Clunking noise on start up

[Dillon Campbell]

Installed a new 355 I built into my k10 this weekend. Got everything wired up and went to start it and it begins to crank but then will make a loud clunking noise. It will then start to turn over again and do it again. Pulled the starter and checked to make sure it was mating with the flywheel properly and it was. Can’t figure out what it is. Any input would be great.

 

[AuroraGirl]

Installed a new 355 I built into my k10 this weekend. Got everything wired up and went to start it and it begins to crank but then will make a loud clunking noise. It will then start to turn over again and do it again. Pulled the starter and checked to make sure it was mating with the flywheel properly and it was. Can’t figure out what it is. Any input would be great.

Is your engine twisting or rocking on it’s mounts. When turning slowly a small block would be quite imbalanced and shake more than when it’s running and fairly well balanced. So a mount that’s loose or worn might work enough when it’s runnin but really show when starting. Mine does that. Also transfer case mount, it’s gonna be your third driveline mounting point that keeps it twisting the other two which are holding it the opposite direction themselves