Pontiac renovations, part 15.

Continuing engine work, I started to clean the engine block deck.

Razor blade to clean the surface of the deck.

There was a moderate amount of carbon buildup in the combustion spaces. The cylinders nearest the center show heavier deposits, of which the deeper sections were a nice deep brownish red, indicating good running conditions. The outer cylinders had a darker color, indicating a different mixture burn. This makes sense due to the style (and length) of the manifold, with the carburetor in the center. The manifold was also not tightened evenly when I got the car and was not sealing uniformly.

VIN

Scraping off the paint and wire-brushing the surface liberated the VIN stamping, which matches the plate riveted to the body. A=Atlanta assembly plant, 8=8 cylinders, U=1951, H=Hydramatic automatic gearbox, 4381=serial

Top end clean

I cleaned the carbon deposits off the cylinders and valves. One valve had stuck open- the exhaust valve on cylinder no. 8- the result of a leaking gasket. It had drawn coolant in and made the valve stem jam in the guide. Gentle, repeated force and penetrating oil freed it up.

Dirty threads.

The head bolts all required very different amounts of effort to undo. Most of the bolts go through the top of the deck into the water gallery, and were both full of sludge and old sealant.

Tap.

I ran a 7/16″ 14TPI (standard coarse) tap through the holes to clean them up. As the head bolts are tightened to a torque, the threads need to be clean in order for the torque reading to be correct. A dirty thread will increase the amount of torque required to turn the bolt and as such, the bolt will not have the correct clamping force applied to it.

Dirt removed

This procedure removed a lot of dirt, but also started to dull my tap. The original sealant was white lead, which is incredibly hard. I shall be using a more modern sealant designed for sealing threads that go through into coolant.

Clean thread

I flushed the threads through with carburetor cleaner and tested for cleanliness by screwing a bolt into the hole, which was able to be inserted with ease.

Cylinder head internals

I bought a new wire brush and finished cleaning the old carbon from the combustion spaces. The engine is quite high compression for the design (7.5:1) and any glowing carbon deposits will cause preignition. Any lumps will also impede flow, which is already limited due to the design. There was quite a lot of carbon stuck to the head around the exhaust valve areas.

Protective coat of oil

Everything was them coated in thick oil to protect the now clean surfaces from rusting.

Wire brush to remove paint and rust

I began to clean the exterior surfaces of the head, as the paint was coming off in places.

Spark plug wells

The spark plug wells were thoroughly cleaned, as they were full of rust and engine grime.

Prepped cylinder head

With the entire cylinder head prepped by wire brush, I wiped it down with carburetor cleaner to remove the last of the oil and dirt.

First coat
Second coat

I had looked at the original colors these engines were painted. There is some consternation among the car club members as to which shade of blue or green or blue-green that should be used. Some people say the grass green color is correct, others the deep Brunswick green, others the mid blue-green. I decided to plump for a color called “deep turquoise”, which is close in hue to the blue-green used in the early to mid-50’s.

Delco R45 new vs. old comparison

I bought a replacement spark plug to get all the plugs matching AC Delco R45. Unfortunately the design has changed and the new plugs are smaller. I may end up ordering 7 more of the newer model.

Spark plug

Older Delco plug in the well of cylinder hole 8. I think I shall get some phenolic resin right-angled plug caps and make up some wires to go to the distributor.

View into the water distribution tube from the water pump

One of the last items to check was the water distribution tube. I had been advised to remove the water pump and inspect it, as the thing is made from thin sheet brass and they have a tendency to disintegrate. The function of this tube is to accept the water output from the water pump and flow out from there into the areas surrounding the exhaust valves. Therefore the hottest part of the engine is cooled first, with the water then circulating away around the rest of the engine before returning to the radiator to be cooled. Mine is in good shape, so now all I need is gaskets and some fresh oil to reassemble the engine. Then, the valve clearances need to be re-set accurately (this is easier with the engine out) and the engine portion of this is done.

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