SBC 400 crank
Burning Brakes
Joined: Nov 2001
Posts: 1,189
Likes: 2
From: Austin TX
The things you need to think about are:
1) Harmonic balancer (dampner) size. The factory SBC 400 is externally balanced and the factory dampner is too big a diameter to clear the crossmember (in a C4 anyway. You can get aftermarket dampners with the 400 counterbalance in the 7" diameter range, or, you can have your roatating assembly internally balanced and use any available neutral balance dampner of around 7"
2) Flywheel size. Same issue as above. The 400 counterbalance flywheel is 168 tooth and takes a different starter. The corvettes I'm familiar with all had 153 tooth flywheel. You'll either need to get an appropriate flywheel, or plan on changing the starter.
3) If you use a 153 tooth flywheel, make sure the block is drilled and tapped for the inside, straight-across, starter bolt hole. Most 400 blocks are, but not all. It's not hard to drill and tap the hole (it has to be counter-sunk also) but it's alot easier to have a machine shop do it before you assemble the engine.
4) Steam holes - I'm assuming you're using the factory block, if that's the case make sure you get head gaskets with steam holes and that the heads you are planning on using have steam holes. Again, drilling the heads for steam holes is something a machine shop can do. There is alot of debate about the necessity of this. If you block the holes your block is likely to develop cracks between the steam holes and the nearby head bolt holes. In severe cases I've seen cracks over into the cylinders as well.
5) have the block checked for cracks before you invest any money in it. And if possible, have the bores sonic checked for wall thickness.
6) Have the block bored and honed with torque plates. On that large a bore small block the head bolts holes are really close to the bores and cause more distortion when torqued than smaller bore small blocks. This is critical, and needs to be done properly, especially if you are running a performance piston with a higher than stock top ring placement. Otherwise, you're likely to have lots of blow-by and oil consumption.
Have fun,
Dan
1) Harmonic balancer (dampner) size. The factory SBC 400 is externally balanced and the factory dampner is too big a diameter to clear the crossmember (in a C4 anyway. You can get aftermarket dampners with the 400 counterbalance in the 7" diameter range, or, you can have your roatating assembly internally balanced and use any available neutral balance dampner of around 7"
2) Flywheel size. Same issue as above. The 400 counterbalance flywheel is 168 tooth and takes a different starter. The corvettes I'm familiar with all had 153 tooth flywheel. You'll either need to get an appropriate flywheel, or plan on changing the starter.
3) If you use a 153 tooth flywheel, make sure the block is drilled and tapped for the inside, straight-across, starter bolt hole. Most 400 blocks are, but not all. It's not hard to drill and tap the hole (it has to be counter-sunk also) but it's alot easier to have a machine shop do it before you assemble the engine.
4) Steam holes - I'm assuming you're using the factory block, if that's the case make sure you get head gaskets with steam holes and that the heads you are planning on using have steam holes. Again, drilling the heads for steam holes is something a machine shop can do. There is alot of debate about the necessity of this. If you block the holes your block is likely to develop cracks between the steam holes and the nearby head bolt holes. In severe cases I've seen cracks over into the cylinders as well.
5) have the block checked for cracks before you invest any money in it. And if possible, have the bores sonic checked for wall thickness.
6) Have the block bored and honed with torque plates. On that large a bore small block the head bolts holes are really close to the bores and cause more distortion when torqued than smaller bore small blocks. This is critical, and needs to be done properly, especially if you are running a performance piston with a higher than stock top ring placement. Otherwise, you're likely to have lots of blow-by and oil consumption.
Have fun,
Dan
