fuel pressure

[FestYboy]

OK so you all know i have a B6 carbed festy by now (stock B3 carb), and it has a butt load of miles on the carb and fuel pump. now w/ the B6 in it i know the carb can't keep up (runs lean, a.k.a. 20:1 at idle)

i know if i up the fuel pressure to the carb i can alleviate some of the hard start and stumble and improve the throttle response. problem is I'm not absolutely sure where to place the pressure regulator seeing that it's a return type pump. I'm thinking that i should place it on the return line from the pump to the tank, but the directions are pointing to placing it between pump and carb. I'm thinking if i do that, the bypass on the pump will just open sooner and make the problem worse.

any ideas?

Arty

[packrat427]

I am not sure what the cfm of a B3 carb is or a B6 is but if bowl is full of gas turning up the pressure is not going to make it start easier , I am thinking if it runs lean at idle it is because of something else a stock pump should keep up at idle ,and put the regulator in line between the pump and carb you don't want to read the pressure you are sending back to the tank ? Directions ,
Someone else may be able to enlighten you some more here .

[FestYboy]

well my whole theory about putting the regulator (not pressure gauge) on the return side of the pump is to restrict the fuel from going back to the tank before it reaches my desired pressure regardless of when the in-pump regulator opens. and if i follow the directions as stated (putting the regulator between pump and carb) and have the regulator set at a pressure higher than the in-pump regulator, then the one i just purchased would be pointless.

this is just my opinion of how the flow works on that pump, i may be way off.

also as i understand the workings of a carb, the higher the bowl level, the easier it is to feed the engine w/ the required amount of fuel.

Arty

[B6T]

Do you still need an RX7 carb? I have one from a 12A that I don't need.

[packrat427]

You will only be able to apply so much pressure on the needle and seat before it bypasses them ,and cause you more problems, the stock pump is only going to supply so much a in line reg won't increase it , I would install a electric pump if supply was a issue and use the regulator to adjust your pressure, Are you sure it is a supply issue to the carb , or just not enough fuel delivery into the engine ,or a vacuum leak, just checking all the possibilities.

[FestYboy]

the vacuum leak is a possibility but I've been all over that intake w/ carb cleaner and there's no change during idle. also i noticed that when I'm at part throttle and goose it a little, the throttle response is great but if i gun it and stay on it the engine falls on it's face until 4000 where the pump develops full pressure and then the engine starts going lean again. to me that's a lack of pressure. one other thing i noticed is during idle, i get a surge from my dashpot because the engine is running so lean and i KNOW that's a pressure problem or at least the fact that the bowls aren't full enough.

anyway, that's not why i started the thread. i just need to know where to place the regulator so that it's effective for experiment's sake. if it's a bad idea I'll remove it and start over again, no harm done.

Arty

[chris]

something else you could try if its running that lean is bust the cap over the air fuel mixture screw and then be able to adjust it to your liking i ran into this problem with my carbed b3 its on the firewall side of the carb its worth a shot if you need further help pm me !