For the past two plus years, we have been bringing a '67 Jaguar Mk 2 3.4 back to life.  It spent the first part of its life in England, having been built, as all Jags were at the time, in Coventry.  So it is a right hand drive and has the original large English license plate still on the trunk.  (See and click "Archives" for previous restoration articles.)  The car has been gone through and was ready for the newly-rebuilt twin SU carbs, new chrome and correct 6:40/15 bias ply tires.  We have all of this ready to go on, so as they say on a "top" TV car show, "What could possibly go wrong?"

        Carburetor installation would be first.  The '67 3.4's had twin SU HD6 carbs.  Ours has been rebuilt and polished by Daytona Carburetor* and they looked great!  This was our first time working with these carbs, but we had taken a lot of pictures when we removed them and had factory shop and spare parts manuals for reference.

        The Jag manuals give adjustment specs, but don't mention how linkages, choke pipe, return springs, etc. go.  Here's what Jag says:  

Only two adjustments are provided at the carburettor as illustrated in Figure 3.28.  These are [a] the slow running volume screw "A" and [b] the mixture adjusting screws "B" governing the idling speed and the mixture strength respectively.  The design of the US carburettor is such that correct mixture strength at idling speed ensures that the carburettors are correctly adjusted throughout their entire range.

        1. Remove the air cleaner and air intake pipe

        2. Remove the suction chambers from the carburettors and screw out both mixture screws "B" until the tops of the jets are flush with the jet bridge in each carburettor body.

        3. Screw in the mixture screws until the jets start to move and then screw in a further 3 turns.  Replace the pistons and suction chambers.

        4. Slacken one clamp bolt on the coupling between the throttle spindles.  Check that both butterfly valves are closed by rotating both throttle spindles clockwise when viewed from the front.  Tighten the coupling clamp bolt.

        5. Screw in the slot running volume screws "A" until they meet their seatings and then unscrew each of the screws 2 turns.

        6. Start the engine and run until it reaches its normal operating temperature.

        7. now the carburettors must be balanced (synchronised) by adjusting on the slow running volume screws "A" until they are sucking equally.  This can best be judged by applying a balance meter to the carburettor air inlet and adjusting on the screws until the readings are the same.  Alternatively, listen to the "hiss" of each carburettor (use a piece of tube; a piece of old bicycle tube is ideal ) and adjust on each of the screws "A" until it is judged that the hiss from each carburettor is the same.

        8. Keep checking as above and continue adjusting on the slow running volume screws until with the carburettors balanced (same hiss), the engine is idling at 500 RPM on cars fitted with the 3-speed synchromesh gearbox or automatic transmission and at 700 RPM on cars fitted with the all synchromesh gearbox.

        9. Re-check that both butterfly valves are fully closed by rotating the throttle spindles in a clockwise direction looking from the front, and noting if any change in engine speed results.  There should be no change in engine speed if the butterflies are indeed closed.

        10.  Check the mixture strength by lifting the piston of the front carburettor approximately 1/32" (0.8mm) by means of the lifting pin (arrowed).  if

                a. the engine speed increases appreciably, this indicates that the mixture strength of the front carburettor is too rich.

                b. the engine speed immediately decreases, this indicates that the mixture strength of the front carburettor is too weak.

                c. the engine speed increases slightly and continues to run without change of speed, then the mixture strength of the front carburettor is correct.

        11. Repeat the above operation for the rear carburettor to test its mixture strength and after adjustment, re-check the front carburettor as the two carburettors are interdependent.

        12.  A check on the correctness of the mixture adjustment is to listen to the exhaust note:

                a.  An irregular note, splashy misfire and colourless emission indicates that the mixture is too weak.

                b. A regular or rhythmical misfire and the emission of black smoke indicates that the mixture is too rich.

                c. A regular and even note indicates that the mixture is correct.

        13. To enrich the mixture, screw in the adjustment screw "B" clockwise and to weaken the mixture, unscrew it anti-clockwise.

        14. Some adjustment of the slow running to maintain the desired 500 or 700 RPM may now be required following adjustment of the mixture strength.  To do this, rotate each screw "A" exactly the same amount and listen at the air intake (or apply the meter) to maintain balance.

        15. Replace the air cleaner and air intake pipe

        16. Re-check the mixture strength as described in paragraph 10."



        We needed more on assembly.  Our pictures didn't show everything.  We have a very good friend, Walt at Vintage Jag* to help us, but he is in Idaho and we are in Georgia, so assembly would still require all the information we could find in more books and online.  These cars don't leave much room to work, so we had to make our own special tools, such as bending wrenches to put on carb mounting nuts, grinding down slot screw drivers to exactly fit carb screws.  The two carbs are connected with a linkage so that the butterflies are in sync.  When the carbs go on, the butterflies must be closed (closed to start).  We put a clean drip pan under the car to catch the nuts, bolts and washers that you knew were going to be dropped.  Jag used UNF* bolts on these engines and a few UNC*.  Fortunately, SAE fine will work for most UNF apps and SAE coarse for UNC.  It is highly recommended that  critical apps like rod, main bearings, pressure plates, etc., only the exact nut, bolt and strength be used."  UNF replaced Whitworth* bolts used on earlier Jags.   UNF bolt packages of 500 assorted are available online from the UK, and have some.  

        We hung the carbs on the studs from the engine, putting on a new gasket, then insulator plate and gasket on each carb and loosely hooked up linkages, vacuum line from distributor's vacuum advance and electric choke pipe.  It is important to make sure that the linkage from the accelerator pedal to the carbs is installed with the pivot going UP, not DOWN.  If it installed down, it will make the throttle work in reverse.

        With everything fitted correctly, the carbs and parts were tightened down.  We did a quick check to make sure the butterfly on each carb was closed before tightening them down.  An exact adjustment would be done later.  Also the damper on each carb must be filled with 20-weight SU damper oil, Part # 220-225 available from Moss Motors*  

        These cars have a choke called an "auxiliary starting carburetor."  The electric element is on the front carb's base and is activated by a wire from the coil's hot (negative) side.  (It is a positive ground car.)  The other contact on the electric choke switch goes to the thermostatic switch, which controls the auxiliary starting carb, and is positioned at the front end of the inlet manifold water jacket.

        After all was assembled and ready to start, we checked our oil and water levels and had a fully-charged battery.  I got in, turned on the key and listened as the electric fuel pump in the trunk pumped up the float bowls in each carburetor.  When it quieted down, I pushed the starter button and the car started! and sounded good.  We still needed to sync the carbs.  This is done with the air cleaner and plenum off so that you can set the Uni-Sync tool right over each carb's throat.  (rubber washer in toward the carb).  The goal is to get both carbs to read the same on the float tube (a ball floats up and down in the tube).  I set each carb so the ball floated near the middle of the tube.  Screw "A" (see illustration) makes this adjustment by controlling air mixture and RPM's.   On the automatic, the RPM's (warm) should be 500 RPM.   For 4-speed overdrive cars, the RPM is 700.  "B" screw is to adjust the lean/rich (jets) mixture and is on each carb.  To see the tops of the jets, remove the suction chambers (dash pots), being careful not to bend the needles.  The screw "B" is turned clockwise to enrich and counter-clockwise to make leaner.  The goal, as previously stated is to flush the top of the jets with the jet bridge, then turn screw in 3 turns.

        Now with the engine sounding good, we quit for the day to let all cool down so we could put on the aluminum air cleaner assembly.  Putting on the 4-piece, restored air cleaner was kind of a coronation of this fine old English car.  We had polished the aluminum plenum and painted the air cleaner light hammered silver and put on new heat gaskets from carb to plenum.  Jason and I took the car out for a test run and everything checked out.  I wanted to tweak the carbs to get the RPM's down a little, so we went back to the the shop.  Smoke began coming from under the hood.  

SOMETHING IN THE ENGINE WAS ON FIRE!  We opened the hood and Jason sprayed the carb area with a fire extinguisher and the fire was soon out.  A closer look revealed that the electric choke wires had overheated by touching the air plenum, burning off the insulation and fusing together.  Fortunately, that was all there was to it, but that was enough!  All of the engine compartment had to be cleaned and cam covers and aluminum parts re-polished, but that would have to wait.  For now, I wanted to hear it run right again.

        I made new choke wires, this time using insulted terminals and a high-temp sleeve to run them through, routing them away and down from the air plenum.  I highly recommend this high-temp sleeving*.  It's great for wiring that is subjected to exhaust manifolds and high heat places in the engine compartment, and for sleeving spark plug wires that are positioned next to exhaust manifolds.

        With the car running good again, I put it in reverse to back up the driveway for another run.  With the gear selector in Reverse, I increased the revs to back up.  Nothing!  I had now  lost  reverse!  Son-of-a-gun!! (My mother reads this magazine.)  The car was put back in the garage so that I could give some thought to the situation.  I bought a book on Borg Warner 35 transmissions.  They are relatively dependable transmissions, being used by Jaguar, AMC, Datsun, Rover, Ford's UK models and others in the '60's and '70's.  I knew this car had sat for 12-15 years and reasoned that the transmission fluid had never been changed.  We drained it, not removing the pan or purging the torque converter, but just draining the ATF out of the transmission pan.  About 5 quarts of the brownest, muckiest fluid came out that I've ever seen, but there were no shreds of metal shavings, and the color wasn't black, and there was no burnt smell, which would have indicated burnt clutches or other internal problems.  After much reading about which type of ATF to usetype A (Dexron) or type F (a mineral oil ATF), I decided to go with Dexron Type A because I think that's what was in it, and it is compatible with most everything.  If I change to type F, it will be covered in depth in a future article.  When I got in and started the car and put it into reverse, the reverse light on the selector came on, indicating that the selector was working (but I didn't feel a click and the RPM's didn't pull down as they should.  The car didn't move.  I still had no reverse.  

        There was one more thing I could doadjust the rear band on the transmission, which can be done from top side.  To do this, remove the console between the two front bucket seats, easily done by removing 3 chrome thumb screws, one toward the back and one on each side of the console toward the dash.  With the console out, the carpet was pulled back on the right side of the transmission hump revealing a large 3" rubber plug.  I removed the plug and found an adjusting screw with a lock nut around it.  I loosened the lock nut and turned the screw clockwise until it was very snug (about 10 ft/lbs), then backed it off one full turn and locked down the lock nut.  The screw and nut had been very loose before I adjusted them.  All was good.  Jason and I put everything back and started the car, putting it in reverse and, BAM!  Reverse pulled like a freight train.  It was fixed!  Sometimes you've got to get away from a problem to think about it.  Just don't give up.  Think about it and fix it!  Now the engine compartment is clean again, the Jaguar is running and driving well and it's finally time to put the chrome back on.  

        Old cars . . . you've gotta love 'em!  

        See you next month.  Keep 'em driving!