Screw fitting pin & spring link

Early and late castings

We stock every unit type pictured above and many more!

State year, vehicle,  distributor and unit number when ordering.

Most new OE units $79.95  Shaft units supplied with 4 piece micro adjuster kit $89.95

1971-76 TR6 special advance $89.95

Duel advance / retard units, units with adjustable limiters and 35D8 Tin units  

Note: Vacuum retard units manufactured with dbl lip Viton shaft seal.

British Vacuum Unit, which is not affiliated with ZF Friedrichshafen AG, the owner  the US trademark for Lucas®.

Our Early Lucas DVX,DM2P4, DMBZ & DM6 Distributor Vacuum Advance Unit Hex Chamber Units are re-manufactured with the early Lucas body casting, 
tin plated chamber and large hex soldered as original with zinc plated shafts. 
​Your choice of aluminum or brass detailed threaded vacuum cap.
Stamped with Lucas part number and code.
​Please request if you want only the code stamped on the cap.  This was how some of the early units were originally supplied. 
​Modern fuel, oil and chemical resistant, fiber reinforced vacuum diaphragm.

Our Products

​​British Vacuum Unit, is not affiliated with ZF Friedrichshafen AG, the owner  the US trademark for Lucas®.

Lucas Distributor Vacuum Advance / Retard and duel Units.
​We have in stock new OE type DVX, DM, 20D, 22D, 25D and most all 35D, 36D, 45D,
​47D  4, 6, 8 and 12 cylinder Lucas distributor vacuum units.

TR6 1971-76 Special distributor vacuum advance units “not retard”

Part # 01816 code 6-18-10,    #01315 code 5-13-10 

 Our unit is engineered to take the place of the original vacuum retard unit and change the TR6 retard distributor into a performance advance ignition of the 1960s. The TR6 distributor body is cast as a retard system with no options until now.

Out special advance unit is a custom OE type Lucas unit easy to install in the place of the factory retard unit. You will experience a significant difference in performance, mileage and operating temperature.

It is highly recommended to have your 1971 to 76 TR6 distributor rebuilt to early advance spec with our special advance.

We offer this service with quick turn around $199.95 includes all new parts.

Must be connected to ported vacuum! Email us with questions. We'll be happy to help.      

Check our ported vacuum page.

$89.95 100% money back guarantee.


1971-73 Your Zenith 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. Call or Email for information.

British Vacuum Unit
​Canterbury, NH 03224 

When placing an order, please use the Lucas number and code.


When ordering Hex units;  be sure to specify type of cap, aluminum or brass and whether you
would like it stamped with code and part number or stamped with just the code.

If you do not give us this information, you will receive the Hex unit ordered with an aluminum cap, stamped with part number and code.

If you find we do not have the advance unit you need, you can send in your old unit to us to be reverse engineered at no additional cost.

All our products have a 2 year warranty.

30-day any reason return policy if any of our products do not exceed your expectations.

Operation of the distributor vacuum advance unit.

Vacuum units are not interchangeableunless they carry the same identification number, as each unit is made up to suit a particular engine.

Additional control of the spark timing is brought about by the vacuum unit. As the unit is connected to the engine intake manifold, its operation depends on the vacuum  present in the manifold.  The vacuum effect varies with the engine load. The vacuum unit produces additional advance when the engine revs are high, but mainly when the load is light. At full throttle when the engine is pulling hard the vacuum unit becomes wholly or partly inoperative. The general effect of the vacuum unit is to increase the liveliness or performance of the engine and enhance a noticeable improvement in fuel economy.

Proper vacuum advance function depends

on a tight vacuum line. Failure due to cracked, chafed pipes or loose unions, result in vacuum advance unit failure to operate !

We'll check your unit free of charge for damage and proper movement. 
​We notify you if your unit is correct to the year, distributor number, within code or defected. 
​Your old unit will be returned with or without a purchase of one of our new OE units. Only return shipping and delivery confirmation charge apply.

Lucas distributor vacuum unit check. Holding vacuum and movement. 

Many vacuum units checked for code operating specs are found defected. 
​Most vacuum gauges are calibrated in inches of mercury. The Mityvac vacuum pump can be use to check fairly accurate movement. 

1- Check for the correct unit. Units are not interchangeable. We list distributor numbers to O.E. units and their codes below or contact us at

2 - Check the unit holds vacuum. If the unit leaks, it needs replacing. 

3 - Check for proper movement. Most over looked, effecting performance, mileage and cooling. 

The vacuum units operates within the range indicated by the 3 digit code next to the part number. Example; the code 5 12 8 indicates, the unit starts to advance at 5 mercury "vacuum", will reach full advance at 12 mercury "vacuum", with 8 degrees total distributor ignition advance / 16 degrees spark advance at the crank. Units that no longer hold vacuum are obviously bad. It seems most people are under the impression that if the unit holds vacuum, it's considered in good operating condition. This assumption is wrong! Whats not obvious is a majority of original units are dry, stiff or plugged with condensed fuel vapor restricting proper movement and many operate well above the coded range. This renders the unit inoperable with very little benefit, if any at all. Replacing an original unit with a fresh new unit, often has a significant improvement in overall performance, mileage, cooling and often for much less that expensive engine modifications.
Installing a new vacuum unit, make sure the point plate is firm and moves freely. 
Information on our Lucas point plate page.

Often a new unit is installed without careful examination of the point plate and often finding the plate unstable and/or lacking free movement, hindering proper vacuum unit movement. The point plate needs to rotate freely but remain stable from rocking. It's often found to be stiff. There are 2 parts to the plate. The lower plate is secured with screws to the distributor body wile the upper plate clips to the lower plate and needs to be firmly supported, at the same time rotate freely. On one side of the upper plate a spring clip supports the plate in a horizontal position and the other side supports rotation with a guide pin in the lower plate grove. Often the pin and grove are found worn and need repair. The center bearing where the two plates rotate often need attention. If worn it needs to be repaired or replaced. Once the plate assemble is in proper operating condition it can be installed along with the new vacuum unit. Make sure the unit connector link fits freely and firmly in or on the plate connector pin or hole.

Non-vacuum advance performance distributors! 

Should only be installed when involved in high performance racing or under constant wide open conditions. Not good for street use. Anyone replacing a OE vacuum advance distributor with a performance mechanical advance distributor doesn't understand the operation of the vacuum advance unit. The original OE distributor with a vacuum advance unit, enhances cooling, engine efficiency, throttle response,and fuel economy. 

Its also wise to check the vacuum line!

A tight vacuum line and all connections are critical to the vacuum unit operation.Leaky elbows, threaded fittings, pinched, plugged or chaffed lines, are often found and need replacing.

Soft Copper" Vacuum Line Sets

1 compression nut & 1 male compression fitting $18.95 / with unit purchase $14.95
​2 compression nuts $17.95 / with unit purchase $12.95
​1 compression nut & 1 straight or elbow rubber connector fitting $14.95 / with unit purchase $10.95
Line supplied with 2 rubber connector fittings $12.95 / with unit purchase $9.95 
Our vacuum lines are similar to original
​Due to changes that may have been made over the years to carburetors and distributors, state the type of fittings needed when ordering.

You may need to reuse your old fitting on some early cars.

Most common lines.

33”  one compression nut,
1 male screw fitting.
MGB to around 1969
24” one compression nut,
1 rubber elbow.
Spridget up to 1969
 26” one compression nut,
1 rubber elbow
TR2, 3, 4
30” two compression nuts

TR4 with HS6
30” one compression nut,
1 rubber fitting
A.H. 100-4 & 100-M
30” two compression nuts

100-6 to BT7
34” two compression nuts

BT7   to BJ8
34” one compression nut,
1 rubber fitting
34” one rubber elbow, one rubber fitting

Jaguar 1950s 6 cyl
20” two compression nuts

early 1960s
20’ one compression nut,
1 rubber fitting
early/ mid 1960s
20” two rubber fittings

Austin Healey Manifold Drain Tubes One set $18.95 with unit & other purchase $14.95
1971 to 76 TR6 Retard (no shaft) ​$69.95

New OE 35D8 vacuum units.

MGB V8   Rover V8   Morgan  TR8  Stag

Aston Martin, Rolls Royce, Bentley  etc

As original OE part numbers and codes

54421965  6 20 7

54424497  5 17 8

54425692  5 11 6

54425859  4 7 5

54428626   2 5 5

​Others available!


Member of the

Special 8 18 10 vacuum advance units used with the Weber 32/36 down draft carburetor.

The Weber down draft carburetor can have as much as 5 + or - vacuum at idle causing vacuum advance when you don't want it.

Manufactured special for the DM2P4, 22D and 25D Lucas distributors. Cost $79.95 

Go to our "Lucas Distributor # to Unit #" page to look up your Year,  Vehicle, 
Distributor # and original Lucas unit part number. 
We Restore early units to new!  $49.95
Restored to original! Fuel resistant diaphragm, Parts are re-plated, replaced as needed to new original specs. 
Our restored units are returned in NOS condition and properly coded.  
​4 pc micro-adjuster kit supplied with all shaft type units.

DM Hex spring link                                     Brass or aluminum cap                                       DM Hex pin link   

                                                                Early or late adjuster kits 

Vacuum blank

OE manifold vacuum

Go to our "Lucas Distributor # to Unit #" page to look up your
Year, vehicle, distributor # and original Lucas unit part number.
Don't find it, email us! We most likely have it in stock!

​Order or questions:

Advance / retard

OE Jaguar 36DM12 with adjustable limiter    or    JLM519              Later retard and advance units                         

DVX 2 stud

OE 35D8 units

New 20D8 units  $79.95
54411675  6 17 9         54412403  4 17 6
Rolls Royce / Bentley
#54415488  8 20 8
54424997 8 20 8

Later push on

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