390 motors

390 & up cid Monster Motors

Re: 390 motors

Postby loman » Sat Mar 03, 2018 5:15 pm

Well she runs! A little hot wire here and hot wire there, loop the heater hoses, hook up electric fuel pump and fuel line,rig a lawnmower gas tank, and a good dose of starting fluid and the truck 390 fired up. I took the 2 bbl that I rebuilt off of my white car and put it on the truck and she just idles away. The valve train is noisy as heck. I didn't pull a valve cover yet to check anything. We put a 1/2 quart of trans fluid in the crankcase hoping that will help clean the motor. After it ran a bit, we got a dose of some old varnish gas from the mechanical fuel pump. The gas tank is out of the truck but there must have been some left fuel in the line. At least now I know the motor runs. After we run it some more we will do a compression check to see what we have.
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Re: 390 motors

Postby loman » Fri Mar 09, 2018 10:31 pm

I tore down my mock up FE block (352)this evening. This has to be the dirtiest motor I have ever messed with. One odd thing I noticed was the main bearing oil holes. On #2 and #4 main, half of the round oil hole from the block was covered up by the bearing. #3 and #5 were perfectly lined up. I don't remember #1. Is this typical for FE's or did someone screw up installing bearings? It wouldn't surprise me if somebody did something goofy because when I dropped the oil pan I found a bunch of plastic timing gear teeth. A few were even sucked up to the oil pump sump. The ironic thing is the timing gear on it was fine. I'm guessing someone changed the timing gears and didn't bother to clean the old broken one out of the motor. I also noticed that the #2 cam lobe was nicked up badly on the back side and the back 2 pistons had the top ring broken. This was supposedly a good running motor that got hot. :shock:
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Re: 390 motors

Postby Lou's Comet » Sat Mar 10, 2018 8:11 am

loman wrote:I tore down my mock up FE block (352)this evening. This has to be the dirtiest motor I have ever messed with. One odd thing I noticed was the main bearing oil holes. On #2 and #4 main, half of the round oil hole from the block was covered up by the bearing. #3 and #5 were perfectly lined up. I don't remember #1. Is this typical for FE's or did someone screw up installing bearings? :


Refreshed a 390 last year for a buddy. Had the same thing. Couple of the oil holes in the main bearings blocked half the oil hole in the block. I also thought this was weird and that something was wrong. But from what I found out this was typical :(
This was a low mileage engine that was never taken apart. Engine also had some broken rings. It did run before taking it apart but smoked a little.

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Re: 390 motors

Postby loman » Sat Mar 10, 2018 8:13 pm

Lou, I looked at mine again and I'm thinking maybe it was done that way to restrict the oil flow to 1 2 & 4 mains while 3 & 5 got plenty of oil for the thrust bearing and rear main seal.
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Re: 390 motors

Postby loman » Mon Mar 26, 2018 7:14 pm

We did a compression test and leak down test on the 390 truck motor. Compression was weak and unequal and the leakdown test showed that the rings aren't sealing. Also, the C-6 trans is slipping. It had a lot of trouble pulling itself, it kept slipping in and out of gear. Well at least I have good cores. So, next step I guess is buying the Crites shocktower kit, and get the motor tore down and rebuilt.
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