Air/Fuel Ratio - 1940 60S

[pauldridge]

In my unrelenting quest to resolve the chronic overheating problems on my flathead 346 (idles all day long at 160F, in dead of summer, but maxes out the temperature gauge under power), I decided to pop an exhaust gas analyzer up the bum and see what kind of A/F ratios that old Stromberg is putting out.  My research indicates that ratios between 12.5 and 13.5 are in the ball park for carbureted engines.

Sure enough, at idle, the A/F ratio was right about 13.3.  But when I rev up the engine to highway speeds (granted, not the same as actually putting highway speed loads on the engine), the A/F ratio dropped to around 14.3, which I believe is way on the lean side, and may be contributing to on-power overheating.

Wondering if anyone else has done measurements on similar carbs, and if anyone has thoughts about what might be causing the carb. to run lean at power (I did unscrew the main jet access plugs, and ran some fine wire up and down through the jets, but that may not have been sufficient)

Finally, the manual calls for a special tool for removing those main jets for inspection.  Anyone know of a source for that tool?

Thanks from Austin

[Gene Beaird]

I'd check the cooling system for an exhaust leak.  I had a Jeep that overheated when driving it, and I got this kit that allowed for testing for exhaust in the coolant.  I'll have to check to see who made it (I think I got it from Eastwood, but not certain at this time).  Turns out I didn't, and I never found out why the thing overheated, even after replacing _every_ piece of the cooling system except for the engine itself, but you may have different luck.

[Brad Ipsen CLC #737]

Don't know if this would cause a cooling problem but you need to check out the economizer jet in the Stromberg Carburetor.  I had this problem during the shake down period.  Get the 37-48 engine diagnosis for a good explanation.  Contrary to the name the economizer jet provide extra fuel for wide open throttle, maximum power running. 

[Glen]

Last I knew NAPA carried the kit for checking for exhaust gas in the coolant.  I imagine that any large parts store would have it. 

[pauldridge]

I AM aware that I have a small crack in center exhaust port, and suspect part of my overheating issues are from that.  Hope springs eternal.. hoping to avoid addressing that issue for awhile, then may try repair via block repair screw-in dowels:

http://www.locknstitch.com/

[kkarrer]

Phil,
      Running a mix that is too lean will make your overheating problem worse and this usually shows with greater deterioration of the porcelain in the exhaust manifold as well, but I'd suspect that your issue resides either with timing (Has the distributor ever been rebuilt? It's easy to put the weights in backwards and that will cause exactly what you're having issues with.) and/or that crack in the block.  You might give Ted Eaton a call.  He's a Y Block man, but he's had a lot of flat head experience and is one of the best engine rebuilders I've ever encountered.  He's just south of Waco.  His number is 254-857-3339. He's great at trouble shooting stuff like this.  I'm assuming that you've had the radiator out and that it flows properly and that you have no thermostat issues.  By the way I'm currently restoring a 41 6227 D coupe and the color combination I'm putting on it (just got the body back on the frame and shot and clear coated) is similar to your 1940.  That's a great looking car you have there.
Ken Karrer 1941 6227D coupe

[pauldridge]

Ken,

thanks for that input.  Yes, in fact, my distributor weights WERE in backwards.  As well, some idiot had connected to dizzy vacuum input to the manifold, rather than the carb.  Those problems I discovered and corrected back last summer after I acquired the car.  I was able to reverse the weights myself, but the timing was still erratic, so I opted for a rebuilt distributor from AllCads.  That helped a lot.

Radiator has been rodded out/cleaned two times since I purchased last June, and flows very clearly.  I've had the water pump off, it looks like brand new inside, and almost no crud in the block behind.

I'll give that expert a call!

Phil

PS.. are you in Texas?  The roof of my car was obviously painted at a later date than the black, and is crazing a bit, so it will get repainted soon.  I'm considering a similar color, but with a mild metallic w a slight blue cast.  The pure silver is a bit blatant for a car like this.

[62droptop]

if the rad is original, even if it has been cleaned and rodded out as yousay, it still may not transfer the heat as it should therefor giving a cooling issue at speed
do you have anything blocking airflow through the grill, any shields or valences missiing around the rad to re direct air through the rad?
do you have  grill badges of a license plate blocking the grill?

how about thermostat?
a stuck open or missing thermostat will allow the coolant to travel too fast through the rad and will not give time to cool enough,specially at speed

how about waterpump drive belt?
not slipping?

another issue could be restricted exhaust
if the muffler is poorly made,undersize,loose baffles ,or pipes kinked or too small could contribute to the issue

air fuel ratio should not be that big of a worry,when you are driving it the throttle will be open much more that when you are static

take a drive with the gauge up the bum as you say and see what real world conditions give

unless you have a fuel delivery issue ,dirty filter,weak pump etc
how does the car perform?

how hot is hot?
have you checked the temperature or are you going by the gauge

[kkarrer]

Phil,
      I think that color should be Berkley Gray Poly which is what I just painted on the top of my 41 coupe (the lower on mine is Gun Metal).   You should take a look at the Auto Color Library (www.autocolorlibray.com) at TCP Global.   They have pictures of the original color chips and correct combinations and they have the original formulas.  They can provide lacquer, base/clear, or single stage urethane or enamel in most cases.  I went with the base/clear.  My advice is not to bother with their reducer as it will only add to the weight and cost of shipping.  You can get reducer locally at Gladwin Paint or some of the parts houses.  I just clear coated the body color this week and plan to cut and polish on Saturday before we start putting glass, rubber, and chrome back on.  You should come by and check it out.  I also have a qt. of the Vincennes Red for the wheels which may be of interest to you.
Take care,
Ken Karrer, Austin, Texas  6227D coupe