The Stovebolt Site Forums The Shop Area Engine Shop Engine Noise - Need help troubleshooting

I've got a '57 3600. I believe with the original engine. Had a strange rattle/knock/tick when under high RPM, but not under all loading situations, or so it seemed. Hadn't looked into it, though perhaps I should have.

Driving along yesterday, I was accelerating and the accelerator got stuck down to the floor. Stuck to the carpet or something, revved very high when I was in neutral shifting to 4th, but it was just a second before I reached down and freed it.

Since then what sounds like it could be the same noise is much louder whenever rpms are increased much above idle.

I've pulled the valve cover, and the rocker arms and push rods seem to look fine. I pulled the oil pan. There was some debris at the bottom of the pan, very crumbly, though it looked rusty metal like. Spun the engine and couldn't see anything amiss. Nothing looks bent or damaged in a visual inspection.

With the engine spinning, it sounds like cylinder 6 is making a bit of a popping noise as the piston is heading up and a slightly different odd noise as it comes down. I'm afraid I don't know enough about what it could be, or where to look further.

I don't want to keep tearing things down without knowing what I can and can't rule out.

Thoughts/Suggestions from more experienced folks?

Rod or main bearings. While the pan is off reach up and see if you can move the rods up/down any at all. If so its time for new bearings and probably a regrind on the crankshaft. Good luck.

That's one thing I was checking, but I couldn't seem to move the rods up and down at all. There seems to be a little bit I can move them front to back, but they all seem to do so the same amount.

Is there a particular point in the stroke this should be easier to feel?

I'll try again tonight to see if that tells me anything.

Thanks.

Pull the rod caps one at a time and inspect the bearings and the condition of the crankshaft. If the crank is still round within about .001" or so and not scored you can probably swap bearings and button everything back up. Very slight scoring can be polished away with a strip of fine emery cloth and a shoeshine motion, followed by a GOOD cleanup to remove any abrasive residue. Be absolutely sure to measure the crank journals for out-of-round with a micrometer, not a dial caliper, to be sure it's within specification.

Drop the main bearing caps one at a time and inspect the bearings while you've got the pan off. Mains are a little more difficult to change than rod bearings, but not impossible. It's a bit more of a problem to measure main bearing diameter in the block, also.
Jerry

I only have calipers, so looks like I'm in the market for a micrometer. Am I correct in thinking something in the 3" range is what I'll need?

Standard-diameter rod journals are 2.311"-2.312" so a 2"-3" mike would be appropriate. Common undersizes are .010"-.030" so the minimum diameter you're likely to encounter would be 2.280" or so. There are 4 different size main bearings, ranging from 2.683 at the front to 2.775 at the back. It takes a very special-design mike to measure mains in the block, something that would be difficult to find outside a specialized engine rebuilding shop. A pretty good guesstimate could be done with a modified set of outside calipers and an inside mike, after a LOT of practice. I've been measuring crankshafts since the early 1960's, and I wouldn't be very confident of getting a good reading that way.
Jerry

if you are looking for a set of micrometers, I got a 1-4" set (4 micrometers) from Shars, for something like $50. If you are only needing these for occasional use, this is a good deal. As far as I can tell these are absolutely accurate, I don't suppose they would hold up in an industrial setting, but if you are only going to use them 30 times in your entire life, there is no reason to buy a $1000 worth of measuring tools.

I do a lot of business with Victor Machinery Co. They have good quality tools and machine shop supplies, and very good customer service. Here's a 0-4 inch set of mikes:

http://www.victornet.com/detail/VME-14.html

A 0-6 inch set is only $99.00.

Jerry

Well, I may be pushing the limits of my mechanical abilities. I did acquire a micrometer. It's not great but seems very repeatable on a square block. I cannot seem to get a repeatable measurement at any single point on the diameter of the journal however. I keep getting a chord instead of the diameter. More practice I guess, but it reduces my ability to trust any measurements I make.

The most likely point of maximum wear will be the vertical measurement with the crank journal at the bottom of its rotation. The least-worn spot will be 90 degrees from that point, side to side with the crank at the bottom of the stroke. It's not uncommon to have 2-3 thousandths difference in those readings, and/or some taper wear from front to back. The maximum allowable wear is .001" out of round, and .0005" taper.

Try measuring something round like a big socket to get into practice measuring crank journals. It's an acquired skill, for sure!
Jerry