Serious Carb/Turbo decision... HELP

[66Sprint6]

I am currently running importkiller's (Dan's) holley 2300 350cfm carb on my car. He is bout to need it back and Im wondering what to do from here. I want to buy a carb that will work for my car now, and be great for my turbo motor pushin 10 psi later. Should I go with the 2300 350 cfm like the one I already have or should I bump up to the 500cfm version? Again, this turbo system will be BLOW THRU and I want to run concervative boost till I can beef up the bottom end to take more. I want the most out of that concervative boost tho using an intercooler as well. What do you guys suggest????? I already have the adapter for the holley, but what about a 4 barrel. I need somethin that will bolt on relatively easily too, hense why Im thinkin the holley 2300 series. Well, let me know, I need to know relatively soon in case I need to swap carbs. Any help would be greatly appreciated and I kow you guys are the ones to ask!!!!!!!
Matt

 

[Anonymous]

what is the ideal size carb for a n/a 200 anyone...anyone at all?

my experience with carbs is very very limited,

altho i do have a general rule of thumb, very crude but get's you in the right direction.

@ 15 psi... in theory, you double the cfm rate of ur cylinder head..
so you would expect a carbie needed would have to be able to support twice that of a carb for a n/a set up.

so taking that 10 psi is 2 thirds of 15 psi, you'd need a carb capable of supporting 66% more cfm then the ideal 200 carb.

so say you have a 350 holley (which i presume flows 350cfm??) on top, and that 350 holley is suited perfectly to ur n/a 200, add 10 psi you'd need a 581 (so a uprated 500 or a down rated 600 holley).

the above is purely an example.

like i said at the top i know absolutly jack crap about the nasty fuel dribling things so if i am wrong i'll stand corrected, but i am fairly sure that would be a good wway to look at it, its certinaly logical.

GO EFI!!! 8)

CHEERS.JOE.

 

[Anonymous]

what is the ideal size carb for a n/a 200 anyone...anyone at all?

my experience with carbs is very very limited,

altho i do have a general rule of thumb, very crude but get's you in the right direction.

@ 15 psi... in theory, you double the cfm rate of ur cylinder head..
so you would expect a carbie needed would have to be able to support twice that of a carb for a n/a set up.

so taking that 10 psi is 2 thirds of 15 psi, you'd need a carb capable of supporting 66% more cfm then the ideal 200 carb.

so say you have a 350 holley (which i presume flows 350cfm??) on top, and that 350 holley is suited perfectly to ur n/a 200, add 10 psi you'd need a 581 (so a uprated 500 or a down rated 600 holley).

the above is purely an example.

like i said at the top i know absolutly jack crap about the nasty fuel dribling things so if i am wrong i'll stand corrected, but i am fairly sure that would be a good wway to look at it, its certinaly logical.

GO EFI!!! 8)

CHEERS.JOE.

 

[66Sprint6]

What would it take to run a holley 600cfm 4 barrel? Would my adapter work? Also, would it be too much to run it on the car NA for a little bit?
Matt

 

[twentyover]

May want to keep a smaller carb on the car- give better throttle response at low throttle positions, and the increased airflow from boost will let have it flow more.

Don't know if I'm right, just thinking alound

 

[CobraSix]

600CFM would probably be too much for a log head that wasn't modified.

It woudl be good for a turbo running 15psi though IMHO.

Slade

 

[Anonymous]

Hey Matt,

On a Blow Through you run the same size carb that you had N/A. The air is compressed so there is no need for a larger carb.
On a Draw Through is when you need to greatly increase carb size.

The 350 Holley sounds like a great choice to me.

John

 

[66Sprint6]

Ive looked online and alot of people running carbed blow thru designes run holley 2300 series carbs. Not sure if they are 350 or 500cfm carbs, but they are 2300's. I like the 350 on right now so it would be nice to stay with one similar, but I can get a 500cfm for cheaper brand new. Would it be overkill especially for my NA driving or would it be better than the 350? Thanks guys, yall are really helping out!
Matt

 

[CobraSix]

John,

IIRC, yes, you flow VOLUME isn't going to change, but the flow WEIGHT will. Since you have more air (weight) going into the engine, you need more fuel. If you are pushing a 350 with a NA engine, a turbo running 15PSI would make your engine way too lean, since your carb is only putting out enough fuel for 350CFM at normal atmospheric weight.
If you didn't add more fuel, you'd burn your head and engine up.

The formula for superchargers is this (and should be the same for turbos, same principle)


CFM required= [(CIDxMax RPM)/3560]x{[(Max Boost)/14.7]+1}

For a 200 running 10psi, that comes out to be 423 CFM at 4500 RPM. When you take into account that a 2V holley only really flows about 280 (XECUTE can help here) it is way too small.

But, I could be wrong.

Slade

 

[xctasy]

In my opinion, a blow through is less of an issue carb wise than a draw through. I'd just use a 500 Holley 2-bbl, get it boost referenced, and get it jetted on a dyno. The worst thing you can do is run a turbo out of fuel at high speed. Its torture.

Remember, a turbo is a gas turbine engine that shares its combustion chamber with a piston engine. The carb is a primary feeder, and must run rich of optimum at its leanest in a turbo car. This is because a carb cant deal with difference in fuel/air density. EFI can, as the MAP or MAF sensor can signal a richening of the fuel air mix. This isn't the case with a carby. It's like comparing an early 286 PC to a Pentium chip PC.

The blow through can be the way to go. With a stock cast iron intake, you need to prevent the fuel boiling due to imense heat from the turbo. Blow throughs are the best compromise. The draw throughs on Buicks can be made to work well because the developement time they spent on the 2jet and Qjet carbs allowed the engineers to safegguard the fuel delivery. These turbo didn't contribute much to under hood heat, as it was mounted away from the intake in a big engine bay.

In most respects, trying to find the perfect combo with a carb is acedemic. Just engineer it to work, and be aware of the pit falls. Injection and turbos is just parts on parts, and is much more complicated. There is a vast array of systems and information available to wade through.

The carb set-up just needs a rising rate fuel pump, and some means of stopping float bowl implosion and air leaks around the throttle blade. That way, all the linkages can stay stock Holley 2300 set up. The dual advance distributor is needed to allow boost retard.

The Holley book by Dave Emanuel covers thE carb mods very clearly, and the V6 Performance book by Pat Ganhal is clear on the various carby turbo set-ups. These are early 1980 bookes, but a very practical.

Read, and feed

The modern EFI and turbo bookes a more a progressive dinner into massive expense. The level of specialisation needed to cover off ignition, timing, fuel delivery, manifold vaccum is very high. You pay up front for a technically superiour system, but to make it work, you have to understand more than with carbs.


The carby turbo is a problem child. But it can be safeguarded if you just follow through the basics.

I've been involved with my Cortina 2.3, and a 202 cubic inch Holden Torana turbo that a mate owned. Both were carby cars which had moderate boost. The six cylinder Holden was a very impressive machine, using a Bensons/ Normalair-Garret turbo with twin SU carbs but when my class mates sister failed to let it idle after a hard burn, it fried the turbo. Asside from that, it was a brilliantly reliable car.

The Cortina was poked when I turbo'ed it, and was in need of a re-build. It was LP Gas, which made the coversion very simple.

 

[66Sprint6]

Thanx X,
Seems the 2300 is the way Im goin, probably a 500cfm, but will it be ok on my NA motor with the mods Ive done so far? I think it would be, but you all are the ones that would know!!!! Let me know before I lay down the money on a new carb. Also, it seems my C4 is dyin out so I might have to push the turbo project back again and replace my tranny. Im planning on going T5. Will that tranny (possibly out of an SVO) hold up to turbo? I just figure if I keep the c4 and its slippin like it is,the turbo will destroy it. Thanx again and let me know what you guys think, I need guidance, lol
Matt

 

[Anonymous]

I think the T5 will hold up fine. Should be a nice compination.

John

 

[66Sprint6]

Yeah,
I figured if it could hold up to a turbo 4 banger it would be good enough for mine!! I am going to try the SVO one but if not a regular 4 banger tranny will work. Now i need to saaaave $$$. What about the Holley 500. Im real close to ordering, will it work NA for now??? Seems like it ought to be fine
Matt

 

[xctasy]

Seems the 2300 is the way Im goin, probably a 500cfm, but will it be ok on my NA motor with the mods Ive done so far? I think it would be, but you all are the ones that would know!!!! Let me know before I lay down the money on a new carb.

The stock 200 may be a little over supplied by the 500cfm carb. It won't be as ecomomical as a 350 carb. If you are trying to have a seamless transition or 2 or 5 year plan, then I'd go 350 Holley. On a 250, I'd go 500 cfm right away. The 350 has great economy, and is the ideal size for a 200. The Schjeldahl brothers at Falcon 6 Performance have affirmed that the Autolite is one of the better 2-bbl carbs, but that any increase in carburation is good. David and Dennis focus primarily on the ideal airflow based on the relative sizes of the existing hole in the head. No point in having 350 cfm going down a 1.5" hole, but a 1.75" log will really enjoy a good 350 cfm carb.


The December 2003 issue of the Hot Rod mag has all you need to know about turbo sizing and carb airflow demand.

Heaps of info on how to size your ricer or V8, nothing much for sixes, although they do have an awesome sizing chart which affirms TO3 60 turbos for most of our sixes. There are a few really helpfull formulaes for help on sizing your carb by the total airflow.

The latest issue has the formulae, while the online additon doesn't. That's why I spend 12 NZ dollars getting Hot Rod magazine. Truley the neatest souce of Americana bar FordSix.Com and Car Craft.

http://www.hotrod.com/techarticles/engine/113_0312_turbo/

Formulae One

Boost Ratio is (psi turbo pressure*14.7)/14.7

10+14.7 = 1.68, (before the loss due to air heating is taken out)
14.7

Formulae Two

The air flow required (in lb/min)is the boost cfm *0.07

eg. A 200 doing 5500 rpm with 0.85% VE needs 318 cfm, or about 200 hp net. With a 10 pound per square inch turbo boost, thats a 1.68 boost ratio, or 534 cfm theoretical. Enough for 333 hp net, or 374 hp gross. Thats 543*0.07, or 37.4 pounds per minute of air needed.


Formulae Three

lb/min = hp/10

eg 37.4 lb/min = hp/10, or 374 hp (gross, at the flywheel). Note this is for sizing a turbo or carb. It doesn't mean thats what its going to produce.

So if you could swing 10 lbs of boost, the sizing is that you'd need carbuartion to match the power potential. A 500 cfm 2-bbl carb is proven to be able to deliver 350 hp on a 289 V8 with the right cam.

Go for a 500 cfm 2bbl carb! It simple, cheep, and a 4-bbl wont fit a log head easily due to the porting and close poximity of the log to the rocker cover.

All other info can be got from here.

http://www.turbofast.com.au/TFmatch.html


Read up on this, and then plan you own attack. Like a lot of things, its better to be able get some info, mill over it, and then use your own judgement. Air flow is very theoretical, and it confuses lots of use. You don't need to understand everything, but you do need to know whats important.

 

[66Sprint6]

Well,
It still seems up in the air. I may have to hold my turbo project back a bit on account of my tranny crapping out. I will prolly do a t5 and then turbo later. I have talked to Mustang Geezer who is running a 500cfm on his 200 and I think Im going to go with the 500. All this is budget, so I will just get the 500 now, deal with the tuning until the turbo then itll already be there for my turbo project. If anyone thinks this is flat out a stupid idea, let me know, or visa-versa. Thanx alot for all the help guys.
Matt

Hey X, you got any idea about how much power my motor would make swapping from the 350-500cfm carb? Also, what about runnin a turbo at 10psi, T5 and electric fan replacing the big metal one? Got any ideas. Thanks alot man!!!!!!!!!

 

[xctasy]

..... I have talked to Mustang Geezer who is running a 500cfm on his 200 and I think Im going to go with the 500......... any idea about how much power my motor would make swapping from the 350-500cfm carb? Also, what about runnin a turbo at 10psi, T5 and electric fan replacing the big metal one? Got any ideas. Thanks alot man!!!!!!!!!

The Geezers Blessed Stang aint no stocker...she's got pistons, extraction and a great head!

The 500 cfm will add about 5 hp on 4-cylinder cars over a 350 cfm delivering all it can. The 500 can give up to 170 hp on a worked Pinto 2000. On a 289, 350 hp is possible apparenrtly.

As soon as you force 10 psi of air into it, the power goes up about 60% or more. Depends how it goes as a natually aspirated combo. If its as strong as Mustang Geezers, then bank on 240 hp at the flywheel after adding a well sized turbo. Well within limits of a correctly jetted 500 Holley.

If you use high boost draw throughs with Holleys, the fuel/air ratio gets unstable over 300 hp. Due to fuel centrifuging out, and the high air-speed with un- atomised fuel.

Stick with a pressurised 500 carb. It may not give you great mileage or economy on a stock 200, but it will work well onm a turbo 200.

I've not minced words over MG's set up. The porting is very good, and it suits the car really well. All worked 200 and 250's logs should have them.

 

[66Sprint6]

Thanx X,
Your right his car is anything BUT stock!!! Its incredible if you ask me. I think im goin 500cfm. I can deal with the tuning to set it up for my NA 200 for now. That way I dont have to buy another carb later, I want to try and do this on as small a budget as possible, lol. The new tranny however is going to set me back $1000 after parts etc is all tallied (seems to be what everyone has spent so far) and thats if I get the chance to do it soon. I will try and keep the turbo project in mind for possibly next winter or the summer after at the latest. Thanx again for the help, I appreciate it all!
Matt

 

[xctasy]

Grab David Vizards book on SOHC Pinto engines. In that, it has a c4 transmission build up. In NZ, a C4 rebuild is 250 bucks kiwi for just the parts. If you are prepared to bench build a C4, using Vizards notes and the Ford shop manual, you'll learn a wholw heap, and have comfort that it will take 300 hp with ease.

There are safeguards everywhere.


Understand that the C4 (and C5) is a fundamental perfromance trans that spaned from 1963 to the late 80's. In America, because you guys value social life and your own time more than Kiwis or Aussies, its more coomon for you to get a specialist to do the work. Thats fine and dandy if you have the money, and there are the best auto builders in the world in USA. But if you do it yourself, you could make three mistakes and still make a saving on a proffessional shop job.

I don't mean to disrespect and tranny builders here. But Vizards book hit the shops in 1984, and theres so much info that you could DIY easily if you decided to do it yourself.

My personal advice is to get another C4 (or the slightly longer C5) like yours as a stand-in, and then re-build one yourself.


Get some other advice. A 1000 buck trans needs to have a v8 clutch pack and all the better durability mods thrown in. You need to sight them before you get the trans in your hot little hands. A good C4 is a brilliant investment that you'll want to keep if anything bad ever happens to your ride.

 

[66Sprint6]

The tranny itself wont be $1000, the entire job of buying one, all the parts and putting it in will be about $1000 but its still $1000, lol. I will debate on either seeing if my c4 is rebuildable or what. It would be good to keep in case. I will see what happens when I get there )
Matt