New engine, Knocking?

[JWadeSchutt]

I just rebuilt my 82 with the mods listed below and i have about 100 miles on it so far but it has a knocking sound really bad when it is under load, it doesn't do it when in neutral. i have heard about piston slap with forged pistons because they expand, but do you think this is it, i dont want to be driving it around too much with something wrong.

 

[Twisted306]

dose it sound like a rod knocking or a rocker knock

 

[86bluecobra]

Can you get the sound recorded for us to listen to? What were your bearing tolerences? Did you plastic gauge evrything to make sure it was within spec?

 

[JWadeSchutt]

yes all of it was plastiguaged

 

[JWadeSchutt]

its not really like a ticking but more of a deep knock and i can hear 4 of them in a row.

 

[JWadeSchutt]

its like maybe one bank of them are doing it could it be firing order or bad wires?

 

[86bluecobra]

It could be an exhaust leak???

 

[cobradvm]

It could be an exhaust leak???

x2 - you may just have a leak at the header - try pulling plug wires one at a time, and see if you can isolate it to one cylinder. I had an exhaust leak, and I was convinced it was something seriously wrong - a real metal on metal sound - turned out to be a crappy BBK header gasket.

 

[JWadeSchutt]

ok so i have an update. i found that the noise was exhaust leak and backfiring. i went ahead and got new coil modulator and checked the plugs and got new cap and rotor. however i am still having the same problem still. i just figured that it was an electrical misfire and the old modulator was the problem. any suggestions now?

 

[302RollinHard]

Simple things first.
make sure you have the plug wires on right.
and make sure the flange surface on the header is flat. If it isn't likely you will get the thing to seal up.

 

[JWadeSchutt]

k well the wires are right and the mani is sealed up nice. but still backfire.

 

[Paul Perreca]

check your timing - make sure its not way off because my timing was WAY off and i had that same type of noise under "heavy load" as soon as i adjusted the timing correctly it was gone and less embarressing - this was also after a fresh rebuild

 

[JWadeSchutt]

today after taking some thing apart i find collapsed lifters and possibly a flat cam. what could cause this? i called the company and the springs are right for the cam. but im not sure if they are trying to get out of buying me a new cam. everytime it is cranked there is soo much pressure that the lifters fall back down after a couple seconds.

 

[krallman]

you could have wiped out a cam lobe. Did you break in the cam properly. What type of cam are you running. I hear comp cams are bad about it if you dont break it in to a t.

 

[JWadeSchutt]

its a lunati cam .522 int. .538 ex. i ran it exactly how the directions from the manufacturers notes said. the problem is that the performance shop i went to gave me too strong of springs and i think thats what caused it. but to cover themselves they are saying that the oil i used made the cam go flat. whats up with that? is this something that is true or am i getting fed full of BS?

 

[izzleon]

prime

did u prime the engine before starting it? what type of valve train u using?

 

[JWadeSchutt]

ya i primed it just before startup. lunati cam, stock rockers, comp magnum pushrods, lunati lifters, comp springs, comp timing chain