Demon carb....

How are the Demon carbs....I have a chance to get one fairly new, it's a 670cfm and I can get it for $150.00....are they good carbs?
I am tired of the Holleys, the guy that is the Holley guru here said I need a 650cfm double pumper on my engine after he heard it run (was tuning my 600cfm for me) I would go with the Demon if it would be an improvement over my 600cfm Holley.

 

I've never tried a Demon but have heard guys like them. Plus I don't see why a mild 289 would NEED to have 650 cfm. 600 should be more than enough flow unless you are revving it to 7000 rpm. Dosnt't sound like much of a GURU to me. Maybe he is just reccomending a new carb and a certain model that happens to be a 650cfm?

 

Well I have such bad luck with carbs...maybe just me, one of the 600 Holleys was new when I got it, it is the kind you can't adjust the floats externally, it has been a PITA since day one, the other I bought from Eric Mathis racing carbs (the Guru) it is 600cfm Holley that can be adjusted externally...the car runs great in some aspects with the "new" one and crappy in other aspects, like wont idle right but when I punch it...it's whoaaaaa takes off like crazy......the guru 600cfm Holley idles properly but doesn't have the same feeling when I punch it, feels kinda sluggish compared to the "new" one.....so thats why I was asking.
So I was thinking I need something bigger or maybe a double pumper like the guru suggested.
And yes I have tried to tune the "new" carb but it still is a PITA at idle.

 

Sounds like it is still in the tuning. Bigger wont fix anything, and a double pumper is just a different style of carb.

I would stick with the New 600. Get it to idle good then start tuning the accelerator pump, adjust when the secondaries come in, or maybe try a different power valve. there should be a holley chart out there or a tech to help you get the righ tpower valve for your combination instead of the old trial and error method.

Oh and FYI, most carbs come out of the box tuned for a small block chevy 350. On smaller applications where less fuel is needed you will need to lean it out a bit. Sometimes this is just a power valve switch but may need smaller jets to get it right.

 

If the guru didn't get this one right,,, well, I wouldn't be buying anutter from him

 

Demons are based on Holleys.


So if you don't like them go get a carter/edelbrock.

 

I have 650 street demon on my maverick. 302, bored .030 over, stage 1 cam, typhoon intake. I love it. Everything is adjustable from the outside of the carb. They recommend that the idle mixture screws be at least 1 turn out from the seated position. Mine are 1.25 turns out and it runs great. It is a little bigger carb than I was going to go with, but it works pretty well.

 

demon

Ive got a couple and would not let one go for $150. 670cfm sounds a lil large but as in the previous post you might have to turn the mixture screws out a lil extra and possibly go up in jet. The increased fuel will compensate for the less airflow on your engine in comparison to a 370ish inch motor that this carb would probably be optimum. If your 600 is a vacuum secondary going to a double pumper will use more fuel at cruizing speeds. The performance on the Demons compared to a Holley have been awesome but ive never tried driving my Demons on the street.

 

Sounds like you should try an edelbrock. When i was driving my old cars i had the same issue with holleys finally went with an edelbrock and never touched it again. Holleys work great for performance but tend to be effected to much by weather changes and dirt in the fuel. I have also saw some strange issues with demon carbs.

 

I have got to try something else, I am growing tired of changing back and forth from one to another....the guru built one hesitates to the point of stalling the engine when I give it throttle from a dead stop thru all RPM ranges, I can be doing 45 and stomp it and it almost stalls out and that wont do at all....I just replaced the accelerator pump just to see if it helped and it did not change a thing, the "new" one I can stomp with no hesitation at all and great acceleration, but it wants to pop and spit at steady cruizing speeds like it's starved for fuel, I know I have to do something, it actually ran great with the 750 DP Holley I had on there but took off and traded, was afraid of cylinder washdown, now I just want it to run decent, as for the eldebrock they are $349.00 at the parts house, don't like that idea, I KNOW I have no vacuum leaks and if it was timing or electronic it would do it with both carbs not just one or the other, both carbs could be crap.
Everything from the pump to the carb is new including the filter, the gas tank was installed new by me and all the lines were blown out with compressed air, particles or dirt is not an issue.
I don't know what internals this engine has, it runs VERY strong and sounds tight so I did not go into it, I was told it has the larger rod bolts and flat top pistons under the 54cc chambered heads, it has evidence of being gone into (old parts in the trunk of it when I bought it)

 

One thing that might help is to buy a book on tuning holley carbs. Im a firm believer that if you cant work on cars you dont need an old car. Theres to many gurus out there to take your money otherwise.

 

Well this is my 13th Maverick, 14,15 and 16 are in the yard, not the first time I have had Holley carbs, not the first time I have tuned one, but the "new" ones have far less adjustments you can do.
I think I just found the problem......IT'S Number 13 j/k

 

I read this guide when I was sixteen, six years later there hasn't been a Holley that I couldn't tune easily.

It's a really good guide, read it once then read it again.

http://www.bob2000.com/carb.htm


Holley made them less adjustable because people who had no clue how to tune kept giving them a bad name.

 

Yup, pretty much the same thing. Just nicer.

I borrowed one for my car on old engine, and it was a little rich out of the box. It wasn't mine, so I didn't do any adjustments.

Only complaint I had was it had a lot of resistance on the throttle pedal. It felt like there were extra springs pulling it back to idle, and didn't snap open and closed like my edelbrock at the time did.

 

Ok well I have studied this problem most of the morning....... then went and put FRANKENCARB together, twas easy, just took what I thought was the best and put it together, used the throttle body from the "new" carb and put the adjustable fuel bowls on it from the "guru" carb...went for a test drive and it runs great no idle problems, no hesitation and no popping at cruizing speeds
I did however have a LARGE problem on my test drive.........................................................................................................................
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I ran out of GAS!!!!