sbc stock timing cover vs aftermarket ac delco cover timing tab location

[Jeff P.]

Men just finished reading John Hinkley and Dukes discussion about the 1969 passenger car timing tab location. My question is... Could the aftermarket chrome ac delco timing cover also be moved 10* ? What would be the simplest most accurate method of checking TDC with the heads on? I will be testing this for 1968 L-79. Can someone give me the part # for a 1968 L-79 harmonic dampener? Not a 300HP dampener! Where might this part # be located? Is there a date code stamped on the dampener? Thanks in advance.

[Joe L.]

Re: sbc stock timimg cover vs aftermarket ac delco cover timing tab location

Men just finished reading John Hinkley and Dukes discussion about the 1969 passenger car timing tab location. My question is... Could the aftermarket chrome ac delco timing cover also be moved 10* ? What would be the simplest most accurate method of checking TDC with the heads on? I will be testing this for 1968 L-79. Can someone give me the part # for a 1968 L-79 harmonic dampener? Not a 300HP dampener! Where might this part # be located? Is there a date code stamped on the dampener? Thanks in advance.

Jeff-----

The aftermarket Delco timing cover does not have an integral timing tab. A bolt-on timing tab must be used. Later GM timing covers also used the bolt on timing tab.

The correct harmonic balancer for a 1968 L-79 is a GM #3817173 WITHOUT "FINS". This is an 8" OD balancer. Sometimes there will be the last 4 digits of the part number stamped on the hub but it's not visible with the pulley installed. The balancer is about 1-11/16" thick and the timing mark aligns with the keyway.

[Steve G.]

Re: sbc stock timimg cover vs aftermarket ac delco cover timing tab location

Locating tdc came up recently so I copied the procedure I posted previously and pasted it below.

Using a tool like this


or one made by knocking out the porcelain centre out of a spark plug and welding a 3/8 bolt in, threaded into the #1 cyl, you slowly roll the engine over by hand until the piston comes into contact with the tool and stops. Make a mark on the damper at the 0 mark on the tab. Now roll the engine over by hand in the opposite dirrection to the way you first turned it. When it stops at the piston stop, make another mark at the 0 mark on the tab.

TAKE THE TOOL OUT

TDC is the mid point between the two marks. Using a flexible steel ruler measure out the mid point and mark it.

[Jeff P.]

Re: sbc stock timimg cover vs aftermarket ac delco cover timing tab location

Thanks Joe and Steve.