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  #16 (permalink)  
Old 11-02-2009, 07:09 AM
Technical Support Barry Grant
 
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Quote:
Originally Posted by Shawn Horan
I figured ya guys had that problem fixed by now. I dnt mean to hiest thisthread but I've got a question while your here... My friend bought an 850 mighty Demon a few years back for an engine he was building but he never ended up using it. He told me that he was thinking about selling it to me to make his money back on it. I asked him if I could try it on my truck first and If I liked it , I'd buy it... He agreed.

I could not for the life of me, get this thing to run on the primary side of the carb. Idle or Cruise...It was totally dead. I tried a new power valve and a few other things and this thing wouldnt work. It was like there was no primary circuit or it was dead. You'd get the primary shooter and once it was gone, there was nothing...it would stumble and stall. I heard there was some adjustment air valve down under the aircleaner stud...but this carb didnt have anything like that. The secondary side was fine.

In the end, I didnt want to play with this thing too much because it wasnt mine, and I ended up giving it back to him. I also know of a guy from Niagara Falls who had an same identical problem with his 850 mighty demon too. What was going on here??? These carbs were both around 5-7 years old.

Thanx!

Shawn
What size engines are you guys trying to run these on as they are intended for 500 inches and larger in most cases. Ohter things we need to know is how much duration at .050 and how much timing in the motor at idle as well as how much of the transfer slot is showing on the front vs the rear.

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  #17 (permalink)  
Old 11-02-2009, 05:19 PM
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Originally Posted by Tech @ BG
What size engines are you guys trying to run these on as they are intended for 500 inches and larger in most cases. Ohter things we need to know is how much duration at .050 and how much timing in the motor at idle as well as how much of the transfer slot is showing on the front vs the rear.
Well, that was 4 years ago when i tried it... dnt remember everything about the carb other than what it was doing.

My engine is a Low Deck 451 cubic inch stroker Mopar big block. The cam is a Hughes Engines HEH3237 Cam (Hyd. 232/237@.050 and .576/.584 lift with 1.6 R.Rockers). The engine is roughly 9.7:1 Compression. Eddy 383 RPM Performer Dual Plane Intake. Ported Iron Heads. 2.14/1.81 Valves.

I typically run 36 Degrees total with a mallory HYFIRE multi spark ignition, cant really tell ya what the initial is due to the multi spark at idle.

The one thing I could tell you is that the only way to get the engine to idle was to crank down on the secondary idle speed screw. Basically, the engine was running on the secondary side at idle. If I tried to get it to idle on the primary side, it would simply quit running.

I decided to run a 950 Quickfuel/Proform on the strip which worked excellent right out of the box. I also tried my fathers 1050HP Holley Dominator from his 9 second Road Runner (493 stroker 14.5:1 compression .700" comp roller cam) with the 4500 to 4150 adapter plate and it handled that carb with out any problems... so i dont feel that the demon was too much for this engine to handle at all.


After giving the Demon back to the guy, he tried to get it to work on his chevy and experienced the same issue's as I did with no luck either... he called BG tech and still couldnt get it to work.

He feels that something is plugged on the Primary Metering block. He also thinks that maybe it was never finish machined or possibly, there may have been a broken tooling issue when some of these metering blocks were being machined.


The other engine I was speaking of (my friend from Niagara Falls) is a 511 CID Stroker Big block Mopar wedge with a .590" (312/312 seat/seat.)mopar purple shaft solid cam. 11.5:1 compression. This engine has a single plane Team G intake manifold. This engine see's more strip duty than street...but does venture out on public hiways from time to time. The 850 mighty Demon this guy had was a completely different unit from the one I tried. He had the same exact problems...couldnt get it to run on the primary circuits. It would just die after the primary shot was consumed. If ya feathered the throttle, or crank down on the idle speed screw on the secondaries, it would continue to idle.

He is currently running a Holley 950 HP with no issues.

Being that there were problems with both carbs, right out of the box, Is it possible that maybe those metering blocks have machining issues? Both Demons were both purchased new around the same time back 6-7 years ago.

Please keep in mind, I'm not trying to bash BG or The Demon carbs in anyway here. I know that they are a very excellent and proven carb manufacturer because I know there are way too many people as well as personal friends who run Demon carbs with much success for them to be a bad product. So please dont take what I'm saying out of context. thanx.

Last edited by Shawn Horan; 11-02-2009 at 05:46 PM.
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  #18 (permalink)  
Old 11-03-2009, 07:57 AM
Technical Support Barry Grant
 
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Quote:
Originally Posted by Shawn Horan
Well, that was 4 years ago when i tried it... dnt remember everything about the carb other than what it was doing.

My engine is a Low Deck 451 cubic inch stroker Mopar big block. The cam is a Hughes Engines HEH3237 Cam (Hyd. 232/237@.050 and .576/.584 lift with 1.6 R.Rockers). The engine is roughly 9.7:1 Compression. Eddy 383 RPM Performer Dual Plane Intake. Ported Iron Heads. 2.14/1.81 Valves.

I typically run 36 Degrees total with a mallory HYFIRE multi spark ignition, cant really tell ya what the initial is due to the multi spark at idle.

The one thing I could tell you is that the only way to get the engine to idle was to crank down on the secondary idle speed screw. Basically, the engine was running on the secondary side at idle. If I tried to get it to idle on the primary side, it would simply quit running.

I decided to run a 950 Quickfuel/Proform on the strip which worked excellent right out of the box. I also tried my fathers 1050HP Holley Dominator from his 9 second Road Runner (493 stroker 14.5:1 compression .700" comp roller cam) with the 4500 to 4150 adapter plate and it handled that carb with out any problems... so i dont feel that the demon was too much for this engine to handle at all.


After giving the Demon back to the guy, he tried to get it to work on his chevy and experienced the same issue's as I did with no luck either... he called BG tech and still couldnt get it to work.

He feels that something is plugged on the Primary Metering block. He also thinks that maybe it was never finish machined or possibly, there may have been a broken tooling issue when some of these metering blocks were being machined.


The other engine I was speaking of (my friend from Niagara Falls) is a 511 CID Stroker Big block Mopar wedge with a .590" (312/312 seat/seat.)mopar purple shaft solid cam. 11.5:1 compression. This engine has a single plane Team G intake manifold. This engine see's more strip duty than street...but does venture out on public hiways from time to time. The 850 mighty Demon this guy had was a completely different unit from the one I tried. He had the same exact problems...couldnt get it to run on the primary circuits. It would just die after the primary shot was consumed. If ya feathered the throttle, or crank down on the idle speed screw on the secondaries, it would continue to idle.

He is currently running a Holley 950 HP with no issues.

Being that there were problems with both carbs, right out of the box, Is it possible that maybe those metering blocks have machining issues? Both Demons were both purchased new around the same time back 6-7 years ago.

Please keep in mind, I'm not trying to bash BG or The Demon carbs in anyway here. I know that they are a very excellent and proven carb manufacturer because I know there are way too many people as well as personal friends who run Demon carbs with much success for them to be a bad product. So please dont take what I'm saying out of context. thanx.
Part of the problem here is that you are comparing apples to oranges but the other part is something we see every day where we tell somebody that a carb is too big or wont work on an application and they try to tell us otherwise.

Our 850 will flow close to 1000 cfm which is why it needs to be 500 inches or more but comparing it to a 950 is not even close. Sure the 950 works because it IS a smaller carburetor. Look at the published dimensions on it and basically it is a 750 with an 850 base. It is 1.400 up top with a 1.750 base whereas our 850 is 1.560 up top with a 1.750 base. See the big difference? the air speed will be higher on the carburetor with the smaller venturi.

The other part as I posted above and the way I see it based on the specs you have listed for both applications is that the Mighty 850 would not be our recommendation for either. Guys will put the wrong carburetor on and then want to blame the carb for what is going on. We have less then 1% defects and the majority of the carburetors we do get back in for warranty are typically because they were adjjusted wrong, the customer got too far off the baseline, wrong applications or just need a calibration change that the end user was not able to do. There are some legitimate defects from time to time but the odds of having 2 carburetors with broken tooling issues around the same time and area you would have better odds playing the lottery.

Base timing is real important as well in tuning and if you do not know what the base is this needs to be determined before any other adjustments are made. WIth the cam listed in the first engine it would need close to 20 in it at idle and with the second combination it would need more or even possibly locked out.

One test that you can do though any time you think there is an issue with a metering block would be to move the block to the rear and see if the problem follows it. The same can be done for needle and seats and some other components.
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  #19 (permalink)  
Old 11-04-2009, 05:30 AM
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Quote:
Originally Posted by Tech @ BG
Part of the problem here is that you are comparing apples to oranges but the other part is something we see every day where we tell somebody that a carb is too big or wont work on an application and they try to tell us otherwise.

Our 850 will flow close to 1000 cfm which is why it needs to be 500 inches or more but comparing it to a 950 is not even close. Sure the 950 works because it IS a smaller carburetor. Look at the published dimensions on it and basically it is a 750 with an 850 base. It is 1.400 up top with a 1.750 base whereas our 850 is 1.560 up top with a 1.750 base. See the big difference? the air speed will be higher on the carburetor with the smaller venturi.

The other part as I posted above and the way I see it based on the specs you have listed for both applications is that the Mighty 850 would not be our recommendation for either. Guys will put the wrong carburetor on and then want to blame the carb for what is going on. We have less then 1% defects and the majority of the carburetors we do get back in for warranty are typically because they were adjjusted wrong, the customer got too far off the baseline, wrong applications or just need a calibration change that the end user was not able to do. There are some legitimate defects from time to time but the odds of having 2 carburetors with broken tooling issues around the same time and area you would have better odds playing the lottery.

Base timing is real important as well in tuning and if you do not know what the base is this needs to be determined before any other adjustments are made. WIth the cam listed in the first engine it would need close to 20 in it at idle and with the second combination it would need more or even possibly locked out.

One test that you can do though any time you think there is an issue with a metering block would be to move the block to the rear and see if the problem follows it. The same can be done for needle and seats and some other components.

You Failed to read in my previous post that I have run a 1050 Holley Dominator Race Carburator on this engine without a single issue idle, part throttle, and wide open.... the truck ran 11.69@116 mph which was my best pass 1/4 mile pass. It is larger than the Mighty Demon.
Venturii Size 1.690
Throttle bore 2.000

My truck also ran 11.70@115 MPH with my 950 Proform.

I don't see where the size of the carb is relevent in any way here because the problem is it part throttle and idle. 340 Six-pack mopars ranover 1200 cfm and those engines were only 340 cubic inch. The venturii size has nothing to do with its idle characteristics...which by the way, these two demons carbs have none because the engines wont idle or run at part throttle. Reguardless, the other 511 engine has a locked distributor...if anything, that carb should've worked on that engine.

I stoped at my friends house (chevy) last might and we were looking at the Demon. We took the primary metering block off and sprayed carb cleaner down both passages that feeds both idle wells. They both seem to be plugged...it just spits back at you. Is there any reason why these would be plugged...right out of the box? Would this cause the engine to have these idle issues?

I'm a machinist by trade and have some very nice inspection equipment at my disposal...microscopes and a machine called a smartscope(uses a camera). I'm gonna take it to work today and take a closer look at both holes that feed both idle wells aswell as where they exit.

I'll let ya know what I find.
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  #20 (permalink)  
Old 11-04-2009, 07:21 AM
Technical Support Barry Grant
 
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Quote:
Originally Posted by Shawn Horan
You Failed to read in my previous post that I have run a 1050 Holley Dominator Race Carburator on this engine without a single issue idle, part throttle, and wide open.... the truck ran 11.69@116 mph which was my best pass 1/4 mile pass. It is larger than the Mighty Demon.
Venturii Size 1.690
Throttle bore 2.000

My truck also ran 11.70@115 MPH with my 950 Proform.

I don't see where the size of the carb is relevent in any way here because the problem is it part throttle and idle. 340 Six-pack mopars ranover 1200 cfm and those engines were only 340 cubic inch. The venturii size has nothing to do with its idle characteristics...which by the way, these two demons carbs have none because the engines wont idle or run at part throttle. Reguardless, the other 511 engine has a locked distributor...if anything, that carb should've worked on that engine.

I stoped at my friends house (chevy) last might and we were looking at the Demon. We took the primary metering block off and sprayed carb cleaner down both passages that feeds both idle wells. They both seem to be plugged...it just spits back at you. Is there any reason why these would be plugged...right out of the box? Would this cause the engine to have these idle issues?

I'm a machinist by trade and have some very nice inspection equipment at my disposal...microscopes and a machine called a smartscope(uses a camera). I'm gonna take it to work today and take a closer look at both holes that feed both idle wells aswell as where they exit.

I'll let ya know what I find.
No I didn't fail to read that but you disregarded my whole statement about venturi shape and air speed. You seem to think you know better then us about our own product so I see no reason to continue to try and argue with you. I believe you started this same type deal on another board so not sure what your motives really are.

For the others who are reading and have an open mind to what we are posting if a carburetor is too big it will not idle properly as the fuel is not being atomized properly and falling into the plenum in droplets. These are characteristics of anybodys carburetor that is too big in it will have poor idle , bad transition and then be lean at wot.

In regards to spraying carb cleaner into the idle well are you referring to doing this at the ifr? If so that makes a 90 right past the bleed.
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Old 11-05-2009, 09:22 PM
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Your right, the fuel does make a 90* turn from the idle restriction into the idle well...but even compressed air will not flow through it either.

Really quick...If this Demon is too big for my engine and it wont idle because of that fact, then why can I make it idle on the secondary metering block with the secondary idle speed screw, but not with the primary metering block?

I'll tell you why...

I looked at this thing under the Microscope





and I found that the idle feed restriction (In picture below) that is supposed to supply the idle well and in-turn supply fuel to the transfer slots is indeed a blind, unfinished hole... Whether its the idle well or IFR thats the problem here...I don't know...but one things for sure, they don't bi-sect each other. Both sides of this metering block are like this. ( I apologize for not having a decent enough camera to show this...)



As the fuel flows in to idle feed restriction it simply put, "hits a wall" or "dead end" ... Now, I'm definitly no carb expert or pro like you guys but, if this passage is dead, how is the engine supposed to idle when there is no fuel there? I understand how venturi's work and the reason I didn't acknowledge your statement about them is that this problem has nothing to do with the size of the carb, the venturi's or engine displacement... it is simply has to do with this metering block being machined incorrectly due to either machine operator error, broken tools, a CNC program error or a bad tool offset adjustment.

For those reading....Like I said before, Im not trying to argue or bicker, bash or put down BG or the Demon Carb. My motive was simply to help my friend out who has been stuck with this ill functioning carb which has been sitting on his shelf for years now.

I'm gonna give this metering block back to him and advise him to contact Barry Grant by phone and let him explain what was found....whether he does or not, is entirely up to him.

Last edited by Shawn Horan; 11-06-2009 at 05:23 AM.
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  #22 (permalink)  
Old 11-06-2009, 07:22 AM
Technical Support Barry Grant
 
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Quote:
Originally Posted by Shawn Horan
Your right, the fuel does make a 90* turn from the idle restriction into the idle well...but even compressed air will not flow through it either.

Really quick...If this Demon is too big for my engine and it wont idle because of that fact, then why can I make it idle on the secondary metering block with the secondary idle speed screw, but not with the primary metering block?

I'll tell you why...

I looked at this thing under the Microscope





and I found that the idle feed restriction (In picture below) that is supposed to supply the idle well and in-turn supply fuel to the transfer slots is indeed a blind, unfinished hole... Whether its the idle well or IFR thats the problem here...I don't know...but one things for sure, they don't bi-sect each other. Both sides of this metering block are like this. ( I apologize for not having a decent enough camera to show this...)



As the fuel flows in to idle feed restriction it simply put, "hits a wall" or "dead end" ... Now, I'm definitly no carb expert or pro like you guys but, if this passage is dead, how is the engine supposed to idle when there is no fuel there? I understand how venturi's work and the reason I didn't acknowledge your statement about them is that this problem has nothing to do with the size of the carb, the venturi's or engine displacement... it is simply has to do with this metering block being machined incorrectly due to either machine operator error, broken tools, a CNC program error or a bad tool offset adjustment.

For those reading....Like I said before, Im not trying to argue or bicker, bash or put down BG or the Demon Carb. My motive was simply to help my friend out who has been stuck with this ill functioning carb which has been sitting on his shelf for years now.

I'm gonna give this metering block back to him and advise him to contact Barry Grant by phone and let him explain what was found....whether he does or not, is entirely up to him.
As I said before not sure really what your motive is here or what you are trying to pull or maybe you are trying to make yourself look good ...who knows but with the majority of your posts in this thread only I am suspicious at best..

Here's the way I see it though as this is a 6 or 7 year old carburetor, you say it is an 850 Mighty Demon but the block you have pictured is NOT off a Mighty Demon as the part number is wrong and the Mighty has the ifr at the top and uses a screw in bleed. For someone that tries to come off as real knowledegable have you overlooked the quick and simple fix for this? Simply drill the hole and put the carb back together.

I do question where THIS block came from but if the guy needs to use it then that would be his best and cheapest route. I'm not going to give the guy a block because you feel I should not to mention the age of the carburetor and the fact the block you are alleging is bad is not even from the carburetor you say it is.

Alternatively I will throw this out there as well if he doesn't feel comfortable drilling the hole he can send us the block, we will drill it and return it to him.

Last edited by Tech @ BG; 11-06-2009 at 03:36 PM.
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