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Whitey's Carb Swap
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Single Zenith Stromberg to Dual HS4 conversion

(all photos taken 7/ 2000 - 8/2000)

   Whitey - 1975 Spitfire Specific Tasks and Procedures

Transmission    The vibration    second rebuild    Clutch    O/D    driveshaft 
Special Update Whitey finally gets it's 6 cylinder engine, Fuel injected at that!
Section #2 - Whitey's Spit6 conversion Process                     F.I home page

USA spec
zs_cleanedup.jpg (15951 bytes)
Here's the Zenith Stromberg all cleaned up.
It runs just fine, but a single 1.5" throat is
just too restrictive.

European Spec (minus emissions)
hs4_cleanedup.jpg (15784 bytes)
  Here's a comparison of the Dual HS4 installation,  with the identical evaporative and emissions plumbing all completed. Yep, even the anti
run-on valve is still in there.

     daulhs4_plumb2.jpg (14215 bytes)
  These two photos (above and at the right) are good shots of how I routed all the breather pipes and emissions plumbing. Yep... even the anti-run-on valve is still functional in the dual HS4 installation. The fuel and crank breather pipes are copper, and brass was used for the the float bowl vents. The white plastic 'T'  I.D. just happen to match the breather and vent line tubing O.D.   Looking at the top two photos, you can see all the emissions hosing is almost in the identical positions,right down to the vacuum line that feeds the bottom of the carbon canisters mounted in front of the radiator.

daulhs4_plumb1.jpg (20417 bytes)
I used a short piece of split 5/8" hose, as a 'gatherer'
to keep the piping lined up between the carbs
The top two, and bottom two photos show a 4th steel pipe. That's the original gas tank vent line (re-bent slightly) going to the carbon canisters.

daulhs4_passrear.jpg (16666 bytes)
Just a final shot to show the fuel tank vent plumbing
and throttle linkages all in place.

daulhs4_passfront.jpg (15087 bytes)
And of course, another shot from the front, to show the crank/valve cover breather plumbing.


     The Dual HS4's are breathing through a pair of K&N filters, running stock European spec. ABT needles. The CO2 readings across the board are great! The exhaust pipe residue is a medium to dark brown (not black)  I'm extremely happy with this setup.


hs4_egr2.jpg (14617 bytes)
Had a big problem here.  I didn't feel comfortable with how close the EGR valve was to the bottom of the front jet. (less than 1") The internal workings of the EGR valve were fused closed as were the threads into the exhaust manifold. So I busted out the trusty Dremel tool and sawed off the top half of the EGR valve to gain a little clearance.  
hs4_egr1.jpg (14379 bytes)
Now it was just ugly, so I decided to cut the valve completely off the manifold   (With the Dremel tool)  After cutting it off, I filled the hole with a short, large diameter bolt covered in exhaust pipe sealer. I  cross drilled the bolt, put a pin in it, and filled it with exhaust pipe repair putty as well. No leaks, and no signs of cracking.


After all  the work on the stock manifold to remove the EGR valve, I ended up swapping it out for a complete Euro-spec 4-2-1 system. (pictured here at left). Sorry. no pics on the car as of yet. But just like the carbs, this too was a very noticeable power increase over the stock setup.
hs4_stripped1.jpg (8686 bytes) hs4_polish1.jpg (9825 bytes)
Stripping and cleaning HS4's is relatively easy. Just take you time and lay everything out so you can remember how it goes back together. The photo above right, shows what 20 minutes of polishing with a buffing wheel can do for the appearance of the carbs. Just do it while apart. (It's easier to get all the nooks and crannies cleaned and polished)
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All material copyright© Teglerizer 1996-2008

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