hey all
not to sure whats wrong with my engine. its makein a sort of rap/nock when i rev it up past 2000 or when its gotta work goin up the big hills i got here in nh. is my engine shot or what? its not real loud but like i said when i make it work or jump on it it makes that noise, thanks in advance for your help you guys are great, oh yeah its a 86 trans am with a carbed 305

 

Could be an exhaust leak.

 

I wanna tell you ‘bout some noise that my engine makes,
It be a knockin' and a rappin' and sometimes it shakes...

Boof - Bump - Boof - Bump

It does a knock and a thump and a little clang.
I don't wanna get beat by no chump Mustangs..

Boof - Bump - Boof - Bump

When I'm slidin' up the hills it does it even mo'
It ain't cool makin' noise when I'm crusin' for hos...

Boof - Bump - Boof - Bump

I bust out from my homies ridin' their Accords
I don't need my ride soundin' like no Fords...

Boof - Bump - Boof - Bump


Obviously, 40-something white guys shouldn't be allowed to write rap lyrics.


Do you notice any cold start noise? Is the noise more RPM-dependent or load -dependent? Oil pressure normal?

 

exhaust leak will sound like a nock? what would be leaking? oil pressure is fine (i think, it always stays right around 30). the noise is more rpm dependent and no wierd noises when i start it just a puff of smoke. by the way that rap was prolly the funniest thing ive even seen :sillylol::hail:

 

It (exhaust leak) will sound more like a metal-on-metal tapping sound, as if a rocker arm came loose.

It just leaks exhaust gases.


And well done Vader!!!

 

but what would make a exhaust leak sound like that? could someone clarify this for me? thanks

 

If it's only occurring under heavier loads, it could be detonation/preignition (spark knock).

Are you using lower octane fuel with higher compression and advanced timing? Hot engine/heads? Lean mixture? They can all contribute to detonation.

 

does it only do it underload or does it do it just sittin there when you rev it? can you narrow down where the sound is coming from? grab a piece of hose or a prybar or something and put one end to your ear and one to various parts of the engine (heads/valve cover area, manifolds/headers, and go over the lower portion of the block) the way you describe it, it sounds like its preignition or possibly a rod knock.. kinda vauge discription.. if it only does it under load i think vaders got ya covered with preignition.. another possible cause for preignition could be excessive carbon deposits..

 

ok thanks guys ill check it out tomm when i can see what im doin

 

ok it def olny makes the noise when its in gear, when i rev it in neutral its sounds perfect, i havnt mess with anything with the car exept puttin a k&n filter in

 

and i use the cheapest gas at the pump

 

check your timing.. it may have slipped.