alky carb question

[scrappy]

O.K. So the 406 in my modified starts doing this in the middle of a main, As I throw it in and rotate the car,I lift off the throttle momentarily, As I start to accelerate again, nothing, it tries to go, but cant. after a second or two, it gets a gulp of air, and hazes the tires off the corner, next turn, same thing. It also happens after a yellow, go to restart, and nothing. Now, I pull the plugs, and they are all wet, and obviously rich. I take the float bowls off and find the floats crushed. I was told by my carb guy that I must have had a leak in my draw and that created too much preassure in my float bowls. I completely re-plumbed the entire fuel system, clean the filter, and put new plugs in. Now it is still doing the same thing, even though my fuel preassure guage never goes over 9 1/2 lbs, it is however, very eratic and kinda jumping up and down quite a bit. floats arn't crushed this time, but plugs are wet again. has anyone ever heard of this, and what was it, could it be regulator( i run a barry grant) how about the pump(runnin a race pumps piston pump) I just went down on my jettng, and never ran TOO rich or had wet plugs before with the bigger jets, so I know this particular problem is not jetting. Or, could something have happened to the carb ( seats or power valves) My carb guy is very reputable, and says there is nothing could be wrong with the carb, It is a quik fuel 750 that has JUST been reworked by the same reputable carb guy, I tend to believe him, but am lost right now. If ANYONE has EVER had or heard of a problem like this, PLEASE tell me what it was. Thanks.

[mudslinger47]

If there is to much pressure in your Float bowls, maybe the air bleed? Is the pump new to you and is the regulator old, You can get rebuild kits for those regs. We had wierd problems with air at one time and if I recall it was a plugged bleed. Chet would take our carb apart and clean every orifice every couple threee races. Borrow another fuel pressure gage, we got chumped on that one too.

Duane

[scrappy]

Well, the pump is fairly new, and the regulator is old, but rebuilt, and I have 8 races on this set up when it just suddenly started happening in the middle of a race, I was told it would get worse as the race went on because the preassure would build, but I though once I pulled 6k down the strait, the preassure would pretty much be gone. I have a race pumps regulator on the shelf, but it plumbs completely different, it's an actual regulator that goes in the line before the fuel log. I'll probably just go buy a small guage that plugs right into the reg. and see if I get any better of a reading.I WOULD rather have this problem again as opposed to blowing aluminum out of my headers cause of not enough fuel preassure, LOL.

[Bobby Kimbrough]

What size accelerator pump do you have on the carb, and what color accelerator cam do you have? Might be dumping too much raw fuel when you get back into the throttle.

What do you think Slinger? I've had this problem before. It's kinda like you have to wait on the car when this happens.

[scrappy]

To tell you the truth, I'd have to look, I had this carb professionaly built jut for my motor, compression and cam set up, and he's right here in my area so the jetting is set up for my tracks. again, this was all working great for 8 races, and just started in the middle of a main. Thats why I went with the assesion that I got a air leak in my draw so easily. but now I know that was'nt it.

[mudslinger47]

If its been workin' and now its giving up, I'd lean toward regulator or dirt in fuel system, air bleed or something. Take the carb off and (don't laugh) in an oil/gas mix, mostly gas and then blow out every orifice you can find. (On the carburetor)

Duane

Make sure there is nothing blocking the return line.

[scrappy]

I have replumbed EVERYTHING, so I know the return line is clear, but I have my suspitions with the regulator. I saw some cars this weekend that came from outta town that were runnin carter high volume pumps that put out about 8lbs, and no regulator. they said it was the most simple/reliable set-up they had ever run. anyone out there ever run anything like this. sure sounds simple, but goes against everything I ever heard when I got into alcohol. sure sounds alot cheaper too.

[mudslinger47]

The guy I help on occasion runs one but has about 10.5 pressure regulated a little, 12.5 with nothing (no regulator). Duane


Ya know, I just thought of something, we had to regulat the fuel pump with pills, much like a sprint car because the fuel pump wouldn't sustain pressure with the regulator and it was new. We were thinking that the regulator is designed for a belt drive pump that puts out a bunch more pressure, there for was unreliable with a block pump. We could be full of crap, but its workin' now and it wasn't before. Just an after thought. Duane

[scrappy]

I plumbed in the race pumps regulator,wich is the kind that goes in line BEFORE the log, dialed it in at about 6 1/2 lbs at 1500 rpm idle- 9 1/2 lbs at 4000, guage is still a lil jumpy, but not near as bad as before. gonna go up and test tonite and see. better than driving a couple of hundred miles this weekend to find everything still messed up. Thanks for all the input guys, and I'll write what the result was when I get back tonite.

[Bobby Kimbrough]

I got the chance to hang around Sean Murphy of Sean Murphy Induction (SMI) and watch him build a couple of carbs (we have a tech article coming out real soon on that), and Sean explained the basics fundamentals of carbs to me. The thing that stuck in my mind most was "carbs like volume but don't like pressure".

I think you are on the right track with the regulator. MudSlinger is a pretty sharp wrench too. He knows that keeping those Alky carbs clean is a battle. Alcohol likes water and will pull it from the ambient air. This can cause a slew of problems. Alcohol fuel is also very volatile. It evaporates quickly. What's left when it evaporates is a gel like substance that blocks openings in a carb. Plus the crap is pretty corrosive. So Mudslinger is on top of the game when he explains to clean the carb with gas and oil.

We hope that you have the problem solved and have a great run this weekend.