[Tom Vaught]

A story on 3-BBLs.
Many, many years ago I was helping Marty Palbykin on his NATURALLY ASPIRATED 1971 GTO. 470+ CID engine
850 CFM Holley Carb, Tilt Front End for easy maint on the vehicle and light weight on the front end.

So Marty decides that he wants to try more CFM on the engine. So we talk about installing a Holley 3-BBL on his car
(a REAL 100 cfm increase in airflow to the engine).

Marty is good with that deal but he says he wants the 3 BBL to be a Double Pumper Carb.
Not a Old School modded (660 center squirter Mechanical Linkage) single shooter removed
and 4 tube shooter installed.) Nope not going to make it. Has to be a Double Pumper 3 BBL carb.

So a Very Good Machinist Friend, Bill Klausing and I decided to build a 3 BBL Douple Pumper Carb
from a 850 Double Pumper Carb that already had the front and rear pump shooter bosses cast into the mainbody of the carb.

Installing a 3 BBL Throttle Blade was easy enough, just a bit more work in the center of the base
and using the same Double Pumper Throttle Shafts.

But now the metal needed to be removed around the rear Power Valve area and that void plugged
with a plug and a two part metal epoxy bonding process. So we did that deal and it looked great.
No need for a rear power valve on a Race Carb.

So we give the carb back to Marty for testing.
Primary works great as it should. Secondary operation was poor (being kind).

So I get the carb back and have it flowed on the Holley Flow Stand and the air/fuel is ok on the
rear but there is a giant lean area between the two rear boosters. So another Carb guy says:
"That is why the boosters are moved inward on a 3 BBL carb, to remove that lean spot in the center of the rear fuel distribution to the manifold.
Got to do that or the rear distribution is bad."

Well we previously found that deal out Bubba. I laugh at the carbs I see in the internet with the
two 3 BBL blades vs the normal 4 throttle blades and bragging about massive cfm increases with
their carbs. Been there done that .

So we need to have the boosters in the 3 BBL spots for the right mixture in the manifold.
1050 carbs use copper tubes to feed the fuel into the secondaries. Might have been easier
to try those (thinking about it today) and more cfm capability but we did modded conventional
boosters (moved to the 3 BBL locations. More metal Epoxy and then more flow testing.

But the mod worked. We retested the carb on the Holley Air Stand and the distribution was great on the rear
of the 3 BBL prototype "Double Pumper". So Marty ran the carb until he decided to go with Boost and then
the carb went to someone else I think.

Marty did say that he thinks with the converter he had that now we really did not need that pump shot on
the secondary side. Thanks Marty (;>( LOL!

So my points are:

1) Holley put the boosters where they are on the 3 BBL (secondary side) where they are FOR A REASON.

2) Holley did not put a shooter on the secondary side of the 3 BBL when they stayed with a Vacuum Secondary
carb (for a reason).

3) The Hot Rod Guys made the 4 shooter kits for the 3 BBL carbs (converted to mechanical secondary operation)
for a reason.

4) Center Squirter carbs and Double Pumper carbs were created because of the work and knowledge learned from
the 3 BBL carb mods and other mods before that time.

Mechanical secondary carbs need pump shots vacuum Secondary carbs can get away without a pump shot on the secondaries.
Big secondary carbs or Four (2 BBL Dominators) need big pump shots when installed on big plenum manifolds.

So now you know a bit more about the 3 BBL story.

Tom V.