When Did Broach Marks Stop?

[Jeff B.]

I assume that at some point, the factory stopped decking the blocks with the machine that left the classis broach marks parallel to the engine block. I'm not exactly sure what followed, maybe a rotary decking method or CNC, and a different process for aluminum blocks, but I'm wondering if there is a definitive year when the classic broach marks no longer appeared on the block.

[Mark F.]

Re: When Did Broach Marks Stop?

I assume that at some point, the factory stopped decking the blocks with the machine that left the classis broach marks parallel to the engine block. I'm not exactly sure what followed, maybe a rotary decking method or CNC, and a different process for aluminum blocks, but I'm wondering if there is a definitive year when the classic broach marks no longer appeared on the block.

Jeff,

I'll be interested in responses to this post.

Granted, my experience in engine plants (where broaching and deck finishing operations - whatever they were and are today - take place) is ancient, but I was not aware broaching machines had been replaced...cast iron or aluminum.

Is there something else you know about this that makes you assume this machining process was ceased - and/or additional info/background you can add on your post regarding your assumption ?

[Jeff B.]

Re: When Did Broach Marks Stop?

In 1997 all Corvettes got aluminum blocks, and those don’t get decked the same way. But I have no information about the engines just before that. My experience is mostly in C2s which of course were all broached. And I know at least the early C3 were, but I was wondering how long this continued…all the way to 1996? What about C4s ?

[Mark F.]

Re: When Did Broach Marks Stop?

Thank you, Jeff

Your post prompted me to search the web a bit and I learned a few things...

This is one link I found interesting...
"Combining Milling and Broaching for Aluminum Engine Components"

https://www.evdesignandmanufacturing.com/article/combining-milling-and-broaching-for-aluminum-engine-components/

I've been in aluminum foundries, but have never seen how the block and other engine parts that need to be perfectly FLAT were made to be just that...

None of this answers your specific question, but more searching may yield a result.

[Pete B.]

Re: When Did Broach Marks Stop?

C4 steel blocks have broach marks.<br />
Early C5's were vin stamped on a cast aluminum surface.<br />
Mid C5's through 2010 and probably beyond were stamped or Lazer etched on a flat milled surface on the left rear side of the block.

[Mark F.]

Re: When Did Broach Marks Stop?

C4 steel blocks have broach marks.<br />
Early C5's were vin stamped on a cast aluminum surface.<br />
Mid C5's through 2010 and probably beyond were stamped or Lazer etched on a flat milled surface on the left rear side of the block.

Thanks, Pete,

I learn something new everyday on this TDB !

Excellent topic for a virtual school if somebody has all the knowledge to put it all together...

Proven by the posts above, I know I don't have the knowledge

[Kenneth B.]

Re: When Did Broach Marks Stop?

If the cases are machined like other castings now days they would be machined in one or 2 operations & would probably on one or two fixtures.With the CNC'S there is no need for multiple fixtures & different machines. This is why tolerances are so much tighter than in the day

[Michael J.]

Re: When Did Broach Marks Stop?

Yes, as I was watching my 2012 ZR1 built, I saw the guy laser etching the VIN into the block.

[Michael J.]

Re: When Did Broach Marks Stop?

1965-chevrolet-impala-ss-409 (3).jpgI am wondering also when they started, not being a C1 person. I know Tonawanda milled the blocks of the 409s they made in the early '60s, swirled marks on the pad. But later, the 427 BBs were broached.

[Jeff B.]

[Ed D.]

Re: When Did Broach Marks Stop?

If it weren't for the stamp pads, would we be interested in broach marks?

[Mark F.]

Re: When Did Broach Marks Stop?

If it weren't for the stamp pads, would we be interested in broach marks?

My guess is no.

Just as we aren't interested in the engine plant cylinder honing station marks - because you can't see them...

[Jeff B.]

Re: When Did Broach Marks Stop?

If it weren't for the stamp pads, would we be interested in broach marks?

Probably not Ed, but there ARE stamp pads! And I do think understanding manufacturing methods and why they were used (and eventually replaced) has some interesting aspects. GM had no intention of leaving broach marks for the purpose of identifying original engines 60 years later, they were just decking the blocks with the most efficient method they had. The difference in the way we manufacturer automobiles now and just 50 years ago is remarkable.

[Steven B.]

Re: When Did Broach Marks Stop?

and the 1969 aluminum blocks, how were they done?

[Ed D.]

Re: When Did Broach Marks Stop?

My rhetorical question, was meant to to bring attention to all the rhetoric about broach marks thru the years, that made these marks so important to judging corvette engines. There have been tutorial and miss information regarding how the broach machine machined the block and how deep and what direction the marks were made. With all the new material, new placement of the vin numbers, and the bar coding system, this all disappears.
Ed