Blow Through Carb Turbo

[WarWagon]

What kind of mods are you talking about? The gaskets or things on the "Hanger 18" list like jet extensions and the like?

Any opinions on the hp limitations of it?

Mainly the throttle shafts and plugs in the meteing blocks need attention. The throttle shafts will leak fuel out and meter block plugs can blow out under boost. Oversized needle&seat, nitro floats, float bowl equalizer all should be used too.
The hp potential is limited to how much fuel can be flowed through the carb. A small venturi carb will pull fuel much easier even with a weak booster signal.

 

[WarWagon]

Should have no probems getting the primary circuit to flow enough fuel on a 3.0l v6 with 390cfm. It would be easy as swapping main bodies and throttle plates to make the 390 a 450 or 500 cfm if a problem came up with the smaller venturi.

 

[CTX-SLPR]

From reading around, these things are 390's in name only. Since they went on Busch 358cid V8's they generally have a ton of work done to them so they will actually work decently on the V8's. There were also mentions of needing to swap the metering blocks to undo a lot of these changes to make them run on motor that are supposed to have a 390 carb and I know I'd have to swap the butterflies since they are drilled.

Debating between one of these, a 500cfm 2-bbl with the normal mods, or trying out one of the secondary squirterless 450's. Don't have to make the choice right now as that carb is not a rare item per se but if I'm going to go 500cfm 2-bbl, I'd have to make plans on how to adapt it onto a 4bbl intake and how much hood clearance that would eat up.

Is the stock 2-bbl intake crap from an airflow and distribution standpoint?

 

[WarWagon]

390cfm is 390cfm... just saying, that particular carb has the small small venturi/butterfly.
The stock 2bbl intake is junk but the stock drawthru intake is worse lol.

 

[CTX-SLPR]

emailed the guy with the 390cfm carb on eBay and asked if it had adjustable emulsion tubes... no was the answer. That would have ment new metering blocks and throttle blades. Now the upside is that it had no choke horn and adjustable air bleeds already.

Still thinking an annular booster 600DP with sealing upgrades would be a good idea. I don't exactly need snappy tip in performance with the slick surface on the Salt. Such a large no mans land between the 390 and the 600....

 

[dr_frankenstein]

if it were up to me............ personally me.......... id run a dominator flanged 950. particularly a dominator flanged carb.

A.j.

 

[CTX-SLPR]

if it were up to me............ personally me.......... id run a dominator flanged 950. particularly a dominator flanged carb.

A.j.

Not sure I follow why?? If people are making 900hp on a 750cfm DP easily, why go for a domi on a 300-450hp effort?

 

[bison]

Don't forget a throttle return system/spring that counter act your boost pressures...Or you'll get a Run Away Car! The boost pressures will force the butterflies open an keep them there....(seen it happen on a twin turbo SB 70 nova )

I missed this before but boost pressure has no more effect on the throttle blades than vacuum in an NA setup for a given air speed which is determined by rpm and engine displacement. Air flow and pressure are different things. Pressure differential is what tries to keep them open. Running a small carb will just create a larger pressure drop at the throttle body as rpm increases and have the same effect with or without boost. If you removed all the rocker arms and closed all the intake valves and pressurized the intake to 200psi the throttle shaft would move either way with nothing more than the friction on its shafts against the bores to cause resistance.Time to brush up on your physics.

 

[dr_frankenstein]

Not sure I follow why?? If people are making 900hp on a 750cfm DP easily, why go for a domi on a 300-450hp effort?

This is why people think im nuts.

has nuthing to do with the physical size of the carb... but more of the pressure drop at which the carb will operate. Theres a reason why the Weiand intake has a dominator flange on it. I ran one on my NA motor for years before switching to draw thru. loved it more then my holley 450 any day of the week.