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Another hot running flathead

Started by Dave Leger CLC #19256, June 19, 2007, 02:27:02 PM

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Dave Leger CLC #19256

Hi Folks,

    I have a 47 coupe which runs hot.  It has a rebuilt engine (Egge components) with about 900 miles on it so far (I know, it will run hot until it breaks in, but it seems I should have seen some improvement by now).  I have tried two water pumps, two thermostats, had the radiator re-cored, and upgraded to an original 5 bladed fan.  I have plenty of flow evident in the radiator once the thermostat opens (currently a 160 degree thermostat).  I have a correct 7 lb deep radiator cap.  The shield below the radiator is in place.  The car does not boil over, but eventually reaches the Hot mark on the guage and it will start boiling fuel in the fuel pump (the aux electric fuel pump helps with that, but still has trouble keeping up when it gets really hot).  I have no signs of head gasket issues.  The distributor has been rebuilt, and the timing checked by vacuum and Sun machine.  The carb has been rebuilt, and the mixture double checked by an expert.  I've drained and refilled the system, with the front jacked up to help prevent air pockets.  I have a 50/50 mix of antifreeze in with Water Wetter added.

   I had read about the different outlet sizes on the cylinder bank's water connections.  Is this a difference in the head itself, or in the pipe fitting for the radiator hoses?  If in the head, are the left and right heads swapable?  I wasn't there the day the person helping me reassmble the car put them on, so if swapable, I guess they could have screwed up.  If it's in the outlets themselves I could easily see that getting overlooked.

   I'm about out of ideas, so any suggestions are appreciated.

Dave Leger
Dave Leger     1947 6207 Club Coupe

Bill Ingler #7799

Hi Dave: You say the gage goes to H but doesn`t boil. If the car doesn`t boil or hasn`t boiled with all you have done to the car then I would make sure my temp sending unit is not giving out false readings. When you put a temp sending unit in the head make sure it is metal to metal with no sealent or tape around the sender threads. The sender won`t give accurate readings if the threads are not clean on the sender as well as the threads in the head. Find someone who has one of the new hand held laser temp guns and then when you have the gage reading on H take some readings at different locations around the radiator as well as the engines. The hottest part of the engine is just where Cadillac placed the temp sender in the left cylinder head. I hope when the engine was rebuilt that the soft plugs were removed and the block as well as the heads were sent out to be de-rusted. You would not believe what amount of rust that 50 plus years will leave in the the block and heads. It doesn`t take much of this to slow down the circulation. Check to see if you have a large spring in the bottom radiator hose. Without a spring a good water pump could cavitate the hose some, reducing flow. As far as the fuel boilng in the fuel pump, that is not  uncommon with todays fuels. A aux pump in the fuel system is a must for any flathead.You did not say at what point your temp was on H. My 47 here in Phoenix when we get in the high 80s will creep over to the H in traffic or waiting for a light but then will start going down once I start moving. It takes something really serious with your cooling system to make a 47 boil. By the way the correct 47 radiator cap is a RC-7 which is a 9# cap. If you look at your heads you will see the left head has an outlet for the cross over tube to your heater defroster and the head also contains the temp sender unit. The right head has none of these. I think if you get a temp reading at various points around the engine and compare what your instrument gage is reading, I think you will find you have nothing to worry about. Enjoy your car.

Dave Leger CLC #19256

Thanks Bill,

   I'll have to borrow, or buy one of those infrared temperature meters.  I had wondered as well if the temperature guage was reading right.  Yes, the block and heads were all cleaned and all soft plugs removed.  I do have a spring in the lower radiator hose.   Maybe the car is not overheating, but there is another issue with the fuel system.  I'd already found one issue with a leak letting air in the flex line, and replaced that.  I've also replaced all the rubber lines from the gas tank forward.  I have insulation on the fuel line from the pump to the carb.  Even with the electric pump on, when I stop for awhile in traffic, and it's hot, when I start up again it stumbles some until I get moving.  Checking after I got home yesterday, with the car still running, I could see a lot of air/boiling in the glass bowl on the pump. 

Dave
Dave Leger     1947 6207 Club Coupe

baxterculver

Quote from: Dave Leger CLC #19256 on June 19, 2007, 05:19:28 PM
Thanks Bill,

   I'll have to borrow, or buy one of those infrared temperature meters.  I had wondered as well if the temperature guage was reading right.  Yes, the block and heads were all cleaned and all soft plugs removed.  I do have a spring in the lower radiator hose.   Maybe the car is not overheating, but there is another issue with the fuel system.  I'd already found one issue with a leak letting air in the flex line, and replaced that.  I've also replaced all the rubber lines from the gas tank forward.  I have insulation on the fuel line from the pump to the carb.  Even with the electric pump on, when I stop for awhile in traffic, and it's hot, when I start up again it stumbles some until I get moving.  Checking after I got home yesterday, with the car still running, I could see a lot of air/boiling in the glass bowl on the pump. 

Dave
Hay Dave,
There are inexpensive infrared temp meters on the internet for less than $50.  It wiill give you an accurate temp reading anywhere under the hood.  Cold, start-up, warm-up, hot running, etc. 

Bill is right, tape or sealant on the temp guage threads can cause a false reading.  Also, as to your fuel problems, remember you are sourcing fuel at altitude (Denver area?) and, as I recall, it is loaded with ethanol (gasahol?) which will change the volativity of the fuel.  Frankly, it boils (vaporizes) at a lower temperature than the gas these old cars were designed to run on.  You might try a pint of Marvel Mystery Oil (available from your local parts house) in a full tank of gas and see if that helps.  Some swear by it as a partial cure for dread vapor-lock. 
baxter culver clc#17184

Dave Leger CLC #19256

Oh, if the sender unit is reading high, does anyone know where I can get a new one?

Dave
Dave Leger     1947 6207 Club Coupe

35-709

Cooper's Vintage catalog lists them at .....

http://www.coopersvintage.com/catalogs.html

Might even find one a NAPA.
1935 Cadillac Sedan resto-mod "Big Red"
1973 Cadillac Caribou - Sold - but still in the family
1950 Jaguar Mark V Saloon resto-mod - Sold
1942 Cadillac 6269 - Sold
1968 Pontiac Bonneville Convertible - Sold
1950 Packard 2dr. Club Sedan
1935 Glenn Pray - Auburn Boattail Speedster, Gen. 2

homeonprunehill

06-20-07
DAVE, No, the heads can not be swapped.  If the hoses are at the front of the engine and at the top, then the heads are install correctly.  The right head (as viewed from the front of the car) has the larger hole in the head. the left head has the "smaller" hole so that most of the coolant doesn't go through the left head.  The hose connectors are the same size. It does sound, by your description, that the trouble is with the heat sending-unit not having a good ground.HTH
Good Luck,JIM
USED,ABUSED AND MISUSED CADILLACS AND LA SALLES

Dave Leger CLC #19256

Hi Folks,

   Thanks for all the suggestions.  Bill was right, things are not running that hot.  I bought an infrared meter and even after 2 hours of idling at 95 degrees ambient the heads showed 200, the water going into the radiator showed 190, the fuel pump showed 170, etc.  The gauge is just reading high.

   With suggestions from John Washburn I disconnected the fuel system from the gas tank and ran the car from a can of gas.  That didn't change anything.  I reconnected the tank and bypassed the fixed line from my electric auxillary pump to the mechanical pump.  That seemed to remove a lot of the bubbles going on.  Apparently there was some leak in that steel line opening up when it got hot.  Since I'd bought 10' of fuel injector line to bypass it anways (expensive stuff!) I went ahead and replaced it with that.  If the car gets hot I still get an occasional burst of bubbles, which probably are from fuel boiling (with our 10% ethanol content I hear complaints from many people about problems like that) but things are much improved.  A friend with an AMX tells me he had to run an electric pump, return line, and cold can to get his car to behave, so I guess I can't complain about an occasional bubble!

    I took the car to our RMRCLC monthly meeting last night.  We did a special meeting with the club providing a great barbeque.  We had a big turnout.  It was 83 when I drove over and the car never went over the midpoint on the gauge (which thanks to the infrared meter I now know is the 160 degrees the thermostat opens at).  I guess now I just need to get some more miles on her. 

   I recently took the car in along with new rear shock links and new front coil springs and had the whole suspension and steering gone through.  Boy what a difference!

Dave
Dave Leger     1947 6207 Club Coupe

Greg Calkin CLC 18288

Dave,

Another cause for flathead engine overheating is a distributor that has the centrifugal advance weights mounted upside-down.

This will cause timing to appear normal at low rpm, but will retard timing rather than advancing it at higher engine speeds.  For example, if the timing advance is supposed to be 15 degrees advanced at 40 mph, it would instead be 15 degrees retarded.  The resulting 30 degrees of timing error will cause serious overheating, poor performance and fuel economy.  The problem will be nonexistent at less than 1200 rpm, but will get steadily worse with engine speed.

At least several CLC members have sent out their distributors to have them "professionally" rebuilt only to have a very difficult to find, overheating problem. The easiest way to diagnose this problem is to connect an advance timing light and make sure the advance is in the correct direction.

Another quick check for the centrifugal advance mechanism is to remove the distributor cap and carefully turn the breaker cam in the direction of rotation (the only direction it should turn).  It should rotate freely a few degrees and then return to its original position when released. If this "spring action" is in the direction opposite breaker cam rotation, then the weights are installed upside-down.

You mentioned that you had the distributor checked on a sun machine. If the operator checked the advance curve at various speeds, I assume that he would have noticed if the "advance" was in the wrong direction. 

If the centrifugal advance weights need to be flipped over to get the correct advance direction, the distributor shaft will also have to be re-indexed with respect to the camshaft.

Greg

Dave Leger CLC #19256

Thanks for the information Greg.  I would never have thought of that.  A local club member rebuilt my distributor for me, so I suspect it's just fine, but next time I'm out working on the car I'll hook up a timing light and double check.

Dave Leger     1947 6207 Club Coupe

harvey b

hello all, my problem isnt really related to this one,but can you use a timing light on a 37 v8? my car is pos ground 6 volt.no one i know has any experience with this setup? i see 2 marks on the pulley?,the shop manual shows nothing about a light,maybe they werent invented then?any suggestions or tips about this?? thanks Harvey Bowness
Harvey Bowness

Dave Leger CLC #19256

Hi Harvey,

    My 47 is negatve ground, so not sure about positive ground cars.  I'm lucky my dad's older timing light works fair with 6 volts, but the best bet is to get an older light set up for that.  There's one on Ebay now:  http://cgi.ebay.com/ebaymotors/Old-School-6-Volt-12-Volt-Timing-Light_W0QQcmdZViewItemQQcategoryZ43989QQihZ007QQitemZ170130047523QQrdZ1QQsspagenameZWDVW

Dave
Dave Leger     1947 6207 Club Coupe

Dave Leger CLC #19256

Harvey,

   I did a bit of digging on the web - some folks have used a 12 v light on 6 volt by uising a separate 12v battery for the 2 power leads, linking the ground on it to the 6 volt system with a separate wire, and using the induction pickup on the 6 volt spark plug wires.  Another possibility would be something like this: http://www.amazon.com/Flaming-River-FR1001-Self-Powered-Batteries/dp/B0002LJR7E which is self contained running off 2 D cells.  Since all it looks for is that high voltage pulse on the spark plug wire, I would think it wouldn't matter what the polarity or voltage was.

Dave

Dave Leger     1947 6207 Club Coupe