Atlas valve train vs Commando differences

Hi
My 1967 Atlas crank is in for a +.010 grind and the head is getting its seats cut. Question … I am going to replace the valves and guides. Are all 750 Atlas and Commando guides and valves the same spec? Looking at RGM’s specs for the Atlas and compared to Kibblewhites specs for the commando, all dimensions seem the same with the exception of the length. The Kibblewhites are marginally longer for both valves and guides. I’m just wondering if this added length may make a difference relative to how the rocker adjuster hits the valve stem. Any info on this would be appreciated. Thanks

After s/n 125871 the valves were lengthened by .100" and the pushrods shorted by the same amount, according to Andover's web site Commando valves have different p/ns

If you put Commando valves in an Atlas/N15/P11 head with the original Atlas pushrods you will not get a proper wear pattern at the rocker to valve stem interface. Shorten the pushrods and check with Dykem or Sharpie ink on the valve head to get a nearly equal pattern from front to rear on a couple crank revolutions. Head gasket thickness or using a cylinder base shim (to lower compression on a Combat engine) will also affect the rocker/valve pattern.

possm said:

After s/n 125871 the valves were lengthened by .100" and the pushrods shorted by the same amount, according to Andover's web site Commando valves have different p/ns

Click to expand...

Good to know. How bout the guides?

jms said:

Good to know. How bout the guides?

Click to expand...

Commando intake guides had seals, Atlas did not. I always use the intake guides with seals. 850s have bigger diameter guides than 750.

With low pressure top oiler system, it is recommended that intake oil seals be ommited.

Slick

He said it was a '67 so therefor it will have a 6 start oil pump and pressure fed rocker gear.