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Help!!!!

4K views 15 replies 6 participants last post by  FFR428 
#1 ·
Im rebuilding a 390 and i got the grank in and it rotated fine i put pistons 1 2 3 and 4 on and it rotated ok it was a little hard to move, then i put piston 5 in and i cant even rotate it by hand now.... is that normal or did i screw somthing up? and what can i use to rotate it now?

someone please help.
 
#2 ·
It sounds like you may be installing the connecting rods backwards. Look at the rods down where the two rods would be riding together on the crank journal. You will notice that one side of the rod has a slight bevel and the other side is machined flat. The beveled side must go on the outside against the crank, the flat side goes next to the adjacent rod on the journal. The more rods you install the worse the interference. If you find that you do have them backwards, depending upon what type of pistons you are using you may have to pull out the piston pins and turn the pistons around as well.
 
#4 ·
oh man.... after i posted this i neglected to check it because i thought it was just because of the piston rings and the friction on them. i put a breaker bar on the crankshaft snouth with the bolt and i can rotate it that way, its stiff but it seems like it should be like that.

the whole motors together now.

what would you do?
 
#5 ·
With every piston you put in it will get harder to rotate but if you hank on it hard enough, it'll rotate and that is normal. Did you oil the pistons and the chambers before installing?? If not that could be your problem! And also you want to put a generous amount of lube (I like to use STP honey oil) on the bearings before installing?? If you don't have any pre-lube on the bearings disassemble now and or you'll be turning the crank again and buying new bearings.
 
#6 ·
yeah i did oil and lube everything. the onlyhting im woried about is the way the connecting rods face, like the whole flat side and concanved side.... i didnt check for that, mainly cause i didnt know. :(



PS... i put a breaker bar on the cranp pully bolt and it rotates its tight cause of it bein a fresh assembly. i made sure the crank rotated freely before i put any pistons in.
 
#10 ·
If your using aftermarket rods you can plainly see the flat side and the champhered side. If your using stock rods there is a square nub on the cap and it is slightly beveled. You'll have to look at them from a side angle. I believe the lower side of the angle goes towards the crank, but get a second opinion in case I'm wrong.
 
#11 ·
im not gonna lie, im completley lost on what to look for... is there anyway you could find a pic and show me what you mean? this is my first rebuild and i really didnt know about the 2 different sides.


im using stock rods, i just dont know what the nub is your talking about.

thank you.
 
#14 · (Edited)
Never installed them backwards so I don't know!!!

When your looking at the connectiong rod cap right in the center there is a nub about one inch long by a half inch wide. The square side faces to the pairing connecting rod and the tappered side, usually champhered and cresent shaped, faces the crankshaft.
Also, the bearing tangs (fitted slots) should face the outward of the engine.
Have you torqued the heads yet?? If not, look at the pistons and they have either a notch or an arrow pointing forward to the front of the engine.
 
#16 ·
You can also check your local library. They might have a Ford or Chilton manual. Ours here has both oem and aftermarket manuals. My kids clued me in on that. Honestly if your not sure about things stop now, take it back apart and be sure you've done it right. Anything your not sure of ask about. Is it a hassle? Yes but you'll be glad you've done things right. These guys know so take their advice. JMO and best of luck.
 
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