I dont usually cry, but...wahhhh I'm out of ideas on this!
1994 Ford 4.9L I6 IFI driving me to insane asylum
Problem: Knocking while engine running, both cold and hot. Knocking started upon crank up after overhaul.
No engine skip or miss, oil pressure ~40PSI min hot (with real oil pressure guage).
Knocking seems to be at Camshaft speed (knocks in time with timing light)
Unloading cylinders (shorting plugwires) Does not change knock character
Knock occurs with belt off (no accessories running)

Background: Complete Engine & Tranny overhaul!

Engine:
Block cleaned, magnafluxed, and honed, new cam bearings.No cylinder ridge, so no reaming needed.
Pistons/wrist pins/Rods, cleaned inspected and retained
Crank: Polished, checked for concentricity, all within specs
new rod bearings, std/.001ovr, juggled to obtain .001-.0015 clearance
New main bearings (std) .001-.0015 clearance all journals
new rings (std oem), end gap within spec.
New oil pump
New Cam, OEM type
New gears, steel oem
New lifters
New head(parts guy used the term "new casting"), complete with valve/springs/seals. Old one was cracked

Tranny E4OD: Complete front to back overhaul, all piston seals, clutch packs, band, all seals, tranny shifts perfectly thru all gears.

Since overhaul....
Re-checked Rod bearings....clearence is .001-.0015 on all, no signs of ware or tare
Pulled Timing cover, VERY minor evidence of a strike...or tool mark while cleaning part during overhaul. Put second gasket on cover to increase clearance to cam gear. Checked Cam and crank gear, both on correct with less than .003 run-out.
still knocks, no change!

OK I give, whats the knock?
BTW: Knock has a "hollow" like sound, not like a classic rod knock
cmoses

 

Is the flex plate cracked? My old 77 f150 had a cracked flex plate and it sounded like a motor knock . just
an idea

 

@MP79: Thats not a bad thought at all, I'll pull the dust cover and look. It wasnt cracked when I re-married the tranny to the motor, but at this point I am out of ideas.
cmoses

 

"knock", or "tick"? uniform "holds a beat" type sound, or random no rhythm white guy trying to rap tempo?

 

Its a knock, sounds like something solid striking something either thin cast or sheet metal. Its beat is regular and to engine speed, seems to be Cam speed (beats at same rate as timing light).
It doesnt change character when I kill the cylinders 1 at a time, although it slows down (as does the engine).
cmoses

 

What kind of cam? Are these i6 flat tappet or roller? Could have wiped a lobe on breakin....collapsed lifters give a "tick" so that sounds ruled out. Could pull the valve cover and run the engine, look for a rocker that's not lifting. Could even isolate the cylinder a little easier that way also.

 

Nope, knocked upon first cranking, but its flat tappet, OEM cam, and the engine runs perfectly other than that damn knocking.

 

Check for a exhaust manifold leak on the head. Dropping cylinders(misfiring them) did not change the noise but you still are pushing out exhaust . That could be a possibility.

 

Something is wrong with the camshaft gear or position of the gear if you have to double gasket the timing cover for clearance.

Did you install the camshaft spacer with the chamfered edge towards the camshaft?

The front face of the crankshaft gear and the front face of the cam gear should be even with each other if you were to put a straight edge across them.

The thread below shows someone who rebuilt their 4.9l, installed new timing gears and said it made a knocking sound. Must have been something wrong with the gear mesh. He doesn't mention if it was a metal gear set.

https://www.ford-trucks.com/forums/9...ml#post9544225

 

I'll check that, Ill post the results one way or the other!
thanks'
cmoses

 

I would agree except....I didnt "have to" put a extra gasket in, I done it just in case, but ....still knocking, so there was no (or there still is) a clearance problem.
The spacer sets the cam thrust clearance, which in my case is factory new tolerance, the cam gear is positioned by pressing it onto the spacer, which sets the clearance. In my case it was also even with the front cam.
cm

 

F150Xlt: Thanks for the link, I saw that before and yes I did install new all-metal gears of the OEM type (not marked as "cloyes" or any other name brand), but honestly if the metal gears knock like that I think they would have been removed from the market. Can you imagine a shop replacing a guy's cam gear or doing a multi-thousand dollar overhaul and then telling the customer "This knock is normal for the replacement parts". I would think these boards would be jam-full of warnings "dont use that xxx gear from NAPA". Having said that, even without the knock those gears do make a signing sound...I'm ok with that though.
I would like to contact F250_Restorer and ask him specifically WHAT about that first set of gears caused the knock, or if by replacing it did he get the second gear all the way tight on the spacer.
cmoses

 

I thought I would post back here. After about 5K miles the knock has subsided, and the engine runs fine. I have had other problems (a bad front tank fuel pump, and today a ECU (see the post)), but it appears the knock was "normal" or at least "normal for a 300 with metal timing gears.
Cheers
cmoses