I'm assembling my 390 and I got the pistons in and am putting the rod bearings and rod caps in. All fit fine except one. When I tighten it down I can't hardly move the crank. All the rest are torqued and the crank moves normal.

I took out the piston and cap 5 or 6 times and pulled the bearings out and cleaned behind the bearing and inspected them and reinstalled them only to find the crank so tight it starts to polish the bearing with one turn of the crank.

Finally I found that when I place the bearings and lay the cap in place, the bearings hit before both sides of the cap hit. So when it is torqued, the bearing is pressed so hard it must be deforming the bearing so it doesn't work well.

With the bearing in place, the side of the cap with the bearing indent rests tight to the rod surface, but the other end of the cap has about .020 gap between the cap and the rod, but the bearings hit.

My rods are 360 rods, but I have another 390 apart so I grabbed the 390 rods and the bearings fit fine in them. The only thing I can think of is that the rod is bent a little on this side of where the bearing rests. I'm guessing the rod bearing surface is bent outward in the direction the force would push it, and that is why the .020 gap between mating surfaces on that side.

Has anyone had this problem, or does anyone conclude with my diagnosis?? Where can I get a new 360 rod?

I guess I need a new rod. Where can I order a single rod? It is a 360 rod which is a little less beefy than the 390. It is a C6AE cap but the rods are C7TE-A.

 

Horsepuller, I would take all the rods to a good automotive machine shop for reconditioning. This will correct any problems or weed out bad rods. The machine can get you a replacement rod. JMHO

 

Could be wrong, but I thought when they resize the rod, they take a little off the cap mating surface, bolt it to the rod and rehone the big end to get the proper opening size. Almost sounds like they took some off the cap and forgot to rehone.

Reggie

 

One question why are you using 360 rods in a 390? Isn't the difference in length going to cause problems?

Reggie

 

I am also rebuilding a 390. When I took it apart it had the long rods also. The guy I bought the short block from gave short rods for it then. I had to buy one more so I went to the machine shop and bought it. Told the guy what had happened and he said some 390's with 2 barrel carbs came with the long rods. Thought he was feeding me a line so I called my uncle, he's been a mechanic for 35 years and is a ford guy. He said the same thing.

 

No, I mis-spoke. This is the 360 I'm putting back together. I am tearing down a 390 while putting back together another 360. These are the 360 rods, for the 360 crank, which are longer but much less beefy than the 390 rods.

 

Now I'm really disappointed because I got rid of all my 360 stuff not to long ago.

Good luck!

Reggie