Author Topic: pad stamp?  (Read 10823 times)

z28z11

  • Hero Member
  • *****
  • Posts: 1179
    • View Profile
Re: pad stamp?
« Reply #15 on: December 10, 2014, 04:51:52 AM »
Note VIN and engine code line mismatch -
1968 Z28 M21/U17 BRG/W
1969 Z28 X77/M20/VE3 LeMans/W
1969 L78 X66/N66 Cortez/BVT
1969 Z11 L48/M35/C60/C06

KurtS

  • CRG Coordinator
  • *****
  • Posts: 4613
    • View Profile
Re: pad stamp?
« Reply #16 on: December 11, 2014, 07:46:59 AM »
Not a great pic, but I don't like it.
What's the VIN?
Kurt S
CRG

z28z11

  • Hero Member
  • *****
  • Posts: 1179
    • View Profile
Re: pad stamp?
« Reply #17 on: December 12, 2014, 04:49:27 AM »
I'm a little surprised -

I helped buy this block for a friend nearly 20 years ago. It's not a match to my '68 Z, but very close in date. I built the long block myself, plus sourced every part going into it.

Block was standard bore when I bought it, deck had never been touched up or resurfaced in any way prior to going to the machine shop. Block was bored .030, fitted with 1st design factory TRW ('67 thin rings)pistons purchased from the same guy, who also included the manifold and original distributor. .010/.010 original 1178 crank, pink pressed rods. If you're concerned with the pad surface around the stamp, it looks like it was scraped - no milling feed lines on the rest of the surface. Surface is completely flat, no signs of tampering or filling. My thought has always been not to try and pass this off as my original; it's someone else's block, but it's an MO, rebuilt with GM original parts.

I asked if this car's VIN was in the database sometime back - the response was negative. If the car should show up, I would gladly entertain a transfer to the owner (otherwise it will power my '68 for the rest of my life/ownership).

http://www.camaros.org/forum/index.php?topic=12082.msg99143#msg99143

Regards -
« Last Edit: December 12, 2014, 05:38:36 AM by z28z11 »
1968 Z28 M21/U17 BRG/W
1969 Z28 X77/M20/VE3 LeMans/W
1969 L78 X66/N66 Cortez/BVT
1969 Z11 L48/M35/C60/C06

69Z28-RS

  • Hero Member
  • *****
  • Posts: 4668
  • owner since 4-Apr-1976
    • View Profile
Re: pad stamp?
« Reply #18 on: December 12, 2014, 04:58:33 AM »
People can have differing opinions on such matters. 

Although insufficient information/imagery was included to be anything close to 'absolute', I didn't see anything in the presented data that would cause *me* to think it was not an original block and stamping.  Just my opinion.
Gary W / 09C 69Z28-RS, 72 B 720 cowl console rosewood tint
69 Corvette convertible, silver/black 350 hp,
60 Corvette white/red, 72 Corvette coupe, '70 Mach I 
90 ZR1 red/red #246, 90 ZR1 white/gray #2466
72 El Camino, '55-'56-'57 Nomads, '55-'57 B/A Sedan

bcmiller

  • CRG Member
  • *****
  • Posts: 2252
    • View Profile
Re: pad stamp?
« Reply #19 on: December 12, 2014, 05:34:31 AM »
it looks like the date code is made with gang stamp and vin was stamped individually because they're out of line.  is that right?

Is this from the car you are interested in?  The image of the V0417MO stamp.

If so, can you have them clean off the paint on the pad with some lacquer thinner and a rag?  Then take a better picture.
« Last Edit: December 12, 2014, 10:32:24 PM by bcmiller »
Bryon / 1968 Camaro SS 396 - now 468 ci, M21, 12 bolt
Looking for 68 Camaro with body number NOR 181016

KurtS

  • CRG Coordinator
  • *****
  • Posts: 4613
    • View Profile
Re: pad stamp?
« Reply #20 on: December 12, 2014, 06:04:42 AM »
Steve,
Sorry, I was looking at the V0417MO pad when I said that!

The V0604MO pad is fine.
Kurt S
CRG

z28z11

  • Hero Member
  • *****
  • Posts: 1179
    • View Profile
Re: pad stamp?
« Reply #21 on: December 13, 2014, 03:47:23 AM »
Steve,
Sorry, I was looking at the V0417MO pad when I said that!

The V0604MO pad is fine.

Kurt,

Thanks for clarifying - I started to question my eyesight.

Regards,
Steve
1968 Z28 M21/U17 BRG/W
1969 Z28 X77/M20/VE3 LeMans/W
1969 L78 X66/N66 Cortez/BVT
1969 Z11 L48/M35/C60/C06

1968z28

  • Newbie
  • *
  • Posts: 17
    • View Profile
Re: pad stamp?
« Reply #22 on: December 15, 2014, 03:23:45 PM »
how were the decks surfaced on these blocks?  someone said they should have broach marks.  is that right?  how does a broach work compared to today's techniques?

69Z28-RS

  • Hero Member
  • *****
  • Posts: 4668
  • owner since 4-Apr-1976
    • View Profile
Re: pad stamp?
« Reply #23 on: December 15, 2014, 03:45:33 PM »
how were the decks surfaced on these blocks?  someone said they should have broach marks.  is that right?  how does a broach work compared to today's techniques?

Here's a wiki article for an understanding of the broaching machine and how it works:
http://en.wikipedia.org/wiki/Broaching_(metalworking)

The type of broaching machine used for the blocks was a linear broach, which machined the block deck in a single pass (from front or rear or rear to front) which leaves fine machining lines running longitudinally (from rear to front) on the deck surface.  Contrast that to the rotary cut marks made by the typical milling machine (rotary) used in machine shops.   When you inspect the front stamp pad (very closely), preferable with some amplification, on an original deck surface you should see fine parallel lines running from under the head and coming straight forward (no angle, no rotary marks).   When a machine shop 'decks' a block, rotary cut marks will be left removing the original broaching marks, and which may or may not (depending on the depth of the cut) remove the original stampings also.  We have some folks on this forum who actually worked for GM or for the Flint or Tonawonda engine plants that hopefully will elaborate (or correct) what I've said here... :)

Beware:  There are rumors of stories of people who totally remove the original stampings and broach marks, and 'simulate' the original broach marks for a new (non original) stamping for profit or misrepresentation.  A 'clean fresh new-looking' deck surface would make me suspicious of this.  
Gary W / 09C 69Z28-RS, 72 B 720 cowl console rosewood tint
69 Corvette convertible, silver/black 350 hp,
60 Corvette white/red, 72 Corvette coupe, '70 Mach I 
90 ZR1 red/red #246, 90 ZR1 white/gray #2466
72 El Camino, '55-'56-'57 Nomads, '55-'57 B/A Sedan

rick 67

  • Member
  • ***
  • Posts: 83
    • View Profile
Re: pad stamp?
« Reply #24 on: December 15, 2014, 04:14:11 PM »
 For the big answer you can google broach marks. The short answer is an engine plant doing thousands of blocks a day had MASSIVE milling-grinding machines. leaving specific marks that your local machine shop can not duplicate with their little machines. Re-stampers try and duplicate but the experts can still tell the difference. I just cannot tell you how they would know the difference.

Rick

JohnZ

  • CRG Member
  • *****
  • Posts: 4362
    • View Profile
Re: pad stamp?
« Reply #25 on: December 15, 2014, 04:38:26 PM »
The Flint and Tonawanda block broaches were about the size of a locomotive, and machined 5,500 blocks per day in two linear passes - first pass did the pan rail and upper half of the main bearing bores, and the second pass did the block deck and front and rear "wall" surfaces. See photo below showing both sets of broach blades.
'69 Z/28
Fathom Green
CRG

bcmiller

  • CRG Member
  • *****
  • Posts: 2252
    • View Profile
Re: pad stamp?
« Reply #26 on: December 15, 2014, 05:42:18 PM »
Awesome picture John.  Thanks for posting it!!!
Bryon / 1968 Camaro SS 396 - now 468 ci, M21, 12 bolt
Looking for 68 Camaro with body number NOR 181016

1968z28

  • Newbie
  • *
  • Posts: 17
    • View Profile
Re: pad stamp?
« Reply #27 on: December 15, 2014, 05:48:46 PM »
yes thanks john, that picture clears it up for me.

69 Zee

  • Hero Member
  • *****
  • Posts: 572
    • View Profile
Re: pad stamp?
« Reply #28 on: December 15, 2014, 07:55:09 PM »
Beware:  There are rumors of stories of people who totally remove the original stampings and broach marks, and 'simulate' the original broach marks for a new (non original) stamping for profit or misrepresentation.  A 'clean fresh new-looking' deck surface would make me suspicious of this. 
Here's something scary !!  Check these guys out.  Re-stamp and re-broach your block and claim that it's good enough to pass judging NCRS Bloomington Gold Duntev Award.  Isn't that something ?    I also remember hearing someone a few years ago (Can't remember where I heard it) tell me they can broach your block by using a T-square and dragging a file across it.   Talk about taking someone for a ride !

http://engineslimited.com/cms/index.php
Darrell

'69 Z/28 03B NOR X77 Dusk Blue, white top, flat hood, all born w/parts and drive train.  Under restoration
'69 Firebird, Veredoro green, blk top, deluxe int, all original, 350 auto