273 Adjustable Rockers with Hydraulic Lifters??

-
Thanatos340

Thanatos340

Well-Known Member
Joined
Oct 23, 2012
Messages
138
Reaction score
20
Location
Marietta
I was hoping someone could walk me through the proper way to Adjust the valves on a 340 that has 273 Adjustable Rockers and Hydraulic cam and lifters.

The engine was built many years ago by father, ran for a brief while and than sat for a long time. I have it running again but there is some slight lifter tapping going on (Sounds like it is just in #1 Cylinder). I am hoping it is just a matter of adjusting the rockers but not sure on the proper procedure for this.
 
There are many threads on FABO about this...try a search. In a nutshell, with the cam lobe on its base circle, tighten the rocker down to "0" lash, then go 1/2 to 3/4 turn more. Set!
 
Not to add any confusion here, but I was under the impression that you wanted to preload hydraulic lifters .040". The 24 thread pitch comes out at just over .040 per turn. Would you not want to load them almost 1 full turn from zero lash?
 
Its not really a critical measurement. Anywhere from 1/2 to 1 turn is acceptable. They are "self-adjusting", after all. Some people don't run any preload...they actually have some lash in there, so they act more like solids.
 
I prefer the preload on the light side. I usually go no more than 1/4 down from zero.
 
Be certain that you actually HAVE hydraulics. There was no factory option for these rockers with hydraulic lifters. Any of them ever made were mechanical..........and the pushrods are different lengths
 
Although they are NOT INTERCHANGABLE 340 TA engines were the only factory LA small blocks that came with adjustable ductile iron rockers over hydraulic lifters. The factory manual (1970 Dart and Challenger) has a detailed description of the adjustment process.
 
FYI, for all you motor heads. Something caught my eye reading this thread . Someone stated that one turn on a 24 TPI bolt/screw is .040?? In machine shop school many years ago my instructor told me "Remember this, .6495 divided by TPI equals the distance traveled along the axis of the bolt/screw in one revolution". This is a constant for SAE 60 degree "V" threads. So a 24 TPI fastener will travel .027" along it's axis in one revolution.
I memorized this "constant" 40 years ago and have used a bizilion times and you'd be amazed how someone responds when they're working a car and turning a bolt a say out loud, "I wonder how much this bolt moves in one revolution". Then I would say (as if I were a genius), ".6495 divided by the number of threads!!". The person would say, how do you know that?? I would say, it's a constant, you wanna bet?? I've won more money that way LOL!!!!

Don't forget this and you can be RICH!!!!


Treblig
 
Treblig said:
Don't forget this and you can be RICH!!!!


Treblig
Click to expand...

Well unfortunately you'd go broke. That figure has to do with "pitch diameter."

The amount a fastener moves along a thread is quite simply defined by the TPI. A 24 TPI fastener moves 1/24 of an inch for one turn plain and simple, and if are in "inches" this amounts to 0.041666667
 
Egg on Face,

When cutting threads on a lathe you would use this formula to determine thread depth. Single depth of the thread is .649519 x pitch(TPI). Must have been too long ago!!

Sorry,

Treblig
 
You must log in or register to reply here.
-

Back
Top