Joe Guinan
Email me at:
spitfirejoe@email.com
Spitfire Carburetors
A friend of mine from the Kansas City area - Ben Bacon - put a set of three Dellorto DHLA side draft carbs on his "Spit 6".  After talking it over, two other local Spit Heads (Mike Nelson and Matt Gelvin) decided to join me and order some for our Spitfire 1500s.  We ordered 4 matched pairs of carbs from a guy in Italy, bought four twin carb rebuild kits from a guy in Germany, and ordered four manifold and linkage kits from JAM Engineering here in the states.  I have been running a couple different sets during the 2006 driving season.  I'm generally pretty happy, but have had little problems.
History - Weber DGAV...
   I went to the Weber when I got tired of trying to get the original Zenith Stromberg to work right.  This was before I got on the internet and on the
NASS email list.  The DGV is actually pretty good.  It's a progressive 2 barrel down draft that is reliable and performs pretty well.  It isn't a "high performance" carb, but it's a good one. The progressive aspect of the carb allows me to drive around at regular speeds without wasting gas using only the "main" venturi.  When I get deeper into the throttle, the "secondary" venturi opens up. The typical "oil blowing" problem was solved with the modification of the manifold to add a vacuum port that sucks fumes out of the valve cover.  The black hose coming around the front of the carb is plumbed into the manifold for this purpose.  Without that, oil blew out the dipstick tube and all over the header.  The vent hose connection into the air cleaner didn't provide enough vacuum, so I tapped a hole into the intake and let the engine suck it's own fumes back in.  NOTE - This did gum up the vlaves after a few years of driving.  I'll need to work on a "vapor trap" to collect the oil vapor.
The Present - Dellorto DHLA 40...
   
The Dellorto side drafts are a lot like the Weber DCOE carbs.  They are exactly the same size and use the same manifolds and air filters.The Italian company copied the general desigin and features of the Weber, but improved upon it in several ways. With Ben Bacon's advice, and some research in a couple of readily available books, I began tearing down and cleaning up the Dellortos. They proved to be pretty easy to disassemble and they cleaned up pretty well.  Note the third photo.
    There are several metering parts that can be swapped around on these carbs to tune them for your application.  Main jets, idle jets, accelerator pump jets, etc. can be swapped or drilled out or soldered shut and drilled smaller.  The chokes (the four "tubes" on the right in the top two photos) can also be swapped. They came with 30mm chokes, but we ordered a set of 28's for experimentation purposes.  Smaller gives better driveability and  low end torque, but larger is better for top speed.
    The photo below shows a pair of the Dells on Mike Nelson's 1979 "1500".  We aren't quite finished here, but the manifolds and carbs are mounted and the fuel lines have been routed.  We were working on getting the throttle linkage connected.  A custom bracket had to be made for the throttle cable.  The vacuum line to the distributor is attached to the front side of the front carb, down low.  Air filters and ports to ventilate the valve cover are also being studied here.  We didn't hook up the vents on the first test drives, and oil pumped out of the dipstick tube - another common problem on Spitfire carb swaps.  The engine needs a decent vacuum draw out of the valve cover vent.
    Bottom photo is my car without the carbs installed yet.  I ran a set of "H" carbs for awhile.  They gave good driveablility once I got them adjusted, and I once got 40 mpg on a long trip.  The engine will rev to over 6000 if I let it - scary for a 1500.  I tried a set of earlier non-emission "C" carbs, and broke a part.  The "H" are mounted again - specced below as Modified Engine #2.  Email me for discussion about these carbs, I'm always interested in ideas and experiences.
CURRENT SPECIFICATIONS
subject to change...
Modified Engine #1 - DHLA40 "N" carbs
(Cam, flat top pistons for 9:1 cr, header)
Main Venturis - 30 millimeter
Aux. Venturis - 7848.3
Main Jets - 129
Air Correctors - 180
Idle Jets - 60
Idle Holders - Original to the "H" carbs, no numbers
Pump Jets - 35
Emulsion Tubes - 7482.10
Modified Engine #2 - DHLA40 "H" carbs
(Cam, shaved head for 9.3:1 cr, header)
Main Venturis - 28mm (still revs strong to 6200!)
Aux. Venturis - 7848.1
Main Jets - 130
Air Correctors - 180
Idle Jets - 65
Idle Holders - Original Emission holders
Pump Jets - 33 (too small)
Emulsion Tubes - 7482.10
Stock Engine - DHLA40 DHLA "F" carbs
(nothing but a good 4-2-1 header)
Main Venturis - 28 mm
Aux. Venturis - 7848.3
Main Jets - 120
Air Correctors - 180
Idle Jet - 57
Idle Holders - Original to the "H" carbs, no numbers
Pump Jets - 35
Emulsion Tube - 7482.11
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