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Grant Magrath

Boiled 39 anyone?

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Grant

You had access to a lathe for the fender lamp lenses. Make a washer about 2mm smaller than the bore in the housing and use a spring similar to the one in the photo on ebay.

1936-41 Buick Thermostat Housing GM# 1295238 : eBay Motors (item 200396105269 end time Apr-16-10 21:01:56 PDT)

It will soon let you know if you have fixed the problem until the correct spring can be acquired.

Danny

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Hey, I'm no tuning expert, but in reference to overheating, seems like I always see suggestions like "carb set too lean" and "timing too advanced", or the opposite, or something like that. Sorry. The details just won't ever stick in my feeble brain.

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..Make a washer about 2mm smaller than the bore in the housing and use a spring similar to the one in the photo on ebay.

1936-41 Buick Thermostat Housing GM# 1295238 : eBay Motors (item 200396105269 end time Apr-16-10 21:01:56 PDT)

The engine in Grant's car is 1947, so not sure if the 1936-41 ebay part would fit. Grant's father also has a 1938 so can check if they look the same.

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Grant:

I had a 39-90 for years. It was a chronic overheater until I got a lot more miles on it. The friction in a rebuild can overwhelm the cooling system. Your engine is freshly rebuilt with new bores. I would get at least 2000 miles on that engine before you do much more to the cooling system. Drive it at night regularly to rack up some miles, bring extra water if necessary. I found this did a lot for my Buick.

You could have a head gasket leak or crack in the head that's sending exhaust gases into the coolant. Most shops have a sniffer to detect exhaust gases in the coolant, might be a good idea just to make sure that's not the problem.

I think the thermostat bypass valve is not your problem. I believe that little shuttle valve to turn off the bypass was not used in a 47 engine -- instead there is just a built in calibrated orfice that passively controls the amount of water recirculated instead of going through the radiator. It has no moving parts.

I did put an RV flexible fan on mine and it was most helpful. This fan was a bolt on replacement for the original and it was a tight fit -- but it cleared everything and really increased the air flow. I suggest you keep an eye out for one, most auto parts stores sell them in various sizes and shapes.

Make sure the timing is set properly and that the centrifugal advance is working on the distributor. Retarded timing really ads to the cooling system load. Make sure the fan belts are tight.

Mostly, though, get some miles on your buggy.

Good luck down under!

Bill S

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Thanks Bill. Taking it out in the evening sounds like a good excuse to drive it! I'll do some research on 1947 engines and see what I come up with.

Cheers

Grant:)

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Here's an interesting thought. The water pump and pulley is a 1947 one and a larger diameter. A visiting engineer from the UK suggested that because the fan is going slower, it could be working in conjunction with the 39's front end design to create a wall effect at highway speeds, and preventing air from flowing through the radiator. Thoughts?

Cheers

Grant

PS sorry to keep going on about it!:)

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Take the grill out and go for a drive ??

However I am sure there are other 39's with 47 engines

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Wow !!!! That's out there.

I guess anything is possible but I think I'd leave that at just a thought:rolleyes: .

It seems you have a ready supply of parts there for a cheap trial and error test. Try the pulley from your father's car.

You said you had no bypass valve but the question now arises that maybe you have the later type housing.

Is it the later type housing with the fixed 1/2" hole??

If so, bypass is not the problem. If not, try the bypass from your fathers pump or use it as a sample to replicate. (I hope you get on well with your Dad:p)

I did put a six blade fan from a Commodore on mine. It is also a slightly larger diameter. It looks the part and unless you are a Buick nut no-one would ever know it's not original. The difference in the air sucked through the radiator was great. I'm one of those that doesn't get bent out of shape over not being 100% original.

Danny

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My '39 has yet to overheat but using one of those new thermometers that you point at something and it reads the temp..... it get to 208+ too close for comfort on a 105 degree day in Texas traffic. (I have no problems on the open road, only in town)

I am thinking of several things in no particular order.

(1) rig a couple of the patio misters to a lawn sprayer and have a way of turning it on from inside the car. It would put a mist of water on the front of the radiator. Again, only needed in town.

(2) an electric pusher fan that would be mounted in front of the radiator (high where there seems to be less air flow) it should be easy to find these on modern cars. although they are 12 volt, they would run half speed on a 6v system.

(3) slightly pressurise the system. Each pound of pressure, raises the boiling point about 2.5 degrees, 4 pound pressure cap would give a 10 degrees cushion. I have found a nifty tank from a Chevy Citation (about 1990) that has three openings. One is about 3/4 inch and would allow tapping into the heater hose. The second one is the pressure relief at the radiator cap and the third one...... not sure what it would be used for. The tank is plastic and is roughly 6 X 8 x 8 deep. I have not started to search for radiator caps that are calibrated for low pressures.

People that have offered their opinions, think that the '39 system would tolerate 4 psi but all seem to think a 12-14 psi cap might cause the water pump to leak. This is all opinions as none of them have tried it.

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Here's an interesting thought. The water pump and pulley is a 1947 one and a larger diameter. A visiting engineer from the UK suggested that because the fan is going slower, it could be working in conjunction with the 39's front end design to create a wall effect at highway speeds, and preventing air from flowing through the radiator. Thoughts?

Man, that takes me back 20 odd years back to first year engineering. It is correct that because the air needs to flow around an object in the way (like a bar on a grill), at high speeds, it creates an area of high pressure in front of the impediment - if the geometry is such that the bars are close enough together at sufficient speed, the air will act as if it is hitting a solid object. Aerodynamics can be really interesting.

That may be why the grill design on '39s had a running change to fewer bars...it may have been creating this issue.

As an experiment, I'm with the others who suggest taking the grill parts off to see if it makes a difference. At least then that might help to verify whether or not you are having an air flow issue.

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Thanks again to everyone who has offered great advice.

Had another play today, and compared to the 38 Sedan, the pulley is way bigger. Also, the 38 has quite a small diameter fan compared to the one the coupe has in it right now. Something else to consider is the size of the gaps in the radiator cores. The 38 has the same pattern as the 39 coupe, but it's a coarser one, for want of a better term. In other words, the air has less of a fight to get through. Tested the waterpump today and it appears to circulate the water well enough. I'm really keen to try a smaller pulley and fan to see how that works. I should point out as well that it seems the 38 Special's engine is in fact a 37, going by the engine number. I don't know whether it's a left over 37 engine they put in from new, or a replacement. But NZ assemblers were known to not waste anything!:)

Cheers

Grant

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So Grant...

What news have yee ???

Danny

Sorry! I've been flat out with my Corvette!

The good news is that after having a dig around the block drain tap, and putting a few miles on her, she's calmed the hell down! And getting better all the time. Took her for a run today and never missed a beat, although we do need to get that noisey 1st gear replaced, and the steering adjusted. I'll do the steering this weekend I think. On Tuesday, she gets her rear carpet and trunk done. That means all we have to do is track down a running board trim piece and we're done! We're entering it in the Restoration of the Year with the local vintage car club post vintage section. Here's hoping!

Cheers

Grant:)

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Whats the deal with the "noisy first gear?" Is it chewed up? Or just making a howling/whining noise? If its the latter, it's supposed to do that. 2nd gear is a little quieter. Its all because of the torque tube. The howl resonates in there. ;) I love it.

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I don't think it's supposed to howl like a banshee Paul! The 38 Special's syncros are pretty much shot, but 1st is quiet. Same with our friend's 39 sedan. The 39 coupe needs the syncro looked at for the graunch when you go from 2nd to 3rd as well. Going back down is good. The trick is to double clutch in the meantime. We have an old cookie tin of gear stuff that has some good bits in it (thanks Owen!), so over our winter, we'll most likely get it sorted.

Cheers

Grant

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Well if it's literally overpowering and you can't hear yourself think then yes I'd say something is wrong haha. :o

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