Recommend a carb for me? **** update***

Need a new one, have always run a 750dp on it. 460, 9.5 compression, .530 hyd cam, glide, leaves on the brake at 4800, shift at 5500, 4.11 gears... Would an 850 be good, or is it too much? I have a Demon 850, it does not run as good as the 750, may be tuning issues, or I got one that is junk (I hear you either get a good one or junk with those) and the guy at BG said they really flow in the low 9's, so that may be too big.
Car currently runs mid 7's in the 1/8, so not much HP...

IMO I'd lose the Demon and call Patrick at ProSystems. He will build you a Holley-based carb that is right for your combo.

Don't be scared by the word custom as they are about the same amount of money as an out-of-the-box piece

The Demon has spent more time in the box over the last ten years than on the car! I am getting rid of it, I just had to stick it back on to verify the 750 is my problem. The car is nosing over at 400' then tries to die after the finish line. Tried new floats, needles and seat, blowing it out, I give up. This carb has been great for 20 years, but it's kicking my but now. Maybe an air blled glogged? 60' is great....

I had a 850 dp on my 460 when I built it was nosing over at the end of a run I went to a 1050 problem fix for me. I have you flow the fuel system to make sure you are not running out of fuel.

on my 460 I had just a little more lift it was .562 .565 intake was a G429 motorsports , dove-c heads with stock bottom end ran 7.20s in the 1/8

950HP

The 750 is fine IMO, learn to do some tuning

69F100 wrote:I had a 850 dp on my 460 when I built it was nosing over at the end of a run I went to a 1050 problem fix for me. I have you flow the fuel system to make sure you are not running out of fuel.

Dominator float bowls are larger, and hold a little more fuel than a 4150. Don't know if this had anything to do with your issue, but if the fuel system is weak, it may act as a bandaid?

YellowStangDuane wrote:The Demon has spent more time in the box over the last ten years than on the car! I am getting rid of it, I just had to stick it back on to verify the 750 is my problem. The car is nosing over at 400' then tries to die after the finish line.  Tried new floats, needles and seat, blowing it out, I give up. This carb has been great for 20 years, but it's kicking my but now. Maybe an air blled glogged? 60' is great....

Did you remove the metering blocks, and blow it from there, and make sure air came out all four holes in the jets?

dfree383 wrote:The 750 is fine IMO, learn to do some tuning

This carb has been on the car for more than 20 years, this condition only showed up 2 months ago on the Holley. The Demon runs ok, just not as fast or consistent as the Holley does. I've blown out passages and tried lots of stuff. Maybe an air bleed clogged that I haven't found?

Borrow a carb from a buddy .

YellowStangDuane wrote:

dfree383 wrote:The 750 is fine IMO, learn to do some tuning

This carb has been on the car for more than 20 years, this condition only showed up 2 months ago on the Holley. The Demon runs ok, just not as fast or consistent as the Holley does. I've blown out passages and tried lots of stuff. Maybe an air bleed clogged that I haven't found?

Don't give up on the 750. It is probably something stupid simple, at least it seems to work that way for me sometimes. On my mild 429 a 750 worked the best. If someone would let you borrow a known good stock 850 to try you could compare the times. I kind of doubt it will help much in the 1/8 mile with your combo, but worth a shot. If you soke the metering blocks in Chem Dip, and blow them out a few times it might help. Sometimes you have to pull the caps for the imuleifiers, for a good cleaning, but I have never had to. Make sure the intake base gasket is sealing good, and the rest of the fuel system is all ok. Hope you get it lined out.

Sunday I swapped the 850 Demon and the 750 back and forth... The Demon wasn't jettted right, I was actually 3 jet sizes too small in the front from factory for some reason, it did not 60' as good, but by 330' it was faster and had more MPH. The Demon has always been strange, when I first bought it, the thing was way rich, I borrowed the EGT off the Jr Dragster to try to tune it. Had to jet it way down, and it never had the same temps as the Holley. Now it seems to want to be jetted up, I've heard you need to take them apart since the qautlity control is bad from them and blow out the aluminum chips, which I've done now. I do need to soak the metering blocks, I bet there is some build up hiding in there.

You may have to play with the shooters and pump cams to try and get your 60 foot time back up close to the 750. You did not say how much slower they where? If your convertor flashes to 4800 RPM or more, I think you should have a good chance of making it work. The Final E/T is what matters. If you drive the car on the street alot you may like the 750 better for response and gas mileage? The outdoor temperature also affects Holleys/Clones alot and whats a good tune at 100 degree's is not good at 40 degrees. You can spend alot of money on jet kits, pump cam assortments, and different size shooters, but it is nice to have them at the track. As for as the 950HP's, a few of my racing buddies used them on SBF's that where not that radical, and they worked really well. I was surprised, as they seemed really over carbed, for their combinations.

Problem with the BG carbs is the damn rating system. Where you would think it would make life easier, it caused confusion because they rated them different than any other industry standard.

A 750, 850 1050 holley is rated on dry flow at 13" of mercury on a baseplate of matching size to the carb.
In short, a little high for the average real engine, but a standard that applies across the board.


BG rated the carbs as Flow as expected on an engine that would use the bore size of the carb. Soooo an 850 would flow 850 cfm on an engine of more than 400 cu in of displacement. It has nothing in common with a holley 850. The bore (throttle blade size) is completely different. A Demon 850 is more akin to a holley 950, and jetting requirements wouldn't be surprising that they were on the small side for a 460 engine.

the holley 950HP is setup pretty darn good out of the box (jetted a little rich, i think it was 74 squared and dual pv) it basically is a 750 venturi with 850 baseplate. i think they flow about 830cfm. the "950" is marketing hype not cfm

jc10000rpm wrote:the holley 950HP is setup pretty darn good out of the box (jetted a little rich, i think it was 74 squared and dual pv) it basically is a 750 venturi with 850 baseplate.  i think they flow about 830cfm.  the "950" is marketing hype not cfm

That would make sense, as to why they work so whell on the little engines. If they are 750/850 as claimed, it would be hard to get 950cfm from them, no doubt.  I would trade the BG off for a 950HP, myself, if anyone would swap, but they probably will not, as BG's don't seem to popular.

Update on the old Holley 750... Bought some Chemdip (which I don't think is as mean as it was 30 years ago) soaked everything, then put it in my crock pot full of anti-freeze that I use to clean the baked on castor gunk on my model airplane engines and cooked it for a few hours to make sure thing were clean and threw it back together, same floats, needle and seats. It no longer starts stumbling after 330', doesn't die after the finish line, runs almost a tenth quicker and it's up 2mph... No clue where the problem was, but it is fixed now.... Demon is back in the box again, it's ok for a test carb, and that's about it, anyone want to buy it???

Just had to get the demons out of it!