TheSamba.com :: View topic

Wed Jun 13, 2012 2:29 pm

In the process of rebuilding my 40mm IDF carbs due to one of them losing control of the float level and began pouring gas in and out of the carb suddenly one morning. Disassembled the carb and found the float would contact the top of the carb before seating the needle. Seems the viton needle tip disappeared.

New needle and seat from a Redline rebuild kit and picked up a new float also. Set the float travel range from the top with gasket to 10mm - 32mm like normal. Things were OK when the vehicle was idling and driving slowly around the block. But when I leaned into the gas peddle a bit it started to run like crap and ended up doing the same flooding thing again.

Looking at the instructions that came with the kit, the diagram showing the float level setting range of 11mm - 20mm was crossed out and the written instructions state setting the float height at 14mm from the gasket and allow 2mm of needle travel with the float drop.

Does this make sense? I haven't touched the other carb yet

Wed Jun 13, 2012 2:38 pm

My parts guy just called me back. He had a talk with someone from Redline who said the float range should be set 14mm from the top when closed and 22mm at full drop. Said it had to do with the change in fuels. Off to give it a try.

Thu Jun 14, 2012 10:43 am

I rebuilt mine not long ago (Redline kit) and they run fine at 10.5mm height and 32mm drop.

Thu Jun 14, 2012 11:57 am

I've always set mine at 10 and 32 never had a problem. Wonder what the fuel has to do with it? As long as the float, well, floats it shouldn't matter what kind of fluid it is in......

brad

Thu Jun 14, 2012 1:28 pm

if you are running Ethanol or an E-* mix, an altered float level helps, but it's the other way. Higher fuel level not lower. Sometimes I wonder if anyone at these places has ever turned a wrench or tuned anything in their lives.

Thu Jun 14, 2012 1:49 pm

I go with 10 and 32.5... Actually sat down and made a small gauge to simplify matters.... Are you holding top plate in vertical plane when setting levels?

http://www.piercemanifolds.com/category_s/317.htm

Dale

Thu Jun 14, 2012 2:14 pm

Is it possible that the needle and seat in this kit is longer than OE???

Thu Jun 14, 2012 7:05 pm

The needle and seat assembly are actually shorter in combined length than the original but it doesn't matter as you bend the tab to suit whatever length they are when you set your float level.

Yes I set the float level with the top vertical and the float hanging. The diagram posted is the same as the one in the instructions but with a big X through the diagram and the box next to it stating the float must be set at 14mm - yes it was bolded. I've used the 10 & 32 setting since getting the carbs and have never had a problem with them until this week. I was just saying to myself I've never felt the engine run so smoothly than it was before this instantanous carb flooding situation.

I originally thought the needle lost its vitron tip but opening up the other carb last night which was running fine, it has no tip either. So I'm at a loss to explain why the left carb started puking fuel all over the place and the float level setting disappeared. I'm even more perplexed as to why after changing the float, needle & seat and other parts of the rebuild kit along with cleaning the carb it still puked out gas as before. I reset the carb to the 14 & 22 setting the redline guy suggested and the carb seemed to be behaving - at least around the block. I was going to wait until the other carb was rebuilt to reset the idle mix and sync and do a proper driving test.

I have a low pressure carter pump with holley regulator and a fuel pressure gauge permanently mounted in the fuel system which reads no higher than 2.9 psi. We've had 10% ethanol in our fuel for some time now. I haven't had much experience working on or experimenting with carbs; my knowledge is largely form these posts, weber books and the trials and errors I experienced getting the jetting set up which took some time but feel that I did a good job with. The bus is my daily driver but its parked until I can figure this mess out. Its so unnerving to have the carb suddenly start puking gas.

What effects does having the float set to shut the needle at 14mm instead of 10mm have on the way the carb behaves?

Thu Jun 14, 2012 7:18 pm

Oil Phil-M wrote:
What effects does having the float set to shut the needle at 14mm instead of 10mm have on the way the carb behaves?

At 14mm this leaves a little more leeway for fuel slosh, changes in fuel pressure, and float movement before the fuel will spill over the venturi booster into the carb throat.

At 10mm this leeway is greatly reduced and the slightest movement or
mis- adjustment could mean flooding.

The only other thing to take into consideration here is that different float levels will affect your main jetting due to the fact that the fuel being pulled up the emulsion tube has to lift from a different level before it actually is pulled through the booster. This may or may not effect your concern for tune, I don't know your combo or how critical you consider tuning to be. A good wide band will tell the tale, and a change in air corrector jets will make the changes you need in "most" cases.
Like you said though, you'll cover the final tune when you get there, this is just FYI.

Thu Jun 14, 2012 9:52 pm

Tuning is very important to me. "It will do" is not in my vocabulary unless we are talking about some roadside repair. I've invested allot of time and money to have a well running engine and I'm not prepared to compromise.

Combo I have is a 2.0L T4 in a 72 Westie. RAT 9550 cam with 1.7L heads, 8:1 CR and 0.040 deck. Carbs are 40mm with 28mm vents and 50-135-200 idle-main-air jetting with velocity stacks and jet doctors. The idle-main combo is a bit different from what others say to use but I have gone up and down in jet sizes for both using every combo and this is what works best both from the way the engine feels, responds and the emission testing that has to be done annually which at $25 for a driving test under load with calibrated equipment isn't a bad price to pay so I don't own a wide band.

So if I understand correctly, a lower level of fuel in the bowl will mean:
1. it will take a higher RPM before the mains will come on
2. the air-fuel mixture will be a bit leaner for the mains

The motor is never "driven" at RPMs over 4K; just the occasional blip up to 5K when there is the need to do a dead stop merge into traffic so I've never had to play around with the air jets. Do they need to be closed down with a lower fuel level?

This float level thing wouldn't be an issue if the carb didn't flood out a second time after the new new needle & seat and float was installed at the normal 10 & 32. I haven't remounted the second carb yet; its sitting on the bench having been set with the same float level as the first 14 & 22. Tonight was going to be the night I ran it and re-tuned it but I'm going to hold off until I fully understand the implications of following the Redline instructions instead of my previous settings of 10 & 32.

Thu Jun 14, 2012 10:03 pm

Don't overly concern yourself with the jetting thing just yet, after all we are talking small changes in float level. I'm splitting hairs because I had a gut feeling you are interested in perfecting your tune, I was right.
Get it together with the new float level, you seem to understand exactly what it is that I'm trying to rely regarding change in float level it's effects on the tune. Once running see how it feels, and do your $25 tune deal to see how the AFR's read.
The only part of this I'm confused on (as you are) is that technically the engine should run just fine with the 10mm setting you have always had.
I know that comment does not help you any, but is there any chance there has been an oversight on say fuel pressure or installation of the seat such as a missing or leaking seat gasket?

Thu Jun 14, 2012 10:09 pm

Thinking outside of the proverbial box;
Since the problem repeated itself even after replacing the float needle valve and seat, I'm thinking that there might be pieces of filter element material becoming dislodged from an inline fuel filter and hanging up between the needle and seat... but it would have to pass the through the filter in the carb's top cover fuel inlet. Check there if the screen is torn or missing. I've seen the nylon and brass versions in these carbs. No mention of the air filters in your post, but perhaps there's a passage for lint or debris to pass through/between the elements and seals. Once again, the valve could be held open by something wedged between the seat and needle. Was there any sediment in the bottom of the float bowl when you opened it up the first time?
Good luck and be sure to post your results!
Aloha!

Fri Jun 15, 2012 1:05 am

Oil Phil-M wrote: Tuning is very important to me. "It will do" is not in my vocabulary unless we are talking about some roadside repair. I've invested allot of time and money to have a well running engine and I'm not prepared to compromise.

Combo I have is a 2.0L T4 in a 72 Westie. RAT 9550 cam with 1.7L heads, 8:1 CR and 0.040 deck. Carbs are 40mm with 28mm vents and 50-135-200 idle-main-air jetting with velocity stacks and jet doctors. The idle-main combo is a bit different from what others say to use but I have gone up and down in jet sizes for both using every combo and this is what works best both from the way the engine feels, responds and the emission testing that has to be done annually which at $25 for a driving test under load with calibrated equipment isn't a bad price to pay so I don't own a wide band.

So if I understand correctly, a lower level of fuel in the bowl will mean:
1. it will take a higher RPM before the mains will come on
2. the air-fuel mixture will be a bit leaner for the mains

The motor is never "driven" at RPMs over 4K; just the occasional blip up to 5K when there is the need to do a dead stop merge into traffic so I've never had to play around with the air jets. Do they need to be closed down with a lower fuel level?

This float level thing wouldn't be an issue if the carb didn't flood out a second time after the new new needle & seat and float was installed at the normal 10 & 32. I haven't remounted the second carb yet; its sitting on the bench having been set with the same float level as the first 14 & 22. Tonight was going to be the night I ran it and re-tuned it but I'm going to hold off until I fully understand the implications of following the Redline instructions instead of my previous settings of 10 & 32.

I'm running a 2056cc T-4 with 40IDF's (28mm vents) and the mains are 120. Yours (135) are on the high side. I'm certain that's very rich.

Should be:

50 idles
120 mains
F11 tubes
200 airs
28mm vents

Fri Jun 15, 2012 6:35 am

I really believe you problem is not float setting but somewhere else on system.... A float should close the needle/seat combination at 10mm or 14mm so it should not be a issue with the leaking down of fuel.... Performance later on with 14mm maybe, but not leak down.... Its either bad needle/seat combination or excessive fuel pressure...

It did it before you cleaned and reset carb and it did it after you cleaned carb, you have managed to do a heck of a lot of work for no reward at this point, you either missed something simple IN carb or you have problem external to carb (fuel pressure)....

Dale

Fri Jun 15, 2012 11:12 am

Quote: Check there if the screen is torn or missing. I've seen the nylon and brass versions in these carbs
Took out the nylon screen; it was in good shape and it appeared to be doing its job. Cleaned out the the entire fuel entry area and blew it out with compressed air. There is also a filter screen between the tank and the fuel pump that I have yet to open up and check out
Quote: No mention of the air filters in your post
I'm using CB Performance's cast alloy filter plates, oiled up pleated filters and UNI foam filter covers installed dry. The crankcase venting system goes through a breather box packed full of copper scrubbing brushes before venting into the top of this carb (bypasses the air filter). The other carb gets the gas vapour recovery line.
Quote: Was there any sediment in the bottom of the float bowl when you opened it up the first time?
Yes but it didn't seem to be excessive or coarse; just dark gunk in the corners of the float bowl
Quote: Yours (135) are on the high side. I'm certain that's very rich
Yes I was a little suprise the mains ended up that big but 130s do nothing but hesitate when I'm up in the 3K-4K RPM range. Trust me, I've done every idle and main jet combo and when I was done and got things running perfect I went and retried different jets again. I have only ever tuned this motor so I'm not familiar with what causes an engine to require certain jets. My engine is a bit unusal in that its a 2.0L bore & stroke but uses 1.7 heads which have smaller intake ports compared to 1.8 or 2.0 heads and the valves are the still the stock 39IN 33EX. Gives the motor great bottom end response but I'm sure the intake flow characteristics are a bit unusal for a 2.0L
Quote: excessive fuel pressure
Is there any chance a holley pressure regulator could produce more pressure out of one of its outlet ports than the other? My fuel pressure gauge is located on the rear inlet port of the right side carb and I'm having problems with the left side carb. The low pressure Carter fuel pump is suppose to be limited to the 3psi range so even if the regulator was somewhat fauty there shouldn't be that much more pressure than the 2.9 psi the gauge is reading so I doubt it would cause such a catastrophic flooding.

The comments that say the float level, whether 10 or 14, isn't going to matter is the answer I needed to hear. My plan tonight is to pop open the carbs, reclean everything with special attention to the needle & seat areas, reset the floats back to the setting I've run them for years without issue and give them a go. The flooding is so bad the engine instantly turns to crap so I know right away to shut it down. I'll just keep the fuel in the tank no higher than 1/2 full. When I installed the regulator I placed it as high as I could in the engine bay to create a bit of a hill for the fuel to have to climb over. It's a way of offering some protection from a stuck needle & seat allowing the fuel tank to drain into the engine but only when the tank is not fully filled.

Fri Jun 15, 2012 11:25 am

with Uni Filters you are choking the intake, but leaving the float vents open. This is going to increase the vacuum signal SUBSTANTIALLY, which is why you use the small mains.

Normal air filters restrict the intake and the float vents the same, thus not affecting the main circuit behavior.

Fri Jun 15, 2012 11:49 am

I use a filter befor the pump at the frame horn& a filter about a foot before each of the carbs,after the pump. I wonder if the 14 mm is due to different spacific gravity of the fuel? not wearher it needs to run ritcher or leener with alcohol. any body ever checked the weight differance between gassohaull&gassoline?&e80whatever?and when the acohaol absorbs water that would also change it. all of witch will change the way the float floats&shuts off the flow of fuel. or am I stupid

Fri Jun 15, 2012 12:02 pm

Your leaving a bit on the table running the 1.7 heads. Especially since your using a 9550 cam which will run it's best with big valves 42x36mm. Likely the reason your having to up your mains to make up for a loss with the smaller valved heads.

Sat Jun 16, 2012 11:02 pm

Got any photos of the old needle/seats? What were the original settings on the float measurements prior to dis-assembly?

Sun Jun 17, 2012 8:16 am

udidwht wrote: Your leaving a bit on the table running the 1.7 heads. Especially since your using a 9550 cam which will run it's best with big valves 42x36mm. Likely the reason your having to up your mains to make up for a loss with the smaller valved heads. ??? up your mains to make up for the small valves???? what??? I dont oil my filters & just use the outerwears over them to keep them kleen.they are about 10 years old and still look almost new and filter just fine,it is the 2nd set of outerwears.