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An early 1999 506 block

n8in8or

n8in8or

I never met a project I didn’t like
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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.

A099 1.jpgA099 2.jpg

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.

A099 5.jpg

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.

A099 4.jpgA099 3.jpg

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.
 
I cut open a failed #8 November 1999 gm block, looking for changes people on hummer forum spoke about. Thicker wall, some casting knob altered, etc. NOPERS. Looked exactly the same as my 95 hummer factory block that cracked identically. I did not test for metallurgy for differences.
Many people said they saw official stuff from GM about upgrades to that last run- but no one ever seems to produce it. Hmm.

They hummer guys saying I was nuts (wrong about there not being a difference) prompted me to offer my may 99 van block for sale since it was supposed to be a way better block. They call all the older ones “at risk”. Amazingly no one bought my spare engine.

I did point out the oldest thing I could find anywhere talking about it was a guy whose hummer (which shortly afterwards went up for sale) - his month/year of engine mfr which is as first non-at risk blocks to come out- later suffered the cylinder failure.

Too hot is too hot. Cylinders expand inwards, physics and all. Cylinder tightens onto piston damaging rings. Keep going and the cylinder is perfectly supported at the deck area and not where the water chambers are. So it expands inward more than the deck area and lateral cracking occurs.
 
WarWagon said:
What did this come out of? MT and a weird V Belt setup looks like.
Click to expand...

It was in an 86 squarebody at the junkyard near me. They must have had to replace the original 6.2 at some point. It had a retrofitted AC system on it as well. Now stop snooping at my pics so closely!! 🧐😝

Will L. said:
I cut open a failed #8 November 1999 gm block, looking for changes people on hummer forum spoke about. Thicker wall, some casting knob altered, etc. NOPERS. Looked exactly the same as my 95 hummer factory block that cracked identically. I did not test for metallurgy for differences.
Many people said they saw official stuff from GM about upgrades to that last run- but no one ever seems to produce it. Hmm.

They hummer guys saying I was nuts (wrong about there not being a difference) prompted me to offer my may 99 van block for sale since it was supposed to be a way better block. They call all the older ones “at risk”. Amazingly no one bought my spare engine.

I did point out the oldest thing I could find anywhere talking about it was a guy whose hummer (which shortly afterwards went up for sale) - his month/year of engine mfr which is as first non-at risk blocks to come out- later suffered the cylinder failure.

Too hot is too hot. Cylinders expand inwards, physics and all. Cylinder tightens onto piston damaging rings. Keep going and the cylinder is perfectly supported at the deck area and not where the water chambers are. So it expands inward more than the deck area and lateral cracking occurs.
Click to expand...

I wondered if you might have some more info on this with your history. This one is going to be the start of my next build. I’ll do what I can to keep it cool, but it WILL be getting the snot out of it. In fact this is exactly what I was looking for, for the next build as it doesn’t have any cracks, but if I throw a rod, I won’t cry about destroying this block.
 
I would toss the AC brackets, v-belt setup, pulleys, etc. on the ads. Someone in AZ doing A/C on a CCUV may have an interest. This looks different than the 1986 A/C setup I got from a parts engine for the banana project.
 
WarWagon said:
I would toss the AC brackets, v-belt setup, pulleys, etc. on the ads. Someone in AZ doing A/C on a CCUV may have an interest. This looks different than the 1986 A/C setup I got from a parts engine for the banana project.
Click to expand...

I wish it had all of the brackets, because I would have saved them for a future project for myself. It had some kind of janky, welded-plate AC compressor bracket with a Sanden compressor plumbed to the truck......that's why you saw that funky crank pulley on it - it was somebody's home-brewed AC solution. So I'm still on the lookout for a V-belt accessory drive myself.
 
Will L. said:
How useable is block filled 6.5 on the street?

I would say the latest block from gm is the one I would play with or trust the most outside of optimizer. I seen the same cracks in non squirters that were in squirters, so I don’t buy that being an issue.
Click to expand...
I was thinking I'd just fill it to the freeze plugs to give the mains and bottoms of the bores a little more support. Since the truck this block will be going in is a play-thing/test-mule, it should be ok to do that unless I hear some info to the contrary.
 
Somewhere out there, some one is gonna come up with a filler that transfers heat really well. Then we could fill it all the way and not suffer heat issues and I think what might do it is some
...HUH, What’s that? Time to wake up for work? Ahh man- almost had it!
Haha
 
Will L. said:
Somewhere out there, some one is gonna come up with a filler that transfers heat really well. Then we could fill it all the way and not suffer heat issues and I think what might do it is some
...HUH, What’s that? Time to wake up for work? Ahh man- almost had it!
Haha
Click to expand...
I used to say that when I was at work, except, wake up, time to go home. 😹😹😹😹
 
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