Broach Marks

[Andrew S.]

I recently purchased a '66 L36 that, during a '93 restoration, had the pad painted along with the block. The numbers match the VIN plate, and the plate was verified before purchase. I had a Master NCRS Judge inspect it, so I knew what I was getting into. He estimated it at a #2 Driver. That inspection saved me $10K off the asking price!!!

I've carefully stripped the paint off the pad using a gel paint stripper, so now I assume the broach marks are visible and I could verify if the stamping is original.

I'm a novice at this, so, what exactly are broach marks? And what the heck am I looking for?

Apologies if this topic has been addressed at length before.

Thanks!

Andy Smith

[Kenneth H.]

Re: Broach Marks

Andy,

Do a search on "broach marks". there are many recent threads concerning this issue.

Thanks.

[Rick A.]

Re: Broach Marks

post a "detailed" picture of your stamp pad and we will tell you what we think

[Tom H.]

Re: Broach Marks

To be simple, broach marks are the machine marks left behind when the block was originally surfaced. They are straight and run the same direction as the cam and crank ( end to end ) They vary in depth and appearance from block to block.

[John H.]

Re: Broach Marks

I'm a novice at this, so, what exactly are broach marks? And what the heck am I looking for? Andy Smith

Andy -

Some 40-year-old pads exhibit broach marks, and some don't. The photo below shows a '66 L-36 pad that still has some - look closely above the VIN stamp and you'll see them.

[William L.]

Re: Broach Marks

I'm a novice at this, so, what exactly are broach marks? And what the heck am I looking for?

This is the engine pad on my 67 and broach marks are very easy to see. But like John said some broach marks are very very faint. I like to take a picture of the pad and then you can zoom in and see what you have?

[Edward J.]

Re: Broach Marks

Bill, was your block double stamped from the factory? im a novice at this myself to,I can clearly see the broach marks.

[William L.]

Re: Broach Marks

Bill, was your block double stamped from the factory? I'm a novice at this myself to,I can clearly see the broach marks.

Ed
Yes it was stamped at the Factory. I am 100% sure. I have owner history and titles back to the original owner and selling dealer. Top Flight at 2008 NCRS Nationals and Bloomington Gold 2009 I have a picture of another 67 big block that was stamped 7 days after mine and the broach marks are also very pronounced.
Bill

[Rick S.]

Re: Broach Marks

Bill,
Very interesting that our blocks assembly was a day apart (different engine plants though) but our cars are over 300 apart.
Rick

[Rich P.]

Re: Broach Marks

Bill, was your block double stamped from the factory? im a novice at this myself to,I can clearly see the broach marks.

Ed,

if you ask me what you are seeing is a ghost stamp from the rebound as the build stamp is good hit.

Rich

[Tom H.]

Re: Broach Marks

Bill, was your block double stamped from the factory? im a novice at this myself to,I can clearly see the broach marks.

Adward:

As you start to study stamps, you will see stamps like this. They are often referred to as "double strikes". Pretty neat to see. The guys who stamped these engines never had any idea anybody would ever look at them !!!

[Edward J.]

Re: Broach Marks

Guys,Im sure that this stamp is one of thousands the factory screwed-up. the derivative stamping looks to be alittle deep on the second time around.

[William L.]

Re: Broach Marks

Bill, was your block double stamped from the factory? im a novice at this myself to,I can clearly see the broach marks.

Sorry Ed I miss read your post.What most of the experts tell me is that its a "bounce" and it is common.

[William L.]

Re: Broach Marks

Bill,
Very interesting that our blocks assembly was a day apart (different engine plants though) but our cars are over 300 apart.

Rick that's neat, my cars build date is K23 and the body # is S6446. Is your car by chance a Smith Body??

[Rick S.]

Re: Broach Marks

Bill,
My body build date is K 16 and my St Louis body # is S8822. Body is St.Louis. The neat thing about my Trim Tag is that it has a typo for color, it should be 983AA. Took me a long time to track down the original owner to verify the color and also have Al Grenning validate that it is a typo.

Rick