Dual Point Conversion for Group Lb Special

Recently completed dual point conversion and re-curve of BOSCH distributor for use on Group Lb historic MG-based special.  Distributor has advance curve tailored to engine, circa 50 degrees dwell and consistent dwell behaviour beyond 7000 crank RPM.  Some details of the car and pictures of completed distributor below.  Vehicle is based in South Australia. 


1947 MG TC Holden Square Rigger



The car has the following summary technical specification:

1947 MG TC – (original engine number XPAG 3306, chassis number TC2675)

  • Registered Number Victoria RZ 685

  • Square rigger style T series MG body.

  • Cycle front guards.

  • Fitted with a modified Holden Grey engine in the 1950’s with triple SU’s and other engine and mechanical modifications (unknown if any competition history).

  • Fitted with both 16” and 15” x 5” wheels in the period up to 1965.

  • Hydraulic telescopic shock absorbers and axle restraints front and rear.

  • Holden grey banjo differential centre and modified axles in TC rear axle housing.

  • Cut down Morris Minor rack operating as a steering box across to the original position LHS steering arm (common modification in the era).

  • Larger twin leading shoe 10” x 2 ¼” front brakes in one off cast iron finned brake drums.

  • Modified finned Monaro Motors 9” MG TC rear brakes.


Competition History

The car was built in the 1950’s as a MG Holden (triple SU’s and modified engine) with modified front brakes, telescopic shock absorbers etc, The car has a confirmed ownership from 1959 and an identified racing history in the period 1963 to 1965:

  • Used as a road car from 1959 to 1963 by Vern Barlow in Victoria as a grey Holden engined MG TC special (triple SU’s, modifications, etc).

  • Sold to Peter Mahony in 1963 in Victoria (entered under BP Heidelberg).

    • Competed at Lakeland hillclimb, Calder and Templestow hillclimb.

  • Sold on then to Rod Cooper, Victoria (entered under SAAS) at some point in late 1964.

    • Competed at Lakeland hillclimb, Calder and Hume Weir.

  • The subsequent ownership history is unknown until 2013.  No history of competition has been confirmed before and beyond the dates above, and its competition history appears to have ended in 1965, due to the car quickly becoming uncompetitive. 

  • The car was then in storage in a semi disassembled state since 1966.

  • The car is currently under restoration to Group Lb specifications in its early 1960’s configuration since 2014.


Engine Specifications:

The following are the key specifications in progress:

  •  EJ Block. (early low number block)

  • Capacity 2350cc (thin wall sleeved).

  • Main bearing straps and girdle.

  • Vauxhall E Model crank (stroked to 3 1/8”). – MGB main bearings / modified rear seal arrangement.

  • Mitsubishi Starion con rods and bearings.

  • Lightweight billet flywheel (8kg), Holden heavy duty 8.5” single plate clutch assembly.

  • Ross balancer.

  • JE 3 ring domed pistons (21mm gudgeon diameter).

  • Modified water pump and head outlets.

  • Vintage Racing Developments special twin point distributor.

  • Modified camshaft grind – approximately 235 degrees @ 0.050” and 0.3” cam lift.

  • Modified head with 1.48” and 1.25”’ valve sizes and relieved chambers – LS1 beehive springs.

  • 1.7:1 rocker ratio.

  • 10.5:1 compression ratio.

  • Triple 30 degree SU 1 ½” (internally modified) on 1960’s Sonic short inlet manifold and common cold air plenum chamber with rolled edge short ram tubes.

  • One off exhaust manifold – 1 3/8” primaries, 1 5/8” secondaries into a 2 ¼” system.