I am building a stoker bbc....its a gen 4....the crank is a 4.250....all parts were bought brand new from the same place....my question is this...mercruiser manual says .013-.023(service)...manufacturer says .018-.024....but my clearances are between .008 and .011....I personally have never herd of machining connecting rods....but maybe I'm missing something....or is there another spec for production? If I need a bigger clearance how would one go about attaining it?
any ideas of how to increase the gap if everything else is correct
Put them in a lathe and turn one side down. Of course that assumes you have a lathe. If one was to go thast route, one would want to make all the rods the same, so future matching would be easier. Then, well....some would worry about the balance.
Stock rods I assume?
Check bearings first as posted.
Run it. If you are not going to turn 8000 it will be fine.
there is a slight bind every 360 degrees of rotation....
Whoa....define slight. Because of ring drag? Rods still free to move the .008 to .011 back and forth?
Now, problem has to be found. Was the crank ground? New? Specs? Rod big end bore? Clearance? Did crank bind without rods on it?
gen 4 bbc
4.320 bore (.070) over
Keith Black hyperutechtic pistons
top ring - .0345
2nd - .016
oil rings - .016
all brand new parts....balanced...naturally aspirated
crank rotated fine
installed piston and rods and there was a slight drag every 360 degrees
Did you rotate the engine to check for drag every time you installed a piston/ rod combo?
What piston is at the top of the bore? I assume it is a certain spot always.
Are these pressed on pistons? Were they all free if so? Meaning piston rocked easily on the rod..very easily.
How are you turning it over? Do you have a breaker bar on a crank socket? Bolt on the end?
Is this a forged crank? Take a rod cap off and look to see if the bearings are either chafered or narrowed. I don't think your rods are seating against the crank cheek, the bearing is edge riding on the fillet. If the bearings are narrowed of chafered they will say upper or lower, some may only have a "U" or "L" on the back side. If they don't, and you have a forged crank, there's your problem. AND MAKE ABSOLUTLY CERTAIN THAT THE CHAFERED SIDE OF THE ROD FACES THE CRANK COUNTERWEIGHT AND NOT THE OTHER ROD!!!!!!!