Ok. I just got done building a 355 which turned over perfectly when I put it all together. I went to fire it up and it fired for about 3 seconds and stalled. Went to try it again, and all of a sudden it started turning over really hard with the starter. Thinking it was the battery I tried to turn it with a wrench and it was very hard to turn over. So I pulled the plugs and backed off the rockers. Still hard. Then I pulled the timing cover and chain and torque converter bolts, still hard.
Thinking it was maybe a rod or main bearing I pulled the motor. Checked all the bearings they were still perfect. Main clearances were .002 and rods were between .0015 and .002. Ever the rod side clearances were at .012. Which is still to spec I believe. It seems like something is sticking as I turn it over. The cylinder walls look fine still too. So i don't think it could be a broken ring.
Everything was balanced, its a new scat cast crank, new rods and srp pistons. I don't want to pull the heads because the gaskets are expensive. Unless i can reuse them since it never actually ran! Any ideas would be great!

Thanks

 

Wrist pins are a possibility. What type of connecting rods did you use?

 

They are the Summit stock replacement ones. I used them and the pistons in a previous engine. I had the machine shop check them. And they are floating pins. How do i check the wrist pin?

 

did you check the crank thrust bearing, if thats ok and you truly checked all other bearings i think you need to remove the heads and pistons and inspect for broken/cracked ring lands or side skirts. I'm assuming you tried turning over after removing the timing chain to eliminate the cam, distributor and valve train (back off rockers first unless to want to bend valves).

 

The heads will need to come off.
Make sure that both the pistons and rods were installed facing the proper direction. Check if the rods are marked with the cylinder numbers and are placed properly.