Products: Carburetion
Forget what you thought you knew about the best carbs for vintage cars. Everything has changed.
In 2003 we needed improvements to the SU and Weber carb setups on our Volvo performance and supercharged engines. So we started what ended up as a year of searching and testing. Numerous carbs were evaluted both on the street and the dyno. The carbs tested included various versions and sizes of the traditional SU, ZS, Weber sidedraft, Weber downdraft, and a few less commonly used carbs. The testing included both stock and modified versions of the carbs. Test criteria included cost, power, throttle response, fuel economy, and ease of installation and tuning. After over a year of work, the carb that came out best in all categories for a wide variety of applications was clearly the Mikuni HSR series of carbs. Other carbs still have their place - where an original equipment look is required for shows or to meet competiton rules. But for street driving with a stock or modified engine, or racing where the rules allow a modern replacement carb, these are the carbs to use - especially if your car was originally equiped with one or more of the SU or Zenith Stromberg carbs the HSR Mikunis were specifically designed to replace.
Mikuni HSR Series Carbs
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MGB and Sunbeam Alphine Mikuni installations are shown in the photos above.
After 6 years of use and well over 100 installations in various cars these are the carbs that I recommend:
1) as a stock replacement or upgrade from SU, Zenith Stromberg, or Weber carbs.
2) for Volvos, MG, Triumph, Datsun, Mini, Spitfire, Sunbeam Alpine, etc.
3) in one, two, three, four or six carb applications.
4) for stock, modiified, supercharged and racing engines.
Technologically superior in design to the typical SU, Zenith Stromberg or Weber carbs that were originally designed more than 50 years ago, the Mikuni HSR flat slide is a modern carb, designed specifically as a bolt-on SU replacement that will do it all - more power, better fuel mileage and easy tuning in one package. These advances are made possible by several innovations, including the use of a flat throttle plate or "Flat Slide" derived fom racing fuel injection systems which allows for increased air flow and produces extremely high manifold vacuum, aiding in fuel atomization while increasing port velocity.
Compared to SU carbs, a similarly sized Mikuni HSR will flow 30 - 40% more air. They will provide better throttle response, support more power - especially at higher rpms, and will equal or exceed the SU in fuel economy. In road and dyno testing dual Mikunis have equaled or exceeded Weber sidedrafts in power while getting 50% better fuel mileage - at less than 2/3 the cost, using the stock SU or ZS intake manifold. Customers are amazed by the degree of performance improvement as well as the ease of installation and tuning. If you are interested in your vintgage car's performance, including its reliability, there is no reason to stick with obsolete, leaky, hard to tune SU carbs or having to chose between a sidedraft Weber for power or a downdraft Weber for economy. The solution is an upgrade to the Mikuni HSR carbs.
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Originally designed and marketed as a performance replacement for SU carbs on Harley Davidson motorcycles, the size of the 45 mm Mikuni, essentially the same as the 1 3/4 inch bore or an HS6 SU, and incorporation of an accelerator pump jet makes it perfect for automotive applications. Carburetor development for automobiles stagnated more than 30 years ago when automotive manufacturers turned to fuel injection to meet emissions and fuel economy requirements, while at the same time, the evolution of carburetor design for motorcycles, snowmobiles and jet skis continued at a rapid pace. The Mikuni flat slide is the most advanced product of those years of continuing development which began with the traditional SU carb of the 1950s.The result is a carburetor that is superior both in power and fuel economy as well as being reliable and easy to tune and maintain. Parts are less expensive and fewer in number than in most automotive style carburetors.
Our Mikuni carb kits are designed to make the Mikunis an easy to bolt-on replacement for SU carbs, right on the stock SU or ZS manifold. The dual kit includes two carbs, two carb to manifold adapters, a throttle shaft, linkage to adapt to the SU or ZS linkage, and two K & N air filters. Similar kits are available for single and triple carb applications. As with any carb swap, expect to do some tuning to match these carbs to your engine and get maximum performance and fuel economy. Tuning recommendations and jet kits are available.
In the Mikuni specific jets meter fuel for various throttle openings. Compared to a sidedraft weber, tuning is much simpler, cheaper and more direct since there are no emulsion tubes, replaceable venturies or the need to guess as to what the result of a change will be. It is hard to describe how much of a pleasure tuning these carbs can be, as compared to SUs or Webers. You really have to experience it to fully comprehend the difference.
For additional details on these carbs, a complete tuning and parts manual is available online from Mikuni. Go to www.mikuni.com/fs-manuals.html and click on "HSR tuning manual."
Our new installation Instructions are in the "Articles" section. Take a look at it even if you are just considering a purchase as it has much more detail on the carbs and their installation.
All of our carbs sold for automotive use are modified to accommodate the higher fuel pressures of automotive fuel systems as compared to the gravity feed systems used in motorcycles. This modification is built into the price of each kit.
The Dual Mikuni Kit
The Dual Kit consists of 2 HSR 42mm or 45mm carbs with extended throttle shafts for dual mounting, including linkage & manifold adapters - $795. With K & N black top air filters -$875. With chrome top filters - $890.
Manifold adapters for various different car models are available.
Choke cables and/or choke cable adapters are not included but are now available for specific applications.
The Dual Kit now includes one pair of larger main jets. Extra jets - $5.50 a pair - recommended .
Add $110 for silver ceramic coated aluminum SU intake manifold - $55 for the manifold used, uncoated. Extra main jets $5.50 per pair - 2 pairs of larger mains recommended. Accelerator pump jets $8 per pair. Re-profiled jet needles $15 per pair.
The Mikuni Triple Kit
Similar to the dual kit, but designed to replace 3 SU or ZS carbs on a six cylinder engine. Perfect for a TR6!
$1195 for the kit without air filters. $1330 with 3 black top K & N filters, $1350 with 3 K & N chrome top filters
The Mikuni Single Mount Kit
The Mikuni Single Mount Kit is a perfect replacement for cars with single Su or Zenith Stromberg carbs. Available with a choice of HSR 42mm, 45mm or 48 mm carb, the basic kit includes one carb modified for higher fuel pressure, with a mounting flange to adapt to your manifold. A throttle cable mounting bracket is also included. Throttle and choke cables are not included but can be provided on a custom basis.
- Single 42 or 45 mm Carb Kit for cable throttle without an air filter - $315 - With extended carb throttle shaft for lever type throttle linkage - $375
- Single 42 or 45 mm Carb Kit for cable throttle with black top K& N filter - $355 - for lever type throttle linkage - $415
- Single 42 or 45 mm Carb Kit for cable throttle with chrome top K&N filter - $365 - for lever type throttle linkage - $425
- Single 42 or 45 mm Carb Kit for supercharger applications with modified accelerator pump without an air filter - $395
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For a more formal look, polished versions of each carb are available. To substitute polished carbs in any of the kits, add $140 to the listed price for each polished carb added. |
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Upgrade your Supercharger Kit with a Mikuni. The photos above and to the right show one of our modified HSR 45 Mikuni carbs replacing the SU carb that originally came on this Moss Motors MGB supercharger kit. When we first saw this kit we questioned why they would take a modern supercharger and put an ancient carb on it. We later found out that Moss had in fact experimented with using a stock Mikuni HSR carb, but had experienced problems with hesitation that they could not solve. Since we had learned how to eliminate this problem as part of the testing and development process when we switched from a Weber DCOE to a Mikuni HSR Carb on our Volvo supercharger systems, we knew how to make it work on the MG. The big change is that the carb float bowl has been modified to increase the capacity of the accelerator pump by approximately 50%. Now, with the proper modifications, including reprofiled jet needles and larger accelerator pump jet, we can provide a Mikuni carb that is a tremendous upgrade for the Moss Motors kit or any other supercharger kit that uses an SU or ZS carb. The basic kit includes the carb with modified float bowl, one reprofiled jet needle, one larger accelerator pump jet, and a mounting adapter that allows it to be bolted on in place of an SU or ZS carb - $395. Air filters and other parts can also be supplied. Additional main jets are recommended. |
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New Quad Mikuni Kit -- The Ultimate Performance Carb Kit
A unique and totally cool setup! 4 HSR Mikuni carbs on Weber DCOE type manifolds for large displacement and high HP racing and street 4 cyl. engines. Will easily outflow Weber carbs of similar sizes due to the much cleaner air flow path.
- Four modified carbs with manifold mounts and linkage adapters -
$1550.$1495 - Four modified carbs, manifold mounts & linkage adapters, Volvo B20/21/23/230 intake manifold & air filters -
$1995$1940 - Email for kit prices whichi include manifolds and air filters for non - Volvo applications
- Six Carb Kit with manifold mounts and linkage adapters - $1995
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Discount Offer
Comments on MIkuni Carb Installations
John, The carbs are working great and are as easy to jet as I rembered from my MX days. Unfortunately I wasn't able to get a dyno comparison between the Mukuni's and the ZS's. I can tell you I shaved 3 seconds off my lap times though. The throttle response is excellent.
Jim Gray TR4 Vintage Racer
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From: "Kevin Hall" <timberline@xxxxxxxxxxx>
Date: Fri, 12 May 2006 22:41:33 -0400
One serious benefit is that you don't require the aid of Merlin to set orjet the things. They respond to jetting changes and adjustments exactly as you would expect, which cannot be said for the old SUs. Jets and parts are much cheaper than they are for SUs or ZS units, and they are much moreeasily available through better bike shops.
The only slightly awkward bit in the installation was the choke hook-up.The carbs each have individual plunger chokes, which I linked to the choke cable in the car by means of a dual-carb cable splitter box meant for a Norton Domi. Those are available through classic bike shops, and are notexpensive. You need to do a bit of messing about getting the inner and outer cable lengths right, but it is simple once you get at it.
I've messed about with SUs for the best part of 40 years, but the only reason I'd go back to them would be if I were doing a complete concours resto. For a daily driver or a brisk hobby car the Mikunis are light years ahead of the game.
KH
On the highway, I seem to be going 10 mph faster all the time. I tend to drive at a speed where everything "feels" comfortable, a "sweet spot" if you will... The "sweet spot" is now 10 mph faster!! Did a gas mileage check and I am right at 24 mpg and that includes a lot of stop light to stop light "scooting" about! not bad, really. A real improvement over the SUs!! The sound the motor makes with the Miks is quite a bit different from the SUs. Thing now has quite a growl. Sounds a bit unusual.
Thanks John. Mike Twombley
go to top | how to orderWeber Carbs
Dual side draft DCOE Weber carbs - the classic performance and racing carb for vintage sportscars. Available used and new, in 40, 42, 45 and 48 mm sizes and can be set up for specific applications and matched to manifolds, porting, cam, etc. Linkage and air filter kits also available. We are not a traditional "dealer" of these carbs and cannot match discount pricing - but with a purchase from us you get advice and help with setup and tuning that can be "pricless". Discount dealers send you the carbs in a box, with the same jetting no matter what the application is, usually with the cheapest manifolds and linkage available, and let you figure out how to make it work.
These carbs are still the standard for vintage racing, though the Mikunis described above are now a better choice for street use and racing where a period correct carb is not required. Production of Weber carbs has been intermittent in the last few years ( as has quality ) but they are now available again, including the newer type 152 - 45 DCOE , and the classic and hard to find classic Type 9 - 45 DCOE . Email for current pricing.
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Intake Manifolds
Manifolds for sidedraft - DCOE type carbs
Available forVolvo B18, B20, B21, B23, B230 engines. These are copies of the original, no longer available, R- Sport manifold . They should not be confused with the cheap, shorty manifolds usually offered in Weber kits that have flow restrictions due to their short length and comparatively tight bends. In a recent dyno test we gained 12 HP by switching from the commonly sold “shorties” to our longer manifolds.
Recommended for all installations with Weber DCOE type carbs ( and similar sidedrafts ) and our Quad Mikuni System. Mandatory for racing, rallying and large displacement engines $325.
SU intake manifolds
These are the original aluminum intakes used on the early dual SU carbed Volvos. A significant improvement in performance applications over the later cast iron combination intake and exhaust manifolds.
Silver ceramic coated aluminum - $110 Uncoated - $55
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Linkage
Throttle Linkage Lever Arms - Top quality, custom made, machined aluminum throttle linkage arms for Weber sidedraft and other similar carbs - $ 33 each. Email or call for prices and availability of other linkage components including custom made, braided stainless steel throttle cables.
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Air Horns
Full radius aluminum air horns - in several lengths for Weber DCOE and similar type carbs - $54 each.
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The air horns shipped with Weber carbs are basically for decoration only. In dyno testing on Volvos we usually get better power with them removed. The full radius horns really work to improve flow and are available in several lengths to help with tuning. On our Volvo engines we usually find that the shorter horns work best.
Mikuni air horns with screen type filters - perfect for race applications or other occasional use - $120 a pair.
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Mikuni air horns with screen filters on Jim Grey's TR4 vintage racer
Filters
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ITG Foam Air filters - Imported from England for sidedraft carbs - email for details and pricing.
Available in various sizes, the rounded shape allows them to fit where square filters will not.
Mandatory for use with Weber sidedraft carbs and the longer manifolds on the Volvo 1800.
go to top | how to orderAccessories
Mikuni HSR jets - main jets - $5.50 per pair. Accelerator pump jets $8 per pair. Re-profiled jet needles $15 per pair.
Soft mounts and spacers for SU and other carbs in performance applications - email for details.
Weber DCOE Jets and Accessories Main jets $6. Air correction jets $6. Idle jets $7. Email for prices on other jets and accessories.
Used Weber Sidedraft carbs We usually have used Weber DCOE carbs in stock. Email for availability and pricing.
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>> Questions - Order Process - Payments
Questions -Email correspondence strongly preferred. Email with questions on your particular needs as we have many other parts and services available. If we don't have it we can usually get it or make it. If you need to call, try 315 478 1229 mornings 9:00 AM - 12:00 noon eastern time. Leave a message if there is no answer as we may be in the shop and cannot get to the phone, or try cell # 315 440 6560 if necessary. There are often periods of 3 - 5 days, especially during the summer, when we are gone due to racing and other commitments. Calls and emails are replied to when we return.
Orders - Where possible email your parts order along with your zipcode and we will reply with information on parts availability and a total price with shipping. Please include information indicating the car model & year with each email.
Payments - Payments are normally made by check, money order, COD, or through Paypal (www.paypal .com) Credit card payments are currently only accepted through Paypal. Payments made by Paypal should be made to the account under our email address: jparker3@twcny.rr.com
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