The Stovebolt Site Forums The Shop Area Engine Shop Knock in the low end of my 327

Well, today didn't go the way I planned.

I was out running some errands in my '62 C10, and I heard some noise coming from the engine bay. I got off the freeway and on to side streets and the noise went away at lower RPMs. So, I nursed it home and parked it.

Started doing some troubleshooting and found the noise is a knock coming from the low end. Sounds like a rod or crank bearing going out, so I dumped the oil and checked for metal. Sure enough, there was a lot of very fine, bronze colored "dust" in it.

Looks like it's parked until I can pull the engine and drop the pan. I guess I know what I'm doing this weekend.

Hy 62Stick, does your harmonic balancer have a retaining bolt? If your balancer does not have a retaining bolt the balancer may have worked loose on the crankshaft, if that has happened your will hear a knocking or ticking as the balancer is rocking back and forth. Check out the balancer first before your pull the engine. If your crankshaft is not drilled for a retaining bolt, Hotrod Lincoln here on the forum has made up a kit that he will loan out that will allow you to drill and tap your crankshaft while the engine is still in the vehicle, hope that helps.

Another thing you can do before a complete disassembly is to remove the oil filter and cut it open. A full flow filter strains out the big chunks of metal from a failed bearing. How difficult is it to drop the oil pan? Sometimes it's easier to just pull the whole engine, but dropping the pan and looking for a loose or discolored rod might be a good preliminary step. By the time an audible knock is there, you'll probably need to regrind or replace the crankshaft due to wear or scoring.
Jerry

Thanks guys! I'll check the harmonic balancer first. Not sure if I can drop the pan in the truck. I've never tried that. I did toss the filter already. It is no longer available. It went out with the recyclables this morning.

Hopefully, it is just the harmonic balancer, but I kind of doubt it. My first thought was a stuck or collapsed lifter, so I put an oil treatment in for that. Knock got worse. I dumped that oil and filter and put in all fresh and it went back to what it was. Makes me think it is bearing related, but I can hope for a simple fix.

Just checked the harmonic balancer, it's a bolt on and it's tight, so that can't be the problem.

I'll pull the engine this weekend and put it on a stand. I'll start the teardown by dropping the pan and seeing what it can tell me.

I stand corrected, my 327 crank is not drilled and tapped for a harmonic balancer bolt. What I felt when I checked was one of the bolts that hold the pulley on to the balancer.

I started disassembly today and now have everything from the water pump forward removed. I can now physically see the end of the crank and there is no bolt. It looks like it is just a tapered hole in the end of the crank, no threads.

I tried to wiggle and pull the balancer, it's not moving, so I still don't think that is the problem. Only things left to disconnect now are the 6 exhaust manifold bolts (I'm leaving the manifolds attached, disconnecting the pipes), the 4 transmission bolts (I'm pulling the bell housing with the engine), the 4 mount bolts (2 on the bell housing and 1 on each side of the engine), the oil pressure gauge line, and the hydraulic clutch line. 4 bolts on the hood and the engine will lift right out.

Be sure to support the transmission. Speaking from 50-something years' worth of experience, it's a LOT easier if you pull the transmission first, or at least slide it back a few inches. Trying to jockey the engine out past nearly a foot of input shaft is a P I T A!
Jerry

If you are pulling the bellhousing with the engine, do as Jerry said and drop the trans first. I would consider leaving the bellhousing and trans in and just sliding the engine forward. and pulling it. I did that more than once on my 59 Suburban. Your truck may be a bit different on the clearance in front than mine was, not sure.

Hmm....

I have a ton of space in the front of the engine bay, but you guys do give me cause to reconsider my course of action. I just hate trying to reach those bell housing bolts, but it sounds like I should reconsider. Thanks for sharing your experiences.

Here's a shot of the engine bay showing how much room I have. I will be following your suggestions though and leaving the bell housing in the truck with the transmission.

OK, I pulled the engine today and dropped the pan. No major chunks of metal, but I did find the issue.

The number 7-8 Rod journal on the crank was hammered. Probably caused by the number 7 rod bearing which was extremely worn and missing a chunk of bearing material and the number 8 rod bearing which had spun in the rod and was wafer thin and both halves were nested on the rod side of the crank.

Looks like I will be doing a full tear down and rebuild. This is an RPO L30 Spec. engine, (275hp). I think I will rebuild it to the RPO L79 Spec. (350hp)

Well that explains it! Good you caught it before it grenaded.🛠

The crank in the picture is a forged item, not cast. Be sure to replace it with the same style if you're going to rebuild it to the higher HP standard. That one can probably have that one journal welded and reground if you have problems finding another forged shaft. Some of the later model low HP 327's had cast cranks. The way to recognize the HD shaft is to look for the wide parting line on the crank throw, like your current shaft. Cast cranks have a very narrow parting line.
Jerry

My research had told me I had a forged crank. I agree, moving up to L79 specs requires the same. I wouldn't trust a cast crank on that horsepower range. I don't use it at that level very often, but occasionally getting on the freeway is fun to open it up a bit.

Usually, I just keep a nice, sedate purr. Shifting from 2nd to 3rd around 15-20 mph, and from 3rd to 4th around 30-40 mph. Plenty of power in an old 327 for my C10. But since I'm rebuilding and my research shows this engine has all the right goodies to upgrade to the higher performance of the L79, I figure "why not?" It's still a factory spec configuration. :-)

One thing I love about these old trucks, they talk to us. A modern vehicle won't tell you it's dying, it just goes out. It might throw a light, but it won't talk to you like these old trucks do.

Well, it's all torn down and reduced to a pile of parts now.

Looks like someone has been into this motor before. Pistons are +.030, and someone went ballistic with the silicon sealer. It was everywhere. It had an aftermarket cam in it as well (Viking 100H). The good news is that there is no perceptible wear in the cylinders and the pistons look good. I think I can get away with a hone and rering. I do plan on hot tanking and replacing ALL the bearings though.

I think since this is by no means a stock engine any more, I will continue this thread in the HiPo forum. Thanks for all the help and suggestions so far.