MonzaRedConvert

Anybody out there familiar with BG carbs please take a look at the pics below. I noticed this strange hole in my primary side metering block next to one of the main jets. Is this normal? It seems to go through to the idle circuit. BTW, the carb is a Speed Demon 650. This could explain a lot of the problems I've had trying to tune this thing!

MonzaRedConvert

anybody???

69vettester

That May be the Idle feed Restrictor to the idle well, but Im not completely sure? It looks like its in the right place to me.
If it is, Then there is a way to lean your BG a little, by Inserting a piece of wire in that hole. This is suppose to be a solution when a BG runs too rich on a mild performance engine.
Maybe someone will confirm this is the idle restrictor hole.

MonzaRedConvert

I think the idle feed restrictors are on the other side of the metering block. This looks strange to me because there is only one and it's only on the primary side. The BG has 4 corner idle circuits so if it was supposed to be there I'd expect to see 4 of them. I think I got a bad casting and it's allowing additional fuel into the idle circuit. This could be why no matter what I do the engine runs rich at idle and cruise. I was hoping someone with a BG apart could take a look at their MB and let me know if that hole is there.

TopGunn

I'm curious too, here's a bump. I'm suprised you haven't gotten more replies.

Phil Zell

ttt

69vettester

I have a speed demon 750 installed so I cant look But I did find this diagram. If your running rich maybe a wire the size of a staple in the Idle restrict Hole will help. Thats what was suggested to me By a carb Pro. I havent try'd it My BG is running pretty, But Still tweeking it some. Keep us updated with what you do and the results. Quite a few here Run BG's and may have tuning issues.

MonzaRedConvert

Been there, done that. It helped but it's still not right. I really hope this turns out to be the problem. I'm going to give BG tech support a call tomorrow. Hopefully that will settle it. I'll post the outcome.

TopGunn

I wonder if you could take a piece of solder and fill the hole up with it, it's pretty soft and would compress well into the hole. A temporary thing to see if it cured anything. Just an idea

MonzaRedConvert

Well, I just spoke to someone at BG. He said that hole is supposed to be there. He said there are 2 things that can lean it out. First drill out the idle air bleeds from .070 to .078. These are the 4 small holes in the top of the main body toward the outside. Also I could install smaller idle feed restrictors (which I already did via the wire trick). I think I'm going to take it to a machine shop and have removable jets installed in both places. I believe the race carbs have this feature and it should make tuning much easier.

TopGunn

You might talk to gkull about it, I think I remember reading where he screwed around with his and finally sent it to some speed shop who straightened it out.

69vettester

I would start there, before any machining.
I may be doing these procedures, Id like to slow my BG from Guzzling so much Fuel without any big performance Gain.
Good Post

Matt Gruber

sometimes a lower float level cures it.
.
or it can be leaned thru an open vacuum port
.
often it is an ignition problem, are the plugs clean after a drive?
sooty black is most often ignition.

Doug S

That hole should not be there!

It looks like someone drilled through from the primary side when changing or sizing the Idle Feed Restrictor. You'll need to plug that hole off. That could easily cause the engine to idle too rich.

Technical Support,

Barry Grant, Inc.

www.barrygrant.com