Loud knock in full throttle

[karayj]

So today I noticed on two separate occasions when I go full throttle after about 20 seconds there’s this knocking sound now I’m not talking about an engine knock it sounds very metallic he somethings loose somethings slipping maybe how do I find the source of the problem. What do I start looking for when I get home. Again when I’m cruising around half throttle no problem it’s only during full throttle after about 20 seconds there’s a petty periodical knocking and banging noise and after about four or five I just back off

 

[QBhoy]

Think the guys will likely want to know details about the engine.
But if it makes you feel better...I’d take some comfort from the idea that it’s not a regular noise suggesting it’s Not a drivetrain or rotating mechanical related noise perhaps.
not being funny but did you have a swim ladder left down ?

 

[karayj]

Sorry it's a 89 3.7 merc alpha 1 the Ladder was the 1st things we thought of. When we heard the knock noise there was no rhythm to it. As if you were hitting the rear gimbal with a hammer. That kind of knock Only on full throttle and after 20 seconds we tested it 3 times, At 1st I thought it was a bad cam pop but it was not all the time and full throttle only. I am trying to see what could make such a load metallic knock. There was no hesitation or skip when this happened

 

[jesse_boston]

Maybe a bad universal joint

 

[karayj]

I saw a few video's and thought same thing but a bad universal would make noes all the time and at any speed. After watching a few YOUTUBE videos of Automotive U joints it sounds the same. What I don't get is why only at full throttle and after 15 seconds.

 

[karayj]

I though I would get more responses ........

 

[Bondo]

I’m not talking about an engine knock it sounds very metallic he somethings loose somethings slipping maybe

Ayuh,...... I'm gonna Guess yer hearin' detonation, induced by a lean condition,........ 'cause ya only hear it at Wot,...

Usually sounds like shakin' a tin can fulla 3/8" nuts,.....

 

[kenny nunez]

2Xs with Bondo on the lean out. Also remove the plate in the distributor and inspect the centrifugal advance weights and spring mounting points that may be loose. This could cause the ignition out over advance.

 

[karayj]

Over advance or too lean ??????

Wouldn't that sound more like a ping or knock with rhythm that is constant ? My noise is after 20 seconds of full throttle and it's a load metallic knock then a pause then 2 more then a pause then another one till I back off to 90 %

 

[kenny nunez]

The only other thing could be valve float from weakening valve springs.