Fuel Tank Crud? Redoing Fuel Lines, Etc. Options

[kenshapiro2002]

So, in my continuing fuel starvation saga (another thread), I'm almost ready to rebuild the webers. Rode her hard again yesterday, and she ran pretty nicely for awhile and eventually started to starve very hard at really hard throttle. Took a very good look in the tank, and the walls look pristine, but in the circular baffle area where the sock is, there were many very tiny pieces of black crud, and the sock, though very hard to see well, looked pretty dark too.

Opinions?

Also, I'm thinking that since my fuel filter was pretty clean, that the sock might be my real problem...should take care of that before making the carbs clean and possibly getting more crap in them.

If I do pull the tank and replace the sock, shouldn't I replace the fuel line back to the engine? Any threads on that? Can I just hook a new line up to the old and pull it through?

Thanks in advance,
Ken

[jmill]

Educate me on that. It's a 1.7 with a 1911 big bore kit. I'm assuming the jetting was done back in 1989 when all the work was done. Even if a 1.25 would be an improvement, it certainly isn't my current problem, is it?

Having mains that are too small will cause those same symptoms. You can verify that by idling your engine for a few minutes and then rev the engine up close to redline and hold it there for a few seconds. Try it unloaded and loaded. If you get a lean pop you can be pretty sure your not getting enough fuel from your mains. Holding it at high RPM for a few seconds takes the accel pumps out of the equation. They can mask small mains if you don't hold it there for a bit. Just be sure to let it idle for a minute before you do the test. Starvation due to fuel delivery problems takes longer to happen because you need to draw down the float bowls to make it happen. If you get no pop in the test your mains aren't the issue.

Look hear: http://www.triumphspitfire.com/jets.html

Check out the Fiat jet sizing. The Fiat ran a 40 idf with 125 mains and 210 ac jet with 32 vents an F11 ET. Swapping to a 210 ac jet will lean you up a bit more at high rpm.

I personally think you have a combination of fuel delivery and carb issues.

[kenshapiro2002]

I'll do the test later, but since she's fine for a few minutes...even 5-10 and will go close to redline, it sounds (thanks to the education I;m getting from you) like it's more the floats slowing draining down.

Educate me on that. It's a 1.7 with a 1911 big bore kit. I'm assuming the jetting was done back in 1989 when all the work was done. Even if a 1.25 would be an improvement, it certainly isn't my current problem, is it?

Having mains that are too small will cause those same symptoms. You can verify that by idling your engine for a few minutes and then rev the engine up close to redline and hold it there for a few seconds. Try it unloaded and loaded. If you get a lean pop you can be pretty sure your not getting enough fuel from your mains. Holding it at high RPM for a few seconds takes the accel pumps out of the equation. They can mask small mains if you don't hold it there for a bit. Just be sure to let it idle for a minute before you do the test. Starvation due to fuel delivery problems takes longer to happen because you need to draw down the float bowls to make it happen. If you get no pop in the test your mains aren't the issue.

Look hear: http://www.triumphspitfire.com/jets.html

Check out the Fiat jet sizing. The Fiat ran a 40 idf with 125 mains and 210 ac jet with 32 vents an F11 ET. Swapping to a 210 ac jet will lean you up a bit more at high rpm.

I personally think you have a combination of fuel delivery and carb issues.