putting in a new crank in a 400 small block and after i put in 6 pistons u cant turn it over . what could it be? turns free with no pistons on it. this is a new out of box crank.
You do have all the caps on the correct rods? I’ve seen that if you have 1 cap on wrong, it won’t turn over…also have seen a turned down crank labeled .010 actually have 1 rod journal not turned down at all.
Is the cam in the block?
I’ve seen the rods hit the cam when using 5.7’s or 6.0’s. (needed small base circle cam)
I’ve also seen H beam rods coming in contact with the oil pan rail of the block. (Had to clearance block)
If you are using 5.7 or 6.0 I-beam rods, chances are you will need to run a small base-circle cam. You will more than likely also need to clearance the oil pan rail and the bottom of the bores for the rod bolts. However, H-beam rods & cap screws will generally clear a standard base-circle cam using a 3.75" stroke.
I always turn the motor over after installing each piston/rod assembly just to triple-check the clearances before moving to the next piston/rod assembly.
are all the bearing clearances good? and when you say you cant turn it over, does that mean not at all, not by hand, or?
all the bearing clearences are good and the caps are all in the same spot as they came off . when it wont turn over i mean with the balancer bolt and a ratchet. well after further notice found that the rods have no clearence between them once on the crank.
The rest of the story.
This is a 400 sbc that neonracer bought off of eurodad. Ended up needing a new crank. So he bought a new Scat. We have found the following issues,
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some of the rod clearances on the counterweights are not fully ground as deep as the stock crank was.
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there is NO side to side rod clearance on the 3-4 journal. The 7-8 and 5-6 journals only have about .007 inch of side to side clearance. My believe is that the no side to side clearance is what is causing the lock up.
I always turn the motor after each piston goes in. And we have check clearance on the bearings and they are actually a bit loose. But still within reason.
So for now it looks like some machine work to the rods to get some side to side clearance.
:doh: should have just bought my 350.
I tried to tell the dumb ass that…
atleast the price was right on the 400.
might be a good time to get the rotating assembly balance too
agreed, I hear a lot of people say they have mixed feelings about scat
Couldn’t agree more.
You still want to buy it? He’s about ready to sell…:rant:
turns out to be the connecting rods are egg shaped than round . the crank was only riding on the rods were the bottom bolts to the rod and not the whole way around… is it possible to have the rod machined without taking the pistons back off?
That don’t sound right…did you put new pistons on the rods???..also some of the aftermarket cranks only take a special bearing.
i had a shop install new pistons and i didnt know anything about a special bearing .i will have to get some more info on the crank.
I wouldn’t believe the egg shaped rod theroy yet. Not to say it can’t happen, but I doubt it…the reason I asked about the pistons. Is it posssible they installed the rods backwards? Again I doubt it, but you never know…
A few years ago I bought a 383 crank from summit. I can’t remember if it was a scat or an eagle, but as I was checking out, the parts guy asked if I needed the bearings for that style crank. Seems that it took different style bearings. Sorry but I can’t recall what they were called…I really think your problem is something simple. It’s just the idea of figuring it out…
I had a machine shop recon a set of Pontiac rods with the caps on backwards…what a mess.
Caps had to be cut so hard to fix they were junk.
My Eagle competition crank has large chamfers on the journals. You would need the bearings to work with that.
That must be what I was remembering…If someone was to use standard bearings, would it cause the binding up problem they are getting?
I don’t even know how you’d fit the rods on the journals with regular bearings. It would probably be like putting the rods on backwards with the chamfers facing inside :o