Can anyone help decoding a block pad stamped number

[old cool]

Hello,
I have owned a 66 GMC for over two years and cannot decode all of my engine numbers. Castings can be found, but not the block pad number. Especially the TAT or the last 5 digits. The full stamped number is F0927 --TAT--02877..
I have tried and tried but not able to get what im seeking. Help. Anyone..

[geezer#99]

F0927-- Built in flint sept 27th.
TAT--- 1970 307.
Look here.
http://www.nastyz28.com/gm-chevy-cod...s-suffix-6.php

02877--- last 5 numbers of the serial number of the vehicle it was put in originally.

[old cool]

Thanks much for getting back to me geezer. Strange part is I found that TAT doing my own search. But I have a six. TA for my year meant six with a 3speed manual. At least for c10s. My stuggle has been TAT and the last 5 digits. I have spotted on other forums that T can mean truck but not sure if it holds up.

[geezer#99]

Easy to solve!!
What's your block casting number?

[old cool]

I wish it were that easy to solve. I have decoded all my casting numbers and I know that I have a 250 6 cylinder dated September of 1965. What I can't decode are the stamped numbers on the pad above the distributor. I have no idea what the tat means or the last 5 digits. It may not even be a truck engine. That might be part of the problem though I hope I'm wrong

[geezer#99]

Sorry!!
Missed the 'six' part.

I used to have the six codes until my computer crashed. Haven't found the site since then.
Sorry I couldn't help!

[aerotruk63]

Took a look in the 1968 Illustration and Special Information Catalog.

Note: Engines are stamped with a source,production date and type on serial pad.

EXAMPLE F0101A
(F) (01) (01) (A)
Flint - Month - Day - Standard 6 cyl. "230"

TA type designation first appears in the 1965 Suffix Chart.
C10-20-K10-20...."230"-6 Cyl. with 3-Speed Trans....TA

There have been noted a few blocks not stamped properly from the factory. Perhaps yours is one such block.

[bruceman1968]

3 digit application codes on truck motors(TAT) started circa 1969.
Partial vin stamps(02877) on truck motors started circa 1974.
TAT for a I-6 decodes to 1973 to 1979 250ci. manual trans.
Yours is probably a 1975 250 ci. 105 Hp. manual trans, 1 bbl.

[old cool]

Dear Bruceman,
THANK YOU BRUCE!!!!!!!!!!!
The reason I have been so mislead is that all my bolt on components are mid 60's in appearance.
-I have the old school distributor with points.
-It has a Rochester one barrel Model B (casting on bottom is 7025382 or 7025882) with man choke. The carbs of '75 look different.
-Bolt on intake manifold 3859381
-Bolt on exhaust manifold 3881825
-Based on finding TDC, I recall flat top pistons (no D cuts for valves) does this make it a 230 inline? Did they even put 230's in light duty trucks from the 70's?

There may be other things to think about but the big difference for me will be getting specs and such for a September 1975 and not a September 1965. I think plugs may be different unless my old school distributor means use plugs as listed for 1965-66 and therefore gap them at .35

One good discovery will be the issue of leaded vs unleaded fuel. If its a '75 or 76, no more lead additives.

Thanks again Bruce. Also Geeze and Aero. Wonderful forum! God Bless!

[old cool]

Thanks again Bruce. I think I was wrong on flat top pistons. Today I looked again and caught one rounded ridge a couple inches into piston. The curve of the ridge rounded away from the plug hole and I could only see one.. I stuck screw driver in whole and did catch the edge of what I believe would be a valve cut away. Hopefully it's a 250 and that will eliminate one mystery.
The other parts all have a five in the date codes but I assume they could represent either a 65 or 75. My hunch is he took them off the first engine and put them on the current engine to keep an original appearance.
If you have any knowledge, please share. Your first response meant a great deal.

[geezer#99]

Just a thought!
Not sure if they had an integral head in 75, but maybe the motor started out that way. Integral head was prone to cracking. Could have been everything was swapped for that reason.

[bruceman1968]

Your welcome old cool, I'm more of a numbers guy, rather that a mechanic, so I can help with your decoding but the engine guys are better for your piston questions. (I've rebuilt several small blocks over the years, but never a I-6.)
I just checked all of the 3 digit application codes for the I-6, from ARA to XGC and couldn't find one for a 230ci past 1970. Leo Santucci's I-6 book doesn't list a 230ci past 1970 either. So I doubt the 230 was still around in 1975.
Your intake and exhaust decode as follows, from Mark Allen's I-6 book.
3859381= intake
1963-71 194ci 120hp
1963-71 230ci 140hp
1963-71 292ci 165,170hp

3881825= exhaust
1963-72 194ci 120hp
1963-72 230ci 140hp
1963-72 250ci 140,155hp
1963-72 292ci 125, 165, 170hp

If you want to post your Block casting number and Head casting number I'll be happy to check those for you too.

What's your date code? The first character should be I for September and the last character should be 5 for 1975. Is there a number or two in between? Something between 1 and 26?

[old cool]

the block casting is 3877178 and correct from my research. The date is I 24 5. I always thought 65 until you communicated. The pad numbers and letters match your input perfectly as a 75. At this point I'm now curious about it once being and integrated head that was dressed up to 65 components or did the 75-76 250 come with either integrated or non-integrated head.
Thanks again Bruce. FYI have not removed valve cover to check hear #. That could certainly help.
Could you tell me the URL address for finding casting numbers on engine component.

[bruceman1968]

OC, I don't use the internet much for decoding. I have several reference materials/books here at home. My GM stuff is packed up right now, but I used Mark Allen's I6 book http://www.msa-1.com/ and Leo Santucci's books http://www.barnesandnoble.com/w/chev...cci/1119499257 for your questions. There are several good sources on the net, Stovebolt.com http://www.stovebolt.com/ Nasty z, http://www.nastyz28.com/decode.php Also a google search using the casting number you want to find info on, will usually turn up a discussion or two on a forum somewhere, of someone asking about it. I-6 info is the hardest to find on the net.