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Discussion Starter #1
Cast date I 285
Number in pad FI 1005 ZB or zd


I am in the process of maybe purchasing this 327 721 block And would like any info on the weird double stamp. Factory mistake?

What are you guys think

Josh



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OK Josh, here's what we know from the information you've given.

The casting date I 285 is I= September, 28= day of September, 5 =1965. You mention this is a 721 block. The 721 was only used until about the end of October, 1965, for 1966 Chevy II production. It was replaced with the 362 block.

The suffix code is the engine assembly information. F= Flint engine plant, 10= October (1965), 05= day in October (1965). Then we have the ZD or ZB mystery. Both these codes are Chevy II 275 HP 327 CID. ZD is 275HP with PG, A.I.R, 4 barrel. ZB is the same, but doesn't list PG, which probably means it was a 3 speed standard transmission application.

What's interesting is that the 'B' is a larger font size than the 'D'. The suffix codes were gang stamped, so the addition of the 'B' probably would have been a single hand stamp. I have no idea what happened here, other than somebody trying to correct a stamping error. Dave B. is an expert on broach marks, so maybe he can chime in with an opinion on this suffix code. Other than the D/B mystery, everything else makes sense.

Bob
 

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721

From M S A suffix codes
ZD '66 275hp 327
ZB '65 300hp 327

Both found in Novas
 

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Discussion Starter #6
Thanks you guys, I am interested in seeing what Dave B thinks about it

Josh


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Well folks, I'll have to say that I've never before seen anything quite like this one.
The machining looks like someone may have tried to lightly true the block, maybe to remove surface rust, leaving just a shadow of the original broach marks remaining. If that's the case, then the machining was done at right angles to the original cut.

As far as the "B" and the "D" go, I'd be guessing again. Maybe a block that was intended to go in a Powerglide car got used in a 3 or 4 speed manual application? If so, why is the "B" larger? All the symbols I've ever seen created by the individual dies used on the 'final' assembly lines have been smaller than the ones used in the gang-stamps...

Even if it were a re-stamp that went wrong, you wouldn't think that the person doing the stamp would use dies with two different fonts.

This is one block that I wish could talk!
 

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Discussion Starter #8
Thanks for the info Dave
Looks like Pretty much either way to be a 66 327 275 hp block



I ended up buying it for one of my project cars


Josh


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Thanks for the info Dave
Looks like Pretty much either way to be a 66 327 275 hp block



I ended up buying it for one of my project cars


Josh


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:thumbsup:
 

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Was wondering if you took a really good magnifying glass under good lighting if you could determine which letter was stamped 1st, by looking at where the lines of the letters cross one another.
 

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Definitely October 66 Nova 327 block. (last of the 3790721's, before the 3791362's)

My guess would be factory gang mis-stamp, then corrected by larger "B" during installation to make it obvious.

I have also see engine rebuilders stamp their own stamp right over the factory gang stamp, which results in a mess!
 

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Definitely October 66 Nova 327 block. (last of the 3790721's, before the 3791362's)

My guess would be factory gang mis-stamp, then corrected by larger "B" during installation to make it obvious.

I have also see engine rebuilders stamp their own stamp right over the factory gang stamp, which results in a mess!

I think this might have been the case. Recent issues have shown that more than a few guys have letter stamps, and they're not afraid to use them, straight, crooked, wrong-sized or whatever.

End of the day, I'm guessing a high percentage of factory 327 blocks for '65-'67 Nova have been laid to waste for a variety of reasons. If someone is building a 327 car to as close to original as they can, this is the best available option unless you get just this lucky again sometime soon and find a date or a stamp more in keeping with the car you are building. If you have a factory 327 car with no block, then this is a far better option than a 283, a non-Nova small block or other choices. Run it!
 

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i have a 327 in a 66 nova. i'm lost as to were you found the Cast date I 285. is it possible to find that date if the engine is installed an running.
 

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i have a 327 in a 66 nova. i'm lost as to were you found the Cast date I 285. is it possible to find that date if the engine is installed an running.
From www.nastyz28.com:
Casting Date
Small block casting date is located on driver side rear of block on flange forward of bellhousing. Big block on the right side of engine above the oil pan rails.

Casting Date Example: E038 - (E = Month, 03 = Day, 8 = Last digit of model year (1978)). This would translate into May 3, 1978.

Month: A = Jan, B = Feb, C = Mar, D = Apr, E = May, F = Jun, G = July, H = Aug, I = Sep, J = Oct, K = Nov, L = Dec

This little data block is very hard to see with the engine in the car; as it is behind the intake manifold, almost next to the firewall. Somewhere, I have a photo of the casting date of one of my engines. If I can find it, I'll post it.
 

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dave B..... thanks for the location. no wonder why i couldn't spot the casting number. the stamps on the front are 3E 4225 V1222 KL. an the 3 not really sure as the alt. is in the way. i'll look at your picture if you post.
 

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I couldn't find the photo, so I went down to the garage and snapped a few... captions are UNDER photos.


1964 283 ("194" Nova block) date stamp "C194" = March 19, 1964


1966 Nova block date stamp "C256" = March 25, 1966. This is an L79 block.


1966 Nova block part number 3791362 ("362" block) also showing time clock. This is an L79 block.

Hope this helps!
 

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thanks dave. a few pics are worth a 1000 words. i'm going to try a bright light an a mirrow to see what i can find. thanks again
 

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1966 327

Do you have an automatic tranny ?? The ZB code is for an A.I.R. smog motor, the ZD stamp indicates an automatic...
 

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Discussion Starter #19
Do you have an automatic tranny ?? The ZB code is for an A.I.R. smog motor, the ZD stamp indicates an automatic...

No idea what transmission was hooked up to it. It was just a block that I purchased from a machine shop. I have No other history on it




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