Is this Holley a good choice?

[350kmileford]

http://store.summitracing.com/partdetai ... 294839063+

Is 600 cfm too much? It seems really high to me, but I do plan on running a ported aluminum head and turbocharger. Since that is a 'supercharger' carb, I assume that I don't need to make any modifications to the bowls, jets, etc??

If this is a bad idea... recommendations?

 

[bigcatchdaniel555]

A 200 really cant take advantage of a 600cfm 4 bbl. A 500 cfm 2bbl pushing it and it only flows 390cfm in 4bbl standards. Go with the 390 cfm holley 4bbl.

 

[Does10s]

If you're going to drive it on the street a lot, get a smaller carb. A Holley 450 or 390 or even better yet go with the Edelbrock 500.
If you're going to run a turbo and a blow-thru carb, stick with a Holley.

We've tried a 600 without much luck, but that may all be camshaft related. So after our cam swap we'll try again.
Runs good with a 450 though!
Will

 

[kirkallen143]

The 390 is nice and about the size you need, this would be my recommendation for a 200ci blow-thru engine. It has all the air bleeds tapped, which will play a major role when tuning your application.

http://www.holley.com/0-80507-1.asp

Kirk

 

[350kmileford]

That seems like a really good idea, but does anyone know where I could get one for about half the price?


http://store.summitracing.com/partdetai ... -0-80507-1

If I were to go with this carb, how much modification would be required for a turbo application? Would I still need to change out the jets and other parts?

 

[Bort62]

You aren't going to be able to order any sort of carb that will just bolt on and work. No matter what, you are going to have to fiddle w/ jets etc to get it running right.

Unless you just get lucky, which does happen - but I wouldn't count on it.

 

[350kmileford]

So I'm basically going to need to spend a grand for a turbo-modified carburetor? If that is the case I may reconsider. This makes me sad.

 

[Inline6Merc]

No, you dont have to spend a grand. Purchase the 390cfm Holley. You can make a few modifications to it for very small price. Does10's can tell you want modifications are needed.

 

[addo]

How far would you get with TBI and a Megasquirt for the same money?

 

[350kmileford]

I was thinking the exact same thing :-/

 

[wallaka]

So I'm basically going to need to spend a grand for a turbo-modified carburetor?

...No. That's not what he is saying. He is saying that you will have to learn to tune and tinker with ANY carb you get. You can't just bolt on a carb and expect it to work perfectly, even a stock carb on a stock engine. You have to modify settings, jets, etc. to be sure it is optimal.

All of these expensive carbs you see have one thing in common. They have to be tuned to the individual engine. There is no 'one size fits all', and especially not for a turbo or blower car.

If you don't think you are up to fiddling with jets, PVRC's, or idle air correctors, you need to either educate yourself or have someone else build your engine. The mods needed to make a carb suitable for blow-through use are simple.

I repeat, even if you have a carb built for you, there is no guarantee that it will work right out of the box. Go to http://www.theturboforums.com and read some of their stickys in the carbed forum. There is also a tutorial on how to modify a Holley four-barrel for boost.

 

[tjnavyblue]

What are the main differences between the Holley 450 and the 390? Does the 390 have mechanical secondaries? It seems this is important for blow through.

Forum experts: Given the option of a 390 or a 450 on a decently modified and blow through turboed 200/250, which would you choose? And why?

 

[kirkallen143]

So I'm basically going to need to spend a grand for a turbo-modified carburetor?

I repeat, even if you have a carb built for you, there is no guarantee that it will work right out of the box. Go to http://www.theturboforums.com and read some of their stickys in the carbed forum. There is also a tutorial on how to modify a Holley four-barrel for boost.

Here, read this:

http://www.hangar18fabrication.com/blowthru.html

Depending on the carb, you might have to fork out $40 for jets, PV, and drill bits, but that will get you running safely with the blow-thru mod's you make to the carb.

REMEMBER THOUGH, KEEP IT RICH AND TOTAL TIMING LOW!
-or-
you will go through what we all have, learn from our mistakes.

Good luck.

Kirk
ps. If you are using the stock head, do not install a 4V carb, stick with the 2V.

 

[350kmileford]

I am saving for the aluminum head. A harder task then originally planned . .

 

[350kmileford]

Ok what do you guys think about this?

http://store.summitracing.com/partdetai ... toview=sku

Holley makes only 2 390 cfm, 4 barrel carbs. This is the other one. About half the price. It will require more modifications and is a little less 'hardcore' performance..... but do you guys think I will be ok with this?

 

[Bort62]

I might be wrong, but I don't think you want to use vac secondary carb in a blow-through application...

What do you mean by "hard core performance"?

I would be reticient to use a 4bbl on one of these motors, regardless of the head. Go w/ a 350 or maybe 500 CFM 2bbl and keep velocity through the venturi up.

 

[wallaka]

Definitely go with mechanical secondaries. And remember: a 390 cfm four-barrel flows more than a 500 cfm two barrel. Might be harder to tune on a smaller engine.

EDIT: That being said, Does10's is using a 450 cfm mech. secondary Holley.

 

[350kmileford]

I was hoping that the vacuum secondaries might allow a more progressive fuel flow, i.e. better mileage around town. I am planning to turbocharge my engine, so I don't think I'm allowed to complain about gas mileage.

 

[wallaka]

Well, not much vacuum to work 'em when you are boosted. Like, none. It would do the exact opposite of what you want. It would probably be hard to open the secondaries with a screwdriver with 10 psi on the diaphragm holding them closed.

At least, that's the way it works in my head

I don't think that they use venturi vac to run, but if so, they might work. There might be too much pressure directly on the throttle plates to work correctly. They might stay open all the time.

It's safer to stick with what is known to work.

 

[Bort62]

Well, not much vacuum to work 'em when you are boosted. Like, none. It would do the exact opposite of what you want. It would probably be hard to open the secondaries with a screwdriver with 10 psi on the diaphragm holding them closed.

At least, that's the way it works in my head

I don't think that they use venturi vac to run, but if so, they might work. There might be too much pressure directly on the throttle plates to work correctly. They might stay open all the time.

It's safer to stick with what is known to work.

That depends entirely on where the diaphragm is referenced.

Keep in mind that w/ forced induction, everything is relative. You don't need or even want a bigger carb on a blow through turbo, because the volume of air you are moving (through the carb) is the SAME as if it was NA. Size the carb for the engine's air requirements NA, and that carb will work well for your under boost. Some may argue that you actually want to undersize it slightly...