Started my 340, IT KNOCKS! fresh rebuild HELP!!

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wyoduster

wyoduster

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OK , Again I pulled the engine tore it down "had the internals balanced" put it back together ..Fired up like a dream .. BUT I'm hearing a KNOCK in the engine. I haven't spent much time on timing it. Just heard this knock and after about a minute shut it down... ANY thoughts??? Did I do something wrong or miss something or is it just sounding that way because.....?????? Need help...????????
 
Sorry to hear that. Take a screwdriver or stethoscope and put it to the oil pan, valve covers, etc. to isolate the noise. Also put a timing light on it to isolate top end or bottom end noise. what is the oil pressure at? Did you prime the engine before firing it up? Lots of assembly lube?
 
redfastback said:
Sorry to hear that. Take a screwdriver or stethoscope and put it to the oil pan, valve covers, etc. to isolate the noise. Also put a timing light on it to isolate top end or bottom end noise. what is the oil pressure at? Did you prime the engine before firing it up? Lots of assembly lube?
Click to expand...

Yes plenty of lube when assembling it... No I didn't prime it... I just hated to run it hearing that.... But i'll go listen.
 
For what its worth, if you dont have a stethoscope I use the old trick of using an old wooden broom handle with both ends cut off flat for isolating where the noise/knock is coming from. Place it around the engine and put the other end up to your ear.
 
I'd take all the plugs out and turn the assembly first to see if the knock is present.
 
It sounds like its under the valve covers??
These are the same heads,pushrods,ect... just had to have crank balanced to the pistons...
Didn't prime it but this knock sounds intense....nothing like just a tick,tick...
 
4 speed tranny ... No its not the tap tap tap of a manifold leak. I did retard the timing seemed to help... But she still Hammers in there. Sounds like lifters with a screw driver in my ear on the valve covers, but why would they be clunking now?? same ones no changes.. Non adjustable.. stock?
oh man and I was hoping to puller out today..........
 
Is it a dull knock? And it is crank or camshaft speed?
 
When You Dropped The Distributor Back In Did It Go In Easy Or?? Could Be Off??a Tooth??just A Thouhgt?
 
Its a thuding hard knock... and I'm 98% sure the distributor is right. With timing light I got it close..so must be there...right?
 
I had something similar, windage tray was offset slightly, crank was hitting one side of the tray, sounded just like a rod knock, even increased with speed, as it would. Pulled the pan, removed the tray and could see 2 shiny spots where the crank was pounding, Bent the tray slightly, now all good.
Easy fix if that's the problem, good luck.
 
ground or pull the plug wires one by one. listen to see if the knock gets louder, if it does.. bad news.
if it dosn't then the prob. 99.9% sure its not crank/rod/piston related.
cheers.
 
What pistons did you use? deck heighth? Is it possible with the overbore piston is contacting the head at the edge?
 
I'm thinking along the lines of 360Z28, but the other way. When you pull each plug wire, listen to see if the noise goes away. Narrows it down to a particular cyl. If there are any bad parts on that cyl, the noise will go away (or ease up) when the wire is off. Wrist pin, mainly.

360Z28: What are you looking for when the sound gets louder?
 
SpeedThrills said:
I'm thinking along the lines of 360Z28, but the other way. When you pull each plug wire, listen to see if the noise goes away. Narrows it down to a particular cyl. If there are any bad parts on that cyl, the noise will go away (or ease up) when the wire is off. Wrist pin, mainly.

360Z28: What are you looking for when the sound gets louder?
Click to expand...
no load on the piston other then the compression stroke.
you can really hear the rod/pin noise when the cylinder dosn't fire on the power stroke.
cheers.
 
If something is knocking that hard in your engine I`d suggest not to run it again until you find out what`s going on inside it.
 
Sounds like a rod knock to me the way it is described. Yes one wire at a time to determine hole and if this is a rod. Maybe one bearing was placed in with tangs wrong or wrist pin issue ?

Man sorry that really sux!
 
my engine had a knock like that,turned out to be the non adjustable rocker arms hitting the valvecovers.1 rocker on each side hit the baffle? area.I guess the gasket flange was crushed or something.It had a very solid sounding knock,not a tinny knock like i would have expected.Took the covers off and all sounded good,so i went with some antiquie cal customs.Also,Forged pistons make a pretty serious knock sound until the engine warms up
 
I had the same problem once with fresh start up of a big block .I had installed new valve covers .One of the rocker arms was hitting a baffle.Just bent the baffle a little and all was fine.
 
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