Float level advice, please.

[siteunseen]

I'm getting ready to put the motor back in after a YEAR!!  My dumb a** thought it would be a few months.   Anyway, I'm getting the fuel supply worked out.  Drained the year old gas from the tank, flushed the carbs then checked the float levels with clear tubing.

Question?  They're mounted level on a wall and the rear has a taller float valve (actually doubled up washers) so could you all look at my pictures and tell me what you think?  The front is a little short but I think that may be because of the way they're mounted, level.

I cut out the rotten fuel line under the battery too.  Found a small pin hole.  That stuff looks like zinc plated copper tubing?

One more thing, is this the right end for the slave cylinder's push rod?

Appreciate any directions/opinions.  Thanks, Cliff. 

 

 

[Mark Maras]

 The slave cyl. rod on the Series 1 was adjustable. Don't know about S 2. I do know that I love having an adjuster on the slave cyl. It allows the clearance between the release bearing and the pressure plate to be set just where the pedal feels right.

 I'm confused about your reference to float valves and the rear being taller. Since the actual float valve (needle and seat) is hidden in the float bowl, Are you referring to the fuel level in the tubes, vent tubes on top or something that I'm missing?

[siteunseen]

Sorry Mark, I was excited!  I did some things yesterday that had me at a stand still, I was a little nervous doing them.  Fooling with gas and an electric fuel pump straight wired to a battery, fumes and such. 

I'm putting a 5spd in place of the 4spd and when I bought the clutch kit I went ahead and bought a slave cylinder and hose for a '78.  I'm pretty sure I have the push rod right after looking at some pictures on the inter web.

Those carbs are mounted level and I'm trying to use the clear tubing to measure fuel level in the float chamber.  I'm gonna tilt the rear down and try to replicate how they'd sit in the car.  Here's where I need them to be and after looking at this, I may be pulling the lids off. 

Thanks for the picture @Jarvo2 and @zKars

[rossiz]

others may chime in w/different opinions, but i found that the only way i could get the float levels right was on the car. something about the angle that the engine is tilted i think... i spent hours fiddling w/clear tubes like you have and in the end wound up using the method of turning the adjustors down the correct amount and adjusting till the fuel was at the top of the jet opening. i've got a thread on here somewhere that explains it... turned out to be the most accurate solution for me.

[siteunseen]

I've read that.  I remember somebody saying it was hard to see the fuel?  I'm gonna slant the carbs on the wall and get as close as I can before I put them on.  Then I can do it the way you're talking about. 

Hey rossiz@, while I have your attention how about answering a few questions?  I'm going to go ahead and put the header on while it's outside the bay.  Did you do that too?  Did you remove the steering rod?

'preciate it.  Cliff

[rossiz]

my MSA 6-2-1 header is very close to the TC rod connection and would probably interfere w/the steering rod as well during install - i put the header in first, lightly bolt to the downpipe flange to keep it in place, slip in the motor then bolt 'em all together. for me it's better to have more room in the "hole" and less things on the motor to get snagged/damaged on the install. putting the steering rod back together after the engine/header are in place seems like a pita for my fat hands...

[jonathanrussell]

My float setting experience is the same as what Rossiz wrote. After fiddling with clear tubes for quite a while, weeks actually, the only way I have been able to predictably set the floats is to pull the domes, turn down the mixture knob 10 turns, and set the fuel level to the top of the fuel nozzle. Yes, it is a bit hard to see but here is what helped me (and my soon to be 50 yr old eyes).

Optimize your eye sight for reading. For me it means removing my contact lenses. For some it may mean reading glasses, etc.

Use a flash light.

Rock the car a bit as you lean over and view the nozzle tops. This will let you see the fuel moving in the nozzle.

Squeeze the fuel hose that connects the float bowl to the nozzle. This will let you see the fuel level rise and fall a bit.

Use an electric fuel pump. You should be able to run the fuel pump and not overflow the nozzle.

The bending of float tabs, removing and reinstalling is a pain but eventually you will get it set. Small changes make a big difference.

I have only done this with the carbs mounted on the engine in the car. Can't envision how one would achieve the same angles on a bench.

The good news is that after setting my floats meticulously, I was able to adjust the mixture / nozzles around the 2 turn mark and get good color using a color tune spark plug. The car runs great now too.

 

[rossiz]

what he said.

it's actually pretty easy to see the fuel level - when it gets up to the top of the jet, the meniscus (little concave section of liquid) inverts/flattens and is quite visible with a small flashlight. you can do it in the reverse order as well: start turning the nozzle down, counting the turns while watching for the fuel to hit the top of the nozzle - it should be exactly 10 turns (10mm). if it's less, you're rich/the float is set too high/too much fuel in the bowl, if it's more, you're lean/float is set too low/too little fuel in the bowl. sounds trickier than it is. hardest part (for me) is remembering how many turns i'm at w/the nozzle...

i found this method to be very precise and it gives repeatable results. i do have an electric fuel pump, which makes it easier as you don't have to crank the engine to fill the bowls at the correct pressure.

[siteunseen]

Thank you @jonathanrussell and @rossiz.

When I get them back in the car I turn the nozzle down 10 turns from the top and leave it there, adjusting the float tabs until I get it level with the top of the nozzle.  I think I'll get new floats when I do this, glue the cork gasket to the lids and hopefully never have to do it again.

I put a four foot level on my other 240 yesterday, marked where the bubble was then stuck it up to the wall and drew a line that closely matches the tilt of the motor in car.  Today I plan on re-mounting the carbs to the new position and checking them with the clear tubes.  I'm thinking that'll get me close enough until I get the engine back in.  I honestly don't think they're bad off, if at all.  I rebuilt them and set them to .55", drove the car a few times pulling 6,200 rpms at the most.  Decided to freshen the motor up then.  Glad too, alot of loose nuts I found when disassembling.  6,200 would have found those loose nuts for me after a couple of times. 

[zKars]

Well I can't test my new cassette deck unless someone brings me a cassette (no Kiddy tapes please), so I've got time to chime in on this..

Please everyone remember that float bowl levels while the engine is RUNNING is what is important. The static level while the engine is off is determined by when the float valve decides to close as the bowl fills.

In the running case, there is a steady or perhaps some open/close cycling of the float valve as fuel is drawn out the bottom and comes in the top to meet demand of what's leaving.  The fuel level in the jet tube is always at the top of the bridge during running, that's how fuel gets to the air rushing in. Or the other way, the pressure drop due to air rushing over the bridge draws the fuel into the air stream from the jet tube. HOW MUCH fuel the engine gets is just the position of the needle in the jet. 

So in my humble opinion, while running, The bowl level just needs to be such that enough fuel is available to keep supplying the demand of the current pressure drop.. It's exact level, or matching level in both bowls isn't really that important. As long as the flowrate into the bowl is always higher than the rate exiting, the car runs just fine.

Now I'd love to be proven wrong. Someone set the floats perfect to spec, go drive and record AFR's across some operating range and note performance, then set the front float down 2mm and back one up 2mm and see if anything changes.

The only thing that changes is the small difference in back pressure generated from the height difference of the column of fuel in the jet tube verses the bowl level. If both level differences in each carb aren't the 'same', then there is a teeny weeny flowrate difference as fuel flows up the jet tube. Is this difference enough to affect performance? I doubt it.  But then again I only know how to calculate flowrates in oil wells...... 

Lets see, about 8.5 kpa pressure change per meter of height for gas, so a 2mm difference is about .00004 kpa, so...  ARGHHHH I'm retired.... I'm not doing this

[Captain Obvious]

10 minutes ago, zKars said:

As long as the flowrate into the bowl is always higher than the rate exiting, the car runs just fine.

Now I'd love to be proven wrong.

OK, fine.

If the flow rate into the bowl was higher than the rate exiting, it would overflow out the tube into the air cleaner.

How'd I do? 

[jonathanrussell]

For me, the 10mm method (without the engine running obviously) works and accomplishes a couple of key things. First and most fundamental, this method allows me to adjust mixture to around 2 turns down on both carbs and have an idle that is slightly rich based on a colortune sparkplug reading….plus other techniques documented where you lift the piston and analyze what happens to engine speed and recovery. Second, this method allows me to achieve a good colortune mixture off idle, at 3k rpms for instance, dependent of course on the needle profile being used. Also, if the fuel float level is set higher or lower, then it quickly becomes impossible (for me) to adjust the mixture to be more rich or more lean. And, if the fuel float level is set higher or lower, then a given piston/needle position ends up meeting the fuel float level at an unintended position. So, I am sure everyone has their own technique, and there are many, but for me this method makes logical sense in my brain and yields good results where mixture screw turns actually cause logical changes in mixture.

 

I am no expert at all on the science and theory of how SU carbs work but I don’t really see how having the engine running matters. There is no fuel pressure once fuel is past the needle valve. The fuel float level should (in my mind at least) remain fairly constant as long as the fuel pump can pump enough volume to keep up with consumption…..but without overwhelming the needle valve.