demon carb
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I'd go with the 750cfm Speed Demon double pumper. I made the same switch on my old 388" motor and picked up a solid 1/10th in the quarter with an out of the box SD 750 -- and the 3310 was highly tuned too.
I'd pick the Speed Demon over the Mighty Demon because the Speed Demon already has the IFR is the lower position and it is capable of having a choke too if you want one. The calibration on the SD will be setup for a slightly milder motor like yours.
I'd pick the Speed Demon over the Mighty Demon because the Speed Demon already has the IFR is the lower position and it is capable of having a choke too if you want one. The calibration on the SD will be setup for a slightly milder motor like yours.
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X2 on the Holley 750 HP
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X3, had a 750 speed demon for about a week.
Tried called BG multiple times, and tried all their suggestions to fix the problem. When they told me to adjust my idle by adjusting the timing and not using the idle screw I threw in the towl.
correct and the 950hp still doesnt flow as much as the BG, A pro systems 950hp would be better yet but do you really need that much?
Thats because you had the transfer slots open too far probaly and they wanted you to get the idle up so you could close the transfer slots to gain control over the air/fuel mix
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:yes:
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Yup and then when I took the carb off for the next time I reset them to squared like BG said and the idle is all off. Maybe I should have ran 50 degrees of initial? No to mention that wasnt even the worst problem I had with that carb.
FYI -- Setting the T-SLOT the same front to back is not the only option with the Demon carb. You can open the front or rear a little more as needed to expose the proper amount of tslot in the front. The "square" setting is just a baseline. The later carbs all have "idle eeze" so you can set the front tslot where they need to be and get the correct idle speed.
I won't defend Demon stuff 100% of the time, but I do like their carbs. I have had pretty good luck with them and they seem to make good power. For some reason the 750 Speed Demon has run better on my stuff than the bigger Mighty Demons.
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I did try also to open the rear up for a higher idle. I was able to get my idle where I wanted but it wasnt from adjusting my timing. Also this carb had the idle eeze and it didnt work at all. Nothing happened when I turned it.
The big problem I had with the carb was the stumble off the line it had. I tried it all and nothing helped, called BG multiple times and nothing they said fixed it. Different cams, squirters etc...
Sent it back, put on a Pro-systems 4150 and problem gone worked awesome right off the bat. It will idle with no choke within 30 seconds if it hasnt been ran for multiple weeks.
Always start with all 4 transfer slots set at .020", No higher, that way if you need more idle you need to go get the "Special Forces" .118" drill bit and drill the front two butterfly's on the metering block side and re-install the carburetor
This is why BG now has the idle E-Z {no more drilling}. Almost all racing carburetors have a slot in the baseplate from the butterfly to the center of the baseplate and they take an ALKY jet to control how much idle by passed air the engine is getting, All BG did was drill out the main body below the threaded air cleaner hole and install an adjustable valve so street/strip guys dont have to pull the baseplate off 2-3 times to change an ALKY jet to control the air/fuel mix
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Butch, did you read that it didnt work?
you set the transfer slots square but did you drill the butterflys out for more idle and air ? You didnt state you did that
i took a custom built 850 AED and replaced it with a 750 BG and it went from 10.88 to 10.615-10.63, AED told Nate he was comparing a highly modified carburetor to his HO series, OK, we pulled a 850 BG mighty demon off the shelf with no mods and it went a 10.65 then unbolted it and replaced it with the AED and it went a 10.91, both carburetors were tuned by me. Its not the fact it was a BG !! The 750 highly modifed BG you can stab from a dead idle in a '70 chevelle 327 and walk away with 1.75 60' times from a dead 1,050-1,100rpm idle
The 750 BG was highly modified by myself. A Pro Systems will probally ET better than both of them
i took a custom built 850 AED and replaced it with a 750 BG and it went from 10.88 to 10.615-10.63, AED told Nate he was comparing a highly modified carburetor to his HO series, OK, we pulled a 850 BG mighty demon off the shelf with no mods and it went a 10.65 then unbolted it and replaced it with the AED and it went a 10.91, both carburetors were tuned by me. Its not the fact it was a BG !! The 750 highly modifed BG you can stab from a dead idle in a '70 chevelle 327 and walk away with 1.75 60' times from a dead 1,050-1,100rpm idle
The 750 BG was highly modified by myself. A Pro Systems will probally ET better than both of them
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Isnt the idle eeze there so you dont have to drill out the butterflies?
Also do you think a 230/[email protected] 50 hydraulic flat tappet cam with .520 lift in a 454 should have any problems with this. The thing idled at 550rpms.
Also why would I have to highly modify any carb to get it to pull away from a stop with a stocker motor without stumbling on its face...no matter how much throttle it had.
Also do you think a 230/[email protected] 50 hydraulic flat tappet cam with .520 lift in a 454 should have any problems with this. The thing idled at 550rpms.
Also why would I have to highly modify any carb to get it to pull away from a stop with a stocker motor without stumbling on its face...no matter how much throttle it had.
Its called the joy of hot rodding :thumbsup: You can have two motors that run totally different and need two different carburetors. We had a 454 with 12:1 with a Ultradyne 231/239 @.050 .550/.575 110° lobe seperation with a 750BG speed demon with "zero" issues, you could hit it W.O.T with no hesitation
Accelerator pump arm adjustment must be correct, We always adjust them out of the box on BG's and Holley's and move the posistion of the pump cam so it opens at a different rate, then you dial in the air hole size, yes this is why they have the idle E-Z now
You could have had too large of a squirter or too small, wrong power valve with a "Stocker" and transfer slots not adjusted proper, or it could have been all of these together. The BG's come with .031" squirters, on an engine like yours {468} i would have started with .028" and worked my way up, .028" would have been best most likely
With your new engine your probally .035" squirters
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I bought a shooter/cam kit for it and tried all different sizes on it. Small/Big different P/Vs, couldnt get anything to work.
I am running the same setup as I had with the 468 right now on the 489 minus jets which I just changed.
rear pv blocked, 35/35squirter, 50cc pumps...dont remember what cam color I have in there though.
Close to my set up,looks the same with the exception of the cam,I have 248* @ .050 and .595" lift.I have a Speed Demon 750 that works fine on my engine,although it's borderline being too big.
I had it on a 350 originally,way over carb'd,and it took a while to figure out.I had to install the idle air bleed restrictors that come with the carb,and modify the idle circuit on the metering block.Timing was the biggest trick,took it from 10* to 18*.
Left it this way when it made its way to the 396.The engine makes very little vacuum and I ended up drilling the throttle plates to help the idle a little,initial timing is 20* with 36* total.This carb is before "idle ease" was built into the throttle bodies.
It has out performed the Holleys on both engines,e.t.s and fuel economy.
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