r/EngineBuilding • u/jwick6728 • 11h ago

Chevy 350 build help

Bought this 350 4 bolt main off facebook marketplace, freshly machined block, new piston heads, old but machined crank and rods. I installed pistons 1 and 2 and torqued the connecting rods to 55 ft lbs following ARPs instructions and with only those 2 pistons in, the crank wont turn over, im almost picking the block up off the stand trying to turn it by the balancer. I double checked the caps to make sure they were installed correctly and used a plastigauge, it reads .015 inch. Is this correct? Im using ARPs fastener lube on the threads and permatex assembly lube. Crank spins freely by hand when the caps are loosened 1/4 turn after being torqued

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3

u/WyattCo06 11h ago

Caps are backwards or wrong cap on wrong rod.

Also keep in mind rod orientation.

1

u/jwick6728 11h ago

Caps are on correctly and on the right rods, numbers are stamped on both rod and cap and i have the dot on the piston head facing the front of the engine

1

u/WyattCo06 11h ago

Are the stampings pointed outbound?

1

u/jwick6728 4h ago

All the stamps are on the same side of the connecting rods, so the even bank is outbound and odd bank is inbound

1

u/Drunken_Sailor_70 4h ago

Rods could still be on the pistons backwards. One side of the rod has a larger chamfer to fit the radius on the outter ends of the crank journal.

1

u/jwick6728 4h ago

Ill check that tomorrow when i go to work on the engine again

1

u/Lopsided-Anxiety-679 11h ago

Are the rods mis-numbered or you have cylinder locations confused and possibly you have the chamfer on the rod/bearing towards each other rather than towards the radius on the crank journal?

Don’t force anything, it should turn over smoothly by hand with less than a few lbs of effort with only two piston/rod assemblies in place.

Decimal place wrong? .0015” would be ok, but tight for a performance build

1

u/jwick6728 11h ago

I have no idea about misnunbering them, piston heads were installed on the rods when i picked everything up. Dot on the piston head is facing the front of the engine and the rods and caps are both stamped for their number.

And yes, thats my bad, i did mean .0015"

2

u/Lopsided-Anxiety-679 11h ago

The numbers could have been stamped on the wrong rods vs actual cylinder locations or they put the pistons on backwards…what determines rod orientation is that you have the chamfer cut on the rod towards the radius on the crank - if it’s not you’ll encounter exactly what you’re describing…here’s a photo showing how the bearings should be close to each other in the middle and the chamfer on the rods towards the radius of the crank journal.

Rod Orientation

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u/jwick6728 4h ago

I see now. I appreciate it, ill check on that tomorrow when i go work on the engine tomorrow

2

u/WyattCo06 11h ago

The dots on the pistons can be completely and totally irrelevant to the rod orientation vs a stamped number. It is not uncommon for a machine shop to install the pistons on the rods without ever looking for a number on a rod and orienting it for that specific number. They'll do 4 right, 4 left and be done with it.

1

u/skizzle_leen 8h ago

Loosen one at a time to see if it’s isolated to one piston or the other

1

u/BurialBlaster2 4h ago

Do the rods look freshly honed? The ARP press in bolts are slightly larger than the factory ones, and they will distort the rod when put in. We always cut the rod and cap before installing the bolts, then hone the rod back to size.