Tag Archives: Chevrolet 235 Six

Mounting the GM 235 Six on an Engine Stand

One of the peculiarities of the 235 c.i. six from our 1956 3/4 ton “Farm Truck” is that the bell housing is installed before the flywheel. Couple that with our desire to clean up, paint, and re-install the oil pan, and it became obvious that we should put the monster on an engine stand so we could rotate it.

All dressed up, the six weighs around 630 pounds, and it’s longer and taller than the Chevy small block V8. So we had concerns about putting it on a stand. We didn’t trust our own stand so a friend’s more stout-looking stand (1000 lb. rating) was borrowed.

Two inch square tube extension added to engine stand.
Two inch square tube extension with wheels, added for stability.

Still, we had concerns about the length of the engine with bell housing installed, and could imagine it tipping over as we rotated it or moved it around the shop. To ease our minds, we added a 2 inch square tube “T” extension, with wheels, to the front of the stand for stability. We had the wheels in the shop, and the 5 foot long square tube set us back $6.50, so it was cheap insurance.

Fixture attached so axis is near vertical center of gravity.
Fixture attached so axis is near vertical center of gravity

Since the bell housing sits considerably below the vertical center of gravity of the six, we attached the stand’s fixture such that round tube axis was much higher than bolts attaching it to the bell housing. It looked odd, but with grade 8 bolts holding it all together, there was no problem. We also backed up the upper bell housing bolts with nuts instead of relying on the bell housing’s internal threads.

Fixture attachment to bell housing, up close.
Engine stand attachment, up close.

We employed a four-foot long bar to rotate the engine once it was mounted to the stand, and we left the chain hoist attached for the first 90 degrees of rotation until we felt the balance was, indeed, going to be acceptable. With the long bar helping matters, it was easy for one person to rotate the engine with complete control. We pinned our “T” addition to the original stand with a spare bolt so that it would stay in place as we moved the engine around the shop.

Chevrolet 235 six on our engine stand.
Chevrolet 235 six mounted on our engine stand, ready for final assembly.

All in all, it turned out to be no problem at all mounting the 235 six to our stand.

Stop the Vacuum Leak (we see the light)

When the 1956 Chevy farm truck entered the barn in January, it was running pretty well. Vacuum at the intake manifold was at 20 inches and a compression check – wet and dry – showed even numbers across the cylinders. After pulling the engine we did a leak down check and again the numbers were similar for all the cylinders, even if percentages were a bit high. We could hear air escaping through the crankcase breather pipe, indicating the rings weren’t sealing as well as they might. But that check was with a cold engine, so we decided against a rebuild at this time.

We cleaned and painted the engine, rebuilt the carburetor, installed new spark plugs, set the valve lash and static ignition timing, and then added a power steering pump and alternator.

The 235 six, with fresh paint and added power steering pump and alternator.
The 235 six, with fresh paint and added power steering pump and alternator.

We went full quick and easy mode to fire up the engine and check for leaks, using the engine stand as our test bed.

1956 Chevy 235 six in our engine test stand.
Our engine test bed worked like a charm, simple and easy.

We hooked up our two essential gauges – oil pressure and vacuum – and fired up the stovebolt six. And it ran like crap. Would not idle, vacuum below ten inches, ignition timing out in left field just to get it to run. We grabbed the aerosol can of carburetor cleaner for a squirt around the base of the Rochester and immediately the RPM increased. Bingo:  a vacuum leak. No problem, easy fix, right?

We tried every combination of gasket, no gasket, Loctite 518 with gaskets, 518 without gaskets, thick gaskets, thin gaskets… no improvement. We used our flat metal welding table and 600 grit wet/dry paper on both sides of the insulator, and on the carburetor base until we were sure they were flat. Still no improvement.

Finally getting smart, we brought out a flat chunk of metal that we keep in the toolbox and laid the insulator on it with a flashlight behind.

Diagnostic tools: a flashlight and a flat piece of metal.
Valuable diagnostic tools: a flashlight and a flat piece of metal.
Light seen shining under carb insulator, showing warpage.
Light seen shining under carb insulator, showing warpage.

The insulator was clearly warped. We installed a new (nine dollar) insulator from Classic Parts of America, and, after doing a static ignition timing reset, put it all back together for the umpteenth time, and… eureka! The old six purred like a kitten and once again showed an excellent vacuum reading.

As you can see, Lance is excited… the engine is purring and he’s holding a Corona. We used a thick gasket between the insulator and manifold, but applied minimal torque on the bolts attaching the carburetor to the manifold. I may disassemble one more time and pitch the bottom gasket as I suspect it was a contributing factor with just two bolts holding down the Rochester 1 barrel.