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. Check before ordering!
This is a new TR6 vacuum advance unit made special for the 1971 through 1976 TR6 with Lucas 22D6 vacuum retard distributors 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.
Most of our TR6 customers report back that they are very surprised in the significant difference in overall performance.
Your carburetor may not have ported vacuum!
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 supplied with vacuum fitting. Call or Email for information.
Three important things to be checked.
1- Distributor mechanical advance is limited to 13 degrees max.
We recommend having the distributor rebuilt and re-curved, $199.95 includes our new advance installed.
See our distributor re-building page.
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 except you can now static time your car 10 to 12 degrees BTDC. 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 the fuel is leaner and slower to burn and 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.
Unit cost $79.95
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Later 1968-72 Jaguar XKE
Convert from vacuum retard to vacuum advance.
If you already have SU carburetors with ported vacuum simply have us re-built and re-curve your distributor to a early advance spec.
Complete rebuild / restore 22D6 XKE 6 cylinder $199.95
Visit our "Lucas Distributors" page for distributor re-build information!
If you have the stock Zenith carburetors, one of them needs to be machined for the correct ported vacuum. Cost $50.
If your having the distributor re-build and re-curved to early spec, machining the Zenith carburetor for ported vacuum cost $25.
Converting to vacuum advance is one of the most cost effected way to enhance performance, driving pleasure, increase mileage and run cooler.
British Vacuum Unit, which is not affiliated with ZF Friedrichshafen AG, the owner the US trademark for Lucas®.
British Vacuum Unit
Briar Bush Rd
Canterbury, N.H. 03224
Special Triumph Spitfire and GT6 Delco D204 distributor vacuum advance units.
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