n8in8or
I never met a project I didn’t like
This weekend I picked up an early 99 6.5. It has some interesting features, so I thought I'd share what I found. I have read that 506 blocks beginning with date code C159 (March 15, 1999) are the first blocks with the final updates GM made to the blocks. This block that I just got has an A099 date code (January 9, 1999), so it shouldn't be an updated block.
What's interesting though is it seems to have SOME of the updates, I'm just not sure how many. It has the updated motor mount bosses on the side like the post-C159 blocks.
It also has the double bars in the valley like the post-C159 blocks. However, it does NOT have the "506" cast into the valley like the later blocks.
I also have an A277 (January 27,1997) GM 506 block, a D199 (April 19, 1999) GM 506 block and an 01 30 K (January 30, 2003) Optimizer 506 block handy to compare to.
I can confirm that the A277 block does NOT have the motor mount updates like the others have. It also does NOT have the double bars in the valley nor the "506".
The D199 DOES have the double bars AND the 506 cast in the valley.
And of course the Optimizer has the diamonds, plus the double bars and 506 in the valley.
I measured the thickness of the #4 main webs of all 4 blocks and they are all right around 1.066", so no obvious difference there.
The A277 block is missing its main caps so I can't measure those, but I did get cap thickness measurements for the #4 main cap for the other 3 blocks:
A099 = .930"
D199 = .940" (which is odd, supposedly the post-C159 blocks got the wider caps like an Optimizer)
01 30 K = 1.015"
I thought the features of this block were interesting. It looks like GM phased in the updates for the latest blocks. It makes me wonder what updates this block has......or more importantly doesn't have, especially regarding the #8 cylinder updates to eliminate the cracking problem.
What's interesting though is it seems to have SOME of the updates, I'm just not sure how many. It has the updated motor mount bosses on the side like the post-C159 blocks.
It also has the double bars in the valley like the post-C159 blocks. However, it does NOT have the "506" cast into the valley like the later blocks.
I also have an A277 (January 27,1997) GM 506 block, a D199 (April 19, 1999) GM 506 block and an 01 30 K (January 30, 2003) Optimizer 506 block handy to compare to.
I can confirm that the A277 block does NOT have the motor mount updates like the others have. It also does NOT have the double bars in the valley nor the "506".
The D199 DOES have the double bars AND the 506 cast in the valley.
And of course the Optimizer has the diamonds, plus the double bars and 506 in the valley.
I measured the thickness of the #4 main webs of all 4 blocks and they are all right around 1.066", so no obvious difference there.
The A277 block is missing its main caps so I can't measure those, but I did get cap thickness measurements for the #4 main cap for the other 3 blocks:
A099 = .930"
D199 = .940" (which is odd, supposedly the post-C159 blocks got the wider caps like an Optimizer)
01 30 K = 1.015"
I thought the features of this block were interesting. It looks like GM phased in the updates for the latest blocks. It makes me wonder what updates this block has......or more importantly doesn't have, especially regarding the #8 cylinder updates to eliminate the cracking problem.