alright i think i have found the perfect carb for my 300-6. Holley makes a 390cfm 4bbl, will this work well it will be going on an offy 4bbl intake.

 

Most people consider that to be the perfect carb for a 300 that is relatively stock.

 

thats whats on mine and i love it

 

I've heard that the only problem with the 390 is the possibility that a "backfire=blown power valve" (this from a "weber lover". Other threads suggest that the 390 may cause a flooding effect on the #3&4 cyls (the ones right next to the carb base).... makes some sense to me that this could lead to a backfire. I've also read of other users who are thrilled with the 390 setup. I'd like to hear more on this as I'm debating the same move, with the Weber 430 cfm 40idf as the "other" consideration.

 

yeah im getting some cash here soon so ill be putting that on whith offy intake soon. The 150 will ride again!

 

I had a holley Mechanical 450 4BBL and on my relativly mild 300-6 it ran out of steam just past 3500rpm (it would start to build vacumm @ 3700rpm which means it was too small) I went with a edelbrock 500cfm 4bbl and it works better and and Got better mileage out of it. the Edelbrock 500 it starts to build vacumm at 4500rpm which is where mine runs out of the power band.

 

This is a problem on any of the "old design" Holley carbs. It is easily fixed by installing an inexpensive kit in the base plate before installing the carb.

I don't see how a 390 carb could cause a rich condition in #3 or 4. Maybe if it isn't set up properly it would do that, but so would anything else. Most rich conditions in individual cylinders are a manifold problem, not a carb problem.

A 390 on an average street engine flows enough air to feed roughly 260 hp. This is the carb used on Busch Grand National engines and they make around 500 hp.

Has anyone tried the new Demon Jr. 525? I have installed several of the 625's, and 2 750's. They have all performed much better than the Holley they replaced except one of the 750's, but it replaced a Holley 600. The kid that owned the car was an idiot and insisted on a 750 even though we recommended the 625. The car never did run properly, but that was a result of being over carbed, not the fault of the carb itself. The Demons are much more forgiving when they are too large.

 

My jury is still out on which carb to go with. Where can I get some info on the Demon jr. 525? Who sells them? I've ALWAYS been a Holley man but when someone says something else is "better" or "the best" i'm willing to look into it. For MY particular setup, the 390 would be the easiest - my manifold has a 4bbl. adaptor on it. Clifford pushes the Weber 40IDF 2 bbl., but I can't get them to talk to me about it.... I'd like to take a look at the Demon.

'just got off the Jegs site, they have the Holley 390 4 bbl/ w vac. 2ndarys - $280 + $14 for "kit" ( filter & vac 2ndary springs) part # 510-0-8007 (+"K" for kit). They mention that this is"recommended for lighter vehicles" lighter that what? Does that sound like a reasonable price?

again, thanks

 

http://www.bgfuel.com/demoncarbs/

If I were to need another carb, i'd probably go with the demon just because noone I know has one on a street vehicle


-=Whittey=-

 

Summit sells the Demon with electric choke for about $215. All Holley tuning parts are compatible with the Demon, but the bowl gaskets are not.