Challenge/Lemons budget carbs for Volvo B20

The Volvo B18 I'm building for my Challenge/Lemons car keeps getting a bit warmer, sometimes on purpose, sometimes on accident. I put a hotter cam in it and found out that a previous owner had bored it out to a B20. I'm hoping for over 100whp.

The engine came with an SU manifold and I bought a DCOE manifold for it. Since then I've read that SUs don't like to idle with big cams and I realized that DCOEs are expensive as hell.

Thinking about either picking up a Weber manifold and a DGEV/DGAS or grabbing two motorcycle carbs to put on the dual SU manifold. A lot of people in the Volvo community talk E36 M3 on the DGEV but I've driven two old Volvos with that carb and they were pretty decent. The only issue I'm seeing with bike carbs is finding a pair that's large enough. I've seen Harley Mikunis on a Volvo a few times but they're a little pricier.

So now I ask the hive, what do I do?

I think its due to the SU Kool-Aid drinking.

All SU owners talk E36 M3 on the DGV carbs; they have to because they have backed themselves into a corner defending the SU technology as being God's own fuel mixer. I have played with both SU and DGV on MGBs and both work just fine if you know what you are doing when you adjust them. The matter was even settled by this Magazine doing a dyno comparison on an MGB engine that was fitted with each induction device. Zero difference.

Off the bat, I cant think of a reason why the SU constant velocity carb would care about the vacuum signal produced by the cam anymore than a variable velocity carb. What might prompt this idea is that a substantial number of SU carbs have worn throttle shafts that leak vacuum. This vacuum leak ( a leak that changes everytime you blip the throttle) causes idle issues even with a stock MGB. Adding a lumpy cam would make matters worse.

It could also just be a calibration thing, after all there are a bazillion motorcycles running SU type carbs in an independent-throttle setup, which plays all kinds of hell on vacuum signal to the venturi.

One thing I found is that Dell'Orto carbs are really cheap on eBay because they are orphans. You can buy a pair of 40DHLAs for about what a single used DCOE of any size would run you. The downside is that jets and other bits are not easy to come by.

SU with a lumpy cam won't idle well, but works fine under load. If you need to stay on budget, stay SU.

The DGV conversion makes them more civilised, and probably more consistent, but no faster.

DCOE will murder the budget, and will work better almost everywhere.

Also, back when I saw 140 Volvos on a daily basis, at least 95% of the "SU carb problems" I had to deal with were ignition or owner fiddling related.

"DCOE will murder the budget, and will work better almost everywhere."

Usually, yes ! ! But this one doesn't seem too bad and it's a runner:

http://www.ebay.com/itm/Weber-40DCOE-Carburetor-40-DCOE-European-Weber-Carb-/132191366941?hash=item1ec7382f1d:g:jbYAAOSw-K9ZF68e&vxp=mtr

Complete rebuild kits are available if at all necessary.

If you think the DGxV Weber is the right option for drivability but want a bit more performance look for the DGxS series instead. Two synchronized throttles instead of progressive ones.

Of course the next step up is also the most grm, and that is a Holley 2-bbl on the Weber manifold with the adapter that they use on Pinto engine circle track cars.

And any of the synchronous 2-bbl carbs is three flanges and 4 exhaust elbows away from bolting on in place of a pair of SU carbs if you are budget limited.

In reply to oldopelguy:

How about two flanges, one exhaust U-bend, and a bank of lawnmower carbs?

I'd looked into the 36/36 DGAS but I couldn't find any info about flanges. I assumed it was the same as a DGEV but weber won't mention how any of their carbs mount.

I might just get a 32/36 DGEV and some jets. The volvo people seem to be the only people who don't like them.

Now a Holley 2bbl on a weber manifold... that would be glorious. The availability of parts and tuning knowledge for the holley is incredible.

I have a (I believe 48mm) DCOE I'd let go for cheap. It was on a 13B parts engine I got. Needs a good going through.

It's a 100hp race car, if it idles at all and runs well at WOT do you really need anything else?

Summit's CFM calculator says I need 213cfm for a "racing" carb.

I find that the 32/36 is rated at anywhere between 240 and 380 depending on vacuum and who is reporting it. Still plenty of carb for what I want. Berk the haters, I'll find a 32/36 and some jets

buzzboy wrote: Summit's CFM calculator says I need 213cfm for a "racing" carb. I find that the 32/36 is rated at anywhere between 240 and 380 depending on vacuum and who is reporting it. Still plenty of carb for what I want. Berk the haters, I'll find a 32/36 and some jets

When you buy the jets, don't go by the ?Redline? Weber site. They need a few steps bigger for modern gas.