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Discussion Starter #1 (Edited)
Hi everyone,

I bought the 1968 Mercury Montego from a dealer. The backstory on the car was this...the father/previous owner of the car had died, the son had either sold it to him or traded it in on something. He said the car had sat around for a few years, then in the 90's the father had "hot-rodded" it, whatever that means, drove it around for a while, but had a minor wreck and the car sat around for 15 years or so, until it was sold to him, then to me.

The engine never leaked a drop of oil in the several years that its been in my garage, but now today, with the engine out of the car, I'm de-greasing it, wire-wheeling the rust off of it, and I flip it over to remove the oil pan and this is what I find. See pictures...

First, the oil pump is a Melling M57HV. This is a high volume pump, according to my research, this can be a problem if other steps weren't taken during a build. However, I'm not sure what these steps are, something about plugging one or more oil galley holes, but I wouldn't know where to look to verify this was done properly. Should I just assume this engine was rebuilt, and done right? The car drove, and shifted fine, and would idle and not overheat, was sending oil up top, and the longest test was about 20 minutes with no problems.

Next thing that caught my eye was this OFF COLOR piston rod. The other 7 are all the same, two different colors, but this one is all orange-ish, what do I make of this?

Third, this is how the oil pan looks after being wiped down. There was some sludge in the bottom, but nothing metal, no shavings, does the location of the black areas mean anything?

Fourth, see that big dent, I'm pretty sure that was part of the "accident": that retired the car or the dad as the driver of the car. Should I try and pound that out, leave it, buy a new pan, what?

Fifth, the old pan gasket was cork, with a LOT of silicon helping out. What are the best value gaskets for not dripping...cork, Fel-pro synthetic, some brand new technology?

Also, I found spring shims too, see thread here, if this makes a difference... Questions about 390 spring shims.

Thank you for reading this far and for any helpful advice you might offer.

melling_m57hv.jpg 390_rods_1.jpg 390_rods_2.jpg 390_oilpan_1.jpg 20200626_214432.jpg 390_oilpan_3.jpg
 

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Discussion Starter #3
Update...the dark areas at the bottom and sides of the pan were rust, seemingly treated with something like Por15 as a quickie fix. My guess is that is the reason the engine was rebuilt, it sat for years and got some water inside the engine. I got rid of the rust, and pounded out the dent in the oil pan, somewhat, just want a driver, not a show car, so it still has some character. But the single orange piston rod is still a puzzle to me. Any ideas?
 

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The rod color is oil baked on it. Some oils will do that no matter what. I get the feeling it was rebuild, to some degree. Rod/Main bearings and piston top will tell you. Piston if they're overbore are stamped how much. Rod/main bearings should say FoMoCo and be standard. Either means someone was in there.
My guess if he over reved it, and kissed a piston damaging it and bent the valve. Replaced the rod/piston with another and changed the valve/did a valve job, and that's where the shims come into play. (Check that rod bearing might tell you) How do I know, been there, done that, have the T-shirt to prove it. Both on a 429SCJ and 390GT.
That's why the pan gasket material is non-factory and he put in a better OP while he was there.
The pan dent? Happens all the time and many engines and auto trans suffer and die as a result of it.
 

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Discussion Starter #5
Hi Ricky, and thanks for the info. Since it was running fine, I didn't want to pull the heads unless I absolutely had to. It would be nice if the P.O. had put in hardened seats so I could run straight gas with no lead additives, but I guess there is no knowing that without removing the heads. Your theory makes a lot of sense, just do enough to get it to run so you can sell it, kind of thing? I'm virtually certain the heads have been off, as well as the intake manifold because the gaskets stick out so far, just doesn't look like any car I've every owned or seen from a factory. I had to file them down, some places they were sticking out almost a 1/4 inch.

I got it painted Corporate Blue yesterday, so when I am stripping off all the masking tape today I'll take a closer look at the bottom end, but I think I'll stay away from pulling a cap and inspecting a bearing, going to leave "running fine" alone. I'm just hoping I can get a few years cruising around out of it, and then completely rebuild the engine with new aluminum heads and intake so I know exactly what I've got.
 

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When you decide to rebuild it, pull it apart first. You might have one punched out to the max. If you still can take the pan off, check the front crank counter weight for any stamping or writing saying it's been machined. They always mark it for the bearing people to order the right ones.
 
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