Thunder AVS? Or Performer?

[71chevylowrider]

Alright You carb gusy & gals, I need some advice, I'm no carb tuner & I'm gettting tired of playing/tuning my Demon carb, I'm about ready to buy a new carb & I need some pro's cons, advice on what to look for, my truck is mildy midified with an isky cam roller rockers, RPM manifiold, decent camel hump heads, ceramic hooker headers, hei, blah blah blah, I just want to jump in my truck & fire it up & go have fun/enjoy it. Has anyone her tried those new Thunder AVS carbs from edelbrock? I had an edelbrock 1406 on it before & it worked fine, but now that I've experieced how much faster my truck is with the DEmon carb, I wouldn't mind going with something a little better.

[fastwillie 696969]

i would go with the model 1407 750 cfm i bet that carb will hookup real sweet with that combo you got i wont use that thunder avs (wasted extra money) get the 1407 and run like hell

[71chevylowrider]

1407 huh? I'm probably gonna go with an electric choke since thats what I've been using, have you had bad experience with the thunder AVS? The perormer I had (1406) worked great, I'm just looking for something with a little more performace so I won't miss the power of the Demon.

[piecesparts]

I have one of the Thunder AVS carbs on my 383 motor. It is a 650 CFM carb and it is really an Edelbrock 1406 with the upgrade in air flow and the control plates on the secondaries. I like it as much as I did the 1406 that I used to have. Once you get the jets calibrated to your driving and the engine requirements, the carb is great. I went with this carb, because the 1407 that I had for awhile caused the truck to run sluggishly on city streets. It was the combination of my cam, rear end gearing(3.42gears) and truck weight. ALL of the sellers of carbs (Holley, Edelbrock, Carter, Barry Grant, etc) calculate motor size and their associated vehicle weight as to CFM size. The 750 gave me a great "Top End", but it was killing me on the street, where the most of my driving was being done. The 650 is the right size and it actually works better than the 600 CFM 1406 carb. I get 15 MPG with my truck and the 383 stroker/700R4/3.73 gears/27" tires. I did upgrade my gearing as I went through the carb changes.

[71chevylowrider]

Hey thanks Piece, that is some great insight/info, now that I've had my fun, (note to self I need new back tires) & gotton horrible gas mileage compared to my 1406, the Demon was only a 625, I just want to enjoy the truck, jump in & fire it up, I guess if I want no fuss no muss reliability, I have to go back to another 1406, I forgot to mention that I'm pretty sure the truck has 4.56 gears in it so it's pretty quick around town & feel light on it's feet (even though it really wieghs around 4,400lbs.) but is sucks on the freeway, I may want to talk to you more about your 700R4 install when I get to that point, anyway, thanks very much for replying, I really appreciate it, I know Carburetors are one of those topics that everyone could have a different opinion on, but if I get advice from people who have first hand experience with whatever carb they found worked best for them, I can use that info to help me make a educated decision, (another great thing about this website eh?) the truck is just too nice to keep having to mess with the carb. Thanks to everyone/anyone who is willing to put in their .02 cents.

[Bowtie67]

All new carbuators out of the box need to be adjusted, in some cases some more than others, Holley and Edlebrock carbs have a tendency to be on the lean side from the factory, while demons are usually on the rich side. The more radical an engine the more tuning required. From some experience with Demon carbs and from past listings on this forum,other forums and from a friend who dynos cars. The speed demon needs to be taken completely apart and fully cleaned/blown out, a lot of these had metal shavings in them from the factory, I have also heard about broken needle seets right from the factory. I have run two different Mighty Demons a 650 and currently a 750 and love them, the 650 I never had an issue with except minor jetting, the 750 on the other hand was a pain, but once issue where resolved it now runs very consistant. Even pushing out over 500hp out of my little 427sbc, 4.10 gearing and a 700R4 trans I can still yeild 15+mpg, if I can keep my foot out of it. Demons and Holleys are quite simular, most people think that while the engine is idling and running extremely rich changing out the main jets helps, both of these carbs have idle feed jets in the metering body that control the idle feed circuit, the main jets are for when you are cruising above a certain RPM even then the idle feed circuits are still used for idle and low speed rpm. There is no properly tuned carburators out of the box, some are close while others need a little more tlc to make them perform. There are a lot of guys out there who claim they now how to tune them, but unless that is pretty much all they do you are no better than taking your car down to the local lube & oil filter change shop and have those fresh out of high school guys fine tune the carb for all out performance.

[71chevylowrider]

I hear ya Bowtie, I actually bought this Demon used, & have been trying to get it dialed in for my application, I'm just tired of screwing with it, & am thinking of going back to the ol simple Edelbrock type carb & was wondering about the performance advantage of the thunder AVS series, or is it just more stuff you gotta play with/tune?

[70c10]

71chevylowrider, I would get yours rebuilt or get a NEW Speed Demon That carb of yours had been tinkered with before you bought it and I think that's the main problem. I love my Demon but you already know that

[Bowtie67]

Originally Posted by 71chevylowrider

I hear ya Bowtie, I actually bought this Demon used, & have been trying to get it dialed in for my application, I'm just tired of screwing with it, & am thinking of going back to the ol simple Edelbrock type carb & was wondering about the performance advantage of the thunder AVS series, or is it just more stuff you gotta play with/tune?

All the Gaskets are the same as Holleys, including the main jets and the Power Valve. You can get all the specs on the carb right from the BG web sight and put the carb right back to factory spec, they also have trouble shooting tips and recommended settings. As I stated above all carbs factory built (out of the box) are a general application and usually need some type tinkering. I am not sure how radical you combination is but this also dictates how much tinkering there will be with the carburation. Idle vacuum plays a deffinate role with holley's & Demon carbs due to the power valve, you dont usually have this issue with the quadrajet and Edle carbs because they dont use these. If the carb was used chances are you may as well have the wrong power valve in the carb if you havent changed it already. Another option and cheaper than buying a new carburator is to find a good dyno shop that the guys knows about holleys and Demon carbs and let him tune it. it is really worth the money if you dont have the expertise of the tools to properly tune them. I have the Inovative's LM1 wide band fuel ratio meter to help with tuning the carb as well as all the tools to drill the smallest air bleads. these cost far more than jumping on a Dyno, but doing multiple vehicles the tools will pay for themselves. Some of these Dyno guys after doing just one run may be able to make the changes needed the first time or get extremely close so that after the second pull they know if you have a real serious issue or put the final tweeks on to finish it up.