea what the noise was) which finally broke out on a trip out of state. If you pull your jugs,wiggle the pistons on the rods to check for play....walt...tulsa,ok

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Re: Engine Knock

#13

Post by panhead_kicker »

Check the tightness of the engine sprocket.

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