C3 - 350/270hp - Install C/S procedure ?

[Jim Callan]

I'm rebuilding a '71 350/270hp. I'm using a "Haynes Chevy small block rebuild" manual for a guide. I checked main bearing clearances, all .001 to .002., did this "dry" with plastigage and torqued all main caps to 65lbs. Removed caps and C/S. Lubed C/S journals and C/S mains, set C/S, lubed main caps and installed finger tight (seal was installed in rear). Now this where I'm confused - torque mains 1,2,3,4 to specified value (65 flb) in 3 stages, only torque rear to 10-12 flb. This step contradicts previous step: Leave #3 figer tight, 1,2,4 torgue to 65 flbs, pry C/S forward and torque #3 and rear main. What I did: torqued 1,2,4 to 65 lbs, rear main to 12 lbs, #3 finger tight, pryed C/S forward and alt torqued rear/#3 mains to 65 lbs. C/S turns smoothly by hand. Is this procedure OK ? Should I do something different ?

Thanks

Jim

[Michael H.]

Re: C3 - 350/270hp - Install C/S procedure ?

Jim,

That is a bit confusing. Here's the deal. All but the rear should be torqued to specs, as you did in your first step. The rear should be just snug, or at their recommended torque value of 10 to 12 ft lbs. The reason the rear cap is left this way is so you can align the cap/bearing thrust surface with the upper bearing thrust surface to establish a proper crank shaft end play spec.

Prying, or lightly tapping the shaft forward and back will automatically set the cap/bearing in the correct position.

I have no idea where their #3 main cap deal came from. There's no thrust brng or flange there at all.

[Jim Callan]

Re: C3 - 350/270hp - Install C/S procedure ?

Thanks Michael,

So... do you think I should "loosen" the rear main cap and make sure the the rear bearing is aligned...or leave it alone.

Jim

[Michael H.]

Re: C3 - 350/270hp - Install C/S procedure ?

Jim,

If you're still at a point in the build where you can check/correct the end play, I definitely would do so. The C/shaft needs some clearance and if the cap alignment is off, there could be zero. It's not critical as 90% of engine builders probably never check or adjust this. I wouldn't be too concerned if you past the point in the assy where it's accessable. I don't remember the exact spec but I think it was somewhere around .005 to .011? Should be in your overhaul manual.

[Jim Callan]

Re: C3 - 350/270hp - Install C/S procedure ?

Thanks Michael,

I can still check it. The more I read those 2 steps, the more confused I got !
Right now the C/S is installed and all caps torqued to 65lbs. I'll loosen the rear cap and re-check the end-play.

Thanks

[Michael H.]

Re: C3 - 350/270hp - Install C/S procedure ?

The end play should be checked with the cap at the correct torque. It is only "set" when the cap is loose. Loosen the cap, wack the crank forward, then backward and then tighten the cap bolts. If the end play falls within specs, then torque the bolts to 65lbs.

[Jim Callan]

Re: C3 - 350/270hp - Install C/S procedure ?

Thanks