All Small Six 170 - oversized pushrods needed?

[wesk]

I'm rebuilding my 64 1/2 mustang (engine overhaul, transmission rebuild, some body work). I sent the engine out to get some machine work done (0.030" over on the cylinders, put in hardened valve seats, etc.). My engine has the unique combination of hydraulic lifters AND mechanical lash adjusters on the rocker shaft - this setup is original to the engine, at least as long as I've had it (1991).

My concern: The mechanical adjuster screws are nearly bottomed out (see picture below). Most of them have a little adjustment room left, but not much. I'd rather be running with them set a little bit more in the middle of the thread range in case I need to made further adjustments. It seems like oversized pushrods would be helpful here, but finding those appears to be a bit challenging... even finding standard length pushrods wasn't super easy (I had to replace one during the rebuild).

I've adjusted the lash by tightening the adjusters down to the point where there it was difficult to rotate the pushrods, and then went another 1/2-3/4 turn. This was done with the hydraulic lifters bled down (they're new and have never been pumped up yet), and with the engine cold. I haven't yet fired the engine after the rebuild.

Thoughts on this? Any ideas why I would be at the extreme end of the adjusters? I did go back to a few pictures before the rebuild, and it looks like they were in a similar position with the adjusters screwed most of the way in (though not quite as extreme as this picture shows here).
Any options out there for longer pushrods? Is this something to be concerned about?

Thanks,
Wes

 

[frozenrabbit]

DO NOT try to start that engine!!! You are lashed beyond what would be correct even for solid lifters! If those lifters pump up, you are going to bend every push rod, or worse. You may have already bent some rods.

My '63 170 and my '65 200 both have adjustable over hydraulic from factory. '63 Ford Falcon shop manual supplement shows adjustment process for adjustable rockers over hydraulic lifters. Image clipped from shop manual.

Clearance measured between the valve stem tip and the rocker, with the lifter collapsed, 0.067"- 0.200".

I would pull every push rod and check for bends. Hopefully you just over adjusted so that the valves were never fully closed, but not so much as to fully collapse the valve springs.

 

[wesk]

Thanks Frozenrabbit. I couldn't find a clear procedure on this (other than what I had posted previously). Even my shop manual (for the Mustang) doesn't handle this detail... maybe I need to get the falcon manual.

I haven't run the engine yet, and all I really did was take up the lash on a bled-down lifter, so I don't have any concern for damage. I'll make the adjustment recommended above. Thanks!

Wes

 

[Frank]

EDIT- follow Frozenrabbit's procedure, as it's specific to your engine. The following is more generic FYI.)

In other words, you appear to have tightened the hyd lifters all the way thru their travel, and the "preload" you added was actually compressing them into a bottomed-out- bind.
It's easy to do! dry hyd lifters can have very little resistance to being compressed into their bores.
Many instructions, including the ones that came with my last set of Comp Hyd lifters, say to set the lash preload with them dry. Personally I prefer to pump them up first, because of this very thing we're discussing. then lash each cylinder one at the time @ TDC compression stroke. After they are internally oiled, the point at which the lash reaches 0 (the pushrod stops rotating freely) is much more distinct. From that point add the lash preload you desire, 1/2 turn, whatever. This has to be done with the cam lobes away from the lifter, and TDC on compression stroke is one of several methods to accomplish this.