The Stovebolt Site Forums The Shop Area Engine Shop Compression Testing (Where is the hand throttle?)

1948 Chevrolet 1/2 Ton Truck with 1962 235ci engine, Carter YF Carburetor on a 6V setup. Running compression tests and needing some help with identifying or finding an alternative to the "Hand Throttle" mentioned in the Shop Manual. Not sure what exactly that is. On my truck, I have the Cab removed, so it's just the engine on the chassis. I have the linkage for the foot pedal throttle installed or in place and I have a short wire attached to my choke to open it as needed.

So with the compression test, I've removed all spark plugs. Now I'm wondering what exactly is the "hand throttle" that needs to be open? Can I use the foot pedal linkage, push it open to WOT and secure it in place with something and run the test or what exactly needs to be done?

I've done the following so far, prior to this compression testing:
- rebuilt the carburetor with a carb kit
- installed new gaskets on the intake & exhaust manifolds, new rings on the intake manifold and secured both tightly
- valve adjustment completed (and re-checked)
- new distributor cap cover, new 6v coil. I used a dis-connect wire auxillary wire from the pos+ terminal on the battery to the coil, shuts the engine off upon disconnect.
- timing w/timing light completed, BB is dead on with the pointer (I used a Bosch Inductive timing light and it works just fine with the 6V setup I have)
- vacuum tested on the intake manifold connector, and is roughly 18-19 inches/Hg

Sincerely appreciate any and all tech tips!

You can just secure the foot pedal in WOT position. Hand throttle is a knob and cable from dash to carb.

WOT - for any period of time would most likely bring the engine up to a dangerously high RPM, especially a cold engine?

The spark plugs are all removed, it's for compression testing, the shop manual says to have the hand throttle fully open to run the tests on a tune up.

Ah, I see, thanks JW. I definitely do not have a hand throttle then, since the cab is off. Will use the foot pedal linkage and push it open, use a board to keep it open "wot" during testing.

I apologize for mis-reading too quickly.

In an engine with a small carburetor, it's important that the throttle disc be as close to 90 degrees (vertical) as you can get. This is the time to confirm that full travel at the pedal actually opens the carburetor all the way - it may not.

Thanks for the question and responses:

"The carburetor choke needs to be open and the throttle held in the fully open position [with spark plugs removed]. This allows the maximum amount of air to be drawn into the cylinders with the minimum amount of fuel." (from hotrod.com)

Use the BBB method- - - - -

Brick (on the gas pedal)
Baling wire
Bungee cord

Just cobble up a way to hold the throttle wide open to get maximum air flow.
Jerry

Many thanks all! I propped the Throttle open and left the Choke open and then ran the compression test. Here are the numbers I get with a warm engine, "Dry" testing, I let each cylinder cycle about 3 times:

Cyl #1: 120 psi
Cyl #2: 118 psi
Cyl #3: 115 psi
Cyl #4: 115 psi
Cyl #5: 118 psi
Cyl #6: 120 psi

This is a 1962 engine, it was rebuilt at some point in it's life b/c when I bought it, had orange paint and the engine serial number is replaced with a "DR" next to a 5 digit # and then followed by "CAL". I've since repainted it grey and added all new ancillary parts (fuel pump, generator, starter, rotor, cap, gaskets, etc.)

My Vacuum pressure is at 17 inches / Hg, @ Idle speed set to 500 RPM.