Rebuilt engine has knock.

lunchbox

Well-known member
Apr 20, 2004
2,043
108
49
St Louis, MO
Engine is a 4.6 out of a Calloway P38. I bought just the block from Will T. It was out of a known running truck with about 100k on it. I took it to a local shop and had everything checked out. details:

New Crower cam
New bearings all around
Honed block
Heads machined
New gaskets everywhere
New water pump
New alternator
New belt, plugs, wires, etc...
All break in procedures followed.


Issue:

Engine starts right up and idles great. After the truck reaches operating temp, it develops a bad knock. Using a scope, it's been guessed that the noise is coming from the area of #5 and #7.


Tried:


Pulled the pan and checked bearings
Pulled the valve cover and installed a new(ish) rocker assembly
Tried several weights of oil
Hooked up an oil pressure gauge. 50 at start up, 25 at idle.
Checked flex plate bolts
Cleaned pan and pick up (again)
All cylinders are firing and have proper compression

I'm sure I'm forgetting something.

Any ideas?
 

squirt

Well-known member
Nov 13, 2008
824
13
Los Angeles
Can you tell if it's an upper engine noise or lower engine? What does the shop that did the work have to say about the situation?

A few things come to mind:

-Lifters and pushrods (you didn't mention them - were they were replaced with the cam?)
-Valvetrain shims - were the rocker shafts shimmed to the correct height range?
 

lunchbox

Well-known member
Apr 20, 2004
2,043
108
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St Louis, MO
It is the loudest when scoping the rear driver side of the pan. It is noticeable at the valve cover as well, but not as loud.

Did not replace lifters and pushrods, to my knowledge. I will verify that.
 

Flyfish

Well-known member
Oct 29, 2004
1,360
194
51
St. Louis
It is the loudest when scoping the rear driver side of the pan. It is noticeable at the valve cover as well, but not as loud.

Did not replace lifters and pushrods, to my knowledge. I will verify that.

More so, loudest on the rear ds of the block, not pan. Almost seems like it runs out of lubrication and then starts to knock and sounds like a plastic mallet when you listen to the stethoscope. (but I've never listened to anything through a stethoscope before to know what particular noises sound like.)

I don't believe there was any evidence of a liner moving when they looked from the bottom end but can't say 100%. Same regarding piston slap (and rod bearings appeared normal).

Pulling the head back off seems to be the only thing left, just looking for any other ideas before we do.
 

JohnB

Well-known member
Oct 18, 2007
2,286
9
Oregon
It is the loudest when scoping the rear driver side of the pan. It is noticeable at the valve cover as well, but not as loud.

Did not replace lifters and pushrods, to my knowledge. I will verify that.


New cam with old lifters? I'm sure you must have replaced lifters>that would be a bad decision if not. Doubt that's your noise but will in deed wipe your new cam flat in no time.
 

ccollins

Well-known member
Jan 21, 2008
347
1
Was the crank checked for excessive wear when the lower rod bearings were replaced?
 

kcabpilot

Well-known member
Mar 26, 2006
334
1
California
FWIW - my brother has an '04 that, based on your description, makes the exact same knocking noise. It started doing it about three years ago, he just keeps driving it. I don't know what the cause is but in all this time it has never gotten worse or changed in any way.
 

lunchbox

Well-known member
Apr 20, 2004
2,043
108
49
St Louis, MO
I will double check the lifters. I did not do the rebuild. I removed it and put it back in.

The crank was checked. All good

No way in hell I'd drive this truck. It is loud enough to be heard from across the lot, inside the garage. It sound great for the first 10 min after starting it.

Thanks for all of the opinions.
 

discostew

Well-known member
Sep 14, 2010
7,275
837
Northern Illinois
If it doesn't change at all when killing cylinders it might be a cracked drive plate or loose torque converter bolt. Possibly a main bearing knock. Cam bearing?
 

lunchbox

Well-known member
Apr 20, 2004
2,043
108
49
St Louis, MO
Well. We tore it apart. The only issue found was some scoring on the cam side of one lifter. My buddy swapped out all of the lifters and put it back together. It still knocks. The oil pressure at idle is about 15. The wrist pins, rings, cam, rockers all looked good. I'm not real sure where to look now. Suggestions?
 

The Fourth Amigo

Well-known member
Apr 20, 2009
641
2
Did you measure the cylinder bores and piston diameters? Get clearances and compare to the specs? If you want to rule out piston slap that's what you would need to do.
 

lunchbox

Well-known member
Apr 20, 2004
2,043
108
49
St Louis, MO
From my buddy who pulled it apart:

The bores were measured in three different places on each cylinder. pistons were measured on the skirt 90° to the wrist pin. Bores had some minor wear but well within clearance no grooves or cuts in the bores and no ridge on the tops of the bores. Pistons had some scrape marks on the skirts but nothing to call for new pistons to be used.
 

lunchbox

Well-known member
Apr 20, 2004
2,043
108
49
St Louis, MO
It's back apart again. There are no signs of issues. I sent the heads back to the machine shop to make sure everything is ok with them. Also going to pull the cam and measure it. It's brand new, but I'm out of places to look. Slipped liner is the last thing. Although there is no evidence that the liner is hitting the head or gasket. We changed oil weight and the pressure is up. Lifters all look good. Rockers have been replaced again. Pistons and bores measure fine. Bearings all look good. The noise is by far the loudest when the scope is on cylinder 7. It's pretty quiet on the valve cover and Valley pan.

I bought the short block from Will with about 100k on it. It was in a running truck that he drove, and experienced no knocks.
 

discostew

Well-known member
Sep 14, 2010
7,275
837
Northern Illinois
Well. We tore it apart. The only issue found was some scoring on the cam side of one lifter. My buddy swapped out all of the lifters and put it back together. It still knocks. The oil pressure at idle is about 15. The wrist pins, rings, cam, rockers all looked good. I'm not real sure where to look now. Suggestions?

Is this a light tick noise or a heavy knocking sound? The other question would be is it fast like a rod when you rev the engine?Main bearing knock is slow, upper end noises usually faster. Make sure none of your cam bearings are moving around. They can make other stuff around them make a lot of noise because the bearing moves enough to block the oil passage. Sometimes you can find a drawing of the oil flow thru the engine and if you look at it you can see how the cam bearing can block oil flow. So if that happened you could have 15 lbs of pressure where your measuring it, but a rod back in the back starving.