Ok my friend just bought this sweet looking 1970 mustang (I know this is a third gen camaro board but I have nowhere else to turn) but it has this egregious knocking sound. So here's what we've done so far to find out whats wrong

• Checked spark plugs (look alright)
• Replaced spark plug wires
• Checked firing order (still not absolutely positive that its right)
• Looked at rocker arms (they're all good)
• Idle evens out when the plug wire to cylinder 8 is removed

It is more prevelent when accelerating. Also when you let off the gas after running at higher speeds it has a loud almost bang.

A couple of other things I'll note too. When we pulled the valve covers off the heads have a "302" stamp on them but my friend was told that the block is a 390- haven't verified that yet (though we don't know if the heads have been ported either). And also the header on cylinder 8 is not connected properly (at all, haven't gotten bolts yet).

I think that is everything. So what are your opinions as to what might be wrong?

 

i'm not sure because i dont really know what kind of noise you're describing....but an exhaust leak at the headers can be VERY loud.

 

Well everyone congratulate me on receiving the award for being the world's biggest moron. Well we figured out what that 'banging' sound was, the header on the 8th cylinder was causing it (we found one of the bolts on the collector out of sheer luck). Still doesn't run that great but hey it's a ford