Ford Mustang Forum banner
1 - 11 of 11 Posts

·
Registered
Joined
·
230 Posts
Discussion Starter · #1 ·
Hello. I am kinda scoping out carbs for a possible change and I was wondering id anyone is running a Barry Grant Speed Demon (mechanical secondaries) on a small block or knows someone how is? I am kinda just wondering how well they work on the small Fords.
 

·
Registered
Joined
·
2,244 Posts
Your better off, with a Holley Double Pumper with mechanical secondaries. Had a Barry Grant, had problems with adjusting the carb ran too rich. Returned the carb, they said it may have been defective and couldn't get that one right either. Returned that one, exchanged it for a Holley Double Pumper with mechanical secondaries. Had no problems with adjusting, and car runs fine idles great starts right up and when you stuff your foot in it, it goes with no problems. Buy the Holley, and save yourself the aggrevation, Mike. SCT Tuner.:bigthumbsup
 

·
Registered
Joined
·
1,976 Posts
If it helps any I'm using a Demon Jr. 625 (single pump, vac. second >auto) and have had no problems, ran 2 different holley 600's prior and couldn't get them to run right for me. The Demons are nice from the smoothed bores down to the built in sight glasses for the bowls, it is my favorite carb I have used so far. Car was a 289 and ran well with the 625, just stroked to 333 with AFR 165's so we'll see how it does with that setup, don't expect it to fall short as i think I'm as high as I need to go CFM wise. BG rates their carbs conservatively, my 625 would probably be rated as a 650-700 in Holley.
Jon
 

·
Registered
Joined
·
53 Posts
Jonk67 is right on that. If you got a high duration cam, Barry grant carbs will make full use of it. I had trouble with the holley 600's as well. The street avengers are good carbs though. Barry Grant 625 would be a good choice for the sbf.
 

·
Registered
Joined
·
2,244 Posts
That's it a 650 CFM Holley, not a 600 CFM. A 650 CFM Holley is the most you want to go, with a small block double pumper though with mechanical secondaries not vacuum. Should be perfect, for what you have. These guys running Demon Carbs, are just a few of the fortunate ones that got a good one. I know too many people, that have had nothing but trouble with Demon Carbs, Mike. SCT Tuner.:bigthumbsup
 

·
Registered
Joined
·
396 Posts
Demon carb

I was running a Demon 650 DP mech sec on a 302 with Winsor Jr ported and polished heads (1.94I/1.6E), X303 cam, Victor Jr intake ported to heads 1262 intake port.

I felt I never really got the tune right on the carb, wasn't sure I could blame it on the carb. I rebuilt the sucker and replaced the power valve up to a 10hg unit to finally get a smooth transition. During the rebuild I found TWO porosity spots in the aluminum that I had to plug up!! Urgh poor quality!!

It seems to me that the accelarator pump didn't squirt clean and left raw un atomized fuel to pool. You could see it trickle out after a throttle burp. My pistons always looked horrible after just a few runs and street time (about 10 pulls and 1000 miles).

I use a A/F ratio gage in my car, I could get it to stay in the proper zone and the plugs looked good, so I assume that I was having drop out due to the big cam, intake, heads on a small CI engine turning low RPM's on the street.

Having never run anything else on this engine I couldn't tell you Holley vs. Demon. I can tell you this, MAN oh man once the R's got up to 4K to about 7K hold the heck on, boy was it fun~! Can't wait to get my 377 running, think a month or two out now, I will put the same carb on it and see how she does.:happyhapp
 

·
Registered
Joined
·
47 Posts
Ive ran demons, holleys, edelbrocks, carters and demons are by far the best for the money, I'd run a 575 speed demon vac sec with annular boosters.

I spent 750.00 on a custom made prosystems holley 950hp for my 408, ran like crap, I bought a reman mighty demon 750 for 400.00 and it runs way better, like it was made for my engine and the WB 02 sensor says its right on.

The reman demons on ebay are a great but as they are gone thru twice.
 

·
Registered
Joined
·
181 Posts
yeah i have a Holley Double Pumper and its great, easy to adjust, looks good and when secondaries are tuned right its amazing!
 

·
Registered
Joined
·
392 Posts
I have a Speed Demon 575 on my 289. Was rich out of the box, being a pill to tune. First problem I had was a metal chip under the primary accelerator pump check ball. Would always stumble off the line. Still not quite right. Will mess with it a bit more, if I can't get it the way I want, I'll go back to a Holley. As someone else said manual = mechanical, auto = vacuum.
 
1 - 11 of 11 Posts
Top