Blown 383, carb???

[jbw0127]

Need some advice from someone with some carb knowledge.

My head is swimming!! I've had Demons, Holleys, quadrajets......all with naturally aspirated motors. Now I got this 383 with a Weiand 142 that I need to put a carb on and want to get it right the first time! I believe the motor will be capable of 500-550 hp and will run a auto-overdrive tranny.

I'm just like anybody else in that I want my cake and eat it too......want the best performance, best street manners, as good as economy as I can expect......etc...etc...

I was thinking the new Edelbrock 800 AVS because I read somewhere that the Carter carbs worked well on blown motors. Holley has supercharger specific carbs, but I'm not sure what makes them special. Called holley tech the other day and was on hold for 30 minutes only to get some moron who was no help at all!

Vaccum secondaries work good on a blown motor?

Is a double pumper (holley,demon) worth that much more performance and is it worth the trade off in fuel economy and street manners?

Anyway.....I've blabbed enough....anyone out there with some sound advice!!??

[bigjimzlll]

Call Ty at TPC racing. He is very knowlegeable. I had him build a custom Holley for me..and its worked flawlessly. He is very helpful.
http://www.tpcracing.com/race-superchargercarbs.html

[tubbedII]

I'm not great with carbs, but I do know some things. Vacuum secondaries for a blower on the street is a great idea. About the DP, I've switched twice from Carters to DP's with the same CFM and it's a night and day difference on performance. That's a lot of HP you are going to be pushing with the 383, I think that a nicely worked over 750 would suit it well (Double Pumper). How much boost are you putting out with the 142?

[COBALT]

I recently saw a blown hemi with the 870 blower. The carbs (yes there were two) were two double-pumper holley 750s. The venturis and boosters had also been modified to allow better air flow versus the stock metal surfaces. For a mini blower I agree totally. I think a customized holley double-pumper with vaccuum secondaries could be just the ticket.

[cableguy0]

they dont make a double pumper with vac secondaries. if your worried at all about mileage you might as well take the blower off now because you arent going to get any. i would run a worked over 750 double pumper personally because you will get the best performance

[Tom]

You guys really think 750cfm of flow is enough for a blown 383? I would reccomend a 750 for a NA 383, with a blower I would want at least 800cfm. I guess a worked 750 could flow that much though....

[cableguy0]

i worked 750 will do it with the choke horn removed and the body milled it will be fine

[tubbedII]

I think so because of the size of the blower he has. There isn't any other info like heads, cam and what not, but I'm guessing this isn't a high dollar motor with real high flowing heads. The 142 does not produce too much boost, but can with a pulley change. But if he has a smaller blower, I don't think he's trying to pull off 15lbs of boost anyways.

[Chevy67Tk]

I have 2 X 750 Holley DP’s on my 383 6-71 and its to much, it will load up if idling for a long time and think it hurts a little on the launch but breaths very well mid range and upper end. I just couldn’t pass on the deal I got for them, and they will work just fine till I can afford injection.

I’m partial to Holley’s because that’s what I grew-up with and have learned on, theirs nothing wrong with Carter they have a very good reputation.

My carb’s are the supercharger specific from holly; they recalibrate the idle air circuits. With the egg beaters flailing around under the carb it causes changes in the flow of air under the carb and to get the proper mixture changes during idle to were the butterflies just start opening there needed to be changes in the orifices. They also re-port the power valve to a port on the side of the carb so it can be referenced to manifold pressure below the blower and install a valve that opens at a higher vacuum.

Yes vacuum secondary will work with a blower but you have to doe some spring swapping to get then to open when you want.

[jbw0127]

I appreciate all feedback!

A little more info about the motor to clarify that this is a little more upper end ( at least for me ) then just a "thrown together" stroker motor.

I'm using Performer RPM heads with 170 cc intake ports which will provide very good intake velocity at lower RPM's. The rotating assembly is all eagle forged with a internally balanced crank and H beam rods with SRP forged pistons. Cam is a Isky flat tappet hydraulic with 490/510 lift and shy of 240 duration, 114 lobe sep. Static compression is just shy of 9:1. The blower will probably make about 4 lbs of boost with the stock pulleys. I could increase boost but the problem with this little blower is that it becomes more inefficient the faster you spin it. It's border line too small for this motor, but I got a great deal on the blower and heads together from a guy that was bailing on his project (they are brand new).

Ideally I would like to put a centrifugal charger on with a multi point fuel injection system and shove some more boost in this thing cause it will handle it, but that gets pretty $$$$ and I'm in this thing quite a bit already and not even close to done with the rest of the truck!!!

I talked to the guys at Barry Grant today and they were very helpful. After getting all info (and I mean ALL) on the motor they recommended a 750 Mighty Demon for Blower applications. The company with the best customer service wins in my opinion!!! That stupid carb will set my back $500 +, but what the hell!!!!

Thanks for input and anyother is welcome!!