427 big block. Casting # 3955270

[Mike Cobine]

There is one of these on eBay. Interesting in that it is cast Aug 11, 1968 because in the normal course of production, it would have been ready to drop in a car within a few days. This made it available for 1968 models, yet they seem to only have gone in 1969 models of Corvettes and passenger cars.

Would Chevrolet have made a bunch a month early for the next model and just let them sit?

Or did the passenger car line start earlier than September?

And apparently, they were a short run, being August to October. Considering how long other casting nubmers seem to run, was this a bad one?




427 big block. Casting # 3955270

[Steve Antonucci]

Re: 427 big block. Casting # 3955270

Hi Mike,

I saw this auction and have essentially the same questions. I'm actually
considering this block for one of my projects.

In my quest for learning as much big block component knowledge as I can,
I was amazed to learn about all of the components developed & manufactured
for the 1969 model year. What redundancy! eg. Three 427 blocks were used
in the 1969 production year: 3935439, 3955270 & 3963512

I do know that the '270 block was considered to be a transitional block -
a bridge between the 3935439 and the 3963512. Why this was done, perhaps
others can explain. I recently found a '512 block with a mid-October 1968
casting date. The date was down by the starter ( early style dating ).

I had read that these blocks were first cast in October 1968, but I never
saw one dated before late November or early December 1968. As you probably
know, the '512 block started life as a 427, but was predestined to become
the 454. Hence, the cast crankshaft reliefs on the bottom of the cylinders.
Engineering & design schedules have to run twelve or more months ahead of the
model year - don't they? If the technical staff at Chevrolet knew the '512
block was going to be introduced, then why the '270 block. I've read that
this block was essentially the same as the 3935439 block. Did engine block
casting programs have a specific life-span? It wouldn't seem practical to
cast another block for such a short run. BTW, I've never heard of any issues
with the '270 casting. Again, perhaps others can elaborate on this.

I'm probably not telling you anything you don't already know. Just adding
my input.

Steve

[Joe L.]

Re: 427 big block. Casting # 3955270

Mike-----

First of all, 1969 Corvette production started in August, 1968. Most other Chevrolet models did, too. Regardless of which car model this engine was originally installed in, it would likley have happened at least a few weeks after its assembly due to transit time between Tonawanda and the various vehicle assembly plants. Also, it could have gotten "stuck" in the back of a vehicle assembly plant engine bay and might not have been installed in a vehicle until quite some tome later.

Engine block casting numbers were not necessarily always "successive" in their manufacture. It could well be that, for some period of time, 2 different casting numbers could have been made coincidentally. In other words, the engine foundry did not necessarily scrap ALL of the molds for one casting number on one day and start using ALL of the successive casting number molds the next day. That would be especially true for block castings that were different in only minor ways that didn't affect engine machining tooling.

Also, I'm quite sure that the engine plants did not "hold" engines of a particular block casting for installation in only a particular model year. They MAY have held assembled engines which were built for and unique to a particular model year, but I'm sure that casting numbers for blocks and cylinder heads were not an issue, at all. These things were totally "invisible" to the customer. They may be important now for restorers, but they were not important then as far as manufacture was concerned.

[Mike Cobine]

Re: 427 big block. Casting # 3955270

Of course, you are right, Joe, which I don't need to tell you. I looked at the production figures for end of each month, mistook June 1968 for July, compared to August 1968 and assumed a full month (about 4600 cars). Then for 1969, the first figure is for end of Sept. 1968 production, and none listed for end of August.

So it looked like the 1969 model only block was made during the 1968 model car production run.

If I had looked at the build dates for 1969, I'd have noticed that '69 car production started in August. Probably '68 car production stopped a week before this block was cast and '69 production started the same week as the block or the next.

Then it is of course all logical and doesn't appear to have produced a '69 block during '68 car model production.