TR6 Special Vacuum advance unit 
​# 01315    5-13-10 advance code
# 01816     6-18-10 advance code


Our new 1971-76 TR6 vacuum advance units are custom manufactured to operate with vacuum advance

performance of the early pre-emission. When properly installed we have had quite the noticeable difference in

overall performance, mileage, idle, cooling and driving pleasure. This is a fairly simple procedure following

the 3 steps below and having a little engine set up and running knowledge. 

Note; not all Zenith carburetors have the proper vacuum port. Ck before ordering! 

This is a new TR6 vacuum advance unit made special for the 1971 through 1976 TR6 with Lucas vacuum retard distributor to convert to a more fuel and performance efficient vacuum advance ignition. We have based our unit operation on the TR250 advance curve built into a new unit that installs in the place of the original emission vacuum retard units used on the 1971-76 Lucas distributors 41342, 41385, 41558. Our new units take the place of the original 54400201, 54423098, 54429013 and 54424200 vacuum retard units. Our testing on a 1975 TR6 showed significant increase in performance, power, operating temperature and mileage 
​without any problems at all. 


Most of our TR6 customers report back that they are surprised in the significant difference in overall performance. 

Your carburetor may not have ported vacuum! 
​Your Zenith carburetor may or may not have the threaded port next to the rear top mounting flange over the throttle shaft for ported vacuum. Some with the threaded hole may or may not have the small vacuum drilled through to the throttle from the factory! Zenith-Stromberg may have drilled them or may have not completed the process. 
​This must be done with precision.
​We now have the tooling to complete the process on your complete carburetor or just the body. 
​Cost $50.00 / $25.00 with unit purchase. Call or Email for information.
​Three important things to be checked.
1- Distributor mechanical advance is limited to 13 degrees. Many are! 
​2- Must be connected to
ported vacuum. This can be found on the upper back side above the throttle shaft on the rear Zenith carburetor. 
The proper vacuum connection is important. 
3- The connecting link from the new vacuum unit will not flex enough to slip over the point plate mounting pin. The pin on the point plate needs to be trimmed down about 3/32 to 1/8 inch to allow the unit link to slip on and connect with free movement. Remove the two screw holding the point plate to the distributor body to allow the plate to be tilted when installing the unit link. Check that the pin is not bent and lines up with the hole in the connecting link. Once the unit is in place install the roll pin same as the original unit was mounted. You will fine the timing is to be set just like before. The vacuum connected to the ported vacuum idle will be as normal but you will immediately notice a difference when driving. The vacuum unit produces additional advance when the engine revs are high, but the load is light. That is when there is high vacuum in the manifold due to small throttle opening. When the engine is pulling hard on full throttle the vacuum in the manifold is low and the vacuum advance becomes wholly or partly inoperative. The spark timing is solely dependent on the centrifugal advance. The general effect of the vacuum advance unit is to increase the liveliness of the engine and a noticeable improvement in fuel consumption.
Location is critical for proper operation. 
The vacuum source for the vacuum advance unit is extremely important to be located directly above the throttle butterfly on the rear carb to properly regulate vacuum advance at high RPMs and light load. At idle the vacuum advance unit does not operate. Use a vacuum gauge, Ported vacuum has no vacuum at idle. You'll notice a vacuum serge and drop as the throttle just opens. Correct ported vacuum will continually regulate and maintain vacuum advance by load and RPMs as you drive.  
$79.95

New for 1969-74 Jaguar Series ll and XJ6

Lucas Distributor Vacuum Advance Unit  7-14-8 “not retard” 

​Made to simply fit the 1969-74 XKE and XJ6 with vacuum retard. This new unit, is roll pin fit as original 'No drilling or grinding" spring link aligns the point plate for proper spark to rotor and cap firing with early pre-emission 1963-67 Jaguar XKE with the
​7-14-8 advance code.
Put the leap back into your Jaguar!
British Vacuum Unit part number # 8417 is manufactured to take the place of retard unit 54422224 or 54424370 used with 22D6 distributors 41312, 41323, 41388 and 41523 in the 1969-74 Jaguar XKE Series ll, 2+2, and XJ6. 

There's more that just replacing the vacuum advance unit!

Your carburetor may not have ported vacuum!

Your Zenith carburetor may or may not have the threaded port next to the rear top mounting flange over the throttle shaft for ported vacuum. Some with the threaded hole may or may not have the small vacuum drilled through to the throttle from the factory! Zenith-Stromberg may have drilled them or may have not completed the process. 
​This must be done with precision.
We now have the tooling to complete the process on your complete carburetor or just the body. 
​Cost $50.00 / $25.00 with unit purchase. Call or Email for information.
The following steps are required for successful overall operation.

#1 - Our new 7-14-8 unit MUST BE CONNECTED TO PORTED VACUUM  Usually found on top of the front carburetor , over the throttle shaft. Use a vacuum gauge, Ported vacuum has no vacuum at idle. You'll notice a vacuum serge and drop as the throttle just opens. Correct ported vacuum will continually regulate and maintain vacuum advance by load and RPMs as you drive. 

#2 - The distributor should be checked or re-calibrated to early specs. Springs control advance through out the RPM range. 

Mechanical advance should  be limited to 9-11 degrees. 

#3 - You will likely need to adjust the carburetors to a richer mixture and/or replace the mixture needles to 1967 specs.
​#4 – Set initial timing at or around 12 degrees before TDC.


When properly installed we have had quite the noticeable difference in overall performance, mileage, idle, cooling and driving pleasure.
​This is a fairly simple procedure following the 4 steps above. 
​price $79.95

Special Advance Units, Jaguar, Triumph TR6 Lucas and 

Spitfire & GT6 Delco D204

British Vacuum Unit
​Briar Bush Rd
​Canterbury, N.H. 03224
​603-783-0566
britishvacuumunit@isp.com
Special Triumph Spitfire and GT6 Delco D204 distributor vacuum advance units.
$79.95
Installation is fairly simple, requires you to drill and thread one mount hole.
Our new units take the place of your original performance robbing Triumph Spitfire and GT6 vacuum retard 7992116 
​and Triumph Spitfire and GT6 advance/retard unit 7953524.
Made to early Spitfire and GT6 6-18-10 vacuum specs.
​Designed to operate with ported vacuum.
​If your Zenith carburetors do not have ported vacuum, we can machine the “ported vacuum” port and supply the line fitting $25.00 with unit purchase.
Please note; if you car only had vacuum retard you most likely don't have ported vacuum.
Contact us for help or if you need a earlier Delco unit .
britishvacuumunit@isp.com


69-72 XKE   73-74 XJ6 Special advance unit