Inhaling Fords...

[KFreddy]

I've been using a Holley 750 3310-3 for about 700 miles now on a ZZ454 motor, performance has been split, sometimes good and sometimes bad. This carb either gives me insane, wheels spinning at 70mph, top end power but a low end dog or it gives me great driveability but the top end suffers over 4700 rpms. I've worked on the carb plenty and even turned it over to a mechanic to no avail. That being said I'm looking towards a BG 750 Speed Demon #1402010VE. Who has had some experience with this carb? How's it run out of the box? Does it have you sleeping well at night?

Thanks

[BB72CHEVKT]

Originally Posted by KFreddy

I've been using a Holley 750 3310-3 for about 700 miles now on a ZZ454 motor, performance has been split, sometimes good and sometimes bad. This carb either gives me insane, wheels spinning at 70mph, top end power but a low end dog or it gives me great driveability but the top end suffers over 4700 rpms. I've worked on the carb plenty and even turned it over to a mechanic to no avail. That being said I'm looking towards a BG 750 Speed Demon #1402010VE. Who has had some experience with this carb? How's it run out of the box? Does it have you sleeping well at night?

Thanks

My speed demon 750 double pumper did great out of the box but that was just on the dyno a few years ago. I new ran it in truck because it is still not in truck.

[jhow66]

What happens over 4700? No reason that carb should not work well on that engine. Got a 850 vac sec. on my 502HO-only had to change the tip in spring to a lighter one. What happens at slow speed?

[HavinSomeFun]

I am running a 400 mouse motor. Balanced, Lunati cam, 202 heads, trw etc, etc. The demon ran good out of the box. With a little tweeking as described in the manual that comes with it, it runs great and pulls hard to red line. Many of the features the demon offers makes it easier to tune and get dialed in.

hope that helps.

[RatPwrd72]

I had a box stock 3310 on my 468 that ran fair (13.10's all night w/3.08 gears and limited traction). I switched to 3.73's and a 2800 Stall converter, then decided to upgrade the carb. I went with the ProForm main body and Billet Secondary plate (allows jetting for the secondary). I also played with the jetting and the secondary springs. It pulls much harder and starts/idles great. Before the carb upgrade I shifted at 5400 RPM, because that's where it felt like it wasn't pulling real hard. Now, I shift at about 5900 RPM because that's about all the cam is good for. Definately worth the money IMO, save the $500 it will cost for the Demon.

[KFreddy]

Above 4700 the power just flattens out, it's still accelerating but not in a progressive sorta way, almost like it's running out of fuel. But I don't think that's the issue. I currently have the timing locked at full advance 36*, I did this to make certain it wasn't a timing/ vacuum issue. I started with 74/82 on the jets and had an 8 PV it didn't drive that well. Then I went to 68/81 and a 6.5 PV the motor ran like a raped ape above 2000 rpms but bogged almost stalling at WOT under 2000 rpms. I figured that it was the pump shot and changed the green cam for a blue one. With the leaner blue cam the bottom end is great but again I lost power above 4700, completely stumped, the squirter shot alone should not have effected the top end. Arrrggg...

[jhow66]

Have you changed squirter size? What is the vac. reading at idle in gear?

[RatPwrd72]

I jetted mine at 72/78 at 900 ft. elevation. I didn't mess with the accelerator pump at all. Started with a 7.5 PV and worked my way down to a 4.5. Idles great, accelerates with no bog and no hesitation. Timing is at 12 initial, 34 total, vacuum advance hooked up.

[KFreddy]

Squirter size is stock 30cc vac reads 12.6 @ idle in gear. RP72 try bumping that timing to 36* you'll be amazed.

Any one else have any demon experience?

[jhow66]

Have you played with the springs in the vac. pod? With just 12.6 vac the secondaries may be open part of the way at idle. Put in a weaker spring and up the squirter size until the bog goes away.

[tavenner13]

yeah i had a speed demon 750 mech. secondaries on my 462 and i had big problems out of the box with burrs on the baseplate causing leakage... but i made a few phone calls and within 2 hours i had a speed demon 850, slapped it on, and it started right up and ran pretty good. it took me a little time to figure out how i liked it dialed in and now it starts right up every time with no problems. only problem is the idle likes to stick up around 1200 RPM after you blip the throttle and thats very annoying, im still trying to get that sorted out i think it might be a vacuum leak somewhere