Member of the
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 sent 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 conformation charge apply, usually within $4.00
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 email@example.com
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.
Go to our "vacuum unit ID 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;Emailbritishvacuumunit@isp.com
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.
New 20D8 units $79.95
54411675 6 17 9 54412403 4 17 6
Rolls Royce / Bentley
#54415488 8 20 8
54424997 8 20 8
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 $199.99 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 / $25.00 with unit purchase. Call or Email for information.
1971 to 76 TR6 Retard (no shaft) $69.95
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.
#423438 code 7 14 10
Early Austin Healey
#421189 Brass cap code only 5 12 8
Our Early Lucas DVX,DM2P4, DMBZ & DM6 Distributor Vacuum Advance Unit Hex Chamber Units, as shown above, are 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.
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.
Early Hex units were manufactured by Lucas in different versions. For example the "early version" Austin Healey vacuum unit 421189 with vacuum code 5-12-8 was supplied with only the code stamped on a brass vacuum cap. Shortly later, Lucas produced all these units with the part number and code stamped on an aluminum vacuum cap. Describe your unit when ordering to assure you receive the original unit as equipped by the factory when your vehicle was produced.
Original type DM, DV, 22D & 25D Lucas units
Early external mount, Early or later Lucas castings
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
Later push on
DM Hex spring link Brass or aluminum cap DM Hex pin link
Early or late adjuster kits
Screw fitting pin & spring link
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
OE manifold vacuum
Go to our vacuum unit ID page to look up your Year, Vehicle,
Distributor # and original Lucas unit part number.
Advance / retard
Early and late castings
OE 35D8 units
DVX 2 stud
OE Jaguar 36DM12 with adjustable limiter or JLM519 Later retard and advance units
Most common lines.
|MGA ||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|
|BJ8||34” one rubber elbow, one rubber fitting|
|Jaguar 1950s 6 cyl||20” two compression nuts|
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