4 bbl

Typrus · Post by **Typrus** » Tue Jun 14, 2005 4:37 pm

What CFM is that Weber? I just found a Holley 390 CFM Vacuum Secondary 4-BBL carburetor kit, for $310. Just how much fab and stress would that take and would a BBL a cyl. blow the head?

GTSSportCoupe · Post by **GTSSportCoupe** » Tue Jun 14, 2005 5:00 pm

Typrus wrote: What CFM is that Weber? I just found a Holley 390 CFM Vacuum Secondary 4-BBL carburetor kit, for $310. Just how much fab and stress would that take and would a BBL a cyl. blow the head?

I think you'd just end up running super rich? The head and intake manifold limit the flow so much, a huge carb wouldn't make much difference in the amount of air sucked in by the engine. It would probably even slow down the velocity of the air, thus letting even less air into the engine. Meanwhile dumping enough fuel for 4 times the engine displacement...

I don't know too much about carbs tho...

shogun · Post by **shogun** » Tue Jun 14, 2005 6:27 pm

it would help if you are using an aftermarket cam, a spacer and a ported head

Lateer · Post by **Lateer** » Tue Jun 14, 2005 6:32 pm

32/36 DGV Webers were standard on a lot of vehicles, from MGB sportscars to Ford Excorts here in Australia.

From what I can read on the pages blow, the 32/36 DGV ranges from 225 CFM to 325 CFM. 325 sounds about right to me. I found once a comparison page between the Webers and the various carbs that Toyotas had out, but Google appears to have lost it...

<a href='http://www.mgbmga.com/tech/mgb19.htm' target='_blank'>MGB info</a>
<a href='http://www.barneymc.com/toy_root/techta ... /specs.htm' target='_blank'>4 Cylinder Block, Piston, Carb, Etc Specs</a>
<a href='http://www.ultimatesubaru.net/forum/arc ... 16949.html' target='_blank'>Ultimate Subaru Message Board - What is the CFM</a>

I hope this info helps. I wouldn't bother with the 4bbl Holley as that'd be way too large for our application. The DGV or its brothers the DGEV and DGAV are ideal for our 1.5L engines.

Although, I have been thinking about a DCOE and a modified intake manifold...

clbolt · Post by **clbolt** » Tue Jun 14, 2005 6:37 pm

The 390 Weber 4 barrels were the hot ticket for really hot 2.3 liter Ford 4 cylinders back in the 80s. You had to have a hell of a cam, high compression pistons, a header, etc. If you put one on a stock 2.3, it turned into an instant bog-mobile. I can't imagine a scenario short of a turbo setup that would make it work properly on a 1.5 liter engine.

Toyota's_Abortion · Post by **Toyota's_Abortion** » Wed Jun 15, 2005 3:54 pm

The Aircooled VW crowd have put 650 cfm carbs on their 2liter engines. I dont know how they work with a carb that size but it is possible. The problem with your 390 holley is that with a carb that size on your small engine, you will not have enough vacuum to open the secondaries. With your barrel per cylinder idea your engine will be a 2cyl 750cc with 195cfm feeding them. The Holley 390 Carb itself is very versatile and goes on everything from the 2.3 ford 4bang to the 300ci inline six. Ive owned many in my lifetime.

Lateer · Post by **Lateer** » Wed Jun 15, 2005 6:20 pm

If you really wanted the one barrel per cylinder look, then head for a set of twin Weber DCOE carburetors on a custom manifold.
That setup is what all the racing mob here use on their four cylinder engines, no matter what size. That way, you can adjust each cylinder individually.

It'll be expensive. Manifolds like that aren't cheap to make. And then you've got to get the carbs, linkage them correctly (do it right, not a lash-up), then synchronise them all, so they're breathing at the same rate, feeding the same amount of fuel in.

Then you'll hear the characteristic growl of a DCOE. Music to the ears....

Typrus · Post by **Typrus** » Tue Jun 21, 2005 5:11 pm

Hehehe.. Just toying with the thought. I'm still looking at the Weber.

Lateer · Post by **Lateer** » Tue Jun 21, 2005 6:27 pm

The DGV is the most customisable downdraught carb that Weber make.

There are heaps of emulsion tubes, main jets, idle jets, air jets and such to make the carb work really well on any engine, from 1.3L up to 3L.

One of these days I'm going to copy the pages I grabbed from a book about Webers and publish it as a pdf for everyone on here to use. It sure as hell made my life easier...

shogun · Post by **shogun** » Wed Jun 22, 2005 5:05 pm

i tried with a couple of weber 36 idf but it was a nightmare to tune and mileage is a bitch and the car i dont know if the jets were bad it bogged a lot

Lateer · Post by **Lateer** » Wed Jun 22, 2005 6:01 pm

The IDF is a single throat progressive carburetor.
It sounds like the jetting was set way wrong on that particular carburetor. <_<
Either they were way too big, or the progression was set up incorrectly.

You've also got to remember that all Webers have a HUGE accelerator pump setup, so slamming your foot on the accelerator will simply dump a whole heap of fuel into the carb and at low revolutions all you'll do is starve the system of air and it will bog down. Webers are great, but they take a little getting used to.
Gently with the right foot is the secret to success with the Weber. And watching the tachometer. At low revolutions, all you'll do is soak your exhaust system in unburnt fuel <_<

You said you had twin IDF's? Well, you might have been getting the same sort of problems I've seen with a 38 DGS. The DGS is similar to the DGV, instead that both throats open at the same time, instead of progressively. This particular engine couldn't handle having all that fuel come in at the one time. We swapped to a DGV and that particular machine ran like a dream. It even won a few races around Baskerville.

I've been working with Webers in various ways, shapes and forms for a while and found that the downdraught carbs are neat and simple to use.

jetswim · Post by **jetswim** » Wed Jun 22, 2005 10:32 pm

I put a Weber 32DAV on my VW camper's 1.8L 4 banger and it was a great improvement to the stock carb. I've had it for 5 years and never a problem. I think it does run a little rich though...Consequently I have the repair manual for most Weber/Holly carbs if anyone needs some info.