Hi, newbie here,
I'm rebuilding a GMC 270 in a WWII Staghound armoured car. My first time working on this type of engine. (There are two of them in this vehicle, coupled up to Hydramatic transmissions.)
The manual talks about a rocker shaft overflow tube coming out of the rear rocker shaft pedestal. The engine I'm working doesn't have this, it's missing. The other engine, does, but the tubing is 1/4"" maybe even 5/16", and it's obviously hand made, with gobby brazing, so I don't trust it as being original.
The supply tubing from the adapter screwed into the front end of the main oil gallery is 3/16" and it runs up to a y-fitting screwed into the head, which also supplies the oil filter.
When I run the oil pump with a drill (room temp 15W40), with no overflow tubing installed in the rear pedestal, and 55 psi in the main gallery, I get oil pissing out of the rear overflow hole in the rocker shaft and no oil coming out of the rear 3 shaft pedestals. So the rear overflow needs some kind of restriction to build pressure in the rocker shaft, especially as the 3/16" tubing on the supply sideis is also supplying the oil filter.
I'm thinking 3/16" tubing from the overflow to the nearest pushrod drain hole.
What was installed originally on these engines on this,overflow?
Thanks,
Malcolm
