What is the spark plug and gap for the MGB 18V 581Y/582Y/583Y engines?

Champion N9Y plugs gapped .024 to .026 in. (.625 to .66 mm.).

What is the ignition timing for these MGB 18V engines?

Static timing is 10° B.T.D.C. for both H.C. and L.C.; stroboscopic timing is 13° B.T.D.C. at 600 r.p.m. for both.

What are the valve rocker clearances?

Set cold: .015 in. (.38 mm.); set hot: .013 in. (.33 mm.).

What distributor and points gap are specified?

Lucas 25D4 distributor with a contact breaker gap of .014 to .016 in. (.35 to .40 mm.), anti-clockwise rotor rotation, and a dwell angle of 60°±3°.

What carburetter needle and jet does this engine use?

S.U. HIF4 carburetters with a .090 in. (2.2 mm.) jet, AAU needle, and red piston spring.

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MGB 18V 581Y/582Y/583Y Engine Tuning Data - Timing, Plugs, Carb Specs

MGB 18V 581Y/582Y/583Y engine tuning data: timing, dwell, plug gap, carburetter specs, page 71

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MGB Engine Tuning Data for 18V 581Y/582Y/583Y engines listing compression 9.0:1, idle 750-800 rpm, valve clearance .015 in cold, ignition timing 10 BTDC, Lucas 25D4 distributor and plug gaps.

AI caption September 2012 · Photo 41 of 101

This is page 71 of an MG B workshop manual (marked 'MGB. Issue 2. 83910', 'Engine Tuning Data 5') giving complete engine tuning data for the 18V 581Y, 18V 582Y, and 18V 583Y engines. It lists engine specifications: 1798 c.c. (109.8 cu. in.) displacement, firing order 1-3-4-2, compression ratios of 9.0:1 (H.C.) and 8.0:1 (L.C.), nominal 170 psi cranking pressure, 750–800 rpm idle, valve clearances (.015 in. cold / .013 in. hot), static timing 10° BTDC and stroboscopic timing 13° BTDC at 600 rpm. Distributor data covers the Lucas 25D4: points gap .014–.016 in., anti-clockwise rotor rotation, 60°±3° dwell, plus centrifugal advance curves for serial numbers 41288 (H.C.) and 41290 (L.C.) and vacuum advance start/finish values. Ignition coil is Lucas HA12 (3.1–3.5 ohms primary); spark plugs are Champion N9Y gapped .024–.026 in. Carburetters are S.U. HIF4 with .090 in. jet, AAU needle, and red piston spring. Electrical specs list Lucas 16ACR alternator, Lucas BT9E/BTZ9E/CA9E/SG9E or Exide 3XCK9L batteries, 12-volt negative earth, and Lucas 2M100 pre-engaged starter. Useful for tune-ups, ignition timing, and carburettor setup on these engines.

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Frequently asked questions

What is the spark plug and gap for the MGB 18V 581Y/582Y/583Y engines?: Champion N9Y plugs gapped .024 to .026 in. (.625 to .66 mm.).
What is the ignition timing for these MGB 18V engines?: Static timing is 10° B.T.D.C. for both H.C. and L.C.; stroboscopic timing is 13° B.T.D.C. at 600 r.p.m. for both.
What are the valve rocker clearances?: Set cold: .015 in. (.38 mm.); set hot: .013 in. (.33 mm.).
What distributor and points gap are specified?: Lucas 25D4 distributor with a contact breaker gap of .014 to .016 in. (.35 to .40 mm.), anti-clockwise rotor rotation, and a dwell angle of 60°±3°.
What carburetter needle and jet does this engine use?: S.U. HIF4 carburetters with a .090 in. (2.2 mm.) jet, AAU needle, and red piston spring.

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