Timing tabs and damper TDC lines SBC
(→The three most common locations for the timing mark on the damper) |
(→The three most common locations for the timing mark on the damper) |
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| Line 5: | Line 5: | ||
The exact years of the type of damper timing marks overlap one another, depending on the exact application. | The exact years of the type of damper timing marks overlap one another, depending on the exact application. | ||
| − | #The pre-1969 damper has the TDC line on the outer ring at the 2:30 o’clock position- or 2º before the keyway centerline- i.e. the line is to the LEFT of the keyway, looking at the front of the damper or engine. The keyway is seen in the ID of the damper nose. | + | #The pre-1969 damper has the TDC line on the outer ring at the 2:30 o’clock position- or 2º before the keyway centerline- i.e. the line is to the LEFT of the keyway, looking at the front of the damper or engine. The keyway is seen in the ID of the damper nose. Includes a majority of the 2.30" small journal main engines and the 1967-69 2.45" large journal engines. |
| − | #The damper used from 1969 to about | + | #The damper used from 1969 to about 1995 (some 1978-86 GM automobiles do not use the 2 o'clock position balancer and associated timing cover where there is some overlap usage e.g. G-series vans which retained the 2 o'clock balancer while the passenger car and C/K light duty trucks transitioned over to the 12 o'clock position which used a centrally located timing pointer spot welded) has the TDC line at the 2 o’clock position- or 10º before the keyway. You'll find that aftermarket dampers are the 10º type, as are the bolt-on tabs sold by the aftermarket, unless they're adjustable. <br>{{Note1}}This includes the SBC 400, although the 400 damper is counterweighted because the engine is externally balanced, and the 1985-present 4.3L V6 with its respective 6.75" damper (raised outer lip) that has both a 2 o'clock and a 4 o'clock position (for some vans eg. G-series, Express, and Astro/Safari). Do not mix and match internal and external balanced dampers (also applies to 1996+ Vortec applications (4.3, 5.0, 5.7)since the balancers are thinner to clear the pressed on crankshaft position sensor used with the associated plastic timing cover; USING THE VORTEC BALANCER WITH A NON-VORTEC MOTOR WILL RESULT IN MISALIGNMENT OF THE CRANK PULLEY WITH THE REST OF THE ACCESSORIES E.G. POWER STEERING PUMP, ALTERNATOR, WATER PUMP AND A THROWN BELT)! The 2 o'clock position was reintroduced during the 1987 model year trucks with the 8" balancer (only with the LO5-optioned 350/5.7L) |
| − | #A third timing mark was used from (some) 1978 to about 1986 (carbureted engines), and nearly all 1984-1995 (exc for 1985-present 4.3L V6 and van (Astro/Safari, G10, 20, 30 and P-series box vans)applications). It is at the 12 o’clock position- or 40º before the keyway. This damper uses a timing cover that has the tab welded on at about the 12 o'clock position - the timing covers with this setup had either the 6.75" (305 and pre-1985 90 degree V6) or 8" (350/5.7 only) - 1987-95 balancer will fit if used with the associated timing tab and front cover. Professional Products lists the years for this type damper line as being 1984-1995 and is a 6-3/4” diameter damper. | + | #A third timing mark was used from (some) 1978 to about 1986 (carbureted engines), and nearly all 1984-1995 (exc for 1985-present 4.3L V6 and van (Astro/Safari, G10, 20, 30 and P-series box vans) applications; with some overlap use e.g. C/K series trucks, marine/industrial, passenger car). It is at the 12 o’clock position- or 40º before the keyway. Harmonic balancers used have a thicker ring unlike the 2 o'clock position balancers. This damper uses a timing cover that has the tab welded on at about the 12 o'clock position - the timing covers with this setup had either the 6.75" (305 and pre-1985 90 degree V6) or 8" (350/5.7 only) - 1987-95 balancer (LO3/LO5) or 1969-80 balancer will fit if used with the associated timing tab (GM 12551537, 6 3/4"; 88960604, 8") and front cover. Professional Products lists the years for this type damper line as being 1984-1995 and is a 6-3/4” diameter damper. |
==Relocating the damper line== | ==Relocating the damper line== | ||
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