SBC Identification Code Help

[SquareBody86]

This is something that's been keeping me up at night for awhile now, when I bought my truck (1986 C10 Silverado) from the second owner I was told it was on its second engine and original trans (305/700R4) the fact that its on its second engine at 160,xxx miles is a bit surprising to me as most small blocks usually go till 200,xxx before major problems come up. I know the truck came with a 305 from the factory but I have no idea if the original owner just did a rebuild on the original 305 and put it back in or if its just some 305 he found or it could be a 350 for all I know.

I know these supposed to be a stamped code(?) on the front of the passenger side cylinder head, took a look and didn't see anything. I know there's also a block casting number on the back but without a jack or a lift getting to it is near impossible in the driveway. I was however able to clean up the brass tag that was on the front of the block and this is what I got off of it:

RC-26A
56990

Any help would be greatly appreciated, I know there's a suffix code list here online but I'm not all that great at reading those codes of if the numbers on that tag are even the suffix code.

[hatzie]

There are stamped alphanumeric code(s) on a flat pad on the block not on the heads.  Usually on the RH front side of the block.  These are engine assembly codes.  Crate engines may not have normal assembly codes.
Behind the LH cylinder head on the block casting and parallel with the bellhousing split is the block casting number.

http://www.nastyz28.com/sbchevy/sblock.html
http://www.nastyz28.com/chevy-engine-code-stampings.php

http://www.73-87.com/chevy_ids/sbcid2.htm

[SquareBody86]

right, found it (RH in front of cylinder head): V0706FAP

[SquareBody86]

Any ideas? I can't find anything anywhere about an FAP suffix code and the ID number is nearly impossible to get to with it still in the truck.

[hatzie]

V= Flint Michigan
0706 = July 6
FAP

Are you sure you read the letters correctly?  Your GMC dealer may be able to decode them.


I've read the casting number with a mirror.

[SquareBody86]

Oh I'm sure I read it correctly, I managed to somehow get a look at the RPO code on the backside and made out GM 5.0LG so it is a 305 like I thought, I'm fairly sure it's an LG4 but not 100%, after the G there looked to be just a raised dot.

[hatzie]

The RPO is not cast into the block.  The 5.0L block could be used with many different configurations.  The casting number will usually tell you whether it's a 2 or 4 bolt main, 1 or 2 piece rear main, and the displacement.  5.0 LG dates it in the 80's and it's a 5.0L engine but it's not the casting number.

RPO LG4 is the whole 5.0L 305 engine package for a specific year including what pistons, crank, intake, fueling, heads, and camshaft etc were used.

The only reference to FAP in GM engine suffix codes I've found is the 1949 Series 1500, 216ci Passenger Car Engine w/HD Clutch