Demon carb. with annular discharge booster vs dogleg booster

[wsa111]

Did anybody read the latest edition of carcraft magazine??

Even though the engine on the dyno was a small block chevy, it is possibly an idea to use on our sixes with the holley carbs with the dogleg boosters.

The dyno test proved an engine with some cam in it produced a substantial amount of power increase with a carburetor using the annular boosters rather than the stock holleys dogleg boosters.

Very interesting reading, its benifits seem to indicate a possible power increase especially for those using a 500 cfm 4412 holley on a 200 six.

From reading the article, it would appear that demon would have to custom fit an existing 2bbl carb with the annular boosters.

Remember stock ford 2 barrels use the annular booster design.

Something I will persue. William

 

[Mustangaroo]

Very interesting, I searched google and found this written by Barry Grant, who makes the Demon line of carbs, read the whole page to the bottom as he talks about annular boosters near the end of the page. The whole page is a must read!
http://carcraft.com/techarticles/56919/

 

[wsa111]

Just called barry grant carburetors & unfortunately because of the small venturi size the annular discharge nozzles are not available in their 2 barrel carbs.
I might call the holley carb tech line & see if they have that option. William

 

[MandarinaRacing]

A long time ago I remember that in a parts house catalog came a Holley 2BBL "designed specially for 4 or 6 cyl engines" and it came with annular boosters.....mind you this was like 10 years ago, maybe more....

Alex

 

[MustangSix]

The Autolite 2bbls have annular discharge boosters. That's part of the reason they are so efficient.

 

[xctasy]

There is a tool that can swap the stock Holley booster venturis.

There are the Truck type booster (found on old Internationals, AMC's etc)

the stock 4bbl type

The later 4-bbl annular discharge type, and then

the 4 and 2-bbl Economizer venturis.


The economizer venturi looses about 50 cfm at 1.5" hg on a 4-bbl. The truck booster is just as bad.

On the later 4-bbls, the venturis were quite smooth, and the economizer venturis lost something like 50 cfm. A 780 cfm when down to 725 cfm.

They all are removable, but you have to have the tool.

The rest of the carb functions around fuel atomisation. if you change boosters, it is easy to sort out the fuel curve like Will has. Most people aren't interested in the economy aspect with 2-bbls, they are used for class racing or straight swaps onto old junkers.

Will, grab some anular discharge venturis, and then experiement with low float and low pressure fuel delivery. Everyone will come to you for advice.

 

[wsa111]

Deano, I am going to send holley a 4412-500 cfm carb for them to install the annular discharge nozzles.

All they want is the body of the carburetor to perform the swap.

The cost is $55.00 labor plus $38.00 per annular discharge nozzle.

The X-factor is the high speed air bleed which will have to be enlarged & smaller main jets 2-3 sizes smaller than the dogleg nozzles use.

I will let the forum know the results.

The loss of cfm air flow will be in the area of 25-50 cfm because the annular discharge nozzles are larger than the dogleg nozzles.

This may be a blessing to make the air flow less so it will match the necessary requirement for air flow volume to the small six cylinder engine.

I'll let you know. William

 

[Anonymous]

There is a tool that can swap the stock Holley booster venturis....They all are removable, but you have to have the tool.

I just use an aircraft rivet countersink to cut the old ones out, and use epoxy to install the new ones. It works OK enough.


I don't see a lot of reason to go to a Holley if an Autolite 2-bbl can be made to work well. I really like them, they are good carbs.