I have a 1966 442 with what I assume is the original stock tri carb 400 engine. The odometer shows 35,xxx miles so I assume 135,xxx on the engine. There is very little history of the car with the exception of at some point it was converted from the factory installed automatic to a 4 speed. When I bought the car it was with an understanding that there was an engine tick, or knock, but it was not noticeable when I bought it and the seller was surprised that we could not hear it upon startup, idle, reving, or normal driving. When I got the car home, I noted an exhaust leak and figured that it might be the source of the noise. Both exhausts were replaced, and other minor drivetrain issues were addressed - a new clutch assembly, flywheel resurfacing, and a complete rebuild of the Hurst shifter.

When I got the car back from the shop and first drove it there was a noticeable knock and the mechanic said that it may have something to do with the new clutch bearing. When they went to check it however, the noise disappeared so it was assumed to be a bearing seating problem or something and no further attention was given to it. However, now i'm finding that when the car warms up and driven, a similar quieter knock is present on acceleration between gears, usually around 2000 RPM. The sound is not there at idle, or reving and usually not there at steady cruising (around 1500 RPM). It does not sound like a lifter, and is similar but not exactly like detonation knock. I have filled the tank one time with premium 93 grade unleaded gas.

I'm wondering if a fuel additive, octane booster, or lead additive may help? Or maybe something like a Lucas oil additive? Anyone have a clue as to the source of this knock?

 

Might be detonation in which case an octane booster could help. If it's not, this would obviously be wasted money. Does it have that telltale "marbles in a coffee can" sound? Audio would help here.

Regardless, if it were mine I'd start by doing compression tests, first dry and then depending on what that shows, wet. Post up here with results and we can help you to determine what the next steps should be,

 

Could also decrease the ignition timing, or disconnect the vacuum advance, to see if the noise goes away.

 

The compression test will also give you a clue as to timing. Too much advance will drain your battery well before you get to #8.

 

I would start by pulling the belts and inspecting all of the pulleys. A cracked crank pulley will make all sorts of weirdo nosies. It also eliminates a lot of white noise which will make your knock seem louder.

 

Hey Warren, put a timing light on it, see where it’s at, compression test etc as suggested. I can come listen to it maybe end of this week if your interested. Be interesting to see what’s going on.

 

When you say the noise is there on acceleration between gears, does it make the noise at the top of the rpm range just before shifting to the next gear?

 

Yes. Normally around 2000rpm. Seems like it's present when the engine is loaded.

 

Thanks. Will followup when I get results

 

thats not what I meant…maybe post a video of you driving it so we can hear it?

talk us through it as you drive

 

So this might be nothing and completely unrelated, but my 1964 Olds developed a knock as it heated up. Research led me to suspect lifters were collapsing, and I found my cam and lifters were worn. 135k miles is a lot, and if you've got a bad cam, then your lifters might collapse when stressed and cause a knock/tick/rap under load that is not apparent at idle. I'm not sure a compression test will reveal this, but that would be the first, easiest way to determine if your motor is all worn out. If you have low compression , that kind of tells you what you need to know.
You could also pull the rocker cover, the rocker assembly and the push rods, then roll the push rods on a flat surface and see if they're bent. Bent push rods can be a sign of a worn cam and lifters, and that might indicate more work is needed. It's one more clue that your tired old engine needs a rebuild. If you do this, be sure to put the push rods back where they came from- don't get them mixed up. That's very important. I hope this is helpful.

 

My 66 developed a slight knock due to a cracked piston,.. likely caused by poor octane quality/too much timing.
It broke between the top 2 rings.

You could hear it under light to moderate load & sometimes at idle.

Check compression & also look to see if you have any vapors puffing from the breather.

 

Knock got worse especially after the car warmed up. The consensus among a group of experts was that a rod bearing was the probable cause so I decided to have the engine rebuilt. At teardown it was revealed that the problem was in fact a rod bearing. Fortunately, the block, crank, heads and valve train are in really good shape so the damage was minimal and the rebuild should be reasonable cost-wise.

As the engine is out, I will have the leaky steering gearbox replaced. Anyone have suggestions as to the best option for this is?

 

Are you happy with the steering, other than the leak?

 

Steering is ok. There's not any excessive play in the wheel or anything. Could possibly be a little tighter but it's not been a problem. Also, I'm thinking that close ratio might be the way to go.

 

So, they're going to tear down the motor and rebuild, and I presume that's the whole job, but you should also get new camshaft bearings because you have to tear down the block for that, and then of course a new camshaft, which would suggest new lifters and a new push rods. Crank should be polished or ground, and even if they don't do the heads, you should have the cylinders checked, and the pistons and rings. All this can be done without doing the heads, and to me- it should all be done. Hone the cylinders and check the pistons, and replace the rings.

Check the pistons- that means inspect them for cross hatching on the skirts. If the cross hatch is still visible, they aren't too badly worn and you can probably re-ring them. Save the rods, just do the bearings, but do the crank.

That's how I did my 394. Heads were good but I had a bottom end knock that also turned out to be a rod bearing. While it's apart, do everything. I had the crank and block done at a machine shop, then I did the rest myself in my garage. Outside of parts, it cost about $800 for the machine shop to do their magic.

About the leaky steering gearbox- if it were me, I'd take it out, take it apart, clean it up and replace the gaskets and seals. Why not, right? What's the worst that happens? You gonna break it? It already leaks, right?

But that's me...