#6487348 - 07/29/12 08:51 AM
Re: Help me choose a carb for my imaginary 408w
[Re: ScottStaypuff]
|
UglyValiant
Post Master Sr
Registered: 10/09/02
Posts: 6364
Loc: Milwaukee, WI
|
Sizing is determined in part due to the weight of the vehicle...the heavier you are, the more you'd want to undersize a carb. The lighter the car, conversely the more fudge factor you've got in oversizing it.
Likewise, gearing makes a big difference too...taller (numerically lower), the more you've got to "get it right" in terms of proper carb sizing whereas lower (numerically higher) gears again, will be fine w/ being oversized.
In general, if you've got an auto vacuum secondaries are more desireable, whereas with a manual, you can go either way.
When it comes to sizing and torque converters, again, lower stall you'll need to err toward undersized. Oversized is okay with loose/high stall T/C's.
Those are your general "rules of thumb" that are nice little guidelines from afar. If you've got a Big heavy truck w/ high gears, stock t/c, auto along with small cam and stockish heads, a 408 could be happy with only 600 cfm. Got a light little mav with 5.13:1 gears, 4000+ stall t/c, 250+ duration cam with a ton of overlap (all BIG cams wil have that despite any lsa), hogged out 225 AFR's...well, then you could go with a holley dominator 1050cfm carb.
They work well for as far as that goes...but in your case, we want specificity, so: What we really need though is the duration and LSA of your cam...I can find the flow numbers for ford AFR 205 heads and all that it'll be easy to determine the approx power it'll make. From that, determining gears and proper torque converter will tell us what the desirable carb will be.
But, I can pretty much guess that the best will likely be a 850 mechanical secondary. The fact is being light, you'll probably also be running a 3000-3500rpm stall t/c, and probably 3.91-4.10 gears at a minimum...
As light, loose, and geared as your car would be, you'd be giving up a ton of throttle response to go vacuum secondary.
Could you go 950? Sure...but for what? Maybe 5 more HP over an 850? Not worth it.
Choke? Well, you could get one with choke...even do an electric conversion...but is it worth it? Nah. After a little idling and keeping it going with the throttle, and a little hesitation and bucking for the first few minutes of driving, the car warms up and drives great...and starts great the rest of the day afterward. Just go without choke and pay less doing so.
Since my truck is an auto with low stall t/c, I went with vacuum 750...but I may switch to my 850 mechanical after I put in the high stall t/c...we'll see. One nice thing I get w/ the carb I've got is that I can really tune this thing to make excellent fuel mileage...and for what it is, It get's that...relatively speaking. I can pull down about 15mpg or so taking it easy, which for a truck with some 425-450 flywheel hp isn't too bad. Not really what I was going for though, lol...but neat never-the-less.
_________________________
1979 Dodge Lil' Red Express Truck
1989 Shelby CSX (#500/500)
The most powerful production minivan money can buy.
|
|
Top
|
|
|
|
|
#6488466 - 07/29/12 10:28 PM
Re: Help me choose a carb for my imaginary 408w
[Re: ScottStaypuff]
|
UglyValiant
Post Master Sr
Registered: 10/09/02
Posts: 6364
Loc: Milwaukee, WI
|
Neither of those approximate "tame" in anything, lol...at almost any cubic inches for that matter.
Let me ask, how fast do you want to go? Given those were the cams you are considering, you should NEVER be considering a vacuum secondary carb...seriously.
You're getting into racecar territory... and I'm not talking about the crappy MX-3 variety. With cams at this level (and required heads, compression, etc) plan on a minimum 4.10 gearing and 3500rpm...but it might work better to say 4.10/4000rpm. This done right with the first cam could easily be a 10 second car...not a very streetable one mind you...but streetable is a relative term, right?
I'd actually start to consider more of the dominator series carbs at this level.
Based on what you probably want based on the desire to keep the gears and keep the stall around 2500-3000rpm, I'd probably look at a cam around b/w 276-284 roller (some of the smallest solid rollers) or 236-244 @ .050 duration. With that head, those gears, 2800-3000rpm stall t/c and around 11.0:1 compression you'll have a mean sounding engine that should live happy with a regular holley mechanical secondary 850cfm carb, and run into the 11's w/ traction/good suspension.
_________________________
1979 Dodge Lil' Red Express Truck
1989 Shelby CSX (#500/500)
The most powerful production minivan money can buy.
|
|
Top
|
|
|
|
|
#6491709 - 07/31/12 11:25 AM
Re: Help me choose a carb for my imaginary 408w
[Re: ScottStaypuff]
|
hustler
Post Master Sr
Registered: 01/09/00
Posts: 6095
Loc: Seattle, WA
|
I ran a BG Race Demon 850 with annular boosters and mechanical secondaries. I replaced it over a regular Holley 750 w/electric choke, vacuum sencondaries. I loved the 4 corner adjust-ability the carb had. I picked it up used on CL for $250 3 years back and later sold it for 500 after I switched to EFI, but if I was to go carb again I would look for another one. I'm not sure maybe someone else can answer if the Holley HP have annular boosters. They are the way to go vs the cheap dog-leg, annulars have better atomization. I had great throttle response even at LOW RPM and it was overcarbed on a big headed standard stroke 351c. I also ran a 1" HVH tapered spacer, helped as well. The units had replaceable venturis as well, only problem is BG went out of business last year.
Also use a Super VIC intake, they are the hot item with the windsor strokers over the last few years. Just not a fan of dual planes and cringe when I see them at shows. Go big or go home 
|
|
Top
|
|
|
|
|
#6493281 - 07/31/12 07:02 PM
Re: Help me choose a carb for my imaginary 408w
[Re: hustler]
|
ScottStaypuff
Post Master Supreme
Registered: 03/05/00
Posts: 27826
Loc: Thailand
|
|
|
Top
|
|
|
|
|
#6494250 - 08/01/12 08:52 AM
Re: Help me choose a carb for my imaginary 408w
[Re: hustler]
|
UglyValiant
Post Master Sr
Registered: 10/09/02
Posts: 6364
Loc: Milwaukee, WI
|
Just not a fan of dual planes and cringe when I see them at shows.
But therein lies the thing: Whichever one uses should be wholly suited for the purpose intended. Sure, I've got a hot engine, but because I've intended to run it in a full-size pick-up w/ stock 3.55 gears running pump premium, I've changed a couple things about the build.
Specifically, if I was building for a small, early dart (2600-2800lbs), I would have been remiss not to have gone with another 1-1.5 pt of compression, bigger cam, carb, and the aforementioned single plane intake. But that same engine in my current truck would not be a very easy/streetable combo.
But I do agree...given what the maverick is trending toward, it'd be silly to use a dual plane intake...the cam size, heads, everything all point toward a big single plane...
_________________________
1979 Dodge Lil' Red Express Truck
1989 Shelby CSX (#500/500)
The most powerful production minivan money can buy.
|
|
Top
|
|
|
|
|
#6498517 - 08/02/12 04:49 PM
Re: Help me choose a carb for my imaginary 408w
[Re: ScottStaypuff]
|
hustler
Post Master Sr
Registered: 01/09/00
Posts: 6095
Loc: Seattle, WA
|
I shouldn't have made such a blanketed statement, dual planes do have their place especially with trucks and automatics. A big 408 will want to breath and move a lot of air. It was fairly common to read about 351w builds on corral for years and people would put tiny port iron heads and dual plane manifolds and wonder why they ran like dogs with 50 more cubes over a 5.0/302 combo. They basically added a boat anchor over a 302. 50 more cubes wants to breath, and in a 408's case 100 more cubes over a 302. Yeah you can swap heads between a 302 and a 351 but the 351 can create velocity even with the larger ports.
I never got a chance to take the pantera back to the dyno with the Race Demon 850 but seat of the pants told me it was faster and more responsive. I know it is pretty common to hear single planes are less streetable or that they give up too much power on the low end for a street car. That was proven a lot in dyno tests on little 302's and 351ci motors. You are talking a 408 though, big block cubes essentially. You want to pull stumps and roast tires or do you want to hook and watch the car keep pulling. A 408 is going to make a ton of torque for the street regardless whether its a single or dual plane. The defining factor will be 1: your valvetrain setup 2: how much street use are we talking (weekend cruiser with track use or daily driver) and 3: how high you plan to turn the motor ultimately. A 408 doesn't have to be wound up hard to make power, but a 408 moves enough air a single plane would still have sufficient velocity to make a ton of low end power on the street.
When I hear 408 build there is no concern for gas mileage, this is out to make as much power as you can out of a small block and keeping it in a smaller package to fit in a car.
when i picked up the pantera it was my first go at a single plane small block naturally aspirated. I would never go back at this point, even though there are no real options with my set of heads for a dual plane. If you want to create a sleeper like denmah a turbo is actually good not just for power but they quiet the exhaust as well. But they add more stuff to break, limited access to the motor, meaning more shit to take a part when stuff breaks. hell i bitch about pulling the discharge tube on the blower nowadays and the stupid one piece longtube headers to get at the starter and plugs. I don't want to kabash the turbo deal, but there are a lot of things to consider and realistically how often you will get to work on the car. Get the Neon finished first then consider a turbo windsor because that will take a lot of your time. A local forum has about 4-5 guys who talked about a turbo windsor and at some point all of them sold the parts and cars and bailed.
If you want to build an exotic ford windsor I can give you plenty of ideas.
|
|
Top
|
|
|
|
|
#6499432 - 08/02/12 11:16 PM
Re: Help me choose a carb for my imaginary 408w
[Re: ScottStaypuff]
|
UglyValiant
Post Master Sr
Registered: 10/09/02
Posts: 6364
Loc: Milwaukee, WI
|
So overall can we agree carbs are less maintenance than a diy efi/turbo system, or at least "easier" maintenance?
As far as annular booster....and dual planes for that matter.
The overall peak torque difference will not amount to much. The highest I've ever seen, dual plane vs. single plane was a 15 ft-lb difference peak, but usually you're talking about a few-to-5 ft-lbs difference peak to peak. The difference is usually in the "area under the curve" that everyone gets geeked about.
As far as annular, it's really about improving the signal at all amounts of airflow, including low rpm's. Peak torque shouldn't be markedly different but area under the curve will improve...and tuneability.
Dual plane to single plane, area under the curve isn't as big a concern in a build like yours...HP is the only concern. Seriously...all you care about is HP (old rule of thumb: build for HP, and torque will take care of itself). Here's the deal...will a dual plane outperform virtually any single plane on an engine from 1500-4500 rpm and thus almost always have higher "average power"??? Absolutely. But your engine properly configured to a chassis should be running a 3-3500rpm stall t/c anyways, so most of the dual planes "advantage" is lost to the slipping converter which will buy you a ton of advantages in it's own right. Then the area where you want the power, and more importantly will be using it in acceleration, it won't be there with a dual plane. Absolutely 100% go with a single plane.
As far as your concerns of "stalling out", it won't. Why? You'll properly configure the car with a good quality high stall t/c. The guys that have trouble are the ones with too little converter that doesn't want to let their "hot engine" (ie, high high HP) idle at the 1200-1300rpm it really would like to idle at.
Really, this is what I'd tell you to do if I was spending your money and hearing what you really want:
-Go with a 408 w/ ~11.5-12:1 compression ratio. Get the necessary items that it'll need to rev (ie, maybe good main bearing caps, definitely a girdle, definitely use studs vs bolts, good line hone, h-beam rods, etc)
-The heads you've chosen are a minimum of what you want...upping to the 220's is a possibility.
-solid FLAT-TAPPET cam might be better...sure, it'll sacrifice a little power to solid roller, but not much. And it'll be happier on the street for much longer. Go with a cam specing 255-260 @ .050, 106 lsa. The best thing is how much cheaper it is too...
-Go with a single plane intake built for 4500 (dominator) carbs
-Go with a 1050cfm 4500 series carb
-High quality ignition
-Run a 3800rpm stall t/c
-Make sure you've got a good drive shaft, u-joints, and a d/s loop
-Make sure you rebuild the rear leaf springs and add-a-leaf and maybe add traction bars (ghetto, but done right, effective) or caltracs.
-Quality, strong limited slip rear such as lockers.
-Make sure you've got roll cage and other frame stiffening device
-Good DR's
There...this is what could be a 10 second car that would be quite liveable on the street. Given it's a 9", most the axle stuff (excepting it's limited slip device if it has any) should be quite adequate to begin with.
_________________________
1979 Dodge Lil' Red Express Truck
1989 Shelby CSX (#500/500)
The most powerful production minivan money can buy.
|
|
Top
|
|
|
|
|
#6510137 - 08/07/12 09:35 PM
Re: Help me choose a carb for my imaginary 408w
[Re: ScottStaypuff]
|
UglyValiant
Post Master Sr
Registered: 10/09/02
Posts: 6364
Loc: Milwaukee, WI
|
Any significant advantages other than weight?
You have to ask, is the cost difference worth 20hp...
_________________________
1979 Dodge Lil' Red Express Truck
1989 Shelby CSX (#500/500)
The most powerful production minivan money can buy.
|
|
Top
|
|
|
|
|
#6521736 - 08/13/12 12:12 PM
Re: Help me choose a carb for my imaginary 408w
[Re: ScottStaypuff]
|
hustler
Post Master Sr
Registered: 01/09/00
Posts: 6095
Loc: Seattle, WA
|
That was a neat article, I can't wait to get my IR setup done. I'm surprised the ProComp stuff isn't cheaper. Kinsler makes a few SBF/BBF IR setups for different heads/deck combinations, and I had heard they were in the 4k range new. I would think the Procomp stuff should be in the 2500 range before taking a chance on their knockoff parts.
I found my setup on a sprint car classifieds section used so you can make dreams happen. You just have to know where to look. EFI SBF stuff shows up once in a blue moon as there is a lot of older mechanical injection chevy equipment but the sprint car guys mostly used the yates style heads and not the traditional inline heads the windsors in streetrods have. I got mine for $1200 it just needed some horns which I promptly measured and found an ebay seller who sold hilborn stuff as well. I needed the adapters for the horns as well so I had to shell out another $500, but I still got the whole setup for 2k. Much less than new.
This one is for a Yates style head but you can see what they go over with mild/light use.
http://www.ebay.com/itm/ws/eBayISAPI.dll...c#ht_500wt_1180
Here is a guy I met who was selling some parts locally. Twin Turbo Aluminum stroker SBF with a Kinsler IR and custom sheeetmetal upper. Pretty exotic.
Here is a BBF Kinsler setup
http://www.youtube.com/watch?v=RaN165eLgYU
http://www.youtube.com/watch?v=-TKwuAs81eU&list=FLCv_XUgG9PuPOs-AZTUtfgg&index=27&feature=plpp_video
Here's the spider single plane setup I was going to run on my 357c spare motor I recently sold. I kept the intake and sold the shortblock.
Here is the Kinsler swapped on the heads.
Edited by hustler (08/13/12 12:25 PM)
|
|
Top
|
|
|
|
Moderator: auxilary, The Mad Paki
|
|
What I'm not sure of and probably could guess is I only have 28 spline axles. Driveshaft is a stocker too. 
