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Old 08-16-2009, 09:47 PM
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ZZ4 Demon Carb

Has anybody tried the demon 650 carb that is designed for the zz4 crate engine? I was going to use a 600 edelbrock for fuel economy and driveability but if a demon will give good power and still work really good I might look closer at it. The price of the edelbrock is hard to beat though!

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Old 08-17-2009, 06:41 PM
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I have a Holley Street Avenger 670 CFM on my ZZ4 in a 1975 Corvette and I really like it. It starts easily, runs strong through all four gears with no hesitation or bogs, and gets decent gas mileage when driven normally.
Terry
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Old 08-18-2009, 04:39 PM
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HOLLEY ALL THE WAY!

My high dollar Mighty demon 750 was replaced by my crusty holley 750 vac. sec. and I'm tickled!!

Even with a wideband and countless hours of tuning the Demon was still "possesed!"

The old Holley recipe just WORKS. The ol Quads are nice too, if you have a knack for them.
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Old 08-21-2009, 07:46 AM
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Quote:
Originally Posted by hotrodf1
HOLLEY ALL THE WAY!

My high dollar Mighty demon 750 was replaced by my crusty holley 750 vac. sec. and I'm tickled!!

Even with a wideband and countless hours of tuning the Demon was still "possesed!"

The old Holley recipe just WORKS. The ol Quads are nice too, if you have a knack for them.
The Mighty Demon 750 is going to flow a ton more then a Holley 750 and an engine that runs correct with a 750 Holley the Demon would be too big and there would be tuning issues. A 750 Demon will flow a little over 900 cfm.
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Old 08-21-2009, 07:57 AM
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Quote:
Originally Posted by Tech @ BG
A 750 Demon will flow a little over 900 cfm.
So the obvious question is: "Why is it rated at 750?"
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Old 08-21-2009, 08:00 AM
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Quote:
Originally Posted by cobalt327
So the obvious question is: "Why is it rated at 750?"
It follows the industry standard for a 1.400 venturi and 1 11/16 butterfly. The added airflow comes from our patented air entry which is very similar to what we did when we were porting the old Holleys.
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Old 08-21-2009, 08:18 AM
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Quote:
Originally Posted by Tech @ BG
It follows the industry standard for a 1.400 venturi and 1 11/16 butterfly. The added airflow comes from our patented air entry which is very similar to what we did when we were porting the old Holleys.
There's also an SAE industry standard that (to my way of thinking) takes precedence in this case.

I believe it would be far more useful to know what the flow was at 1.5" of Hg than by sizing it by the dimensions of the hole in the carb. To call your carb a 750 when it flows 900 cfm or whatever, is misleading- size of butterflies and venturi's aside.
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Old 08-21-2009, 08:28 AM
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Quote:
Originally Posted by cobalt327
There's also an SAE industry standard that (to my way of thinking) takes precedence in this case.

I believe it would be far more useful to know what the flow was at 1.5" of Hg than by sizing it by the dimensions of the hole in the carb. To call your carb a 750 when it flows 900 cfm or whatever, is misleading- size of butterflies and venturi's aside.
Problem is you can't make everyone happy. In a perfect work that might be the case but lets say we did that and a guy buys one of our 650's that flow 750 thinking he just bought a 750. He measures the venturi and sees it is 1.280 and now HE feels misled. We do tell people when we give carb recommendations what the flow is as well as the size so it's not like we are trying to keep it a secret. This subject has been covered time and time again as well in many forums including here.

Here's one for you to look at... take a 950 Holley and look up what the dimensions of it are and then compare them to the dimesions of their 850 and let me know what you find.
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Old 08-21-2009, 09:02 AM
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Quote:
Originally Posted by Tech @ BG
Problem is you can't make everyone happy. In a perfect work that might be the case but lets say we did that and a guy buys one of our 650's that flow 750 thinking he just bought a 750. He measures the venturi and sees it is 1.280 and now HE feels misled.
Would it hurt to include an actual, factual measurement of the flow, as well as the dimensions???

If you market a carb as a 750, that's sufficient, in most cases. If you also include the dimensions that's fine, too. But to extrapolate the dimensions into a (wildly inaccurate) CFM measurement- and then publish that CFM "guesstimate" as fact- does the buying public a disservice, IMO.

It would take no stretch of the imagination to realize that just the size of a hole is not the do-all end-all of what that hole will flow. To "dumb it down" because some dude might measure it and it's not the same as a Holley is not the way to go about it. If it flows "X"- say it flows "X"! It is a no-brainer, IMO.

Quote:
We do tell people when we give carb recommendations what the flow is as well as the size so it's not like we are trying to keep it a secret. This subject has been covered time and time again as well in many forums including here.
I have NO DOUBT it has been asked any number of times- as well it should. And it will continue to be asked (rightly so) in the future, until the decision is made to either give an accurate representation of the carb's flow, or the other companies adopt your unorthodox methods- but I wouldn't hold my breath for the latter of the two.

Bottom line- If it flows 750, say so. If it flows 900, say so. To call it a 750 because the holes are the size of Holley's 750 is just wrong.
When was the last time someone called your tech line and asked for a carburetor by the size of the butterflies and/or venturi?

Quote:
Here's one for you to look at... take a 950 Holley and look up what the dimensions of it are and then compare them to the dimesions of their 850 and let me know what you find.
What of it? I didn't look it up- it does not matter. The 850 is an 850, ditto for the 950- as it was (presumably) correctly measured by a manometer, et al- not because the holes were one size or another.
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Old 08-21-2009, 09:19 AM
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Quote:
Originally Posted by cobalt327
Would it hurt to include an actual, factual measurement of the flow, as well as the dimensions???

If you market a carb as a 750, that's sufficient, in most cases. If you also include the dimensions that's fine, too. But to extrapolate the dimensions into a (wildly inaccurate) CFM measurement- and then publish that CFM "guesstimate" as fact- does the buying public a disservice, IMO.

It would take no stretch of the imagination to realize that just the size of a hole is not the do-all end-all of what that hole will flow. To "dumb it down" because some dude might measure it and it's not the same as a Holley is not the way to go about it. If it flows "X"- say it flows "X"! It is a no-brainer, IMO.

I have NO DOUBT it has been asked any number of times- as well it should. And it will continue to be asked (rightly so) in the future, until the decision is made to either give an accurate representation of the carb's flow, or the other companies adopt your unorthodox methods- but I wouldn't hold my breath for the latter of the two.

Bottom line- If it flows 750, say so. If it flows 900, say so. To call it a 750 because the holes are the size of Holley's 750 is just wrong.
When was the last time someone called your tech line and asked for a carburetor by the size of the butterflies and/or venturi?

What of it? I didn't look it up- it does not matter. The 850 is an 850, ditto for the 950- as it was (presumably) correctly measured by a manometer, et al- not because the holes were one size or another.
When I and my tech guys do a carb recommendation we are strongly looking at venturi size and butterfly size as this has an effect on the signal any given carburetor will have for an engine. A carburetor will only flow what an engine needs and at that point venturi and butterfly size become real important.

In regards to my question to you since you kinda side stepped it here is the answer for the others reading the thread. A Holley 950 has a 1.400 venturi and a 1 3/4 butterfly while their 850 has a 1.560 venturi with a 1 3/4 butterfly.
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Old 08-21-2009, 09:40 AM
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Barry Grant makes it very easy to find the carb needed for any specific application,they have an online guide;
http://www.barrygrant.com/demon/default.aspx?page=5
As well as tech help,either on line or via the phone;
http://www.barrygrant.com/demon/defa...ge=techsupport
Or Tech @ BG himself is very helpful,and is on other forums than just this one.As far as I'm concerned,how they rate their carb's isnt that important,rather,taking the time to provide all your specs and taking advantage of their experience & resources is time well spent.When I was wanting a new carb,Tech @ BG was more than happy to help me,and answered my many questions,and helped with getting additional parts.Sometimes,you have to "read outside the box",dont be scared to explore new ways of doing things,(get your head out of the sand,so to speak).Personally,after using both Holley & BG carbs,I would never consider using a Holley again,the BG out performs by a considerable margin.
I would also add that I'm sure Tech @ BG is a very busy person and puts in lots of hours at work.Rather than criticise his help,we should be saying a big THANK YOU for taking time out of his busy schedule to offer his help.I havent seen any tech help from anyone from Holley on any other forum that I am a member of.
Guy
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Old 08-21-2009, 09:45 AM
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Quote:
Originally Posted by Tech @ BG
In regards to my question to you since you kinda side stepped it here is the answer for the others reading the thread. A Holley 950 has a 1.400 venturi and a 1 3/4 butterfly while their 850 has a 1.560 venturi with a 1 3/4 butterfly.
Again- what of it? If anything- that's a great reason NOT to judge a BG carb's CFM by what a Holley carb measures! Thanks for making my point for me.

As for "sidestepping" anything, I'll just take a pass on any further discussion w/you in re the 750 cum 900 CFM BG's. If that's your companies shtick, so be it.

That it does not sit well w/me is a moot point, as I do not use BG carbs, anyway. Not because of the inaccurate CFM rating, or any other real or perceived fault of BG, mind you- simply because I'm fine w/what I currently work with.

Should a BG happen to come my way, however- I will keep this idiosyncrasy of how the BG carbs are rated as a highlighted note.
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Old 08-21-2009, 02:18 PM
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Cobalt327,why dont you re read my post,then read the original post.If you cant say anything constructive,then please dont say anything at all.
Guy
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Old 08-22-2009, 12:09 AM
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Quote:
Originally Posted by Guy Hiltz
why dont you re read my post
You mistakenly assume that I read your little post in the first place- I didn't and haven't.

You see, Tech @ BG is plenty able to answer any of my concerns, which he did.

BTW, why would I have any interest in what you have to say about something as technical as carburetion, when you are stumped by the replacement of a HORN. ? LOL
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Old 01-17-2014, 06:18 PM
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Demon is junk !!

Been building Hot Rods since 1957. Love Chevy crate engines.
Since the ZZ4 came out, I have done many in Street Rods.
Tried the Demon with ZZ4 part number.
After break in, I did the pedal to the metal on a one mile stretch.
Throttle stuck open !!!!!!!!!!!!!!!!!!!!!!!
Some teen ager that assembled the carb forgot the jesus clip by choke shaft. Shaft is stepped, counterweight, dropped, then angled & wedged throttle open.
Called Demon in Georgia to alert them about liability...."no way" was the answer.
Installed a Summit #MO8600VS, dual feed AFB 600 cfm.....I am in love .
Last count was 11 used on ZZ4s.
Always use a 1" phenolic spacer for about $16 on Ebay.
Just ordered another today for a '33 coupe/ZZ4
Jim, School of Hot Rod Hard Knocks, since 1957
410 535 1933
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