[Formula jg]

Does anyone have (or know) the center to center bowl vent tube distance between a 4150 Holley and Mighty Demon? Are they the same?

Also, is the O.D. for the bowl vent tubes the same between the Holley and Demon?

[cdrookie]

i will check in a little bit

[shaker455]

Originally Posted by Formula jg

Does anyone have (or know) the center to center bowl vent tube distance between a 4150 Holley and Mighty Demon? Are they the same?

Also, is the O.D. for the bowl vent tubes the same between the Holley and Demon?

Yes to both & it's been a long time my friend..how you been?

[Tom Vaught]

Lots of BG stuff was a direct copy of Holley Engineered parts and the pieces were bought from the same sources. At one time the calibrations were amazingly identical with the Holley being a older carb. Hum?

Tom V.

[Cliff R]

Copying someone else's "engineered" parts and using identical calibrations sounds like a good way to get yourself into a lawsuit........FWIW........Cliff

[Formula jg]

Wow Jeff you remembered me, nice!
Thanks for the feedback as I have both style of carbs but just not with me this week and needed to know before ordering this:

http://blp.com/cart/index.php?main_p...6f6acef2bda509

Spent the past 2 years on the suspension, brakes, axle and general undercarriage restoration and now it handles and brakes so good that the Mighty Demon is flooding the engine when brake hard (verified this with the AFR data logger).

I did lower the rear float and it help a little but not enough and I'm not about to tweak that carb anymore after tuning it (with your help of course) for 3 yrs, all circuits have been functioning just beautifully since then.

On a side note I also re-engineered my 750 Speed Demon w/vac. secondaries and ran that on an RPM manifold but it could not match the 850 MD on the T2 with 1" 4-hole spacers in idle, cruise and power so it sits in the box as a backup.

I miss this site but will probably be posting more now that the car has been back on the road for a couple of weeks, heres a dark pic of the car as it sits now:

[Tom Vaught]

Originally Posted by Cliff R

Copying someone else's "engineered" parts and using identical calibrations sounds like a good way to get yourself into a lawsuit........FWIW........Cliff

Holley waited until a lot of the other guys carbs were built and then collected on every carb that was a copy. The "Claw" basically went away after that suit.

Tom V.

[60man]

Must say they look much better than a piece of hose....suck as mine..

[shaker455]

Originally Posted by Formula jg

Wow Jeff you remembered me, nice!
Thanks for the feedback as I have both style of carbs but just not with me this week and needed to know before ordering this:

http://blp.com/cart/index.php?main_p...6f6acef2bda509

Spent the past 2 years on the suspension, brakes, axle and general undercarriage restoration and now it handles and brakes so good that the Mighty Demon is flooding the engine when brake hard (verified this with the AFR data logger).

I did lower the rear float and it help a little but not enough and I'm not about to tweak that carb anymore after tuning it (with your help of course) for 3 yrs, all circuits have been functioning just beautifully since then.

On a side note I also re-engineered my 750 Speed Demon w/vac. secondaries and ran that on an RPM manifold but it could not match the 850 MD on the T2 with 1" 4-hole spacers in idle, cruise and power so it sits in the box as a backup.

I miss this site but will probably be posting more now that the car has been back on the road for a couple of weeks, heres a dark pic of the car as it sits now:

Of course John, we worked together quite a bit back I the day!
Car looks awesome!

So you gonna get that one piece vent tube from BLP?

Some of my 4-wheeling guy's use that tube for off road & you can test before you buy with a rubber fuel line with a notch cut in the middle connecting the 2 vent tubes.

I do a lot of custom road racing units and the mairne j-hooks work well too.

[Tom Vaught]

I am a fan of the Marine "J-Hook" Vents first, then the "Bottom Opening Marine" Vent, and finally the "Top Opening Marine" Vent, (from the link above). The top opening vents can pressurize the bowls slightly and change the fuel calibration slightly.

Tom V.

[Formula jg]

Made my own vent tube connector using old 90* spk plug boots and a short piece of 3/8" hard fuel line:




However, the problem persists when braking hard engine stalls out (not what I want to happen in an emergency). I think there may be fuel entering the venturi from other areas like the booster because once the inertia forces all the rear bowl fuel to hit the metering block like a tidal wave it must be finding its way back out through the booster channels.

Is my theory out to lunch?

[Tom Vaught]

Originally Posted by Formula jg

Made my own vent tube connector using old 90* spk plug boots and a short piece of 3/8" hard fuel line:




However, the problem persists when braking hard engine stalls out (not what I want to happen in an emergency). I think there may be fuel entering the venturi from other areas like the booster because once the inertia forces all the rear bowl fuel to hit the metering block like a tidal wave it must be finding its way back out through the booster channels.

Is my theory out to lunch?

Do you have jet extensions on the rear metering block?

Without them the fuel can easily rush forward, with hard braking, pressurize the main jet/booster circuit and force fuel upward and out the booster.

Tom V.

[Formula jg]

Tom, no jet extensions.
Will I also require hump back floats to allow space for the jet extension tubes??

So what are/is the symptoms when you accelerate hard and the front fuel bowl flash floods the front metering block (just wondering if I also need extensions in the front, I might as well do it all at one time)?

[shaker455]

John,
Nice job!

Do you have the plastic vent passage on your metering blocks?

Are they long or short?

Check the main body passage for the vents as I found the holes obstructed by drill burrs from the factory where it breaks thru into the casting to meet the metering block.

It could be causing pressure in the bowl.

As we speak I'm live testing a mighty demon 850 annular for another forum member.

The boosters are screw in and I found some loose so make sure yours are in tight.

Also, I found that Demon did not do a bang up job assembling the boosters (I bet your surprised to hear that!)

Besides not being pressed in all the way into the banjo

All 4 boosters were not orientated correctly and pressed into the banjo with the discharge holes in the annular booster right in line with the banjo feed passage.

For even distribution the holes in the booster are to be staggered to either side of the banjo feed passage.

Take a close look at yours and see how they're assembled.

Try the float level to the lower mark

[Formula jg]

It's been at least 2 years since I needed to open up that 850MD but I don't think it has the vent whistles.

I found a couple of pics dating back about 7yrs when the carb was brand new:





Can't rember if this was the replacement 850md that Demon sent me and if it is (which I believe so) then that's the one I'm currently running, not pretty for a brand new and not cheap carb. Looks like the carb is coming apart this weekend just like old times.

[shaker455]

Nasty!...Yes I remember now. this is what triggered my "Demon's Demise" post back then.
You sent them your 825 main body & they eventually replaced it with that nasty second...boy that's customer service!

Those boosters are swedged and not a good job, bottom line it can be fixed.

You need vent whistles if you don't have them

[Formula jg]

What is the O.D. of the main jet (want to try and make a temporary jet extension and test if it solves the stalling problem)?

[Tom Vaught]

TRUE Holley Jets are .312" on the outside diameter +- .0005"

Tom V.

[Formula jg]

So approx. 3/16". Thanks Tom.

[455-4+1]

Not surprised to hear about the booster install. Had an 850 MD annular at one time and at the end of a run the car started acting up funny (after cleaning swarf from all parts of the carb and passages not drilled properly)

It had been Wet flow tested (yeah right) with all circuits confirmed, it seemed funny it only needed a squirter on one side as the other primary one wasnt even drilled LOL)

Took a look after the run and one of the booster inserts had jumped out of the banjo holder during the run and jammed itself between the banjo and the main body

Luckily it didnt end up below in the engine at WOT

Funnily enough I don't have that carb any more but my BLP (Bowlaws) Annular is a very nice piece in comparison. All of the machining etc and hard anodized parts are a world away from the Demon stuff which looked like it was carved by hand from a bit of silver soap with a blunt knife and some BBQ skewers