justus, pro systems, barry grant pictures

[vector1]

so it's slow, and here a few pictures of the three carbs for comparison, hard to tell from the pics and jet size is not included, but i'll include a few observations.

in the order above, in the pic 2nd from the left the justus plate has the two holes lower in the plate, 3 spread emulsion bleeds, 2 with inserts, the pro systems has 3 e bleeds closer together with inserts, the bg has 5 e bleeds with inserts, bg block has threaded inserts and not all holes are used, pic on left of bg plate has extensions i added.

[vector1]

few more pics

justus carb on left has boosters epoxied with what appears to be modification to the inner diameter radius, i imagine the boosters were aligned then epoxied, throttle bores on justus carb have cnc'd diameter and an additional hole next to the idle bleed for what i'm not sure.

[vector1]

additional pics

bottom of the bg carb, and all three carbs together.

looks like they all have plenty of adjustability and differences such as emulsion location and sizing. the justus carb has holes drilled in all the butterflies, the pro systems has holes drilled in the butterflies on the primary side only, the bg has no butterflies holes drilled. the justus carb is square jetted with pv caps on both blocks, i'm surprised there were no jet extensions. the pro systems carb was jetted different front to back with pv in front, bg was again square jetted with pv front and back. the bg is the rr 850 version, the pro systems was ordered for the jbl, the justus was bought used and presumeably for a "sporty" vehicle, not sure.

[vector1]

almost forgot, here is what efi looks like

[Tom Kirkham]

Thanks for the pictures.

[cdnus]

Re post#3
The Pro Systems carb appears to have the holes drilled in the secondary's only---just like mine.
See photo in post #2 W/red billet baseplate.


Craig

[StanJ]

Originally Posted by vector1

additional pics

the justus carb is square jetted with pv caps on both blocks, i'm surprised there were no jet extensions.

Just to clarify --

The "caps" you're referring to aren't a means of eliminating the power valves; they are baffles which keep the power valve's fuel entry ports from becoming uncovered during hard cornering. In the case of the carb in question, the PVCR's in both metering blocks are .063" in diameter, which equates to roughly nine jet #'s worth of fuel metered inlet area -- quite a bit to lose...even momentarily...when the PV's start sucking air.

Jet extensions on a road car are almost never needed if fuel control issues in the float bowl are properly addressed. More to the point however, they often cause problems (engine stalling) of their own upon hard braking. For years, the "catch 22" was that if your engine made enough power...and your chassis and tires could hook that power to the ground...and your driver didn't run low on talent, then a car that truly benefited from jet extensions under acceleration would suffer a like amount from them on braking. The true solution to the problem -- metering blocks with lowered jet locations and float bowls designed with a "sump" to accommodate them -- didn't come around until just a few years ago.

[Rick Parker]

Remember when Barry Grant used to modify Holleys before he formed the Demon Carb product line.


[IMG][/IMG]

[lovehamr]

Re. the BG not having drilled throttle plates; remember that the BG has the center air bleed in the base plate between all the venturies (can't remember what it's called right now. Hey, it's early!) which obviates the need for the drilled plates.

[SwiftDB4]

Originally Posted by StanJ

Just to clarify --

The "caps" you're referring to aren't a means of eliminating the power valves; they are baffles which keep the power valve's fuel entry ports from becoming uncovered during hard cornering. In the case of the carb in question, the PVCR's in both metering blocks are .063" in diameter, which equates to roughly nine jet #'s worth of fuel metered inlet area -- quite a bit to lose...even momentarily...when the PV's start sucking air.

Jet extensions on a road car are almost never needed if fuel control issues in the float bowl are properly addressed. More to the point however, they often cause problems (engine stalling) of their own upon hard braking. For years, the "catch 22" was that if your engine made enough power...and your chassis and tires could hook that power to the ground...and your driver didn't run low on talent, then a car that truly benefited from jet extensions under acceleration would suffer a like amount from them on braking. The true solution to the problem -- metering blocks with lowered jet locations and float bowls designed with a "sump" to accommodate them -- didn't come around until just a few years ago.

Interesting comment about the jet extensions. My Quick Fuel carb has them, but only on the secondaries. Presumably on braking the secondaries are closed so lack of gas doesn't hurt? I'll be interested to see on track days if the primaries go dry under sustained braking.

[Gaz64]

Originally Posted by lovehamr

Re. the BG not having drilled throttle plates; remember that the BG has the center air bleed in the base plate between all the venturies (can't remember what it's called right now. Hey, it's early!) which obviates the need for the drilled plates.

Barry Grant modified Holleys didn't have "idle-eze" until he released his Demon carbs.

Originally Posted by SwiftDB4

Interesting comment about the jet extensions. My Quick Fuel carb has them, but only on the secondaries. Presumably on braking the secondaries are closed so lack of gas doesn't hurt? I'll be interested to see on track days if the primaries go dry under sustained braking.

Jet extensions are only necessary on the secondaries since g force under hard acceleration may uncover the secondary main jets.
Can never be a problem on the primary since the primary main circuit under heavy neg g force (braking) is not operating.

[lovehamr]

Of course you're right Gary but the OP's first set of pics included a BG Demon and that's why I mentioned the idle-ez:


Steve

[vector1]

Originally Posted by lovehamr

Of course you're right Gary but the OP's first set of pics included a BG Demon and that's why I mentioned the idle-ez:


Steve

neither this carb or the bg 750 like it that i have in my possession have the idle-eze.

[lovehamr]

Dang man, that's what I get for thinking. Mine has it and I just made the leap that they all did. It's a great idea though.

Steve

[diegokid]

What size are the holes in the butterflies and why are they there?

[FUNFER2]

vector 1- Have you used the BG FI ?

[vector1]

Originally Posted by diegokid

What size are the holes in the butterflies and why are they there?

not sure what size, they vary according to what the engine needs. instead of opening the butterflies to raise the idle which uncovers the transition slots, holes are drilled in the butterflies to allow enough air through the carb.

[vector1]

Originally Posted by FUNFER2

vector 1- Have you used the BG FI ?

not sure what the bg fi stands for. looks like barry grant fuel injection.

[diegokid]

I'll bite again, why would you need to drill holes in the first place and what would the symptoms be if someone needed to do this.

[Gaz64]

Originally Posted by diegokid

I'll bite again, why would you need to drill holes in the first place and what would the symptoms be if someone needed to do this.

If your engine now idles at 800rpm with 5 inches of vacuum instead of 800rpm at 16 inches of vacuum (after a cam change), it is consuming more air.

Opening the butterflies to compensate exposes the transfer slots and makes the mixture screws less responsive to uncontrollable.

It also shortens the idle/transition phase of the engine and produces off-idle flatspots etc.

Drilling holes in the butterflies allows the extra air, but you need to drill in small increments to sneak up on the optimum.

The transfer slots should have about .020 exposed when looking from underneath.