We went ahead and bought the 70 (inline 6, 3 on the tree) that I talked about when I was asking about tires/wheels. When we went to look at it the second time, we fired it up. The engine starts up just fine, but has a loud rattle sound. However, since the body was in such great condition and nearly everything is original (right down to the radio delete cover) AND they came down on price, we went ahead and pulled the trigger on it with the expectation that the engine might be bad. Still a good deal I am happy with.

At any rate, our only option to get it home was to drive it. It drove fine, seemed to have plenty of power- I would say it ran pretty close to flawless- except for the rattle noise.

Got it home, pulled the valve cover and checked valve adjustments- everything was fine (funny, once I had the cover off, I felt like the noise was lower down somewhere). Checked the compression- all good. Pulled the fan belt off to see if it was the water pump- noise remained. Surfed the Internet- tons of flexplate noise issues, but this is a manual. Oil pressure is fine. Exhaust is normal.

I know I went into this thinking an engine replacement was in the cards, but man, this engine is clean enough to eat off of. The PO did put headers on it, but as far as I can tell, that is the only mod from stock. Noise is constant, and the best way I can describe it is it sounds like someone filled a bucket with old pistons and rods and started shaking it. It doesn't sound like any rod knock I've ever heard.

What do you all think?

 

Maybe at the wrist pin location?

 

toss some Marvel mystery oil in and see if it helps . I don't like snake oils but Marvel just works !

 

9A430/9460 in this diagram MAY be your problem.

http://www.fordification.com/tech/im...anifold-I6.jpg

 

That can't be it- truck has headers.

 

Previous owner said he thinks it is the throwout bearing, but I don't agree. Noise doesn't change when the clutch is used. It is proven difficult to pinpoint the noise location since the truck has headers and glasspacks right off the headers (with no further exhaust).

The PO also said it was a 300, but the VIN code is A. But it has been 46 years, sooo...

I'll have to say, this is my first classic vehicle with a 100% unmolested and undamaged wiring harness. Even checking out the area behind the radio delete plate, there is no evidence that a radio has ever been placed in the truck. The only modification ever made was the headers.

I do have to contend with a few missing pieces though, such as the grille inserts, side marker covers, dome light cover, rear bumper. The grille shell is usable but dented up pretty good. Other than that, I'm mainly looking at a bed floor center section due to it being used as junk storage for years.

 

FYI.. the 70 grill shell is a one-year only spec. IIRC, the inserts' tab locations are slightly in different locations than the 71/72 shell.

70 inserts are not reproduced but unbroken inserts do pop up on eBay or CL.

 

It is not the throwout bearing. That is out of the picture when the clutch is in.

It could be a leaky header gasket. Take a piece of garden hose, one end to your ear, the other end poking around exhaust. If you locate it, pluck the plug wire to confirm. No pop if no spark.

Or, a dreaded rod or wrist pin. Remember, these are very long stroke motors so sounds will be different than you V8s. Again, pluck plug wires one-by-one and see what goes away or doesn't.

As the poster above said, Mystery Oil in the crankcase can do wonders for freeing up sticky stuff.

These are very, very tough durable motors. Congratulations.

 

Ah, I missed mention of that the first time I read your initial post.

 

Does the noise change when the engine is under a load ?

 

I had a 240 with one lifter that would stick once in a while. If I revved it up a bit it would stop for a while. Ran it for years like that.

 

The only other weird noise I have heard was a fuel pump with a broken return spring that would come and go as the pump would build pressure the noise would stop for a few seconds then start again.

 

So let me run this past you- I went under it to look at the flywheel inspection plate. It is a home made deal. Is the inspection cover supposed to sandwich between the bellhousing and the starter? Because that isn't happening here- the starter is right against the bellhousing, and with the cover off, the starter body is unbelievably close to the back of the flywheel.

Do you think it is possible that the starter gear isn't retracting enough? Could that cause the noise?

Also, these headers have got to go- it looks darned near impossible to change the starter, they hit the frame in three locations, and you almost can't route the starter cable anywhere without touching. The headers rubbing on everything makes some noise, but it isn't the noise I'm chasing...

 

What you are finding could be the cause. The plate that is missing also is what keeps the starter located to properly mesh with the flywheel. Also since the plate is missing the clearance between the clutch fork and pressure plate may be too close.

 

Okay, I found the mangled shield that used to go there (it was with the bed junk). I took thickness measurements by the starter bolts with a micrometer and made me up some temporary shims.

Noise still exists.

I got a hold of a mechanics' stethoscope and started probing. Noise is worst when probing the driver side of the block between the 5th and 6th cylinder. After letting it warm up, I listened around the exhaust. I'm not sure what brand the headers are, but they are two separate headers (bank 1-3 and 4-6). There is a noticeable stumble from the 4-6 side, and the exhaust smells oily.

I'm going to go ahead and use the "stick a fork in it, it's done" phrase now. I'm gonna check out the two I-6's I found on Craigslist.