Monthly Archives: March 2019

Pontiac renovations, part 16.

I was reviewing finances and made an executive decision. I cleaned up the head gasket to see what condition it was in.

Cylinder head gasket, block side (copper)

As it turns out, really very good shape. I figured I’d reassemble the engine using it- which isn’t really a very good idea, but changing the head gasket with the engine installed in the car is a simple task so down the road it can be done with ease.

I purchased a roll of 1/32″ gasket paper from NAPA up the street. I began tracing out the water pump gasket to create a new one, as the original was in poor shape.

RTV sealant

I found the tube of RTV (room temperature vulcanizing) sealant I had bought to redo the GTA’s engine. Still in good condition as it is actually really very high quality stuff.

A light smear of sealant added to the water pump back-plate face to aid in sealing, as the surface is only moderately good.

Gasket applied, sealant to the other side and torqued down to the engine block again.

I ran a die through the threads of the manifold studs to remove rust and dirt. This aids in reassembly quite significantly as once the manifolds are on, access to the nuts is limited, and being able to spin the nut on with one finger is a help.

I’m not totally sure what happened to this stud, but there are signs that the engine had fallen over at some point. Either way, the metal surrounding the hole for it was distorted. This was leaking through into the exhaust port (the hole goes through to the water gallery behind) and had caused the valve to stick.

I gently filed the surface to try and make it flush.

You can see the high spots around the stud hole, looks like it’s been leaking for a while judging by the amount of rust. The surface is now only recessed, rather than raised. The recessed sections are not very deep at all, so a new gasket should now be able to seal properly rather than being lifted off the surface by the high points.

I then set about cleaning up the head bolts with a steel brush and die. Cleaned the head and shank first, ran the die down the threads to clear them, then wire-brushed the threads before giving each bolt a light coating of engine oil.

Repeat x30.

With the deck of the block cleaned, I placed the head gasket down.

Then cleaned the head and laid it down onto the gasket, aligned it and did all the bolts up finger tight. I then added the spark plugs to prevent any dirt falling through the holes into the engine.

Taking a copy of the factory manual’s tightening sequence, I first did all the bolts up to 25 lb/ft to gently settle the head down, then did them all up to their final torque of 60 lb/ft.

I made some (admittedly far too thin) gaskets up for the manifolds. I need to order a set of the correct metal/composite sandwich gaskets, which are nearly 1/8″ thick.

I refitted the manifolds, carburetor, vacuum line for the distributor, spark plug cap and wires, coil, fuel pump and blocked the vacuum port on the manifold with a bolt. I hacked together some pipework for the fuel pump, to test and see if it was going to operate. Took a little while to prime but it did draw fuel successfully through.

It started up and ran nicely. I did see that the gearbox is not leaking from the tailshaft, rather from the engine end of the casing, possibly the front seal where the torus connects.

I then cleaned up the thermostat housing, the head surface and added a little black enamel to the bolts and washers.

Spent a little time bending and hammering the bracket for the air filter assembly. With the engine removed from the car, access is greatly improved and I was able to see underneath to measure and adjust the bracket correctly. I learned also that the air filter sits much closer to the engine than I had originally thought.

I dug a tachometer I had out of storage- I bought it way back in 2004 from a now-defunct store in the UK and brought it with me.

Connected it up and presto! It reads nicely- it’s even more accurate if I select it to 4-cylinder. The gearbox bands need to be set with the engine running at 700 RPM, so it’s important I have a working tachometer. It’s also much easier with an electronic one, rather than having to hold a mechanical one to the crankshaft pulley. Plus, I cannot see that AND adjust the gearbox at the same time…

The fuel pump has become a little wet around the seams too, so that needs a new gasket.

Finally, I fitted the thermostat housing to check for clearance between it and the air filter.

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.