The Stovebolt Site Forums The Shop Area Engine Shop COE 261 re-build

I took the head off today because the engine is seized. Nothing obvious but some rust in the water ports. Cylinder walls are smooth and clean looking. I'll clean the head up to determine the next steps. I'm soaking each cylinder with Marvel's Mystery Oil and will try to move the pistons in a couple days.

If anyone sees anything alarming in these photos, please let me know.

Top half of head
Bottom half of head

Probably a little rust on the rings has the pistons stuck....

John

Ritchie, just finished getting a 261 unstuck that had been sitting for almost 15 years. A good recipe is 1/2 tranny fluid and 1/2 diesel.

In the end the BIG culbrit that had it stuck was 3 of the lifters so I recommend you pull the side cover and check all the lifters.....if you have not already did it. Let us know how it comes out.

So, the two small holes between #1 and 2, and #5 and 6, would be the infamous "steam "hole, would they?

Those 4 holes and the 2 holes between #3 & #4 pistons are the extra coolant passages needed in the 261.

Those infamous steam holes (a term coined by Jim Carter, most likely) must have been in an overheated engine?

I missed the ones between 3 and 4. They are so tiny, I could see them getting plugged easily.

When they increase the size of the cylinders in engines to get more displacement in the same basic block, the cylinder walls get too close together. That means there is no good path for coolant to get between the cylinders, so small vent holes, or steam holes, are put in to allow coolant in the area.

Most older engines just relied on coolant to flow through the block, to a passage in the deck at the back, up into the head, and back to the pump. Eventually they figured out that additional coolant holes along the way helped cool cylinder walls and hot spots in the head as well. Even in the 80's they still were not doing them right.

The term is "siamesed cylinders".

Siamesing the cylinders, and the extra water holes (passages) were described by GM in this 1954 Engineering Features manual.

Here is a cross-section illustration of the 261 block and the siamesed cylinder bores.

Is the engine still hooked the trany? Have you checked to see if clutch is free or stuck. Just one more thing to check.

Engine & tranny are still together. Pretty sure the clutch is free. I lifted / jacked the rear end and moved the wheels while it is in gear to try and prod the cylinders into action. I'll try again this weekend.

Hard to determine what gear it is in with the shifter somewhat loose.

I have had good luck freeing 'stuck' ( within reason ) Engines, but, soaking the Piston Tops and Rings as mentioned above, with ATF and Acetone or AFT and Diesel...let them soak a few days.

Any visible Rust in what can be seen of the Cylinder Bores I clean off with an Electric Drill with a Wire Brushchucked u in it.

Then, with a large Screw Driver or short Crow Bar, with the bottom Cover of the Fly Wheel off...I pry in the Teeth of the Flywheel, from the side, just to get a little movement...some back-and-forth movement is fine also.

Soon as I get a little movement, I pry to get it moved several inches, and maybe several more inches...and then have a peek in the Cylinder Bores.

Wire Brush on an electric drill, to clean the Bores as far as possible in this position...then, turn some more till two of the Pistons are as low as possible...clean the two lowest Piston's Cylinder Walls then, and repeat till all six are done.

I used a Dremel with a little Wire Wheel on it, last time as well...

Once all are clean, Lube well and crank it over a few times to get everything slick again.