wonderful. Just about the time the car runs we are going to have to pull it apart again...
At idle, there is a distinctive knocking noise coming from the engine.
Above idle, you can still hear the knocking though it's less pronounced.
We obviously screwed something up in the rebuild of the bottom end.
Can we pull the oil pan off and oil pump and re-tighten the connecting rods from the bottom without pulling the motor?
frustrated in Austin.
Joe

 

ttt

 

I forgot to mention that it isn't always knocking.
It doesn't get louder or more intense as the revs pick up, either.

 

is this a 6spd car? if so, it could be the flywheel...

I think the oil pan can be removed with the engine in the car...


[Modified by bogus, 9:28 PM 11/27/2001]

 

Yes you can pull the pan without lifting the motor.

I would pull the oil pan and check a couple rod and main bearings. I'd also make sure all the bolts are torqued correctly on the rods and mains. You may have left a bolt loose and have gotten lucky enough to find it before it fails. Knock at idle usually means main bearing problems. Rods knock when the engine decelerates. :)


[Modified by AquaMetallic94LT1, 7:29 PM 11/27/2001]

 

Yes, you can pull the pan with the motor in the car. But I don't think there is anything you can "tighten up" to fix the problem.

Did you pre-lube the motor after the rebuild?

 

Hmmmm. Okay, well, I did pre-lube the motor, both with the pre-oiler and with the engine rebuild lube as I was installing the bearings/etc. My gut instinct is that I just didn't tighten a rod properly.
A knocking rod is indicative of what? Is the rod loose @ the wrist pin or loose at the crank? Any way to tell from the sound?

 

Make absolutely sure that it's not a torque converter to flexplate bolt being loose, or if it's a stick, make sure it's not a pressure plate to flywheel bolt. Both of these may sound like a lower end bearing knock.
Also, a rod big-end knock has a very distinctive sound, it has a bit of a ring to it, not just a tap. The flywheel bolt looseness is very similar.
Also, if it's real bad, you'll notice very low oil pressure at idle.
-Matt


[Modified by kd4pbs, 2:33 AM 11/28/2001]

 

Hey...just a side note...ALL Chevy 350's make a little rod noise that can barely be heard while at an idle to around 1500 RPM, where engine noise makes it inaudible.

Thats normal...so if you have a quiet exhaust, it may be what you are hearing.

 

I don't suppose you reused your old rod bolts did you? You might have over stretched one and so it will not achieve a proper amount of torque. Been down that road before. Good luck. :smash:

 

I did reuse the old bolts. The manual did not say they should be changed.
Also, the car only has 1-2 psi of oil pressure at idle.
It's fine when it's revving, but that does seem low.
I guess I'll replace the bolts first, then if that doesn't fix it, I'll go after the flywheel.

 

next observation, the motor only knocks when it gets warmed up...

 

ARGH!!! That would be the first hint that something is wrong. BTW, yes you can remove the pan with the motor in the car, you might want to get the tranny out of the way so the motor can tilt backwards and give you better access to the front oil pan bolts.

 

okay I lied, I went out and checked and it has 8 PSI of oil pressure at idle, what is it supposed to be @?

 

The low oil pressure certainly points to a bearing problem, most likely rod bearings. New rod bolts at rebuild is an excellent idea. But it is a strength/reliability issue not one of fit. New bolts and nuts will NOT affect oil pressure or rod knock. Even if the nuts weren't properly torqued, the rods shouldn't knock if they were tightened. Improperly torqued nuts WILL cause a problem, but not likely in the limited amount of running that you have on this engine, so far. To me, this sounds more like standard bearings were installed on a turned crank. Before you change the bolts, check to see if they are tight. Otherwise, unless you broke or stripped the threads on a bolt, new bolts won't solve the problem. The correct proceedure in replacing the bolts MAY cure the problem, but it will be the proceedure, not the bolt, that is the cure.

 

Great advice, it sound like you know what you are talking about. Again, excellent information from the people who use this forum.

Well I don't know what else I could have done with the rebuild.
I torqued them all in the proper order, using the proper process with the called-for torque settings.
The crank was turned 10 over, and the bearing Clevite 010 over I had fit snugly and (but not tight) on the crank and in the rod end.
I guess it's time to pull the oil pan out and try again.

 

Running down the problems here...
Okay so when the motor first starts up, she is running @ 35-40 PSI on the oil. That's great. After 10-15 minutes of driving the PSI gets down to the 8-9 level. That's bad. That's when the car starts making all these knocking noises.
So, does that shed any light?
On the oil pump there is an intake. It looks like a 4" diameter saucer that stay down in the oil. If this were to not be installed correctly, could this affect the oil pressure? I remember it seeming to just not fit right when we put it in the motor.

 

You've got a bearing problem.

The sure sign is low hot oil pressure and the knocking sound you heard.

It may be possible to correct it IF no major damage has been done to the crank journals.

Jack the car, drop the pan and start with the mains. Run your finger over the main journals and you should not feel any ridges. If you do, just installing a new set of bearings won't work because they will soon become worn because of the grooves in the crank.

Make sure that the bearings were installed correctly. That the bearing with the oil hole is in the block. Check that the oil holes align too; occasionally they are off quite a bit and the main bearings will need to be re-drilled to get the oil holes to align properly.

Check the backside of the bearings to make sure they are the correct ones. If your crank was turned .010, the bearings should indicate .010.

In the past, when the scoring on the crank was minor, I have used 400 then 600 sandpaper and smoothed out the crank journals, put everything back together and the engine ran fine for thousands of miles.

It's not the preferred way, which is to pull the engine and have the crank polished, etc., but it can work if scoring is minor. You can buff out the scoring using a method similar to the shoe-shine buffing way of old.

If your crank has chamfers, make sure the chamfer side of the rod bearings face the crank cheeks, not the other rod on the journal.

If you caught it in time, things may be salvagable, so don't run it any longer.

If everything looks fine - mains and rods - (which I doubt), could be the plug was left out of the rear of the block when the work was completed.

Lots of possibilities here, keep us posted.

Jake

 

I agree with most of what Jake says. But I am afraid at this point, I would be pulling the engine back out. I know that you don't want to do this. To my way of thinking, it is very difficult to inspect and affect a repair, properly, laying on your back with limited visibility. If the crank DOES need some polishing, where does the grit go? You may be able to wipe away and recover most of it. How much of this in your oil system and bearings is acceptable?

It's my feeling that if a plug were left out of the block, that you wouldn't have the cold oil pressure that you DO have. The pressure drops after it has been running and warmed up. The hotter oil is less viscous (thinner) and more easily able to flow throught small openings. Oil pressure is created by resistances to flow in the oil system. Somewhere, in the oiling system, you have a lack of resistence. The rod knock points to excessive rod bearing clearence, for what ever reason. You bought .010 OVERSIZED bearings to match your .010 undersized crank. Like Jake suggested, it would be a VERY good idea to look at the backside of ALL of the bearing shells for the .010 marking. Some people will mix and match oversizes to get the clearence that they want. Although not as accurate as a dial bore and micrometer, plastigage (sp?) does a good job of determining bearing clearences.

The oil pump pick up is a press fit into the oil pump. Racers weld or braze the pick up to the pump body to prevent it from working loose and falling out under abuse. It should have been positioned a 1/4 to 3/8 of an inch from the bottom of the pan at installation. A poor fit between the pump and pick up would tend to have LOWER oil pressure when cold, because the resistance of the colder thicker oil cause the pump to suck more air, then when the oil is warmer and thinner.

Did you install a high volume oil pump? I have one in my pick up truck. Unless my oil level is dead nuts full, the pan gets sucked dry at moderate rpms. In my case, the first clue that I need to add oil, is that the lifters collapse and start making noise. I really don't think this is part of your problem, based on your description.

In short, if it were me, I'd be yanking the engine and going back over EVERYTHING with a fine toothed comb. Others, here, will disagree with me, but that is MY opinion. Good luck and let us know what you find.

 

I usually hesistate to recommend unorthodox procedures because they always meet with someone's disapproval. Occasionally, though, I do; but only if it's worked for me..

Without a doubt, the bullet-proof way is to pull the engine, take it to a reputable machine shop that does performance engines as its main business and have the complete assembly gone through.

The alternate procedure that I suggested still leaves this as a final option. All you'd have lost would be a few hours laying on the floor under the car.

Dealing with the grit is pretty simple with a roll of paper towels and a can or two of spray carb cleaner with the thin straw attached.

With the main bearing removed (one at a time) it's a simple matter of threading a strip of sandpaper around the crank and begin "sawing" away. Periodically spray the journal with the cleaner, use the paper towel to wipe and gravity will cause the grit to fall downward. The oil hole in the crank be plugged or with the hole at the 6 o'clock position, sprayed with the cleaner to cause any grit to run out.

If you attach a hand held bump starter to the "S" and + terminals on the starter solenoid the engine can be bumped as you work. KEEP YOUR FINGERS OUT OF THE WAY IF YOU DO - ASK ME HOW I KNOW.

It's a pretty simple procedure and with your favorite sounds playing in the background, time passes quickly.

Now, if there is considerable damage to the crank journals, then pulling the engine is the way to go. But if it's just minor scratches, I'd give it a try. As I said, you can always pull the engine later if steady, high pressure doesn't result.

If you go the unorthodoxed route (or any route for that matter), when reinstalling the main cap bolts, make sure you can HAND SCREW all of them down until they are flush with the cap. This helps insure the caps are on straight. If you cannot hand screw the main cap bolts all the way down, the cap is cocked at tad. A slight hammer tap will straighten its alignment.

Make sure the caps are oriented in the correct direction and on the correct journal, too, with the arrow pointed forward. (This could be your problem too; one or more caps on backwards or on the wrong journal).

As I said it worked for me; but it's up to you to decide.

Hope this helps.

Jake