460 Funny knocking noise

Reply Subscribe

Thread Tools

Search this Thread

Dec 9, 2009 | 02:25 PM

IDIDieselJohn

Thread Starter

Post Fiend

Joined: Feb 2009

Posts: 8,005

Likes: 7

From: Ottawa, Ontario

460 Funny knocking noise

Hi y'all

First time posting in this forum. I need some help here!

Looking at this nice 1977 Mercury Grand Marquis with a 460 4bbl and 32,000 original miles. Fires up without a problem and is the smoothest running 460 i've ever seen, i'd say to the point of being able to balance a dime on the air cleaner cover. Anyway makes this fairlly loud knocking sound on the drivers side of the block right at the front of the engine. Would it most likelly be a leaky exhaust manifold/gasket or spark knock? It's not a constant knocking sound, it changes a bit at the same RPM, but knocking gets faster as RPM's go higher though. But has this perfect idle, smooth, not missing, engine doesn't move, you'd swear it's bolted right to the frame.

Personally I think it's a bad manifold or gasket, cause wouldn't a knocking engine at least shake? But just to be sure i'm asking your opinion on it.

Thanks

Any thaughts appreciated!

Dec 9, 2009 | 04:42 PM

wdfp

Elder User

Joined: Nov 2003

Posts: 778

Likes: 2

From: southeast Idaho

I had one sound like that once, it was the original 460 in my 77, ended up being the timing chain was so loose it was hitting the side of the cover.

Dec 9, 2009 | 07:10 PM

IDIDieselJohn

Thread Starter

Post Fiend

Joined: Feb 2009

Posts: 8,005

Likes: 7

From: Ottawa, Ontario

Interesting....never thaught of that. Thanks! Is it a big job replacing a timing chain?

Dec 9, 2009 | 07:13 PM

gstanfield

Senior User

Joined: Oct 2003

Posts: 176

Likes: 3

From: Wyoming, USA

I was going to say the same thing, timing chain. They are not hard to change, as long as you have a basic understanding of things mechanical anyone can change one.

George