The Stovebolt Site Forums The Shop Area Engine Shop 1955 235 Valve Adjust

Quick Question,

I'm adjusting the valves on a 55' 235 with pushrods. The engine is clean and in running condition.

While doing the valve adjustment I've noticed that while on TDC it seems like I have to push the rocker arm down onto the pushrod in order to get the right clearance from the valve.

Is this normal?

When the push rods are resting "static" with no valve spring tension, I can push them down with the rocker arm a couple of mm's.

Let's assume you have a mechanical lifter 1955 235.

At TDC, yes, 6 of the valves should be loose (adjust to appropriate gap).
Then, rotate 360 degrees and the other 6 valves should be loose (adjust to appropriate gap).

Here is an adjustment procedure.

Here is a Tech Tip for valve adjustment

Thanks Tim.

I assume if they are adjustable with pushrods, they are mechanical. How would I determine if they are hydraulic? Would the lifter mechanism be at the bottom of the pushrod?

Is it normal to have to push the pushrod down, as if it has spring tension?

Others will post lifter-identification techniques. Yes, the lifter is at the bottom of the push rod. What you describe does sound a little like a hydraulic lifter (I misunderstood your first post).

The best ID technique is to pull a lifter and inspect it, but that requires removing the side cover. You might not want to do that is the seal on the side cover is good (no oil leaking out around it).

What is your engine's serial number - it is pressed into the block to the rear of the distributor. That code should indicate hydraulic-lifter or mechanical-lifter.

With the valves closed on any cylinder, use a long screwdriver or a pry bar to put firm pressure against the pushrod end of a rocker arm for 2-3 minutes. A solid lifter will not allow the gap to change between the rocker arm and the valve stem. A hydraulic lifter will bleed down and end up with a gap close to 1/8" between the rocker and the valve stem.
Jerry

There is a cast number to the right of the distributor 3837004 with GM20 below it

The numbers stamped to the left of the distributor read F523A R750

3837004 is a 235 block casting code used from 55-57. During those years it might or might-not have had hydraulic lifters.

F523A
F = Flint, Mi plant
5 = May
23 = 23rd day of month
A = standard engine (not Powerglide) - in 56-57 it would have had hydraulic lifters

all code locations are shown here
date casting codes would confirm the year (block date code would confirm lifters)

Okay Tim, you've been very helpful

I came up with
CON4 E207

So, it must be a 57' meaning it has hydro lifters. That would make sense. I found some instructions for making those adjustments.

Originally, I set out to check the lash as a beginning to diagnosing a valavetrain type noise I'm getting at speed under partial load.

It always occurs in high gear aprx 40-50 mph. Not on decel, not under heavy load, not during no load reving. Maybe it's a defective lifter. But from my experience they bleed down and tap consistently.

I would normally lean towards a worn bearing considering the symptoms but the sound is high pitch similar to a failing valavetrain component.