Technical What is this engine sound? More '54 Nash Rambler diagnosis, things are looking bad...

So I've been trying to get my '54 Nash Rambler on the road for the summer, which I've been working on here and there over the past couple years. I'm a fairly decent sheetmetal/body man but a very novice mechanic so I need a lot of hand-holding. I had carb issues that I worked through with help I got here, and after taking the car on it's first drive all warmed up on public roads, the engine made a noise while driving that I never heard while it was just idling or just starting it up to move it around the parking lot.

I thought it might be spark knock/detonation, so (again with help from other HAMB members) I set the points and adjusted the timing (which was advanced a fair bit) but the sound remains. I'm confident now that everything is at book-spec. I also set the idle mixture (using a Mikes Carburetor Youtube video) and I even tried the old trick of running a little water down the carb while it was running to see if maybe it was carboned up and I could clear it out, but that didn't seem to help, so now I'm pretty sure it is not a spark knock/detonation issue.

I took a video with audio, which isn't the best audio but I think you get a good idea. I'd really appreciate it if any engine-knowledgeable people could give it a listen and tell me what you think it is.



The sound only seems to be at part throttle, and if I'm very careful, I can drive the car around without triggering the sound (or at least minimizing it).

I guess my questions are, #1, what do you think that sound is? #2, is there anything that can be done to quiet it short of an engine teardown? and #3, is there any hope of me being able to drive this around some without imminent danger of the engine exploding suddenly?

I'm getting married in about a year, and I have a ton of other non-automotive projects that need to get done in the next couple summers, plus I'm an extremely novice mechanic so there is zero chance that I'm tearing this engine down, certainly not in the next couple years. I don't have the time to do it and I don't want to make the car immobile either.

If the engine is ****ed, it'll have to get parked and I don't know what I'll do with it or when I'll get back to it, that would be pretty crushing disappointment but I need to know. If there's a chance this is an easily fixable issue, I'd love to hear it (but I'm not holding my breath). If I can maybe put some additive in it and drive the car around very gently/carefully and that wouldn't be some horribly foolish choice, I'd love to have your opinion on that, too.

Break it to me, I can take it. Thanks in advance for any thoughts or replies.

 

do you mean the rod knock? or something else?

But it's hard to tell from the video exactly what's going on.

I'd be inclined to pull the oil pan off and look at the rod bearings. I think it's not very difficult, but then I can't look at the car.

 

Does it have a oel filter? Cut it open and look for any surprises inside

 

That was my fear.

It does not have an oil filter.

 

Yeah, sounds like rod knock. This is when the crankshaft journal clearance to the rod bearing has opened up (rod bearing wear) to the point where the oil cushion between the two is no longer a solid.
As Jim says, it's typical to remove the oil pan and inspect. You can try thicker oil and/or additive, but it's not going to get better and continued use can cause much more damage, such as rod bearing spinning, damaging the crankshaft, or even if ignored longer, 'throwing' a rod or seizing.
I can't walk you thru the procedure better than the manuals, and there are videos to cover the basics, I'm sure. Realize it's one of those 'not fun' jobs, but can be done by a novice provided the oil pan comes down and off fairly easily and you take your time and pay attention to details.
Best case, it's just bearing wear and you can swap the bearings out. Worst case (it doesn't sound like it, but I have seen 'quiet' messes) is the crank needs work which means the engine out is the best route.

Here's the first video I found showing a knock. Not fantastic, but covers the main points well and you can hear the knock.
www.youtube.com/watch?v=CyxTNuW4apo

 

Drain the oil into a clean container, look for glittery stuff. One thing you could do is put some 20w50 oil with -gasp- some Lucas oil stabilizer and see if the noise quiets down if so probably is a rod brg as @squirrel says, he’s good so I lean towards a rod bearing. If it’s s bearing and the crank isn’t scored badly you could replace the bearing and run. Kanter has under size 0.001 and 0.002 bearings. The job isn’t all that bad if you can remove the pan with the engine in place. Wish I was closer.
https://www.kanter.com/products/engine-connecting-rod-bearing-rb664
Dan

 

@RodStRace beat me to it
Dan

 

Well, at least you won't have to worry about the timing for a while.

 

Sometimes a Mechanical Fuel Pump can sound like a Rod Knock, an old broom handle makes a decent stethoscope, and can give you a good idea where exactly the sound is coming from.

 

Well, first he's got his feet wet getting into mechanics and is willing to listen and learn. Kudos, and knowledge is power. Second, if it can be repaired with a rod bearing swap, it's another skill gained and it will be fairly cheap. Confidence well earned.

I will also mention something else. A person who has the experience would feel the oil on the dipstick and know if it's diluted. While the noise indicates an issue, an oil change with a fresh thicker oil might confirm. If he decides to dive in, save this and reuse = no additional cost. @Sharpone covers this.

 

I saw a mechanic friend of mine at the bank and he said he'd stop by and listen to it for me, he says it sounds like a rod knock, he thought it might be coming from #1 or #2 cylinder. He has a hoist and he said he might be able to help swap rod bearings out but it wouldn't be until this winter.

Just for the hell of it, I drained a quart of oil out of it (which was pretty fresh, had basically no miles on it but was just ever so slightly g***y smelling from having to prime the carb to start it before I had the carb/choke issue figured out) and I put a quart of Lucas in it.

It is a lot quieter now, like very noticeably so, but I still know the issue is there.

I suppose I could take the mechanical fuel pump off, block it off and run it off of a gravity fed can just to confirm it's not the fuel pump making that noise but I'd be pretty shocked if it was, especially because adding the Lucas to the oil really quieted it down.

I'm not really sure what to do, I think I need to set this one aside for a while and come back to it at a later date. I really want to drive this car, but I do NOT have the time or the mental capacity to tear into the engine right now. It's a heartbreaker for sure, but it's not the end of the world. At least it could still theoretically be fixed without a complete rebuild. I'll circle back to it when I have a clearer head and a bit more free time.

 

Sometimes a loose piece of carbon can end up in the cylinder and make a similar noise. If the carbon can manage to find its way past the exhaust valve the noise may go away. For what it's worth you might be able to isolate the noise to a single cylinder.

With the engine warm and running disconnect one plug wire at a time and slightly rev the engine. If the noise stops or diminishes by decreasing the combustion load for one specific cylinder that will narrow things down a bit. If you have a bore scope you might try to take a look into that one cylinder and see if there's anything su****ious looking.

Do these engines have full pressure oiling? How much oil pressure are you seeing? If you decide to change oil you won't need anything fancy. Just some old fashioned 10w30 or straight 30w should be fine.

A quick check for oil dilution? Drip a couple drops of oil off the dipstick onto a dirty or dust covered panel under the hood. Or even onto a clean paper towel. If the oil drops spread out quickly that's probably because of fuel dilution.

 

On the bright side, it Yard drives.
Not bad for a 54 Nash
I bet Squirrel has a Nash motor in his garage.

 

If the oil is fresh, that ends the dilution concern, provided it's not some 0W40 or something goofy.
That it quieted is a decent positive. As I said, I've seen quiet motors with bad cranks, but it bodes well.
Taking a step back and not having to get it back into daily operation is a luxury, so relax.
A friend who has experience be able to listen in person is good too. It can confirm or dispute a bunch of us keyboard warriors. The pulling of plug wires is a common quality test, but if it's what we all suspect, you will check them all while apart.
When you can come back to it and research gaskets and bearings, plus read up on the job with a fresh outlook, it will go smoother.

 

Well, that’s a damn shame, you were really on a roll with that baby. I know exactly how you feel, I had a nice Olds Rocket engine that did the same thing. I would put it on the back burner for a little while and formulate a plan. You could probably use it for short runs if you can learn to keep it out of the knock zone.
In-line sixes are pretty easy to work on, the hard part is usually getting the oil pan off if it’s trapped in by a tight front crossmember. Otherwise it’s just straightforward unbolt and bolt back on stuff, nothing you haven’t done before. Do you have a hoist? It’s way easier with it up in the air.

 

Nope.

I had a 59 Rambler a few years ago with the OHV version of the 196. It burned a lot of oil...I took it out, removed the head and pistons, but left the crank in, and did a quick ring job and lapped the valves. That mostly cured the oil burning, and I drove it several thousand miles before I sold it. So I have a little experience with Nash motors, but not much.

 

There's a crossmember connecting the bottom of both of the front suspension units and the steering linkage in the way of getting the oil pan off. The Nash book says that both of those things need to be removed to get at the pan, but does not mention what the effect of removing that suspension tie bar is. Like, does the body need to be suspended with the weight off of the suspension to remove that? Is **** going to move around once that's unbolted, is there some sort of adjustment there? The car has no frame, so there's nothing else really holding the bottom of the suspension in place, I don't think. An alignment on this car would be a nightmare since you can't get gauges on the front wheels, so I wouldn't want to disturb that. This car's bizarre design isn't making any of this easier.

I need to find the answers to these questions and more before I dig in here. I would need a hoist and some very accurate measuring tools to have any confidence in my work. According to the book, the engine is removed by dropping it out the bottom on it's crossmembers (like a front wheel drive car) so I definitely don't want to do that either.

The Iola car show/swap meet starts tomorrow and on Saturday is flathead racing at Sanford Field so the car is going to sit awhile and I'm going to start talking to friends and experts about this issue. If and when I do dig into this, I want to go in armed with knowledge and not just grasping in the dark.

 

If the engine comes out the bottom ON the crossmember, that should mean the engine mounts are on it. That bodes well for structure of the body, BUT it also means the engine must be supported when the crossmember is removed. This can't be under the pan, or removal is blocked. Can't be under the balancer either.
FWD stuff uses a support bar across the engine bay and chains and screws to hold from above. I doubt this is the Rambler method! More research required.
It could be done by supporting the engine on the pan (use a chunk of wood to keep from denting), remove the crossmember and mounts, leaving the engine side brackets on. Then support the engine at those brackets and remove the jack and wood from the pan. Often the idler arm removal will allow the tie rod/center link to droop enough to remove the pan.
On the ground, you would lift and support the body for room. Probably a good idea to do this even on a hoist, so the weight isn't on the unsupported lower control arms.
I would put location marks on this before removal and try to get things back in the same position whichever method used. Just like a hood or door, since that's your field.

 

'Long time ago, I was told
"Son, your Knocks are Roddin'- "

 

Drop the pan
Polish up the offending journal
Install the closest sized bearing

that’s traditional

 

There's 3 crossmembers under the engine, the center one in the way of the oil pan is not holding up the engine in any way. Reading through the Nash repair book, it does seem like that crossmember can be unbolted without messing up any suspension settings, it's just a tie bar for the suspension apparently, so that's a huge plus. It's the other two that support the engine and trans and those are not in the way of the oil pan. It looks like the car should be supported with weight off of the suspension before removing that center one, but that's no big deal. So that's encouraging, if I'm reading my book correctly. The book even says engine removal is not necessary for rod removal, so I'm pretty sure some bearings can be snuck in there.

This is what is going to happen, as soon as I have the time and equipment to pull it off without pulling my hair out. I hope that's sooner than later, but it very well may have to wait a while, we'll see what fate deals me.

I'll do the best I can, when I'm able to. And however it turns out once that's done, is how it's gonna stay. If it still makes noise after that, I'll run it until it blows up.

 

Gettin that pan out, from here, doesn't look too bad.

 

My rambler had the mounts attached to the front of the engine, the plate that goes on the front of the block

 

If one bearing is failing, others probably close to doing the same thing, more running is going to do more damage. It really sounds like a rod in the video, take it apart when you have the time and money to repair the engine correctly.

 

they copied my flathead dodge truck engine mount!

 

Definitely a rod knock. Don't worry your hair will grow back. Maybe. Definitely change all of the rod bearings while you are in there and pull off a main cap to check on them also. If the mains look OK then a re-bearing of the rods is about the same as an 18-wheeler in frame rebuild. No need to pull the engine, bore it to clean up the cylinders and buy new oversized pistons and rings, grind and all new oversized bearings not to mention the valve guides and. You are building a driver not a daily that you intend to drive across the country. They usually will also replace the mains and possibly the rings to gain another few hundred thousand miles with an 18-wheeler in frame rebuild..

 

But before you do all that work, think about how many miles you really expect to drive the car. No need to do a 100,000 mile overhaul if you're only gonna drive it a few thousand miles.

 

Yeah, I have helped with an in-car overhaul. Even bored and honed it.

I'd go with a rod bearing swap, a crank polish and check mains. If it gets any deeper, I'd look to swap a good runner. They may be tough to find, but the value in time and money would tip it to one and done. Otherwise, it drifts into mission creep.

 

Yep need to nip that in the bud, as Barney said. Nash should have a forged crank and you don't want to let it get damaged.

 

When I was growing up, one of our family cars was a 57 Chevy 210, with a six cylinder engine.
The thing developed a rod knock on a trip to the farm and my daddy took it to a local guy in a little shade tree shop in the small town closest to the farm. It was an old corrugated metal building, but it had an outside ramp to pull the car up on.
My uncle, who was a real mechanic for a dealer, was also at the farm and had diagnosed the rod knock, so once on the rack they dropped the pan and found the culprit. No parts store even close, much less open on Saturday afternoon.
So they used a piece of a check from daddy’s check book and cut a shim. My mechanic uncle said that the check paper would hold up. Shimmed up that bearing insert and it ran for years until my brother wrecked the car.