1100 miles into my rebuilt motor (pre-emissions 350), it's knocking. Sounds like the bottom end in the back of the motor. Utmost care was taken when I bolted the machined parts together. All bearings were plasti-gaged, all torques on all bolts correct. Cam was degreed in and piston clearances and rings checked. Motor was pre lubed before starting (2000 rpm- 20 minutes).

Ran it real easy driving the first 500 miles, then changed oil and filter. Ran motor normal driving for another 500 and changed oil and filter again.

Now at 1100 miles, I can hear knocking from the block, I think? Sound increases with engine speed, load or not. Oil pressure is the same as when I first started it, 15-45 psi.

Here's what I have done so far:

Took a stethascope to the motor, sound coming from the bottom rear, hard to isolate.

Pulled 1 plug wire at a time (thinking a rod)- no changes.

Disconnected torque converter from flex plate (maybe tranny or TQ conv noise), ran motor- no changes

Removed all belts from accessories (just in case sound was transmitted down)- no changes

Removed fuel pump (weak spring in pump might cause rod to slap cam lobe)- no changes

Checked crank end play, no problem there.


HEEELLLPPP, I really don't wan't to take the motor back out, but I will if I have too, I figure it will cost about 100 bucks just for fluids and gaskets:mad:- not including my labor. I hope it turns out to be something stupid:zzz: and cheap:question: . Somehow, I doubt it though........

Any other ideas????????

www.coloradok5.com/gallery/75K5

I see you checked the torque converter but did you check the bellhousing bolts to the motor?Also check the flexplate fo cracks.I had a bad knock in what I thought was the motor and it turned out to be the bell housing bolts were loose.And the motor and trans were seperating.Tightened the bolts and the noise was gone.Also when you rebuilt the motor did you use a new oil pump or used one?15psi seems low for a motor with so little miles.All my motors run more than this.My 400 rebuilt stay at 60psi and my 305 was rebuilt 8 years ago and still runs atleast 25psi.Just some thoughts.Hope its somthing easy.Blazin:rasta:

you should be able to pull the oil pan off with the engine in the chassis still right? the oil pan gasket and oil are cheap if you can pull it off, make sure you don't have a weak rod bolt or loose oil pump or something. I must agree with blazin, 15 psi is sounds a little on the low side for a rebuilt motor, was it that low when you first started it?

What about an exhaust leak? I threw a rod in my engine and got a new one- the sound was horrible when it knocked. Like 2 months after it was replaced it made another sound and I thought of geez not this again this stinks why is it doing this? Turned out to be a bad exhaust leak from when the engine was put back in...... it's wasn't like the tick you usually hear why it really freaked me out and I thought the worst..... only other thing I can think of would be a rod that's getting ready to break loose and punch some holes in the oil pan. Worth it to simply make sure those are ok and get a new fluid and gasket for the pan. Way cheaper then a new engine that you can't even get a core fee for because it's got scrap metal all on the inside..... :eek:

Sounds like you had a rod bearing going out. If it's like 1 I saw in my buds motor it "shifted" under the rod and was causing the piston to hit the head :eek: ....looks like you might wanna pull the pan and look for glitter and check the rods for "extra" play.....:beer:

Thanks for the ideas guys. Something is really screwy with the main bearings[crazy]or crank. I get wear marks (shiney- not the usual grey colored wear) on one half of a bearing and none on the other half. For example- The bottom half front bearing has one wear area towards the rear of the motor, and no wear on the front, the top half is shiny all around except for 3/8 inch on the sides. It's really bizarre.......I've never seen anything like it......Anyway, I'm taking the bearings to my machinist for further evaluation.

What did you find out? Did your oil pump shaft shift and you loose oil pump.....IE: cook bearings......:( :eek:

If you are running an oil cooler and did not flush it out then you mostlikely had metal shavings in it if a previous motor went on it.
Whenever you blow a motor always replace the oil cooler. I learned the hard way.

Originally posted by scott-885
If you are running an oil cooler and did not flush it out then you mostlikely had metal shavings in it if a previous motor went on it.
Whenever you blow a motor always replace the oil cooler. I learned the hard way.

I saw a guy "toast" a tranny buy using the old $40.00 "tranny cooler" ......:eek:

Originally posted by Shaker
What did you find out? Did your oil pump shaft shift and you loose oil pump.....IE: cook bearings......:( :eek:

Nope, bearings ok, according to several people, including machinist. Still looking further. If I can't find it- I'm running it til it blows up. I've had a gut-ful of it.:mad:

Sure you didn't have a lifter collapse, that is if your running hydraulic lifters.
Normally your oil pressure will drop down to zero if your mains go out, a knocking noise that increases and decreases with rpm is usually a rod knock.
One tip about rebuilt motors, you should always change your oil and filter right after run-up and adjustments....
Drive it 500 miles then change the oil and filter again....
Every 3,000 miles after that...
:skull:

Just a thought

you probibly all ready checked this but my bros 350 with 400 tranny had a knock only whene coled thow and what it was was the felx-plate had cracked all the way around the bolt hols that hold it to the cranck it looked like a stop sing. Honestly we chould of pulled it off with out un-doing any of the bolts to the cranck and be left with a little stop sing thing bolted to the cranck..


just my .02