Revisiting the big block Chevy rattle

348tripower · October 11, 2007, 10:45:10 AM

Monday I dropped the pan off the engine. I gave it a complete visual inspection, checking for any metal in the pan etc. I rolled it over and inspected all the cylinder bores and found no scuffing in any of them. Everything looks great.

I did notice one thing. I can move the oil pump shaft up and down about 3/16 to 1/4 inch. By doing this I get this metallic noise, that would closely mirror the rattle I can hear. The shaft is the one with the steel bushing pinned to it.
I wonder, could this be the culprit? I would assume that under load this shouldn't move, but could it?

I am having a hard time convincing myself of the wrist pin rattle. It just doesn't sound like a steel to aluminum sound to me.
I can make this rattle by revving the engine in park and it starts at 2000rpm at cruise and goes away about 3000.

Ok gang have at it!!!!!!!!!!!!!!!

Don

Charlie Chops 1940 · October 11, 2007, 11:36:39 AM

Is it the extension that is moving or the shaft coming out of the pump? Anything look out of whack with the distributor pump drive?

Charlie

348tripower · October 11, 2007, 12:08:18 PM

Quote from: "Charlie Chops 1940"Is it the extension that is moving or the shaft coming out of the pump? Anything look out of whack with the distributor pump drive?

Charlie

Charlie,
It is the shaft. The pump is fine. I sent a email to melling about this and they said it was a first for them. They recommended putting in a different shaft with a plastic bushing (their part numbers) and trying it again. Their thought, Try the least expensive first.

Don

wayne petty · October 11, 2007, 02:02:18 PM

warning.. the plastic caps on the pump shafts will brake on high volume pumps. leaving the pump without a drive...i cannot guarentee that this will happen.. but on small blocks it does...probably the reason the steel shafts were made...

you can remove the pump and spread the tips of the pump shaft by tapping a chissle tip into the gap.. this opens the tips a little.. if you notice there is a releif just below the tip on the pump shaft.. this snaps onto a notch ring machined into the steel collar this keeps the shaft from bumping up and down.

so the pump shaft should snap on to the pump... you might even need a little hammer to tap it on...

is there any chance while you are under there to mark the harmonic balance with a stripe of nail polish. 90 and 180 degrees off the tdc mark. to verify the dizzy is not sending spark to one pair of plugs to early because of a bent or cracked reluctor or magnet. an ajustable timing light moved from lead to lead you might be able to see random sparks./..

i dont know which dizzy you have.. gm small HEI'S will send random sparks do to a cracked magnet sandwitch on the shaft. it is hard to see.

heat cycles do it to the whimpee ceramic magnet riveted between two pieces of steel pressed onto the shaft....

348tripower · October 11, 2007, 02:24:40 PM

Quote from: "wayne petty"warning.. the plastic caps on the pump shafts will brake on high volume pumps. leaving the pump without a drive...i cannot guarentee that this will happen.. but on small blocks it does...probably the reason the steel shafts were made...

you can remove the pump and spread the tips of the pump shaft by tapping a chissle tip into the gap.. this opens the tips a little.. if you notice there is a releif just below the tip on the pump shaft.. this snaps onto a notch ring machined into the steel collar this keeps the shaft from bumping up and down.

so the pump shaft should snap on to the pump... you might even need a little hammer to tap it on...

is there any chance while you are under there to mark the harmonic balance with a stripe of nail polish. 90 and 180 degrees off the tdc mark. to verify the dizzy is not sending spark to one pair of plugs to early because of a bent or cracked reluctor or magnet. an ajustable timing light moved from lead to lead you might be able to see random sparks./..

i dont know which dizzy you have.. gm small HEI'S will send random sparks do to a cracked magnet sandwitch on the shaft. it is hard to see.

heat cycles do it to the whimpee ceramic magnet riveted between two pieces of steel pressed onto the shaft....

So Wayne,
It sounds like you may thing I am on to something and not totally out of my mind?

I always prick punch the small block shafts to keep them on the pump. And I always use the steel one.
Don

Charlie Chops 1940 · October 11, 2007, 02:29:55 PM

I have broken a couple of those nylon, or whatever, sort of plastic sleeves some years back but have used the steel sleeve end shafts since. No difficulty. There really isn't a lot, or shouldn't be anyway, of room for that steel shaft to move up when the dizzy is in place, and I can't think of anything that would cause it to move up. The dizzy is locked in place vertically and should only have a little play in the shaft anyway. The dizzy end doesn't fit the pump drive tight enough to pull the pump shaft up during rotation.

I'm not convinced yet that the steel sleeved shaft is at fault...nor is Wayne, I think?

Charlie

enjenjo · October 11, 2007, 03:11:07 PM

One more thing to check, I had a 402 that would have a knocking sound at moerate rpm, after chasing it for some time, it ended up the fuel pump pushrod was too short, and would bounce between the cam and fuel pump under load. A new pump pushrod cured it. I suspect someone ground the shaft to make it easier to get together.

348tripower · October 11, 2007, 03:55:14 PM

Quote from: "enjenjo"One more thing to check, I had a 402 that would have a knocking sound at moerate rpm, after chasing it for some time, it ended up the fuel pump pushrod was too short, and would bounce between the cam and fuel pump under load. A new pump pushrod cured it. I suspect someone ground the shaft to make it easier to get together.

Frank,
That was the first thing I checked.

I'm stll leaning to the oil pump. Mallory has a distributor with a adjustable collar. They recommend .015 to.030. Seems to be a lot beter tha 3/16. I think I will order a new rod and compare.
Don

model a vette · October 11, 2007, 06:59:08 PM

I know there is a difference in the oil pump drive shafts when you install a BB pump on a SB. Maybe there is a difference in the shafts between a SB and BB? Maybe you have the incorrect shaft?

oiler · October 14, 2007, 09:37:45 AM

Quote from: "348tripower"Monday I dropped the pan off the engine. I gave it a complete visual inspection, checking for any metal in the pan etc. I rolled it over and inspected all the cylinder bores and found no scuffing in any of them. Everything looks great.
I did notice one thing. I can move the oil pump shaft up and down about 3/16 to 1/4 inch. By doing this I get this metallic noise, that would closely mirror the rattle I can hear. The shaft is the one with the steel bushing pinned to it.
I wonder, could this be the culprit? I would assume that under load this shouldn't move, but could it?
I am having a hard time convincing myself of the wrist pin rattle. It just doesn't sound like a steel to aluminum sound to me.
I can make this rattle by revving the engine in park and it starts at 2000rpm at cruise and goes away about 3000.

Ok gang have at it!!!!!!!!!!!!!!!
Don

I chased a rattle like that on a big block for a while
I was sure it was a fuel pump rattle or a wristpin
replaced the fuel pump and even pulled the engine and disassembled
Turned out I had 2 worn valve guides on #2 and 4 cylinders
Could'nt really tell until I disassembled the heads
Don't know if you've eliminated heads or not
Thought I'd let you know
Jeff

348tripower · October 14, 2007, 11:08:33 AM

Look!!!!!!!!!!!!!!!!!!!!!!!!
http://i178.photobucket.com/albums/w268/dcolliau/bearing.jpg

slocrow · October 14, 2007, 11:21:07 AM

Oh crap.............................even with that tough to see bearing area, it doesn't look goodly. Sorry bud...................

348tripower · October 14, 2007, 12:07:48 PM

Quote from: "slocrow"Oh crap.............................even with that tough to see bearing area, it doesn't look goodly. Sorry bud...................

Good news is the crank looks great. Checks to the bottom of the clearance tolerance but maybe a +.OO1 bearing set.
The bores in this are perfect so, change the rod bearings and go!!!!!!!
I'll check the mains while I am at it.

model a vette · October 14, 2007, 12:26:21 PM

Try to be absolutely SURE the crank is ok. I put one engine be back together after a bearing looked like that. I checked the crank and all seemed well. Later the bearing knock came back and I got a crank turned 10-10 and changed the bearings again. At $108 for the the replacement crank I wished I had replaced it the first time.
A friend had a 327 crank checked by two different places. They both said it was ok. After that engine seized I decided I wouldn't put an old crank back in a rebuilt engine without having the crank turned.
Cheap insurance!