Carburetor Advice

[ben23f]

Hi Everyone,

I am at the stage where I need to get my carburetor rebuilt for my patrol.
I am just trying to figure out how I should proceed. I have 2 carburetors at the moment both needing rebuilding.
The first is the original Hitachi VHA model.

The second is a Stromberg but I don't know what model it is or how to find out.

I was just wondering what people thought about the two? Which would be better to go with? I want one that will drive smoothly and with better performance.

Thanks

[RiverPatrol]

Other Australian members have stated that the Stromberg is a better carburetor. If you can post up a picture of it someone can identify it for you. I have one Patrol with a Stromberg on it and it runs well.

[Johnny Roadkill]

Hi Ben,

I have the WW Stromberg ( ex Holden ? ) carburettor on one of my G60s - it works a treat. Not sure that it makes any more power than the Hitachi but the twin throats should make it a smoother proposition at part throttle. I can't speak for its off-road performance though - i.e. how much angle you can crank into the truck before the main jets start gulping air in the fuel bowl - yet to be tested for me.

cheers,
D

[ben23f]

Here's the stromberg i have. After searching the internet i think its a BX Stromberg.

stromberg carburetor SMALL.jpg

If anyone can confirm that'd be awesome

[Johnny Roadkill]

ben23f, I found this page, hope it helps you ID your carb :

http://www.scribd.com/doc/68315221/4/St ... el-Numbers

Yours looks like a single throat carb, not sure if it's an upgrade or downgrade for the Hitachi, sorry.

The WW Stromberg, fwiw :



good luck !
D

[Johnny Roadkill]

ben23f,

thanks for your post - got me looking at the specs for Strombergs, which I had been meaning to do for a while...

Page 6 of that linked document should help you get an ID on your Bendix Stromberg - but I had a look at the cfm ratings on p79 and I reckon the BX might be a bit underdone on a 4 litre P motor :

Stromberg BX - 1x 29mm venturi - 210cfm
Stromberg BXU - 1x 28mm venturi - 201cfm
Stromberg WW - 2x 22mm venturi - 280cfm
Holley 350 2bbl - 2x 30mm venturi - 350cfm
Hitachi VHA - 1x 36mm venturi - ??? cfm

cheers,
D

[Esteban]

Johnny, great info.

Without knowing exactly how the cfm (cubic feet per minute) number works on a carb, the followin is my calculation of cfm that the engine will displace in a minute of operation at the max 3800 rpm.

4000 cc = 0.141 cubic ft or cf

0.141 x 3800 = 536 cfm

Would need to look further into this number.

[Johnny Roadkill]

Hi Esteban, ben23f,

to my understanding, we would need to halve your 536cfm calculation to account for the 720 degree cycle of the four stroke I.C.E - 278cfm ( edit: D'OH, make that 268cfm ) - then multiply by the volumetric efficiency of the P motor ( somewhat less than 100 % ), and then build in some headroom on the carb's cfm rating depending on the individual's balance between economy, smoothness and power ( this is the intangible part of carb specification where specific experience would no doubt help ).

In short, it seems to me that 210cfm won't be enough to satisfy a P motor at full noise. The 4.2 litre Holden 253 V8 used the 280cfm WW Stromberg and is similarly lazy in character from the factory, so it sounds like 250-350cfm would be around the sweet spot, depending on any mods like extractors, electronic ignition, compression hike, etc.

cheers,
D

[Esteban]

Excellent comments and information, Johnny. The clarification was needed. Your numbers make so much sense.

Guess I'll have to return my 4 barrel pronto! Ha ha ha

[Johnny Roadkill]

Guess I'll have to return my 4 barrel pronto! Ha ha ha

Just the thing for mud bashing !

horses for courses - if you build a hot 2 litre Datsun L-series motor the displacement rate is about the same as the P motor ( half the capacity, twice the rpm ), but the accumulated wisdom suggests twin big bore DCOE Webers or similar, with a combined flow rating of around 900cfm so a 4bbl might be fun, but you'll need to stop for fuel when going to the shops. And again on the way back !

cheers,
D