69 390HP 427

[Verle R.]

We are starting to assemble the original engine after machining.

With the block upside down on the engine stand numbers are visible on the pan rails. I noticed them before sending to the machine shop.

The numbers are stamped adjacent to each cylinder and are:

driver side 9 8 8 9
passenger 9 7 8 12

There are some other stamps near the oil filter mount, one is an "R"

Does anyone have a clue what they may be?

Thank you,

Verle

[Ted S.]

Re: 69 390HP 427

Verle, My understanding is that the numbers on the oil pan rail correspond to the piston size that was to be placed in each cylinder. Until recently the machining varied enough that the assy line measured the cylinders after they had been bored to determine which pistons to use. Then a set of pistons with rods were put together for that specific engine. Hope this helps. Ted

[Terry M.]

Re: 69 390HP 427

Ted has it exactly right. At least that was the practice at the end of Mark IV production. Flint did the same thing through Gen I and most, if not all, of Gen II production. I suspect that practice continued for a while at both engine plants. As Ted said: "Until recently...."

[Dick W.]

Re: 69 390HP 427

I think that you will find this was (is?) common in the automotive industry. Chrysler did the same on the "B" and hemi engines.

[William C.]

Re: 69 390HP 427

Was is the appropriate term. The focus on improved stastical process controls over the last 15 years in the auto industry has eliminated this practice, at least in GM. An eye opener in the early eighties was a competitive analysis that showed Honda with process controlsm and one bore size, one piston size had less variation in piston to wall clearance than GM had with the "measure and select" process was a big part of the incentive for process controll improvements. It is just one small part of the GM drive for Quality inprovement over the last 20 years.