Graham’s Corvette Blog and Studebaker bits ‘n’ bobs

In my latest perusal of the internet re-AC I realized that I might have missed the mark with my AC in the Stude. I knew that the Sandan compressor came charged with oil and I must have found a comment that it was sufficient for the whole system.

The Sandan I have is a SD-508 which from what I read, contains 4.5 to 6 oz of oil in it. The total for the system should be between 6 and 8 from what I read. I spilt a bit of the oil out when I installed the unit so maybe it has between 4 and 5.5oz which my system has be operating with for the past couple of years.

Rule of thumb is it is better to have too much oil in the system rather than too little – within reason. With this in mind I picked up a 4 oz can of … AC system oil that is compatible with all the newer PAG oils. with this in place I will have from 8 to 9.5 oz in the system so. If the compressor loads up and causes the belt to squeal I’ll have to drain the system and do a reload of oil and refrigerant.

With the extra 4 oz of oil in the system I’m getting a reading of about 28 on the low side and a bit over 200 on the high side. the original readings were 25 and 180. These fall nicely with the 25-55 and 150-250 recommended pressures. When I installed the system I went for higher pressures, but the system didn’t put out much cold air. My son Chris recommended dropping the pressures and that did the trick 🙂

On the test run there was a high pitched vibration, almost a squeal from the evaporator when the compressor was engaged and gas was being pushed through the expansion valve. I assume there is an issue with too much pressure/oil for the expansion valve. The can of oil also comes with some gas for the oil transfer.

I hooked up the gauges again – low pressure blue an the middle yellow to a pail to collect any oil that might come out with the gas. I opened the low side whenever the compressor was engaged until I got the pressure down to about 25 psi. Not a lot of gas needed to be removed for the pressure to drop 3-4 lbs. That was all it took to take away the noise from the expansion valve. No oil came out with the gas so it seems I’m not too over on the oil content.

All’s good now with lots of cold air coming in the cabin. Now I can enjoy the rest of the driving season.

A tin pie plate and a flattened tin pie plate – so what!

I don’t have any original insulation for the temperature sensor on the side of the expansion tube so I’m using a double wrap of header insulating tape. If it can keep heat in it should be able to keep heat out.

And now for the pie plate. I cut out a portion of the heavy aluminum and wrapped it over the exhaust manifold tape to help deflect the heat that will be coming from the exhaust manifold that is less than 6″ away. I may also cover the heater box in heat deflecting sheeting (that is also used on fire walls, floors, and engine hoods) to help keep heat away from the AC system.

AC gauges hooked up to the low (blue) and high (red) pressure fittings. I am using adapters on the original R12 fittings so I can attach the R134A fittings on the AC gauge hoses. I will be filling the system with R12A a substitute for R12.

It is at this point that my inexperience with AC begins to show. I realized I hadn’t considered the oil needed in the system. The manual says that it needs 6 oz of oil. Checking at NAPA I found that it needed PAG46 oil for ’79 Chevys. Now I needed to know how much oil was already in the compressor. I couldn’t for the life of me find the compressor information slip so no choice but to remove the unit. Turns out there was just enough to keep the unit oily inside.

Checking the internet I found that 2oz of oil should go into each of the compressor, condenser and dryer. In the photo the high/low pressure connection is back on the compressor. While it was off I was able to get 3-1\2 oz into the condenser line and I put 2-1/2 oz in the compressor – A compromise since I couldn’t get any into the dryer.

With everything hooked up it was time to vacuum down the system.

Here the vacuum is pump hooked up. I’ve used it a couple of times so it has paid for itself. A pump and a set of gauges plus a few fittings is all that is needed to service an AC system. There are a lot of videos and information on line on how to do the work.

Pump started and the gauge ( blue is showing a 30 lb vacuum that will be plenty to cause any vapour in the system to boil and be vacuumed out. I ran the pump for about 1/2 hour and then shut off the red and blue lines to see if it would hold vacuum. Sadly the gauge slowly dropped down to zero. It is likely a pin hole size leak and maybe even in the gauges. I’ll add a can of stop leak to the mix when I charge the system.

The low pressure gauge (blue) shows the vacuum starting to fall.

The system needs approx 16.5 oz of R12A which is less than if it was charged with R12 – I got the conversion from the web. Two 6 oz cans of R12A and one 4 oz can of system sealant.

The AC low pressure switch turned on and started the compressor with less than one can of R12. It was cycling quite quickly and each time the compressor started it would suck in a bunch more coolant. I next added the sealant and went on to the second can of R12A. By the time I had most of the second can of coolant loaded the compressor was in operating almost continuously which I understand to be correct.

I took the Chevy out for a run and the AC is working beautifully. It will take time to see if I am loosing gas or the system is sealed properly. In the meantime I’ll enjoy being able to keep the windows up on hot days.

Next: this about ends my work on the Chevy until the fall when I will be re-doing the front end and adding cruise control to the car.

The lockup is still hunting and not dropping out easily on acceleration even with the switch turned CW to it’s limit of 1.5 turns.

The vacuum is being taken from the base of the carb – the hose crossing low down to the base of the carb. I’ll move it to the main vacuum port at the back of the intake manifold.

I’ve run it from the switch (behind the aluminum bracket on the left) to the vacuum lines for other devices in the car. But still not luck. So now I’ll try by running it directly to the vacuum port so there is not chance that the vacuum is affected by other than what is happening inside the intake manifold.

Using a Y connector I joined the vacuum switch directly to the intake manifold.

Even so with the vacuum switch set back to 1 turn CW it is still hunting on moderate speeds.

It’s been awhile, maybe a year or more since I worked on the lockup and vacuum switch and while digging around on the internet for ideas I saw a vacuum delay switch and realized I had forgotten all about it. The main use of the switch is to stop the hunting at moderate speed when the lockup wants to kick in.

I installed it in the line to the intake manifold. Now to get a test run in and see how it works.

Ran a test run and all seems OK now:-)

Next: time to get the AC working.

After I made the changes I now had heads, rockers and push rods from the crate engine. A fellow Chevy buddy Barry cleared up the rocker/push rod issue. Seems that GM changed the heads sometime after 1979. The earlier heads had small push rod holes that helped keep the rockers centred (in the photo above of the original ’79 head the holes are narrow). The later heads had larger push rod holes and different rocker design which keeps the them centred on the valve tops. So when I used the old rockers and push rods couldn’t keep them in place. Good to know that there was a specific cause to the problem of mixing and matching heads, rockers and push rods.

A couple of test runs and all seems OK. So now I’ll re-attach the AC bracket – the bracket has to be loosened before the right hand valve cover can be removed.

I reconnected the lock up torque converter vacuum switch and did another test run. The trans is trying to lock up shortly after getting in 3rd gear and hunting when trying to drop out at moderate speed. It’s trying to work and only needs adjustment.

It is adjusted by an allen wrench in the vacuum input port. I am starting by turning it 1/2 turn in a CW direction which is supposed to increase the vacuum needed to trigger the lock up. Now for a second test run.

Ran the engine for a short time and it sounded like I had a loose lifter. Then the sound changed and I turned off the engine. this is what I found -again- on the #4 exhaust. The rocker to the left is also not centred properly.

#1 exhaust is also moving off centre!

The rocker on the left is from the crate engine and on the right is the one from #4 cylinder. It seems that GM became aware of the issue and modified the rockers to stay centred.

The push rod from #4 is slightly bent compared to one of the original units. I’ll use the old push rod as a replacement.

I’m now swapping out all the original rockers with the units off the crate engine – the crate engine had very little wear before it spun its bearings. I’m using a pad to tick off each cylinder as I give the lifters one turn down from zero lash. I’m following the service manual and adjusting half the valves at TDC and the other half after a full turn of the crankshaft.

This is the right bank with the engine running. All the rockers are staying centred on the valve heads. When the engine was warmed up some I reset the valves. Oddly enough I had to loosen the valves over 1-1/2 turns to get the valve to rattle. With zero lash I turned them down 1 full turn. Internet references often say that cold adjustment is fine, but I also found references saying that one full turn hot or cold is correct. I prefer to set them with the engine warmed up. Not so messy If you cut the top off an old valve cover and use clips for something similar to stop the oil squirting from the top of the rockers. I add an old towel over the exhaust manifold just in case.

Next: time for a test drive.

On about the third test drive and about 20 miles from home the engine starts to bang and clatter. Sounds like something isn’t right under the valve cover. So stop the car, call CAA and get the Chevy back in the garage. This is what I saw when I took off the right valve cover.

Something nasty going on here. Looks like a weakened push rod that decided to go south.

I have a used push rod from a slightly used ’86- ’90s crate engine. Newer style with welded in ends. I replaced the broken rod and re-set the all the lifters to one full turn after zero lash.

Ready to start up and see what happens.

My second bug was a buzzing sound on acceleration. I suspected that the exhaust system was contacting the body at some point. This is what I found. I had 1/4″ or less between the left tail pipe and the rear cross frame.

I needed to loosen the band clamps between the tail pipe and the muffler, the hanger clamp at the mid-crossover pipe and the band clamp (not showing) between the exhaust and tail pipes. This where band clamps come into their own. Once loosened the pipes can still rotate or move in and out easily.

I was then able to drop the tail pipe to match the right side giving 1/2″+ clearance.

Next: time for another test drive to check the engine and exhaust clearance.

Hooray! the seats are done and almost ready to be installed in the fibreglass buckets. The vinyl is buckskin and the cloth is matching period Chevrolet hounds tooth,

The only hitch is that the upholsterer didn’t realize the seats are held in place by the wires at four spots – seen here where the foam is cut out for that purpose. So the hog clips need to be removed from those four openings.

I dug out my hog ring pliers and some hog rings and attached the vinyl to the seat wire on either side of the mounting opening and then removed the problem hog rings.

Seat pads in place. Not the easiest thing to install, but once done that will be the end hopefully. The vinyl on the upper section is puckering some. To fit in the seat shell the upper cushion had to fit into a concave position for the wires to grab the seat clips. Something I will have to live with unfortunately.

Before the seats can go in the hinge covers need to be installed. The lower covers on both seats are hidden by the console once the seats are in place.

The decorative acorn nuts need to be driven on. I used a socket of the proper size with a small washer so that the nut is just outside the socket. They go on quite well with a sharp push using the palm of the hand. They seat with a snap and the hinge cover is held in place snugly. The old nuts are toast. You need to buy new sets of nuts each time the hinge covers are removed. Impossible to pull up the small tabs on the new style nuts (made in China) once they are removed.

A nice tight fit.

Seats in place. The new buckskin vinyl is a bit darker than the photo shows, but it is a good match to the carpets and to the seat buckets and console in the original beige tone. The buckskin is a tad darker than the original doeskin.

I’ve been waiting months for the seats so that I can start the test drives to work out any bugs. Since it has been so long I decided to spin the engine on the starter until I got some oil pressure ( I have an oil gauge mounted on the front of the engine).

The gauge is just behind the heater pipe in the red rectangle. After I got enough pressure the engine started right up as the carb had been filled. I ran the engine till warm and then disconnected the vacuum advance pipe and plugged it. I then set the initial timing to 10 degrees and found the total at 2500 to be about 30 degrees. I tightened the distributor and rechecked the timing. It moved the initial timing to 11 degrees and the total still at about 30 at 2500. Good enough for my initial runs which hopefully will start tomorrow. I’ve disconnected the lockup converter for the time being and I’ll re-connect it and make adjustments later. After all is working OK I’ll tackle the AC.

Needless to say I am a happy boy to have the “Chevy back on the menu”.

A few areas needed a second go-around with spot putty to fill in the spots were the first application of the filler shrank.

I’ve given the underside of the repaired cover a coat of white rustoleum oil based primer

Outsides with a double coat of white rustoleum primer. Good enough to paint. I’ll leave them for a day for the primer to set properly.

After a day I have put on two coats of sun yellow Rustoleum oil based paint. I’ll leave them for three days and then rough them up with 1000 sandpaper before adding two coats of Rustoleum clear coat.

All nicely finished in bright yellow that Studebaker V8s had from the factory. In front is a 1/2″ spacer for the AFB on the 289 R1 engine in the ’66 Commander. I’ll add it to the existing 1/2″ block under the carb to get a full inch that is supposed to be optimum for the original intake manifold. On a trip to PEI the Commander got about 22 mpg with the AC on. So maybe it will give me 23 w\o the AC. It gives me 17 on every day driving. So not bad I think. I don’t expect anything especially noticeable from the extra space except maybe a bit crisper response and a wee bit better mpg. It will be interesting to see how the engine performs when I swap in the 3.07:1 Twin Traction rear end – I’ll be doing that next winter along with a complete refurbishment of the ’79 Chevy front end.

Still waiting for my Chevy’s seats.

The left cover has a bad section of the inside gasket lip. It’s passable, but not the best.

I cut out the bad part of the lip and then cut a strip of 1/32″ steel as a replacement. The corner made it a bit tricky.

I don’t make any claim to be a welder. I don’t get to do it that much so I trained on a bit of scrap metal before attempting the job. Came out good enough to do the job. I drilled the strip with a 1/4″ drill over the spot where the original spot weld was located – about midway. I then welded the strip at that point as well for a solid fitment.

Sand blasted, repaired, spot weld ridges removed and spot puttied. I’ll leave them for a day and then get to the final sanding.

Next: Yet more valve cover work

Still waiting for the seats for the Chevy. The upholster lost his helper of 8 years and so is even later than expected. Seats were promised a couple of weeks ago. In this business you need to have patience otherwise best do something else!

In the meantime I’m restoring a set of Studebaker valve covers. I’ve twisted the spark plug brackets off the top of each one. They are rusted and it’s easier to remove them than repair them. I’ll be doing them up in yellow as was the originals from the factory. My plan is to make them up and let the paint cure longer. Last set I put on before a full cure and the paint took on oil stains that I can’t polish off.

The inside of one is OK, but the other will need to be sandblasted

I’ m scraping some of the easy crud off before sandblasting. My equipment is hobby class and so takes a lot to clean off old glue and hardened paint – even with “0” grade media and 100 psi.

Cleaned up nicely

Next step is to use the dremel with grinding burr to take off the spot weld remains on top and also the ridges and burrs on the spot welds around the bottom that hold on the gasket lip on the inside. The little bits of paint left after sanding blasting I’ll take off by sanding.

Next: filling and sanding