[Shotimes] Engine noise identified
Leigh Smith
leighsm@comcast.net
Thu, 26 Aug 2004 13:01:21 -0400
As some of you know I installing a brand new Factory fresh SHO crate motor in
my 100k mile '94 MTX
due to engine noises.
In comparing the brand new Ford motor to my old one, I have found 2 things so
far:
I had a soft knocking noise which sounded like rod knock.
It did seem to be in the front valve cover near the coil pack.
It turned out the front cam chain was stretched, overpowering the tensioner.
It had 3/4 inch slop (+ or -) between the sprockets
That is the absolute limit of travel on the chain tensioner, which looked
almost new.
The rear chain had less slop, + / - 1/2 in slop, so the adjuster could still
function.
but the chains in the factory fresh engine only have 1/4 inch slop, and have
13mm of adjuster movement available to tighten chains in the future.
Note that the trensioners are not available anymore, but the chain seems to be
the part that wears, and they are still available.
Second issue was bearing clearances.
My old motor had 4.0 thousanths clearance on the rods, out of spec, and was
not trusted to drive daily.
The bearings were very worn (much copper) but new rod bearings did not help
the clearance.
The new Ford motor spec'd out at 2.0 exactly on the mains and the rods.
I am assuming the old crank is worn, but will know more shortly.
Lee
(Inquiring minds want to know...)