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Old 12-14-2012, 12:29 AM
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Originally Posted by TNCHEVYMAN View Post
I have a 97 roller cam sbc 4 bolt motor, i will soon start building, it nas the plastic cover on the timing chain. it says on it to replace it if removed. why is this. should i get the oe unit or should i go aftermarket? what cover should i use? THANKS
I think it is supposed to be replaced because the front crankshaft seal is non replaceable. If the cover wasn't leaking from the front seal I see no reason to not reuse it.

Below is a side-by-side shot of a plastic cover from a 1997 Vortec engine and to the right of it is a '80s non-roller steel timing cover for comparison.

Some differences are:
  • The plastic cover has more room around the crank gear. This cover was equipped with a crank sensor, so the additional room may be to make room for the crank position sensor rotor.
  • The steel cover is deeper, from inside the front to the sealing surface.
  • Generally, there seems to be more room around the inside of the steel cover, even though the photos don't look that way due to how the covers are shaped. This is except for the area around the crank gear.
  • The plastic cover has fewer bolt holes at the top.
  • The plastic cover has male pins or dowels to locate the cover onto the face of the block; the steel cover has holes in the same position for the dowels that are used in the older blocks.
  • The plastic cover's bolts are shouldered to prevent over-tightening the cover.

The older block uses dowel pins (male pins in block, holes in tin cover), while the Vortec block (below) has the holes for the plastic cover's pins.

This 880 block has all the holes present and tapped. As said the dowels are absent, instead there are holes. The dowel holes in the 880 block are >15/64" and <1/4" (right for a press-fit 1/4" dowel pin, I'd guess).

The p/n for plastic cover w/sensor hole is: p/n10244600.

The number for plastic w/o sensor hole is: p/n12552557.

The last thing that needs checked is the type of front oil pan-to-cover seal is needed. I would guess it would be the later, thicker seal- but I'd check it first if the older cover was going to be retrofitted to the Vortec block.

To check what front seal is needed, put a straight edge across the front of the pan and measure down to the lowest part of where the seal rests.

2-1/4" = thin seal
2-3/8" = thick seal

I would think using a '87-up steel timing cover w/the 1-piece oil pan gasket would be the best bet, although any steel or aftermarket cover may well work as well.

Good luck.

Last edited by cobalt327; 12-14-2012 at 12:41 AM.
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