Small Block & Big Block Chevy Specific - SBC 400 Camshaft Play

I'm building a mild SBC 400 and I noticed that the camshaft can move about 1/4" front to back with the timing cover on. I discovered this while installing the distributor. As the dizzy gear contacted the cam gear, it pushed the camshaft forward. After the dizzy was installed, I could move the camshaft front to back by turning the rotor.

I put on a new timing set, and everything is lined up there and the chain is snug, it's just that the cam can walk out from the block while pulling on the chain. Has anyone ever seen this? Will it stay aligned in the block while running, or do I need a button on it? BTW, the cam is not a roller.

If I remember right they are supposed to move a A LITTLE but don't quote me on that. Been a while since I built an engine.

If it is a conventional flat tappet camshaft (solid or hydraulic does not matter), the way the lobes are ground will cause the camshaft to be pulled back into the block. This is why the cam gear has notches in it to aid in lubrication of the area between the cam gear and block. This is also why some blocks get worn badly and have to have work done to that machined face around the cam. If you convert this block to a roller cam setup you have to either have it machined to accept a thrust plate which will prevent camshaft movement or set it up with a cam button which will go between the cam and front cover to minimize cam walk. The camshaft button can also be used on a flat tappet set up and is especially useful in cases of extreme engine deceleration such as road racing, power boating, etc.

Thank you guys, I think I'm ok then. I also found this that verifies your info at Comp Cams.

"Flat tappet cams are ground with taper on the lobes to force the cam to the rear of the engine. Roller cam lobes are ground flat, so a thrust button must be used to keep the camshaft to the rear of the block."

I wonder how much work is required for me to use a OE style roller cam in a 400 and use a thrust plate? I like that idea.

You can weld on both sides of the camshaft hole, be careful that you don't work too long and warp the metal. Then have it machined down to accept the camshaft retainer like newer blocks.

That takes care of the cam retaining portion, you now have 2 options for lifters.

You can get yourself a fancy pants setup of aftermarket roller lifters with ties, or you can go oldschool.

Oldschool method:
Get yourself a lifter hold-down plate from a roller cammed engine, mock it up on top of the lifter valley, mark your holes, drill and tap, and insert studs to hold it down. Yes it's into the oil gallery, yes it's ok as long as you don't go too deep with the studs and block a big chunk of the passage. Just use sealant around the threads of the studs. You can use lifters from the 2.2L Chevy engines (S10 w/4 cyl), 3.1/3.4L engines (older V6's). You need the dogbones with them too to keep them from rotating, and you'll need to clearance the block for them a little bit (not hard). I have a guide for the whole process; if you want it, PM me.

Hell, i thought welding on cast was not a good idea at all anyways...


Im going retro fit lifters ither way.