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Old 08-24-2012, 12:53 PM
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New Demon "Street Demon" 625cfm carb

Just thought I'de share my thoughts about this new carb since there seems to be little info on it out there so far. Demon Fuel Systems*-1900*-625 Street Demon - Ball Burnished Aluminum
I have a 59 Chevy Wagon w/ 350hp 350 SBC that had a Holley Street Avenger 670 on it. I went thru all the typical BS with trying to tune the stumble that carb is known to have. Ended up way rich on the primary jets, plus a good amount of tuning to the accel pump to get most of it away. It wasn't perfect by any means, but it was something you could deal with. Stomp on it and it was great.. the stumble was still there on light throttle regular driving however. The fuel milage sucked with the primary's as they were too.
I have had good luck with the Edelbrock carbs and drivability and was planning on going that direction, just never got around to it over that last year or two.
Soooo... I saw the ad for this new Street Demon 625 and it looked like it might fit the bill.. something more along the lines of the Edelbrock, but with smaller primarys so the fuel milage should be decent. You can look at the ads for the carb to see all the details.

Demon Fuel Systems*-1901*-625 Street Demon - Polymer with Ball Burnished Aluminum

Anyway, ordered one up with the composite fuel bowl (link above), as I live just outside Death Valley and we can see temps up to 120 occasionally. I had issues with heat soak on the Holley, so the plastic fuel bowl sounded like a good idea.

Here's the good with the carb so far.... The throttle response is nothing short of excellent. No matter what throttle setting, how light you roll into it, or how quickly you stomp on it, it does exactly what you would expect. After all the Holley issues and just living with some of them... the throttle response of the new carb is a breath of fresh air. Milage has increased as hoped (from 12mpg to 15mpg) thus far. Overall performance is very good... in fact, it may be better than the Holly was. The car seems to go thru the gears quicker... but that could be wishful thinking. I have ZERO complaints about how the carb performs in any instance.
I've had no issues with heat soak at all, and we've had a week or so in the 115 degree area. The Holley would be hard to start when hot, this carb, no issues.
Lots of easy adjustability. I like how easy it is to tune how quickly/slowly the air door for the secondaries can be tuned. I'm a fan of metering rods and did swap out the factory ones for a set with the initial section one step richer.

Here's the annoyances thus far... The ads show that the carb is all setup for different Chevy trans kickdowns from the factory... T350/400, or 200/700r4 areas for hookup. That was great and needed....BUT when I got the carb and went to install, that's when I discovered that if you have a Chevy throttle linkage, you need an optional part. First time I've had a carb that didn't have the big hole for a Chevy throttle. That alone sucked, as I had planned on having it usable that same day, and that wasn't going to happen. (seems stupid to set it up for Chevy trans but not throttle)
So I hooked everything else up... and then went to put the air cleaner on and dicovered it wouldn't fit. The elec. choke sits very high on the side of the carb and the regular reliefs in a low rise air filter base wouldn't work. I noticed then that Demon sells an air cleaner just for this carb and it's goofy choke position.I ended up ordering a 1/2" air cleaner spacer to fix the problem and still use my same filter.
The linkage location on the throttle with the optional Chevy throttle part was far enough away from the Holley location that I had to buy some additional threaded stock for my adjustable linkage to get it to fit correctly.
Let's see..what else.... Oh yea... the fast idle adjustment for the choke is accessed thru a hole in the back of the choke, facing the firewall. It's about impossible to adjust without a mirror.
The linkage to the choke plate is in the way of removing the metering rods on one side of the carb, so you have to remove a TINY E-clip to move the linkage. It's so small and right at the carb opening that it's scary to remove. I made sure to have a magnet right at the area it was..just in case.

I think that covers my initial impressions. Main thing I would like to see changed is for the carb to come with the Chevy throttle linkage hookup....or at least somehow make sure any ads show that it is needed.
Got any questions that I can answer.. fire away.
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