Best torque for main 455 caps

[Houtan]

Hi everyone,

In Buick service manual torque for main bearing caps for 455 BBB is 115 lb ft. I send my engine to machine shop and after they done I find out that they test the clearance with lower torque number and now with 115 lb ft. crank will lock and dosen`t rotate. It is machine shops fault and I will send it to another machine shop for correct this clearance. but I saw some other rebuilders using lower torque on main bearing 90 lb ft. or lower. It is just lack of information or they use lower number torque for a reason? I must going for exact 115 lb ft or I should use lower number?

 

[BillK]

What did they torque them to ? My books all show 100-110 lb ft

To be honest with you the difference between 90 and 115 should not cause the crankshaft to lock up. If it does then something else is probably wrong also.

When all is finished you definitely should use the correct torque, not lower.

 

[rcull]

The bolt torque changed in the manuals in 1973 from 110 to 115. As mentioned, should not make any difference.

It sounds like perhaps the machine shop did not do the assembly, and you are doing that.

Usually, if the crank is ground, the shop simply supplies the appropriate bearings, and the crank is never test fit. Are you sure they actually installed the crank? If not, may be the wrong bearing size was supplied.

 

[Houtan]

I send the engine block and crank to another machine shop, we torque them to 115 lb ft and our clearance in each 5 caps was different. In fact the caps on 455 only will seat correctly in their positions when you torque them to 110-115 lb ft because of those fits end of each cap. when the cap seat in their position and you torque them you may think and saw that caps are fit in but actually caps will fit correctly only when you torque them to 110-115 lb ft and because of that the number of their torque are so high. the previous machine shop dosen`t know that and they torque the caps very lower than true number and because of this their work end up like this. now we work on caps again and problem solved and our clearance on each cap is about 0.0023 inchs.