1973 Stamp Pad Opinions wanted

[David C.]

My first NCRS forum post. I have a 73 coupe that I'm restoring, and before I put too much effort/money into it I'd like an opinion on the originality of the engine block stamp pad. The numbers are correct/plausible, but I'm worried about milling marks on the pad. I have no experience judging the pads, so I don't know if the milling marks are acceptable. NOTE: I am not selling this car, and I won't be telling anyone "the NCRS says...". I hope to attend my first NCRS local chapter meeting this month in Las Vegas.

Also, let me know if I'm asking the wrong question, or in the wrong way.

[Mark F.]

Re: 1973 Stamp Pad Opinions wanted

Hi David,

Welcome to the TDB !
And your question is perfectly legitimate and you're not asking the wrong question, nor are you asking it in the wrong way...

I know nothing about '73s, but I do know engine plant factory broach marks on the castings were parallel to the crank shaft.

It appears from your photo that you might have diagonal surface grinding marks...do you know if your head mating surfaces were decked at some point in the past ?

Fortunately, if they were decked - and if circular grinding tools were used to do that - it doesn't appear that they obliterated all of the pad stampings - except maybe right in the middle of the engine assembly code.

I'm sure others more knowledgeable about this will be chiming in...stay tuned !

[Edward J.]

Re: 1973 Stamp Pad Opinions wanted

David it looks like someone tried to clean up the top of your pad with sand paper, which was not a good thing it removed some of the broach marks. I can see some of them closest to the cylinder head. Your VIN number area will show the broaching. As it appears the letters and numbers appear original. Let some of the other members chime in. I would try and take a few more pic.s with a close up of VIN area, and take one of a casting date. I believe it’s on the back of block.

[Patrick B.]

Re: 1973 Stamp Pad Opinions wanted

Like Edward said the stampings look original. The squarish 0 after the V is a distinctive factory font used at that time for example. But someone has sanded the pad and removed the broach marks.

[David H.]

Re: 1973 Stamp Pad Opinions wanted

David

Welcome to Tech Board!

As Mark Francis stated above, looks like block was lightly decked. Decking took out original machining marks (broach marks).

You indicate numbers are correct - presume you mean partial VIN and engine assembly stamps.

Check Block Casting Number and Date on rear of block. (Expect you'll see 3970010 or 3970014 casting number)

NCRS "Birthday Book" has VIN 28933 as an approximate 1 June 1973 build.

Link below is to a John Hinckley article on reading casting numbers. (Lot of other useful information on that site as well)

http://www.camaros.org/pdf/cast_codes.pdf

From a judging standpoint, absence of those machining marks would be a 38 point deduction during Flight Judging. 4500 total points in Flight judging, so 38 point deduction is minor. That is, best to leave it alone - trying to add broach marks over an existing stamp not likely to work.

If you don't already have these documents, then Technical Information Manual and Judging Guide (TIMJG) for your year car, and Corvette Judging Reference Manual (JRM) 9th Edition are available from NCRS Bookstore. TIMJG tells you WHAT to judge, JRM tells you HOW to judge. Judging Engine Block Cylinder Cases is by Standard Deduction Guideline #1. Standard Deduction Guidelines are a section in JRM. There is also a handier laminated single sheet available. Talk to Dave King at NCRS Store.

David

[David C.]

Re: 1973 Stamp Pad Opinions wanted

Thanks to all for the informative answers! Looks like I asked at the right place.

It looks like engine has been rebuilt at some time. The block has the correct casting number and a reasonable casting date (3970010, E228). The heads are probably original, as they have the correct "geometric figure" cast into the front face, although I haven't yet seen the casting numbers/dates (I'll have to take the covers off for that due to aftermarket covers not having a fill opening). This had me a bit confused because why would someone go the trouble of sourcing a correct engine, including date, just to alter the stamp pad.

I have the TIMJG. I'll have to get the JRM next to help with applying the TIMJG info to my car.

Thanks again for the help everyone. I'm looking forward to my first chapter meeting this month. I'm already enjoying the restoration process.

umc_car_show-small.jpg

[John S.]