SPEED DEMON 575, or 750 Annular?
#1
SPEED DEMON 575, or 750 Annular?
Hi All.
I'm (still) keen to find a Speed Demon 575 or 750 (annular) user, their thoughts on it, and a brief desription of their engine spec.
I have a mildly rebuilt 350 in my 75 with auto trans. Forged pistons, roller rockers from Summit and an Edelbrock manifold and cam, -surely a popular combo.
I had a new Holley 600 but it turned out to have internal problems but it was dicovered far to late to return. I currently have a beaten up Holley that I originally borrowed from fellow UK Corvette Club member which I bought cheaply to keep me going.
The car and engine bay are pretty clean and I though a BG carb would look good in there, plus it's newer technology.
I was going for a 575 Speed Demon but the BG techies reccomended a 750 Annular which seems huge to me. Interestingly, Jegs, with the same info, reccommend the 575. The thing I'm really after is low end torque, and reasonable gas mileage would help too with UK prices!
Cheers, Rob.
I'm (still) keen to find a Speed Demon 575 or 750 (annular) user, their thoughts on it, and a brief desription of their engine spec.
I have a mildly rebuilt 350 in my 75 with auto trans. Forged pistons, roller rockers from Summit and an Edelbrock manifold and cam, -surely a popular combo.
I had a new Holley 600 but it turned out to have internal problems but it was dicovered far to late to return. I currently have a beaten up Holley that I originally borrowed from fellow UK Corvette Club member which I bought cheaply to keep me going.
The car and engine bay are pretty clean and I though a BG carb would look good in there, plus it's newer technology.
I was going for a 575 Speed Demon but the BG techies reccomended a 750 Annular which seems huge to me. Interestingly, Jegs, with the same info, reccommend the 575. The thing I'm really after is low end torque, and reasonable gas mileage would help too with UK prices!
Cheers, Rob.
#2
Hi All.
I'm (still) keen to find a Speed Demon 575 or 750 (annular) user, their thoughts on it, and a brief desription of their engine spec.
I have a mildly rebuilt 350 in my 75 with auto trans. Forged pistons, roller rockers from Summit and an Edelbrock manifold and cam, -surely a popular combo.
I had a new Holley 600 but it turned out to have internal problems but it was dicovered far to late to return. I currently have a beaten up Holley that I originally borrowed from fellow UK Corvette Club member which I bought cheaply to keep me going.
The car and engine bay are pretty clean and I though a BG carb would look good in there, plus it's newer technology.
I was going for a 575 Speed Demon but the BG techies reccomended a 750 Annular which seems huge to me. Interestingly, Jegs, with the same info, reccommend the 575. The thing I'm really after is low end torque, and reasonable gas mileage would help too with UK prices!
Cheers, Rob.
I'm (still) keen to find a Speed Demon 575 or 750 (annular) user, their thoughts on it, and a brief desription of their engine spec.
I have a mildly rebuilt 350 in my 75 with auto trans. Forged pistons, roller rockers from Summit and an Edelbrock manifold and cam, -surely a popular combo.
I had a new Holley 600 but it turned out to have internal problems but it was dicovered far to late to return. I currently have a beaten up Holley that I originally borrowed from fellow UK Corvette Club member which I bought cheaply to keep me going.
The car and engine bay are pretty clean and I though a BG carb would look good in there, plus it's newer technology.
I was going for a 575 Speed Demon but the BG techies reccomended a 750 Annular which seems huge to me. Interestingly, Jegs, with the same info, reccommend the 575. The thing I'm really after is low end torque, and reasonable gas mileage would help too with UK prices!
Cheers, Rob.
It has all the modern adjustment capability.
Last edited by Little Mouse; 06-19-2009 at 02:23 PM.
#4
Le Mans Master
put it this way,
the tech at barry grant also recommended the 750 annular for my 454.
i dont know how much stock you put in math but there are formulas out there that will give you a good idea on what carb size you need.
the tech at barry grant also recommended the 750 annular for my 454.
i dont know how much stock you put in math but there are formulas out there that will give you a good idea on what carb size you need.
#6
I don't see any mention of annular boosters on speed demon carbs?? mechanical or vacuum. down leg booster.
Looks like there chokeless 820 race demon is there smallest carb with annular boosters.
650 cfm should be good for a mild 350, fuel milage there is only so much you can do without an overdrive trans.
Small DP carbs are not a problem on auto cars, I had a 4500 pound
pickup 350, auto trans, 307 rear end, 650 cfm holley DP it was a daily driver.
from a performance stand point that 650 annular booster after what your used to bet you would be shocked.
Looks like there chokeless 820 race demon is there smallest carb with annular boosters.
650 cfm should be good for a mild 350, fuel milage there is only so much you can do without an overdrive trans.
Small DP carbs are not a problem on auto cars, I had a 4500 pound
pickup 350, auto trans, 307 rear end, 650 cfm holley DP it was a daily driver.
from a performance stand point that 650 annular booster after what your used to bet you would be shocked.
Last edited by Little Mouse; 06-20-2009 at 02:56 AM.
#8
Hi All.
I'm (still) keen to find a Speed Demon 575 or 750 (annular) user, their thoughts on it, and a brief desription of their engine spec.
I have a mildly rebuilt 350 in my 75 with auto trans. Forged pistons, roller rockers from Summit and an Edelbrock manifold and cam, -surely a popular combo.
I had a new Holley 600 but it turned out to have internal problems but it was dicovered far to late to return. I currently have a beaten up Holley that I originally borrowed from fellow UK Corvette Club member which I bought cheaply to keep me going.
The car and engine bay are pretty clean and I though a BG carb would look good in there, plus it's newer technology.
I was going for a 575 Speed Demon but the BG techies reccomended a 750 Annular which seems huge to me. Interestingly, Jegs, with the same info, reccommend the 575. The thing I'm really after is low end torque, and reasonable gas mileage would help too with UK prices!
Cheers, Rob.
I'm (still) keen to find a Speed Demon 575 or 750 (annular) user, their thoughts on it, and a brief desription of their engine spec.
I have a mildly rebuilt 350 in my 75 with auto trans. Forged pistons, roller rockers from Summit and an Edelbrock manifold and cam, -surely a popular combo.
I had a new Holley 600 but it turned out to have internal problems but it was dicovered far to late to return. I currently have a beaten up Holley that I originally borrowed from fellow UK Corvette Club member which I bought cheaply to keep me going.
The car and engine bay are pretty clean and I though a BG carb would look good in there, plus it's newer technology.
I was going for a 575 Speed Demon but the BG techies reccomended a 750 Annular which seems huge to me. Interestingly, Jegs, with the same info, reccommend the 575. The thing I'm really after is low end torque, and reasonable gas mileage would help too with UK prices!
Cheers, Rob.
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#9
Le Mans Master
Estimate VE based on HP/CID:
HP/CID / VE
<1 / 75.00%
1 / 85.00%
1.2 / 95.00%
1.4 / 100.00%
I take "mildly built" to mean < 350HP at the crank, so....
RPM/CFM
1000/76
2000/152
2500/190
3000/228
4000/304
5000/380
6000/456
7000/532
7500/570
8000/608
8500/646
We look to see that on a square-bore we're not using more than 1/2 the carb capacity at cruise RPM to be sure we're not into the secondaries.
That mild 355 will need to turn 9800 RPM to use 750 CFM
The 575 will give you the best throttle response and all-around driveability. A vacuum secondary 650 would be fine. The 750 is just too big.
#10
Drifting
Member Since: Apr 2006
Location: gold coast queensland
Posts: 1,911
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if your above 400 hp go the 750
if your below it go the 575 - 650
i like demons too and have the 750 Dp
those holleys look nice 76 sting
im with billa, a 750 will make a nice cruising motor a slug
if your below it go the 575 - 650
i like demons too and have the 750 Dp
those holleys look nice 76 sting
im with billa, a 750 will make a nice cruising motor a slug
Last edited by gingerbreadman1977; 06-21-2009 at 12:58 AM.
#11
NCM Grand Opening Veteran
Member Since: Sep 2005
Location: South of giving a damn
Posts: 20,899
Received 358 Likes
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250 Posts
St. Jude Donor '11, '17
CFM = ((CI x RPM)/3456) x VE
Estimate VE based on HP/CID:
HP/CID / VE
<1 / 75.00%
1 / 85.00%
1.2 / 95.00%
1.4 / 100.00%
I take "mildly built" to mean < 350HP at the crank, so....
RPM/CFM
1000/76
2000/152
2500/190
3000/228
4000/304
5000/380
6000/456
7000/532
7500/570
8000/608
8500/646
We look to see that on a square-bore we're not using more than 1/2 the carb capacity at cruise RPM to be sure we're not into the secondaries.
That mild 355 will need to turn 9800 RPM to use 750 CFM
The 575 will give you the best throttle response and all-around driveability. A vacuum secondary 650 would be fine. The 750 is just too big.
Estimate VE based on HP/CID:
HP/CID / VE
<1 / 75.00%
1 / 85.00%
1.2 / 95.00%
1.4 / 100.00%
I take "mildly built" to mean < 350HP at the crank, so....
RPM/CFM
1000/76
2000/152
2500/190
3000/228
4000/304
5000/380
6000/456
7000/532
7500/570
8000/608
8500/646
We look to see that on a square-bore we're not using more than 1/2 the carb capacity at cruise RPM to be sure we're not into the secondaries.
That mild 355 will need to turn 9800 RPM to use 750 CFM
The 575 will give you the best throttle response and all-around driveability. A vacuum secondary 650 would be fine. The 750 is just too big.
#14
Le Mans Master
A Holley 3310 750CFM vacuum secondary carb. This was with an engine making > 1 HP/CID (if you believe the stock specs, which were conservative) and a high-revving engine not REALLY intended for the street.
DZs and LT-1s (not LT1s) apply to a mildly built 350 how, exactly? IMHO, this is where folks get into trouble - racing parts used on the street.
DZs and LT-1s (not LT1s) apply to a mildly built 350 how, exactly? IMHO, this is where folks get into trouble - racing parts used on the street.
#16
Thanks for all your replies so far. Pretty much what I expected and I think I'll go for the Speed Demon 575. Still would love to hear from someone actually using one.
YOU MUST BE OUT THERE!!!!!
Cheers, Rob.
YOU MUST BE OUT THERE!!!!!
Cheers, Rob.
#17
Le Mans Master
Member Since: May 2003
Location: Fernandina Beach FL
Posts: 8,481
Received 3,220 Likes
on
1,732 Posts
2023 Restomod of the Year finalist
2020 C3 of the Year Winner - Modified
I've been running a Speed Demon 575 on my warmed over Hyd Roller- Brodix headed 327 w/ a 4 speed for a couple years now.
I could not get the car to idle good w/out being too rich w/ a 600cfm Holley. I was reading the articles about drilling holes-when I found the Barry Grant article.
I bolted on the Demon and was able to get it to idle great and not too rich- in minutes. Plus my gas mileage went up a 3-4 MPG. I've been really happy w/ it.
Richard
I could not get the car to idle good w/out being too rich w/ a 600cfm Holley. I was reading the articles about drilling holes-when I found the Barry Grant article.
I bolted on the Demon and was able to get it to idle great and not too rich- in minutes. Plus my gas mileage went up a 3-4 MPG. I've been really happy w/ it.
Richard
#18
Race Director
My turn.....
I have a 400+hp/tq at the wheels on my 383. I have been running a Edelbrock 750, and have ordered a BG 750 Mighty Demon Annular yesterday. It should be in this week; I will put it on, run another dyno and post the results to you. The techs over at BG claim I will be gaining somewhere around 20-30HP....Hmmm... we will see. I will also post the drivability comparison between the two...
I have a 400+hp/tq at the wheels on my 383. I have been running a Edelbrock 750, and have ordered a BG 750 Mighty Demon Annular yesterday. It should be in this week; I will put it on, run another dyno and post the results to you. The techs over at BG claim I will be gaining somewhere around 20-30HP....Hmmm... we will see. I will also post the drivability comparison between the two...
#19
Race Director
I JUST pulled the trigger on a Speed Demon for my '75. Should have it by Wed.