BG Annular 750

[BigBlocksOnTop2]

A video from 2005 running the mentioned 351W with that carb. Nice mild street/strip combo.
https://youtu.be/9zT2Pko7QGk

Nice

[427dart]

Rick1999...yes it had a couple of multi angle cuts on the top of the booster. I ordered just their main body and built the carb using a 1 3/4 throttle plate with mechanical secondary. Tried it on my new 427 in 2010 on first few miles and it wasn't right of course...needed larger carb like my 950...then it RAN!

[Rick1999]

Rick1999...yes it had a couple of multi angle cuts on the top of the booster. I ordered just their main body and built the carb using a 1 3/4 throttle plate with mechanical secondary. Tried it on my new 427 in 2010 on first few miles and it wasn't right of course...needed larger carb like my 950...then it RAN!

Yeah, an annular discharge booster simply refers to how the fuel is delivered from the booster with multiple holes under a step that the fuel comes out of. The "typical" annular booster is much larger in diameter to a D/L therefore displacing air flow. It is possible to make an annular out of a D/L with a custom insert, therefor no extra air displacement. Several carb guilders have done it, I have too but never found a good enough market for them to justify the cost of mass producing the inserts.

[427dart]

Here is a picture of that carb. You can see the Super Booster of Brad Urban design. The other deal was my Air Valve Secondary expierment!

[Bob Hollinshead]

427Dart, How did the air valve secondary experiment go? with the secondary pump shot or without? great fabrication skills!

[Rick1999]

Here is a picture of that carb. You can see the Super Booster of Brad Urban design. The other deal was my Air Valve Secondary expierment!

That appears to be a traditional Holley type annular with the entry modified. Not what I was thinking it would be.

[jmarkaudio]

I have done a LOT of booster testing. The original carb shop annulars that I saw in Dominators were stock .500 boosters opened up to around .550-.560. Those had a straight cut just before the step and had good signal and airflow. The newer versions are billet, they have an angle cut leading to the step and do not signal/flow as well. The angle all the way to the step created a ski jump of sorts, compresses the vena contract smaller as the flow increases, when there is at least a small straight before the step it doesn't. The best booster to use for the 4150 on gas is a .600 ID booster, modified to open the center to about .635 with a straight cut thru the center. When the fuel channel becomes a restriction for larger carbs, higher HP, or E85/Methanol a .500 center with a straight cut to about .555 works well. A .500 center signals around 43" H2O with a 20.45" H2O bench depression no matter what carb size, with a Dominator no matter what skirt size. .555 will hit around 50", .600 around 52", and I have seen 63" with the .635. The step must be retained, it will kill signal if there is no step. Added benefit with a larger center is it flows more air. Smaller discharge holes are also a plus, they improve atomization and distribution.

[427dart]

427Dart, How did the air valve secondary experiment go? with the secondary pump shot or without? great fabrication skills!

I designed it to be a simple bolt on for any old style mechanical secondary carb. You would remove the secondary accel pump arm.
The air door had an adjustable tension spring. Worked really well on the street and did a back to back test at the track..with and without.
On my 351W powered Mustang it was just a bit slower than the DP carb setup...I'll have to go back and find the ET slips.
But on the street when the secondary flap opened up,if you had the lighter adjustment it would blow the tires off!
I also made another one for the HP style air entry carbs. If I recall I had to go to a larger High Speed air bleed to get the A/F ratio back in check.
Now I wonder if I put a mechanical 600 base plate on my new dual quad setup and put a pair of these on the 1850's woop...waaaah...screeeech!
Isn't basic hot rodding fun!

[Bob Hollinshead]

could be done on the 1850's with mechanical linkage added, cool stuff!

[427dart]

could be done on the 1850's with mechanical linkage added, cool stuff!

Yes and with that setup you know the secondary throttles are wide open!

[BigBlocksOnTop2]

Up date, 68's in the pri. and 75's in the sec. PVCR was .059, and now is .046. This change, and only taking data on no. 1 cylinder for now, the A/F is 12.3. Only did 3 second gear runs. Each time the A/F got better. Could this be from the carbon build up being burned? Im still going to try .028 in the place of the .026 HSAB's. Shooting for 12.8- 13.1 as I have read.