Supplying the Assembly plants with engines.

[firstgenaddict]

How would the supply of the Z28 L78 L89 engines proceed towards the end of the production year?
I know that orders were not released by the central office, for production, until all parts were on hand... 

Would the engine plants build an anticipated number for stock and then as the supply was exhausted out of the engine plant's inventory it would be refilled with newly built units?
Were engines called out of Engine Plant stock upon order from assembly plants?

Or would engine plants supply units based on forecast production? 
What about an order entered within last month of production?


 

[william]

I wasn't there, but worked in Supply Chain for much of my manufacturing career.

All mass production of this magnitude begins with Demand Planning. Chevrolet determined that they would sell about 225,000 Camaros annually. Next, how many 6 cylinders, how many converts, etc. This is further divided into how many of each model/option is forecast by Marketing. The plan drives manufacturing capacity at the parts plants.

Z/28s sold far better than anyone anticipated so for '69 the production plan [stated in the January '69 Hot Rod] started out higher than ’68. You have to start someplace so maybe Chevy initially planned on 15,000 Z/28s for ’69. That means over 50 weeks of production, you’re going to need 300 DZ engines, 1,500 15” wheels & E70 x 15 tires, et cetera, per week. Breaking it down further, that’s 60 DZ engines per day from the Flint engine plant. That’s enough to put them in continuous production aka Make To Stock; nearly everyday Flint built DZ engines and shipped them to each Camaro plant. Engine plants did not stock finished goods. The production schedulers knew they could release 60 Z/28 orders every day because Flint shipped 60 engines every day.

Low-production 396/427 engines do not appear to have been produced on a continuous basis. Prior to releasing a production order, someone would have to verify it could be built. Known as Material Assurance, it is easily done in todays’ ERP systems. No idea how it was done in those days; wouldn’t surprise me to hear someone went out on the floor and counted.

Production Control at the assembly plants probably knew the forecast and maintained a small inventory of L78 engines. When stock dropped below a certain point, an order was placed and a batch of maybe 50 JH/JL engines would be built. That’s why it is common to see the same engine date on cars built weeks apart or widely varied dates on cars built at the same time; the engines remained in stock much longer. Some 03B COPOs have January 23 MN engines, some have early March MN engines. Never happens on Z/28s; all the 03B cars I know of have early March engines.

Appears the same strategy was applied to L89 engines, but in smaller quantity. I have data on 31 L89 cars [10% of the total]. There are 27 engine build dates; 1 group of 2 another of 4 with the same date. In the group of 2, the first engine was installed 21 days after build, the other 49 days. Maybe built in batches of 5 or 10.

As production shutdown approached, I’m sure production control tightened up ordering. No Plant Manager wanted to get stuck with obsolete inventory at the end of a model year. It is common to see L78 engines built July 24th & 25th in Camaros built through the end of production. When those last engines were fully committed to dealer orders, Central Office would notify dealers L78 orders could no longer be accepted.

Z/28 engine production concluded about two weeks prior to the end of 1969 production.

[KurtS]

I know that orders were not released by the central office, for production, until all parts were on hand... 

No. The orders were released to the plant and the assy plant schedulers were the ones that released them to production when the parts were on hand.

They did weekly forecasts. xxx JK engines, xx JH, etc. One week would generally be the same volumes as the next week, so there weren't many surprises.
The last weeks get tighter - the plant wants to run out of parts as the last car comes down the line. Not too hard on fenders, but more complicated on wiring harnesses and other option dependent items. As Bill mentions, the last vehicle orders were counted and matched with inventory and component orders. They knew exactly how many JH engines they needed 49 years ago (to the day!) and had them on hand to finish the 69 MY.

[cook_dw]

Good thread and great replies.  Nice change to the recent norm.

[JKZ27]

Thanks for taking the time to write this stuff. It never gets old, IMO.

[william]

Many years ago I was involved in the restoration of a '67 Z/28. The car was routinely questioned because it has an 06E date on the body tag but the engine was built July 6, 1967. The engine has a no-question VIN stamp and matched the Protect-O-Plate.

How can a June car have a July engine?

The cars’ VIN tells the story. The normal VIN range for 06E builds in N242500-N247900. The VIN for our Z/28 is N251xxx, final-assembled on or about July 12, 1967. Other N251xxx builds have 07B tags. VINs were assigned as the finished body arrived from Fisher and was checked into the Body Bank at Chevrolet assembly. What that indicates is the order was initially released to production during 06E but quickly went on hold, most likely because Chevrolet Production Control learned they were short on Z/28 engines. There are a few other 06E Z/28s in the normal VIN range and those have July 3rd engines. Another batch of Z/28 engines was built July 6th. The build order for our Z/28 could then be released. Z/28s built through the end of the 1967 model year usually have July 6th engines.