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I hope I haven't overlooked anything already posted. I bought a LM4 shortblock go a LS swap in an S10. Does any one know how to identify the year a LM4 block was cast. Here's my understanding so far. The casting # 12566910 was used for 3 years. 2003-2005 and was considered a transition motor from gen 3 to gen 4. All years used dished pistons. 2003 had first design headbolts and pressed piston. 2004 used 2nd design headbolts and pressed pistons. 2005 used 2nd design headbolts and floating pistols. I can see a stamping
or etching on the left rear the block. The # is C46160460. Is there a Julian date or identifying marking on the aluminum LS blocks?
Looks like it was only a gen 3 (24x crank). Get a m11x2x155 bolt and see if it fits into the head bolt holes. If it fits in 8 spots you have an 03. If it's too long to seat you have an 04/5. It looks like the 05 was mechanically identical to the 04
Looks like it was only a gen 3 (24x crank). Get a m11x2x155 bolt and see if it fits into the head bolt holes. If it fits in 8 spots you have an 03. If it's too long to seat you have an 04/5. It looks like the 05 was mechanically identical to the 04
You don’t even have to thread a bolt in. I check the depth of the upper corner headbolts by sticking a Phillips head screwdriver down the hole. I mark the depth with my fingernail, and see how it compares to the headbolts hole beside it.
You don’t even have to thread a bolt in. I check the depth of the upper corner headbolts by sticking a Phillips head screwdriver down the hole. I mark the depth with my fingernail, and see how it compares to the headbolts hole beside it.
I do most of my measuring that way. I don't usually admit it though since it sounds a bit redneck when you say it out loud lol
I have ready looked at the LM4 block spec from onallcylinders. That helped clear up one bit of incorrect information. I already did that with a scribe and all lower bolts holes were the same depth. I assume it is an 04 or 05 at this point. I have been trying to find an old head bolt too. 11mm x 2.0mm thread is not something you can buy at the parts store or hardware store. Every one I talk to about a head bolt, has just thrown them out...
I was hoping for a more definitive answer, like Gen 1's stamped code on the passenger front corner. It told the year/day & what it came in on the stamping.
All because I really don't want to take a rod & piston out of it. The cylinder's still have the crosshatch and no ring ridge. Low mileage TB that was totaled. I am trying to document all my swap parts into a bulid book.
Look for a casting mark in a format like K142. That particular string would translate to the 14th day of month K (the 11th, Nov) in a year ending in 2. Won't tell you the year of the engine or vehicle it was built into but rather the date the block was actually cast. Usually it's not too hard to figure out the year of the motor from that though, a block takes about 2 - 3 months usually, to go from casting foundry to assy plant. The only ambiguous months are therefore around April - May, since the next model year's production usually starts around mid-July, so that it will be on stealership showroom floors by around Labor Day.
Look for a casting mark in a format like K142. That particular string would translate to the 14th day of month K (the 11th, Nov) in a year ending in 2. Won't tell you the year of the engine or vehicle it was built into but rather the date the block was actually cast. Usually it's not too hard to figure out the year of the motor from that though, a block takes about 2 - 3 months usually, to go from casting foundry to assy plant. The only ambiguous months are therefore around April - May, since the next model year's production usually starts around mid-July, so that it will be on stealership showroom floors by around Labor Day.
Thanks for the information. Is that what I'm seeing in the stamped code from my original picture? It is a C followed by a 461..
That stamping code doesn't tell you a damn thing about any of that. It's the partial VIN of the vehicle the engine was installed into.
I'm not sure where on this type of block the date code is; but that's not it. It'll be just those 4 characters. Cast into the casting, not stamped after machine work (deck prep) was completed.
If you don't plan to swap out the rotating assembly it doesn't matter much if it's 04 or 05. When you decide to open it up you'll be able to figure out what pistons to get once you get the original out.
Block ID 
