sounds like a knock please help if can

[dquicks78mc]

i have an issue and hoping someone with a more knowledge of engines can help me out. first off i have a 78 monte carlo with a 350/350 for drive train. I recently rebuilt with and added a set of heads i bought off a somewhat trusty individual. the head is the same as the ones i pulled off but have been milled and screw in studs/guide plates put on not sure on spring size or valve length. i have roller rockers and stock push rods i plan on doing a check for geometry of rods tomorrow. have went through and adjusted rockers 3-4 times even while engine running just to make sure set properly. when the timing is spot on it starts right up and runs like a champ in idle no matter rpms. when i put it in drive and put a load on it usually above 1800 rpms it sounds like the rockers are chattering. i was told by a couple people that it could possibly be spark knock and that i need to retard timing to allow for vacuum advance to do job so i did. it quiets the knock quite a bit but doesnt really get rid of it but you feel it in the performance. i have a msd street fire hei distributer in case you need to know. so my question is if any one has any idea as to what can cause this can pushrods being to long or short cause a knock i really dont want to rebuild again if i screw it up driving it like it is please give advice thank you

 

[Dennyboy]

get a stethoscope put it on your oil pan. if it sounds like someones pounding with a hammer it is most likely a rod knock. Did this happen randomly? did it start right after the rebuild? whats your oil pressure cold and hot? also make sure it's not and exhaust leak by the block.

Is it more of chatter or is it a solid knock?

 

[dquicks78mc]

its more of a chatter then a knock i suppose it literally sounds like a loose rocker but i dont honestly think ive ever heard a rod knocking before so i couldnt really tell you

 

[pacman350]

make sure your transmission is top off and torque converter full because if the torque converter is low it will make a chattering sound that really sounds like the rocker arms. if your standing over the engine with the hood up it actually sounds like its coming from the top but put your ear down behind the front tire you can hear it. I hope this helps.

 

[pacman350]

make sure your transmission is top off and torque converter full because if the torque converter is low it will make a chattering sound that really sounds like the rocker arms. if your standing over the engine with the hood up it actually sounds like its coming from the top but put your ear down behind the front tire you can hear it. I hope this helps.

saturday night my buddy install a th 400 in his 83 buick park avenue and it made that same noise until it was completely topped off with fluid.

 

[CHRIS.O]

Rod knocks are unmistakeable from a chattering rocker in my experience. However I have heard things that sound like a rod knock that weren't. One cutlass I had started to rod knock, atleast that is what I thought it was. Turned out to be a loose torque converter bolt. Tightened it up and it went away only to come back a month later. I loc tited the bolts after that and never heard it again. As far as the spark knock issue, when I had a 455 in my other cutlass it would spark knock on low octane gas. This sounded somewhat like a chattery lifter but only happened under load in part throttle conditions. I put race gas in and it went away. Try to pin point when it actually happens. If it happens at idle then I would eliminate spark knock. Have your rockers been coming loose? I have had that issue before on a 355 chevy. I would adjust them, no chatter, ran well, a mile later i heard chatter and had to adjust again. Finally I bought poly locks and they no longer loosen up. Good Luck.

 

[dquicks78mc]

ty ill try the torque converter had to replace the kick down cable not to long ago the transmission is full its actually a little to full according to dipstick while its running in park. i had poly locks on the rocker arms already they did come loose so i just bought some locking nuts for them. i put those on and i still have the same problem. so to the converter it is lol

 

[dquicks78mc]

oh and in while its parked there is absolutely no chattering or knocking of any kind no matter the rpm so maybe it is the torque converter

 

[CHRIS.O]

Well if it does not make any abnormal sounds while stationary then I would eliminate a rod knock or rocker arm. Both of those would be apparent without driving down the road.

 

[565bbchevy]

Years ago I bought an Olds 98 with a 455 and a rebuilt 400 for $100, the owners wanted to just get rid of it because it sounded like it had a rod knock but to me it seemed to run good other than the noise, it ended up being the torque converter bolts were about 1/4" too long and bottoming out before fully tightening the converter to the flexplate.