Reply to "Backfiring"

DannyP posted:

Ok, so you have twin 1 barrel carbs. I can't tell what brand they are, but I'll wager in the 34mm or so size. Take the air cleaners off, and then you'll see. 

I can also see an alternator(good) and is that a Berg breather?(if so very good) I also see a fuel pump blockoff with a hose going to the breather(good because you have an electric fuel pump, but need to check your fuel pressure). I can also see a hose running manifold to manifold for a vacuum balance tube, also ok to have.

Ok, here's where more info is needed. Carbs: If they are Weber or baby Dellorto, 3 psi for pressure. If they are Solex, NO MORE THAN 1.5 pounds! Exceeding this will overwhelm the float valves in the carbs, and flood the engine with too much gas, and also, dilute your oil and ruin your motor. The fuel pressure needs to be verified, engine running, with an actual test gauge. You can't guess and say oh, I have a regulator set to 3, because you really won't ever KNOW what you have. You need to start with the basics, and check stuff in the order I listed above. When you get to the carbs, check the pressure, it's really that important.

I would bet you have something in the 1600-1835cc range as far as displacement. But I'm only guessing.

Twin 1 barrel carbs are less of a problem with intake leaks, they just don't weigh as much as Weber or Dellorto dual throats. So the 1 barrels put less force on the manifolds. But hey, check them anyway. Squirt some carb cleaner around the base of the carb and base of the manifold while the engine is idling. If it picks up speed momentarily while spraying you found your intake leak.

The picture is nice, but we really could use some actual specs. If you don't have them, fine, but if you do, they'd be really helpful to us so we can help you. At this age a serial number and 1973 mean nothing. It is extremely doubtful that the motor has never been rebuilt at an almost 40 year old car and almost 50 year old motor.

Hi Danny

The Carburetors are Solex 40/44 EIS

How do I check the fuel pressure while the engine is running with a test gauge. I have a test gauge where do I place the hose of the test gauge?

i still need to spray some carb cleaner around the base of the carb and manifold while the engine is idling to see if there is an intake leak.

i am not sure about the engine displacement, how can I work this out?