Seeking help please – suspected carburettor flooding: 53 Hornet

Doctorvaux

The car is a 53 Hornet with twin H, electric fuel pump, fuel pressure regulator/filter and ignitor electronic ignition. The Carbs were rebuilt about 5 years ago (not by me).  The engine has around 1500 miles on it after a rebuild around 2 years ago. The car was running OK last year.  The car was started in January after 2 months of inactivity in November/December.  The car started easily but would not run smoothly, stumbling and hunting once warmed up.  All 6 spark plugs were very sooty and the exhaust was very sooty.  The plugs soot up very quickly after cleaning. 

I checked the float levels in the carbs and they were about 1/8 inch too high, so I reset them.   This made no difference. I bypassed the fuel system with fresh fuel in a can and a different electric fuel pump. This made no difference.  The metering rods were clean and not gummed up, although I have not stripped the carbs down to examine jets. I have plugged the vacuum advance port on the front carburettor to eliminate a possible vacuum leak in the distributor.

There is no obvious visible sign of fuel running down inside the carburettors.

Compression pressures are all good around 150 psi.  Ignition timing is correct.

I used a “colourtune” glass spark plug and this indicates all cylinders to be running rich (orange flame, rather than blue flame).

To eliminate the possibility of a weak spark causing the problem (for all 6 cylinders), I have changed the following:  Coil, distributor (for a points unit), refitted original distributor with a different ignitor, rotor arm, distributor cap, plug leads.  This has made no difference.  The car starts easily, so I am thinking the problem is not a weak spark.

I now suspect this is a carburettor problem, but it seems to me unlikely that both carbs would have the same problem. Alternatively, perhaps the excess fuel from one carurettor is able to richen the mixture in all 6 cylinders via the tube inside the manifold?

Can anyone help please, with advice concerning what might be causing this problem and where to look next.

Many thanks, Brian.

Uncle Josh

Contact Geoff Clark.  He's the guru but I'll bet the floats are set too high for the new gas as it is lighter.  Gas is certainly slopping over into the manifold.  If you have plastic foam floats, I'll bet they are soaked.  Had one of those on a Pontiac.

Doctorvaux

Thank you, the strange thing is that everything was fine before Christmas and nothig was changed. I have reset the floats per the manual, to 1/2 inch at the float seem. I am running on 5% ethanol fuel which is available here in the UK.  The floats are the original soldered brass type.  The valve has the flat rubber style seal, which seals  against a circular brass seat.

MikeSheridan

Let's say that it was running fine yesterday, but today it is getting way too much gas into the engine. Ok, the carbs need to be rebuilt. But yesterday... Doesn't matter- way too much fuel today. What changed? Don't know, but the carbs need to be rebuilt. Either your diagnosis is bad, which it doesn't seem to be, or the carbs need to be rebuilt. Rebuild both, because even if it is just one, the other is probably not far behind. We have places that could do it in the US. I don't know who could do it in the UK. 

Doctorvaux

Thanks Mike. The carbs were rebuilt in the US about 5 years ago, so I was not expecting that they would need to be rebuilt again so soon. They haven't been driven for more than 1500 miles. If the carbs need rebuilding then I am prepared to rebuild the carbs myself. My experience with using third parties has very often been disappointing, so I now tend to do most things myself.  If possible,  I would like to identify a specific fault, so that I can be sure that I have addressed it when rebuilding the carbs. So if anyone has any advice on what to look for in the carbs, that would be helpful.

Rocket

I may be wrong here but the last time I had a problem with getting gas into my motor I took the car to a friend who took my carb apart and found a very small chunk of rust stuck in the needle and seat allowing the gas to flow right by and the car ran like crap you may want to check this out on your carbs. 

Glowplug

Rocket said:

I may be wrong here but the last time I had a problem with getting gas into my motor I took the car to a friend who took my carb apart and found a very small chunk of rust stuck in the needle and seat allowing the gas to flow right by and the car ran like crap you may want to check this out on your carbs. 

While not being able to physically review the carbs in question... Rocket gets my vote... the other thing I would offer is:  I have changed my fuel from alcohol infused gasoline to gasoline without this product.  Previous to doing this I encountered dried deposits inside the carburetors (white colored) that was hard and blocked the internal metering.   I attributed this to the fuel evaporating inside the carburetor leaving the deposits.  Since making the change these deposits have not returned.   I own three Hudson Stepdowns.   Good luck... 
 

Geoff

My guess would be a stuck/dirty needle valve.  Just one of the carbs with this problem would affect  the whole motor.  

Doctorvaux

Thank you for all the helpful suggestions. I will take a look at the float valve again. If that does not cure the problem then I will pull the carbs to pieces and look further.

Can anyone suggest a good source for the T-109-102 metering rod gauge. I will need to order one and have it sent to the UK.

Glowplug

A person who posts here on occasion has created a copy of the gauge and you can obtain your own at this url: https://www.shapeways.com/product/68E4KYFVR/carter-t109-102