Carb Sacrilege?

Lotuss7

Lotuss7

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I've been a big Weber fan for decades. Have the Zeniths on the coupe and will stay that way, but if I were looking at a carb swap (side drafts) I've always thought DCOEs. Had them on my Alfa, 2002, Lotus 7, Cortina. Love their tune-ability and I've had pretty good success in getting / keeping them dial in.

Also tempted by the injection route, but another alternative popped up last week. My son has been looking at picking up a Volvo B122 Amazon as a daily driver. He likes 2002s but the Volvo makes a significantly lower price point and can be tweaked into a reasonably quick (period standards), decent handling rear wheel drive sedan. Looking at tuning a Volvo he came across Vintage Performance Developments. These guys are big fans of Mikuni HSR Series carbs...true side draft carbs engineered for bikes years after everyone else in the car world gave up and went FI.

Mikuni??? Sacrilege...maybe. But performance is performance. New to me, VPD's assessment is worth reading.

http://www.v-performance.com/products/air_fuel.html

John
 
No, not sacrilege, common sense, I always had an inkling motor bike carbs were a good way to go.
It's just typical Japanese efficiency, they are very very good at perfecting things, motor cycle carbs are probably the zenith of carburettor development.
If I was going the carb route I would be using 6 bike carbs for sure, not the traditional look, but a sacrifice I could live with
 
+1

If I hadn't finally got my SU knockoffs dialed in on my 2000 Roadster, the Mikuni's were definitely in the plans. I've dealt with a lot of bikes (my other addiction) and the Mikuni's are the best. Set them and forget them. Instant throttle response and not loss of power on the bottom end. A lot of Roadster guys have replaced the SU's with Webers and nearly all complain about bad low end response. Not so with the Mikuni's
 
6 carbs under the hood would look pretty cool if you don't care about period look. I wonder how reliable synching them all together accurately would be or how challenging. Parts/jetting availability for BMW applications? What manifolds to use?
 
My TR has Strombergs and they work well enough I'm not going to mess with them, otherwise I'd be all over this. Just to see how much better they may be if nothing else. More HP / better fuel economy / throttle response / tuneability all at what seems to be a fair price point. No FI electrics to deal with. Seemingly a winner.

For the coupe they apparently mount in a straight forward way to DCOE manifolds so I would imagine linkages might be available. But if not probably could be developed easily enough. As they are individual chokes the idea a straight shot inlet would seem optimal...getting closer to FI. If I were going the 3.5 hot rod FI route????

John
 
Stevehose said:
I wonder how reliable synching them all together accurately would be or how challenging. Parts/jetting availability for BMW applications? What manifolds to use?
Click to expand...

The guys at Vintage Performance Development seem to have thought all of that out. From reading their (lengthy!) website, I learned that they sell Mikuni carbs in pairs, with adapters to fit Weber manifolds. I assume that the two carbs in each pair come pre-synched, so the job of synching the three pairs would be no more difficult than synching three Webers.

I'd say that if the idea of using Mikunis on an e9 has a downside, it is COST. Those carbs don't come cheap! The most pertinent thing I could find on the Vintage Performance Development website was: "Six Carbs modified to mount in pairs on Weber sidedraft type manifolds - with manifold mounts and linkage adapters - $ 2,650". Weber Carbs Direct sells new DCOE40's for $340 apiece (*); a set of three would cost $1,020, or about 40% as much as the Mikunis. For either brand of carb you would also have to buy the manifolds, air cleaners, and linkage, but those should be about the same for either.

*) See: http://www.webercarbsdirect.com/Weber_Carburetors_s/2.htm
 
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I've got a '66 Volvo 1800S with a pair of HSR45s from VPD. They are great carbs. They can provide all the response, power, and sound the DCOEs do, but without sacrificing any fuel economy if tuned well. That being said... The flat slides don't seem to like the higher vacuum you see with car engines, so the slides tend to wear pretty quickly. So they aren't the cheapest to keep up over time. I also had to put my fuel metering needles on a Dremel and take off a bit of material to get the right profile.

I love them in my Volvo overall, however.

-Scott
 
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I have a set of four Lectron slide carbs for my 2002 race car, they came on the car when I bought it. I have since replaced them with side draft webers. They worked well, looked cool, but were not far superior. Also not vintage legal.

http://www.lectronfuelsystems.com/
 
I think 6 Mikuni flatside motorcycle carbs would be a little much to tune...

But 3 Mikuni PHH44's would be awesome. I have been running these for years and they are excellent carbs. Unlike the Webers, they have an accelerator pump diaphragm, they have a homogenous pilot-main circuit, and they are cheap and easy to rebuild. And they make a great baaaaa-waaap sound when you goose the accelerator too :-)

I have never run Dellortos but I hear they are even better.

HTH
James
 
That Volvo will give 150+ hp with the right period treatment (double 1 3/4" SU, K-cam, 11 CR and a reworked head. Even 180 hp is possible. There are ways to get that old push-rod engine to rev 7k rpm...

Why Mikuni when the SU-set-up do the trick?

Cheers
A
 
DerSchwede said:
That Volvo will give 150+ hp with the right period treatment (double 1 3/4" SU, K-cam, 11 CR and a reworked head. Even 180 hp is possible. There are ways to get that old push-rod engine to rev 7k rpm...

Why Mikuni when the SU-set-up do the trick?

Cheers
A
Click to expand...

That was my comment on the Strombergs on the TR. Good enough? Yea..certainly given how I use it. But if they were dead? and I could get over the period correct thing I would look seriously investigate a more modern carb if one were available. These look to be more efficient and if in fact have better throttle response, irrespective of additional power might be worth a shot.

Maybe a bad corollary, but think Edelbrock for the big block guys.
 
The Mikunis have a couple of advantages depending on how you look at it. One is instant throttle response. The SU pistons rise in response to demand, and there is a small delay as a result, while the Mikunis are opened directly by your foot and use an accelerator pump. This doesn't add horsepower, but it does make a significant impact on responsiveness.

The Mikunis, being flat slide carbs, also have no butterfly to obstruct airflow, which can contribute to higher WOT horsepower on the right engine, even without changing the intake manifold at all.
 
jamesw said:
I have never run Dellortos but I hear they are even better.

HTH
James
Click to expand...

I have always run Dellortos in the past on my old Toyota starlets (road - Twin25's and Race - Twin 45's) They are an excellent Carb, only thing to adjust was Idle mixture and balance, and even that wasn't very often. And yes, they gave brilliant throttle response with their diaphragm acc pumps.
In the end we had the little 1476cc push rod making 147 flywheel HP at 7K rpm, and that was on standard pistons, rods and crank! (all balanced)
 
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