Need carb size and brand advice

[pparaska]

I've searched and see that some people are using the Proform 750DP carb, others the BG carb. Anyone using a Quick Fuel carb? I also want some particular advice on carb size - the tradeoffs being having enough carb signal, enough to make power at and near redline, but also to have good drivability and therefore tunability.

 

I have a 10.3:1 406 ci SBC, with Canfield 215 heads, 275/279@.020", 244/249@.050", .57/.577" lift, 112 LSA solid roller cam, running a Victor Jr intake. Desktop Dyno thinks this thing will be putting out 500+ hp. When this engine was together before with the stock 400 block (I'm assembling it now with a Dart block), the cam was quit mild. Hardly any lope, lots of low end torque. That was with TBI fuel injection using a 700cfm Holley TBI and a megasquirt. I'm going to start the engine out on a carb though, for several reasons. One is to be able to have the engine dyno'd easier, the other is to not melt it down during breaking with lean fuel maps, etc. and not having a big enough TBI (and not wanting to buy one, as I will move LATER to either a CrossRam Offy manifold with 2 670 TBIs or a Hilborn injector manifold converted to EFI).

 

I need a carb. I have experience with Holleys, so I want to stay with that and not go down the learning path for another style carb (i.e., Quadrajet, Carter, Edelbrock, etc.)

 

First, I don't want to go broke with a $600+ carb here.

 

The application is a my 2800lb 240Z with a manual trans (G-force enhanced T-5 with 2.95 first gear) and 3.7:1 limited slip with 25" tires. A double pumper is wanted. Mostly street, some road race track days, a few drag runs. Drivability is very important. I'd like to have a choke, but that isn't paramount. I'd just make due with a throttle-up solenoid if I didn't have a choke.

 

Calculators tell me a 750 to 900 cfm carb is needed. I've heard the typical 750DP holley flows more like 700cfm wet. So I wonder if I should look at an 830 carb. This is especially true I would think, if I went with annular boosters. One carb that comes to mind is the 5423020GC BG Mighty Demon, 825cfm, Annular boosters http://www.barrygrant.com/demon/default.aspx?page=... The other one I am looking at is the Quick Fuel SS-830 Super Street carb . It has an added benefit of a choke. Same with the Proform 850cfm Street Series carb.

 

Of course, there is the Holley HP series stuff too, but the others above offer a good bit more tunability (replacable idle feed restrictions, some with tunable emulsion feeds and PVCRs.

 

I imagine all of these carbs, even the Proform ones are pretty good pieces. IMO, with Holley you end up paying for the name, and get less tunability even though you are paying more.

 

Any brands/models to stay away from?

 

Thanks in advance.

[jt1]

Pete, I'm running a Holley HP830 annular on my junk. It picked up 30 ft-# in the midrange compared to a 750dp, and about 20 hp on the top end. I've been very pleased with it.

 

John

[v80z]

http://www.4secondsflat.com

 

Call and talk to Don 541-942-5920

There is a carb sizing guide on his site as well.

[dr_hunt]

I run a 800 cfm aerosol billet by C&S specialties on the 350 and I run a 900cfm aerosol billet by C&S also on the 406. IMO your going to be looking for at least an 830cfm to get the most out of your combination. annular discharge boosters offer the best signal. aerosol billets top that by a few hp on the dyno but are pricey. check out http://www.candsspecialties.com

[Forces]

IMO, stay away from the edlebrock performer series. I have read (on this site) and other forums that when compared to other aftermarket square bores, they are pretty much junk. I have FOUND by using one that they are correct, not to mention that their tech dept. sucks. The guys you end up with on the phone are useless as tits on a boar and sound like they are reading right off of a 'trouble shooting' guide with no prior experience with carbs.

 

"Some guy" told me that id your looking for a good carb, look for billet bodies. Something about billet aluminum being less pourous than cast aluminum and doesn't interupt the fuel flow.

 

This will probably replace My edlebrock on an engine with a similar build to yours...

http://www.barrygrant.com/demon/default.aspx?page=10

 

I think you might be a little overkill on 850CFM. Bigger isn't always better.

 

With an engine pushin 500+ HP, spending $600 on a carb might not be a bad idea, if your buying a quality product.

[Mikelly]

Pete, I've got a 750 double pumper you're more than welcome to try... But I tend to agree with the others here... You'll need to start thinking about the cubes you're feeding and I think a 900 would be more sufficient for your application...

 

As to the comment about Edlebrock carbs, I think for a daily driver, they're decent and reliable, if you're using a mild cam with good vacuum, like in stock type applications. If you are running something more radical, even a mid level cam, they can be hard to setup. The Edlebrock is probably going to get you only 85% of the power a Holley will, but it will be more consistantly drivable in changing weather conditions.

 

That's been my experience in the past anyway...

Mike

[fastzcars]

Pete, I just purchased the BG mighty w/ anguler booster's and I have to say that i really like it. I had the Holley 3310 vac sec carb and I couldn't get it to idle much lower than 1000 rpm. But when I installed the BG, it idles down to 750 rpm! Although I did have to change out the boosster skirters from 31 to 45 to eliminate a bog under heavy acceleration from a dead idle. PLus the fact that it has all of the adjustment's I could use. I'll have to take my car to a dyno to tune it in.

[pparaska]

Dr hunt - that looks like a great carb - I only wish I had a spare $1000 to buy one with!!!

 

Forces and Mikelly - I agree - no Edelbrock for me - I'd have to buy all the tuning stuff anyway - not going that route.

 

 

Thanks, all, for your feedback. I can see that the BG may be a good way to go. The Barry Grant Mighty with Annular boosters is about $550 at Jegs and others. The SS-830 Quick Fuel is only a bit less, $515. The Proform, which I believe has less tunability, is $450. Not a HUGE difference in prices, and they are all a bit different. Actually, if I am going to be looking at the Mighty Demon, the Quick Fuel Q or Professional series carbs are a closer match, and 6 to $700.

 

I am leaning towards a BG Mighty Demon, probably an 850 with annular boosters.

 

I just need to remember that I will have no choke . Maybe I can hire a gnome to sit on the fender and hold their hand over the inlet when the engine is cold, LOL. Seriously though, I have one of Holley's idle-up solenoids and I will just set it up with a switch so I can hold the rpm up at 1500 or 2000 rpm while it warms up.

[Guest Saylore]

I understand your relutence to spend the money on a carb you only intend to use as a break- in piece, you might look into a predator 9000 series carb. It is a variable venturi carb that is able to flow from 390cfm to 930cfm depending on the motors air demand. It only has seven moving parts, and the mixture is adjustable by changing an internal cam, which can be done without removing the carb from the engine. It is a good piece for tuning a new engine as it takes the carb tuning out of the equation, so you can concentrate on the timing and cam dial-in. You can not be to lean or rich as the fuel is metered in to match the air flow. You can usualy find them on ebay for around $150 and the rebuild kit runs about $65. Go to predatorcarb.com for the whole run down or you can contact my for more info.

[pparaska]

Saylore, thanks for that input. Will these work well on a street application?

The predator is kind of like a huge SU carb (variable venturi) - ahhh - my Z might have a V8 with a huge SU type carb. LOL

 

One concern is that it probably won't fit under the hood with an air cleaner since I am using a Victor Jr. A Holley just barely fits there with a 3" high, 14" drop-base air cleaner.

[Michael]

Pete, by way of comparison, I e-mailed the Barry Grant tech-line for advice for my application. I told them that mine was no daily driver, seeing maybe 200 miles/year on the street, that it weighs 2600 lbs (about right) and should have its torque peak at 4000 rpm (probably about right, too). The rest you already know. Well, the recommendation came back today: "750 Mighty Demon P/N 5402010GC". The recommendation is reasonable, but probably errs on the side of conservatism. The fellow said that "this carb is capable of 900 cfm..." Well, he's right - but at what pressure drop? Even a 390 CFM Holley 2-barrel can flow 900 CFM, given enough pressure drop - and consequent VE losses.

 

What are your thoughts on downleg vs. annular boosters?

[pparaska]

Michael, thanks for the info. I am going to call and talk to the people at BG and Don at 4secondsflat.com and get into a discussion on this.

 

I "read" that annular boosters are better at atomizing the mixture, and better at part throttle and idle.

[pparaska]

The guy at BG, who seemed very knowledgable (didn't catch the name) suggested a Mighty 650 mechanical secondary. Saw no need for the annular boosters, due to light weight of car and manual trans. Interesting. He said it would flow upto 830cfm. I questioned at what depression, and he said at 1". He said that they name the carbs based on industry standard throttle bore size, but the way that the carb is machined (venturi entry, etc.) allows them to flow much more air than others. One thing that bothers me was that no questions were asked about the manifold I'd be using or the head flow.

 

jt1 - what size is your "junk" engine - displacement? Cam?

[Mikelly]

Still got that 750 double squitter you're more than welcome to borrow...

 

Mike

[pparaska]

Thanks, Mike - I may just do that.

 

I spoke with Don at FBO (4secondsflat.com). Don has been at this stuff for many decades. He independently suggested the 650 Mighty Demon mech. sec. He advised to use jet extenders and notched float. If I go BG, I will buy through him, if new.

[jt1]

Junk engine is a 355, 10.6:1, Canfield 195's with light cleanup, ported air gap, Comp solid roller something like 248/252, 580/586 on 110, S&S's, MSD ignition. The 830 annular noticably fattened up the midrange, to be honest I can't tell much difference on the top end although the dyno did. If you want to try them, I've got a good 700dp that's been cut & polished, or a spare 830 annular you can borrow.

 

jt

[pparaska]

Thanks, jt. How long of a period of time would you like to loan the 830 for? I will probably not have the engine ready for a few months, and would want to use it for at least a few months after that.

[jt1]

Right now I don't see any problem with that. It's quietly gathering dust on the box in my shop. Let me know when you're getting closer, and we'll work it out.

 

John

[pparaska]

Thanks, Jon. I'll let you know when/if.

[dr_hunt]

Pete, I have a C&S aerosol billet 800 alky carb with bypass log attached. If your interested in running alky. Comes pre-jetted and ready to run, no tuning necessary.