Gas Depth in Float bowl, when excluding float volume

[hogie]

I am having one heck of a time getting my 240 tuned up. I have a 72 with 3 screw SU's, and E88 intake manifold, pertronix ignition set to 17 btdc, and new NGK plugs gapped to .032". On top of that I have replaced my fuel filter, added all new rubber lines, and thoroughly blown out the hard lines. Also, I have 20 wt oil in the dashpots.

Before I figured out Bruce at Ztherapy was the way to go I picked up some GP Sorensen carb rebuild kits and replaced all of the seals in my carbs, cleaned the screens and reset the float bowls per the rebuild kit instructions. Which at the time said 14.28 mm, this allowed my car to run with the choke open, but I could never get the car set rich enough. It always wants to die with the lift pins up on either carb. Even if I run the mixture adjustment nuts underneath are turned all the way out.

When looking at the notes on http://www.teglerizer.com/sucarbs/techtip6.htm. I noticed the fuel level is supposed to be at 22-24 mm below the cap of the float. After using a piece of fish tank line I was able to find my level was at 30 from the top at the rear and around 35 on the front carb. This was done by pouring gas into the fuel line, not pressurized by the mechanical fuel pump.

I was able to screw around with the floats and ended up with 9.5 mm front and 11.5 on the rear carb to get the gas level closer to spec. Though Way out of float height spec per the manual. With these settings and the front pin lifted the car will rev up and then idle back down. Though in all honesty the mixture nut can be all the way up or all the way down and it wont make any differance.

The front carb appears to be doing nothing at all. I am getting spark to the front 3 cylinders, but pulling the wires wont change my idle. I dont appear to have an intake leak (I fixed it a night or so ago) as it wont change idle if I spray starting fluid or carb cleaner near the manifold. If I spray starting fluid directly into the carb it will start to stutter almost as if I am flooding the engine. Also, when lifting the rear pin the engine dies almost immediatly. I have tried 2.5 turns out as a start, all the way down and get nothing all across the range.

Both carbs have been synced at idle and at 1500 RPM with no problem. I guess to get to the point. Does anyone know what the level of gas should be in the bowls if you have removed the floats? Should I go back and try to reuse my factory float valves? I am not real confident in running the car with my little fish tank line and gas hanging out above a hot exhaust manifold. Oh, and the fact that it only runs on the rear carb doesn't help with that anyways

On lighter note, my son was born two weeks ago today and my car has taken a back seat to him!

[Pop's Z]

Sorry, no help with the problem. Bruce will chime in I'm sure. BUT what a cutie-pie!! Your life has now changed forever. Speaking as a Dad of 3: 44, 41, 30, and the Grampa of 3: 12, 5, 3, you will never stop being a dad. Welcome to the world baby boy.

Cheers, Mike

and congratulations.

[hogie]

Thanks, it has definately changed a ton. I was hoping to get everything knocked out on the car before he got here, but he came 2 weeks early and pretty much stopped me in my tracks. He was at 38 weeks so baby still came out perfect...well other than the fact he poops and pees everywhere all the time!

I am sure you are enjoying your grandkids, my parents can't beleive how much they love mine already.

[Gary in NJ]

Congrats on the birth. Parenthood is awesome. But so are 240's and SU carbs....

Have you tried removing the carbs and cleaning them? If the fuel bowls have fuel, but the mixture screw has little or no effect, I suspect a clogged jet. Seafoam or other additives wont help here. You will need to open or replace any clogged orifices.

[hogie]

I have cleaned the top half of the carb as much as possible. When I had the replacement hoses from the rebuild kit on the carbs I was able to squeeze them a little to get fuel to come out of the nozzle. This was both while the engine was running and viewed from above with the carb apart.

The bad part is they both sprang a leak so I am back to temporarily using 1/4" line on the bowls to nozzles that was on the car when i bought it.

When I spray starter fluid in the front carb it bogs the engine....could I be so rich that my front cylinders arent actually igniting the mixture throroughly and it just seems like I am not running on the front carb?

I know that when I had the intake leak spraying the front half bogged the engine, while the rear revved up slightly.

[Gary in NJ]

Spraying starter fluid in a running engine can be dangerous. Don't do that anymore, please.

When you say that you cleaned the top half of the carb as much as possible, are you referring to the outside or the inside? I'm suggesting that the carbs be removed, disassembled and clean the internal jets & passages. While the carbs are off the car, they will be easier to inspect.

This may not solve your problem, but it will eliminate one possibility.

[hogie]

I pulled the dome and piston section apart cleaned all the passageways as much as possible with carb cleaner and shot carb cleaner down into the nozzle until it poured out the line. While I had it apart the float valves were replaced as well.

The only thing that hasnt been dissassembled is the nozzle assembly. Which I have heard is a PITA to put back together afterwards. Also, it already moved quite smoothly with the replacement lines on it.

I was only giving it a small spray, not a full on blast, but I see how that can be dangerous either way and will cut it out.

[hogie]

I made a new bowl sight out of a drilled out bolt, right angle brake bleeder fittings, and some fish tank line that allows me to get a much better reading with the engine running. I have the front carb set to 23 mm on the dot and the rear carb is closer to 22, but I am still getting the same sort of problems. The front carb appears to be working fine at a 1k idle, however if I drop it down to 750, it doesnt do much if anything.

What doesn't make any sense is that when I lift the front pins the engine idles up and then drops down to a near normal level in a couple of seconds. Is there anything that would cause it to not be idling on the front carbs and yet have the mixture set right per the normal instructions?

The rear carb is idling much better than before, but I still can't get the RPM blip to happen when I lift the pin.

Edited May 11, 2010 by hogie

[Gary in NJ]

Vacuum leak. Is everything properly connected?

Are the nozzles moving correctly? Do you have a restricted nozzle or fuel tube?

Are the needles seated properly in the slide?

Is the based seated against the spacer well? Have you tried spraying the base with carb cleaner (while the engine is running) to see if the idle increases? I'd spray the butterfly as well.

[hogie]

No more vacuum leaks that I can find. I blocked off the vacuum to brake booster to make sure I didnt have a problem there as well. I then double checked that my intake manifold and throttle shaft bushings didnt have a leak by spraying them with the carb cleaner. There wasnt any perceptible decrease in idle.

The rear nozzle is a bit stiff, but was pushed up as if the choke was off.

I have used a straight edge to set the shoulders of the needles flush with the bottom of the piston. I have also tried loosening the needle and using the bottom of the nozzle to set the position. It seems to run the same both ways.

I am not sure by what you mean with the "base seated against the spacer well". I assume you mean is the jet centered and the piston makes a good thunk when dropped on either carb.

If you spray carb cleaner into the mouths it will decrease the idle on both carbs. Starter fluid (which you said not to do) will increase the idle.

Thanks

[Gary in NJ]

I am not sure by what you mean with the "base seated against the spacer well". I assume you mean is the jet centered and the piston makes a good thunk when dropped on either carb.

Where the base (side) of the carb connects to the manifold. If you have a bad gasket or spacer it will cause a vacuum leak.

It seems as though you have covered all of the bases of carburation, so you may need to start looking at other symptoms. I went back to your first post. You say that you can sync the carbs at 1500 rpm, but not at idle. You also mentioned that "the front carb appears to be doing nothing at all." Can you elaborate on this? Do you mean that the engine only appears to be running on the three rear cylinders, or that you can not change the idle on the front carb?

Have you checked your linkage to ensure that the idle screw is in fact changing the butterfly opening?

Is the engine running smoothly?

[hogie]

I havent tried spraying the bottom of the carb manifold connection, and I have new gaskets, so I may as well. I have no problems syncing them at any rpm currently.

At around 750 rpms, if I pull the front plugs the rpm wont drop. Also, if I pinch off the fuel line the rpms don't change dramatically. The rear carb does most of the idling. At 1000 rpm or so, this is not the case and the engine rpm will change if pulling the plugs or cutting off fuel.

Oddly enough it will sometimes idle just fine on the front carbs, but more often then not it doesnt. For instance if I use Beandips method of carb tuning and lift the rear carb all the way it will usually die or come really close.