i have two new Stromberg 97 (from speedway motors) on a French flathead (4,2 liters)!!! when I fired up, have many detonations in exhaust !!!!the timing is correct , but I thing the gas is passing into the engine !!!i have some gas into the engine oil ( to much oil and oil is very liquid ) what is wrong with this carburators !!!!!
If there is fuel in your oil then fuel is definitely leaking(pouring) into your engine. I would start looking at your float and the needle valve, which is maybe stuck. I'm not familiar with The 97 and I'm sure someone will chime in. I have 94's and had the same problem with old original carbs but I changed to new made carbs and have no problems, touch wood.
There are many threads on this subject. Here is one: https://www.jalopyjournal.com/forum/threads/speedway-97-carbs-opinions.1018893/#post-11520485 The bottom line is these carbs are bad. Merde.
Have heard they are hit or miss. The floats can crack during adjustment and sink which will do what you describe. Pull the tops and check them first. Make sure level is correct. Then make sure you have the correct fuel pressure of 2-3 psi
I would make sure you have both needle and seats, as well as the flat that don't melt using today's gasoline. You also need to make sure the line pressure is between 3 to five psi. Get a regulator and gauge. Make damn sure to use a real filter with a disposable filter, preferably one of the canister models. Dirty fuel wreaks havoc on the delicate nature of carburetors. Also follow the advice of the poster who said make sure the float is not soaked, or if of the soldered copper style it does not have a leak and is filled with liquid. You should also have a board of jets, and a spark plug magnifier. Learn to read your plugs and have a couple of sets hotter and colder than the ones you have, now. A modified, and multi-carburated Flathead needs tinkering with to make it purr. And, yes, they are like cats. You can't expect to do exactly what you want, unless you romance them with TLC.
Are the Speedway "9Super7" carburetors rated to handle 5 lbs of fuel pressure? They may be, but I wouldn't run that much pressure with any regular "Ford-type" two barrel.
Given where you live I’m really surprised that you have the Speedway garbage Stromberg imitation carbs. They might look right but they are poorly made junk. You could have ordered the good ones from Clive in England at Stromberg 97. Unless I’m wrong and you’re dealing with something someone else ordered. https://www.stromberg-97.com/
Real Strombergs prefer 2 pounds. Not 5 pounds. Do you have real Strombergs you just ordered through Speedway, or do you have Speedway 9super7's?
In order of most likely; #1 would be you failed to use less then 4psi or less pump or also no reg.{ I like 3psi my self}.#2 is crap stuck in seat for float,from you note cleaning your tank an lines out an having a filter. #3 float sunk or wrong too high adjustmint. After those it gets less likely but with cars anything can happen.
I bought mine from Clive in England, they are great carbs. I had to install a Holley 12-804 regulator to decrease pressure from 4 pounds to 2.5 pounds because I was having some of the issues you described. Perfect now! Try regulating that fuel pressure asap.
thanks for your help; I have a mechanical and original gas pump!!! I will try with a regulator, last year I have try this pair of carbs on an other flathead engine and had very bad results then I bought a new pair in England ,it was perfect
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