Rod knock

Good Day!

I have a lemons race this coming weekend. I froze the original block over the winter and cracked it.

I put in a "known good" motor. This motor had sludge all through it.

I cleaned the sludge out with kerosene (cleaned the sludge off under the intake and the top of the heads). I then took the oil pan off and let the motor sit for a few hours.

Then I installed the engine in the car. As soon as we started it, it made a horrible clanking type sound. My buddy thinks it is a rod knock.

The sound changes with the engine speed.

Sooo, I took the oil pan off. I took off 6 of the 8 connecting rod caps. The bearings are showing some copper. The crank looks fine (really good actually).

I did not find a spun bearing. Can you have plain old wear cause a rod knock? Should I be looking elsewhere? Should I look at the mains (I looked at the two rear mains and the bearings looked good)?

I would really like to get this thing done before the race this weekend.

Thanks guys!

P.S. 350 chevy GM goodwrench crate motor (perimeter bolt valve covers, 8.5:1 compression, 2 piece rms, 4 bolt mains). My guess is the motor is about 10 years old.

Could be a lot of things. We had a noise in our lemons transplant that turned out to be the water pump. Try isolating accessories first, alternator, PS, you never know. A rod knock isn't going to hurt anything for the hour or so that it will take to isolate everything else.
You actually may want to check the valve covers first - could be a broken rocker arm or something bouncing around. Just do a visual and wiggle everything around to make sure it's all seated nicely. Report back. We'll see you Saturday!

tuna55 wrote: Could be a lot of things. We had a noise in our lemons transplant that turned out to be the water pump. Try isolating accessories first, alternator, PS, you never know. A rod knock isn't going to hurt anything for the hour or so that it will take to isolate everything else. You actually may want to check the valve covers first - could be a broken rocker arm or something bouncing around. Just do a visual and wiggle everything around to make sure it's all seated nicely. Report back. We'll see you Saturday!

We run a serpentine belt set-up. I will remove the belt and see what happens. Obviously I can't run it that long in this manner (water pump wont be driven).

I hope to make it down.

Thanks,

Rob R.

wvumtnbkr wrote:

tuna55 wrote: Could be a lot of things. We had a noise in our lemons transplant that turned out to be the water pump. Try isolating accessories first, alternator, PS, you never know. A rod knock isn't going to hurt anything for the hour or so that it will take to isolate everything else. You actually may want to check the valve covers first - could be a broken rocker arm or something bouncing around. Just do a visual and wiggle everything around to make sure it's all seated nicely. Report back. We'll see you Saturday!

We run a serpentine belt set-up. I will remove the belt and see what happens. Obviously I can't run it that long in this manner (water pump wont be driven). I hope to make it down. Thanks, Rob R.

A few minutes with the hood open won't hurt anything. Do that and then both valve covers. Only panic then, and even then, it's a small block chevy. Find the problem, go kick some rocks until you find whatever it is (connecting rod, piston, block) sitting there on the ground and swap the parts.

Are all the flywheel/converter bolts tight?

You shouldn't be seeing copper on a rod bearing.

Zomby woof wrote: Are all the flywheel/converter bolts tight? You shouldn't be seeing copper on a rod bearing.

They are probably worn, no doubt, but they could or could not be causing a rod knock. Even then, I've seen engines live for a while with knock. You could check rod/rod clearance with a feeler gage, but you're only checking it against factory specs, not against some "knock/no knock" gage.

If it is knocking you could just throw some 50 weight in it and see how long it lasts. I had a Chevy 3/4 ton with 4.3 V6 that ran for a few thousand miles with rod knock before we replaced the engine(it was still running when pulled).

A set of rod bearings for that thing is probably $12.00. I'd throw a set in and a oil pump. Check the obvious stuff under the valve covers and fire it up.

Damn, I was wrong. They are $13.95.

http://www.summitracing.com/parts/SUM-171000/

The oil pump is $19.95.

http://www.summitracing.com/parts/SUM-121155SV/

Have you let it run long enough to warm up? Does the sound change as it warms up?

If you know it was good before the cleaning I'd start looking at all the accessories and damper for the source.

An old piece of garden hose can make a grass roots stethoscope for narrowing down the source of the noise.

Did you pull off one spark plug wire sequentially to see if the problem is one cylinder?

A rod knock sounds more like some one with a hammer is in the block and trying to get out. Changes on acceleration,deceleration, generally not at idle. A clanking noise could be a lot of things including a broken flex plate. Bearings showing copper are worn out.

good info guys! Thanks!

I have procured new rod bearings and will install today.

Any tips or suggestions to make sure I don't mess up the installation?

I have installed a new oil pump.

It does sound like somebody trying to get out of the engine by using a hammer.

I have not yet pulled off any sparkplugs to see what was up.

Keep the suggestions coming!

Thanks!

I will report back once I put the new bearings in.

Even if you don't fix it, show up to the race! You've paid your fees. Wrenching is more fun with fellow lunatics around. I'll help wrench when I'm not driving or wrenching on our car.

Okay, new info:

I changed the bearings. None of them were spun or had unusual wear. I COULD see copper in a few of them.

The mains look pretty good.

I started it up and it starting knocking right away. The pistons seemed okay from the bottom and the con rods moved back and forth freely.

The engine does not make this noise when just being spun by the starter.

Every so ofter there is a new noise that sounds like a pushrod hitting the top of the valve cover. I opened up the valve cover and adjusted the rocker arms and it still makes the noise every once in a while. It sounds like washers in the valvetrain. This noise goes away as suddenly as it starts.

I am wondering if all of these sounds can be attributed to a lifter that is either stuck, or not properly "pumping-up" (hydraulic). This could cause a valve to not open fully or not at all.

Just a reminder that this engine was GUNKY! I had to clean most of the lifters. Some were difficult to get out of the block.

What say you GRMers?

Lifter noise is possible. Change them, shouldn't take but a few hours. Have you isolated the accessories yet? Checked flywheel/converter bolts?

I have the ability to spin the motor over with just the starter.

The noise is not there when it I spin it with the starter.

I figured this eliminated the accessories and flywheel.

If you feel this is not the case, I can take the belt off the accessories. The flywheel would be WAY more difficult to check.

wvumtnbkr wrote: I have the ability to spin the motor over with just the starter. The noise is not there when it I spin it with the starter. I figured this eliminated the accessories and flywheel. If you feel this is not the case, I can take the belt off the accessories. The flywheel would be WAY more difficult to check.

Hard to say. Lifters are cheap $3 a piece) but then you have to break in the cam again.

wvumtnbkr wrote: I have the ability to spin the motor over with just the starter. The noise is not there when it I spin it with the starter. I figured this eliminated the accessories and flywheel. If you feel this is not the case, I can take the belt off the accessories. The flywheel would be WAY more difficult to check.

starter spins the engine at only about 250 rpm, which may not be enough to get the accessories to make noise. i'd pull the serp belt and run the engine for a minute or two, enough to hear whether or not the noise is still happening.

Collapsed lifters can make a pretty good clatter. Difference between a rod knock and lifter, other than sound, is that the rod noise will change as you accelerate and decelerate the engine. Lifters remain constant.

collapsed lifters can make a horrible frightening racket. I bet the kerosene freed up some gunk that then blocked the oil feed to one of the lifters.

Either replace the lifters or run some more engine flush/atf through it. On my Saab that had horrible lifter noise getting some hot ATF through it at idle fixed it in no time.

Toyman01 wrote: A set of rod bearings for that thing is probably $12.00. I'd throw a set in and a oil pump. Check the obvious stuff under the valve covers and fire it up. Damn, I was wrong. They are $13.95. http://www.summitracing.com/parts/SUM-171000/ The oil pump is $19.95. http://www.summitracing.com/parts/SUM-121155SV/

berkeleying Chevy cheap assparts.

One of these days I may drink the koolaid.

Change the lifters as they said above.Thats my guess on the noise.There not pumping up.This may have been ask,but whats your oil pressure? You may not have enough to pump them up.If you ajust the lifters to tight you will collapse the lifters and they will make the same noises.

spitfirebill wrote: berkeleying Chevy cheap assparts. One of these days I may drink the koolaid.

With bearings, it's cool, but it can actually be a curse. Lifters, for example. Lifters are one of the biggest contributors to ruining a cam upon break in, mostly due to crappy Chinese knock offs. Hard to tell which are cheap because Chevy and which are cheap because crap. Please, no jokes there.

The noise doesn't change pitch based on engine speed. I am thinking more and more that it is a lifter. I will put some atf in there and run it for a bit.

Thanks guys!

I have some previously used lifters from another sbc that I could put in. Would I still need to go through the break in process?