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What's the best block to bore and put marine pistons and 20 lbs of boost with head studs
- Thread starter spdgofast
- Start date
Will L.
Well-Known Member
Optimizer 6.5 is best metallurgy and castings.
But as you unfortunately learned, still none are bulletproof, so All of them benefit from chryo.
But as you unfortunately learned, still none are bulletproof, so All of them benefit from chryo.
Even to bore? I just thought I saw some talk the the 6.2 left more meat on the cylinder walls after boring than the 6.5. Does the 6.2 blocks have the casting for the plate where the turbo oil return drain goes? Maybe 6.2 red blocks?
Will L.
Well-Known Member
The walls are thicker on 6.2 than 6.5 until you bore it to the diameter of a 6.5. Then they are the same. Now it becomes a question of the metallurgy.
The advantage of the rear main seal is worth wile imo also.
Afaik they all have the opening where a mechanical Fuel pump could be bolted on that is used for oil return on side mount turbos.
The advantage of the rear main seal is worth wile imo also.
Afaik they all have the opening where a mechanical Fuel pump could be bolted on that is used for oil return on side mount turbos.
Twisted Steel Performance
Anything worth doing is worth overdoing.
Until the P motor came along, it was a toss up, I have NEVER seen proof the metal content was changed to benefit much, EVERY casting has seen it's share of cracking, either due to poor quality castings, unbalanced assembly's, bad flywheel balancing, etc etc...
IMO, they all are a 50 -50 chance...
IMO, they all are a 50 -50 chance...
FellowTraveler
Well-Known Member
MAY 1999 GM and newer are thicker castings, I've read over ten years ago that rebuilders prefer to rebuild them and not the older blocks.
Will L.
Well-Known Member
I can’t disagree with Chris a lot on that, but some. They are all subject to fail. Its all just tilting the odds in your favor. I had my gep and gm blocks checked by a jeweler that has the metal spectral analyzer just to see. The higher nickel and chromium is correct. Nice deal just for giving a couple a jump start on evening.
The last update that Gm did to the block that was supposed to ease the #8 cylinder wall cracking was released in April of 99 (my gm is a may one). I checked out the difference- not tremendous but there.
There is a lot of folks that go for the 6.2 but imo they lasted longer because low power numbers from no turbo and less rotating weight. Also they were kept at a lower top rpm range- all of which lessen the effect of out of balance issues.
The difference of the rear cylinder failure cracking (especially #8) into the cooling chamber is way obvious to hummer owners where overheating is far more common than pickups.
The last update that Gm did to the block that was supposed to ease the #8 cylinder wall cracking was released in April of 99 (my gm is a may one). I checked out the difference- not tremendous but there.
There is a lot of folks that go for the 6.2 but imo they lasted longer because low power numbers from no turbo and less rotating weight. Also they were kept at a lower top rpm range- all of which lessen the effect of out of balance issues.
The difference of the rear cylinder failure cracking (especially #8) into the cooling chamber is way obvious to hummer owners where overheating is far more common than pickups.
Will L.
Well-Known Member
FT: you reading my mind again and quickly posted! Haha
FellowTraveler
Well-Known Member
Check the site below out has images of May 1999 enhanced block and pre-enhanced block.......my Burb came w/enhanced version.
Cracked Block Problems in GM Turbo Diesels
www.flashoffroad.com
MrMarty51
Well-Known Member
That is some mighty interesting information FT, thank You for posting that.
Will L.
Well-Known Member
Flash off-road is a tie in of the hummer forum. A lot of good info there, but also some misinformation. Part of what is wrong about this article is -how many gm blocks that went into vans had same issue? Special blocks weren’t cast for hummers. The blocks are same blocks as trucks, except had the oil holes drilled for center mount turbo after rolling through assembly line. A jig is placed figure 8 recess cut, then 2 holes drilled.
If only the years mentioned had the issue, how come almost all the hummers before that time of production had the same exact issue including my 95? When I started that S-storm over there, many older and newer than stated dates owners spoke up about their engines failing in the same way.
Also the failures aren’t only in one spot in the cylinder. Some very high, some at bottom of stroke. And in any position around the cylinder from between 6&8 to pointed to the oil pump drive.
The cut open blocks that show the redesigned changed “weak spot” is only 1” high and 2” wide. Far different than the range of failure areas.
GM made a change in an attempt to avoid lawsuit from AM GENERAL, which it didn’t, and that along with the known 4 bolt waterpump vs spin on waterpump balance flow issue is what led to gm being forced to sell the production rights to AM General and forced AM General to form a separate company- GEP who actually makes them. GEP never wanted to, and still doesn’t want to sell to the public. They are required to from the agreement of GM not producing them anymore in the settlement that ended the lawsuit.
Putting my $ where my mouth is- my optimizer and my May99 gm block have similar mileage on them. Yet I am still building my Optimizer to go into my hummer, keeping the GM as a future replacement for my son that would get the hummer when i die. Spare parts jic. The only reason I bought the gm engine was I wanted the turbo, manifolds, etc and the engine was in great condition.
That service bulletin states 1996 and newer because that was when turbo hummer first became available and the turbo hummers have worse overheating than n/a because of the trapped heat from the up pipe and turbo against cylinders 8&7. The 99 hummers started the balanced flow water pumps on them. Many hummer owners put in the “improved” post 99 gm blocks and still cracked #8. Why? They still overheated with the 4 bolt pump much easier.
I could make the same offer here as I made there.
If anyone is convinced I am wrong and think the May 99 block is all that, bring me some cash to have my May 99...
If only the years mentioned had the issue, how come almost all the hummers before that time of production had the same exact issue including my 95? When I started that S-storm over there, many older and newer than stated dates owners spoke up about their engines failing in the same way.
Also the failures aren’t only in one spot in the cylinder. Some very high, some at bottom of stroke. And in any position around the cylinder from between 6&8 to pointed to the oil pump drive.
The cut open blocks that show the redesigned changed “weak spot” is only 1” high and 2” wide. Far different than the range of failure areas.
GM made a change in an attempt to avoid lawsuit from AM GENERAL, which it didn’t, and that along with the known 4 bolt waterpump vs spin on waterpump balance flow issue is what led to gm being forced to sell the production rights to AM General and forced AM General to form a separate company- GEP who actually makes them. GEP never wanted to, and still doesn’t want to sell to the public. They are required to from the agreement of GM not producing them anymore in the settlement that ended the lawsuit.
Putting my $ where my mouth is- my optimizer and my May99 gm block have similar mileage on them. Yet I am still building my Optimizer to go into my hummer, keeping the GM as a future replacement for my son that would get the hummer when i die. Spare parts jic. The only reason I bought the gm engine was I wanted the turbo, manifolds, etc and the engine was in great condition.
That service bulletin states 1996 and newer because that was when turbo hummer first became available and the turbo hummers have worse overheating than n/a because of the trapped heat from the up pipe and turbo against cylinders 8&7. The 99 hummers started the balanced flow water pumps on them. Many hummer owners put in the “improved” post 99 gm blocks and still cracked #8. Why? They still overheated with the 4 bolt pump much easier.
I could make the same offer here as I made there.
If anyone is convinced I am wrong and think the May 99 block is all that, bring me some cash to have my May 99...
FellowTraveler
Well-Known Member
This is an age old debate for sure and the last time I had checked which was long ago GM 6.5td MAY 99 to 02 cracked block numbers seemed to be a mystery I'm guessing there must be some confirmed numbers of failures by now "but where do we find them is the question?"
Truth be told GM screwed most every owner of vehicles equipped with the 6.5td including defense contractors from cracked blocks crappy cooling and fuel delivery issues when I think of the $$$$$$$ spent I should have done my Cummins swap a decade or so ago and the taxpayers had to bail them out and for what?
I remember a HMMWV prototype that had a Mercedes 8 cyl diesel and always wondered if that would have been a better choice of power? Then we had the global shortage of fuel system seals that could not hold up to the reduced sulfur fuels that damaged every Mercedes fuel system this is when I ditched the Mercedes diesel......this was the early 1990's after the Swedes warned the world low sulfur was a bad idea after their tests showed fuel system seal failures....no one listened "I suspect because it was a good way to remove older diesels off the roadways."
Will L.
Well-Known Member
Idk about anyone confirming any number counts, but like I mentioned, many of the hummer owners on the forum had trucks before the mentioned time that cracked blocks, and many with engines in that time frame that had issues.
On the Hummer forum, there has been no optimizer failures as of yet. So successful that when I mentioned a optimizer main failure I had several folks outright call me a liar.
Thinking about the optimizer failures and better metallurgy helping- there has been a few on here that had main webs failures. Emmott and Hink are two. Emmott’s had been rebuilt and someone added the dsg 3 hole girdle/ studs (WHICH I come to believe are all being WAY OVER TORQUED adding to the issue). I can’t remember who else has had it happen, anyone here?
But what I have not yet seen is any optimizer that I recall is a cylinder wall failure. When talking to Ted’s about their issues in all the take outs they bought- they said cracked heads, warped heads, head gaskets, lack of oiling damage, but no cylinder into coolant area failures that they came across on optimizers.
As to hummers with different engines- many upfitter companies modifying hmmwvs however they see fit snd try to, sometimes with success, change a ton of stuff. Narrowed & widened hummers, shortening and lengthening. All kinds of engine swaps including Super and turbo charged merlin 770 big blocks. Complete different suspension systems. All electric. Self driving. Ones that float like a boat. Only thing I haven’t seen is self propelled flying hummer, or one that can fix itself. Oh wait, Darpa is worked on the flying one since 2011- 2015 but all tests were first done on the personnel transport body before bolting the rig to the hmmwv for testing. That was a FAIL!
On the Hummer forum, there has been no optimizer failures as of yet. So successful that when I mentioned a optimizer main failure I had several folks outright call me a liar.
Thinking about the optimizer failures and better metallurgy helping- there has been a few on here that had main webs failures. Emmott and Hink are two. Emmott’s had been rebuilt and someone added the dsg 3 hole girdle/ studs (WHICH I come to believe are all being WAY OVER TORQUED adding to the issue). I can’t remember who else has had it happen, anyone here?
But what I have not yet seen is any optimizer that I recall is a cylinder wall failure. When talking to Ted’s about their issues in all the take outs they bought- they said cracked heads, warped heads, head gaskets, lack of oiling damage, but no cylinder into coolant area failures that they came across on optimizers.
As to hummers with different engines- many upfitter companies modifying hmmwvs however they see fit snd try to, sometimes with success, change a ton of stuff. Narrowed & widened hummers, shortening and lengthening. All kinds of engine swaps including Super and turbo charged merlin 770 big blocks. Complete different suspension systems. All electric. Self driving. Ones that float like a boat. Only thing I haven’t seen is self propelled flying hummer, or one that can fix itself. Oh wait, Darpa is worked on the flying one since 2011- 2015 but all tests were first done on the personnel transport body before bolting the rig to the hmmwv for testing. That was a FAIL!
- Staff
- #15
The thickest cylinder wall block I know of is the 92/93 599 6.2l block. This is only because it was the same casting as the 6.5l 599 block, but was only bored to 6 2l standards. If you bore it to a 6.5l, it then is just like any other 599 6.5l block. I know back 10-15 years ago when people were still using GM blocks and the optimiser castings were virtually unobtainable, the 141 block used in 96-early 97 seemed to be the go to.
Will L.
Well-Known Member
$25 is worth a gamble if you don't mind swapping parts around. Rip it open and see how it looks.
- Staff
- #18
It all depends on the casting date. 506 is the current casting code for optimizers as well as back to 97 when the squirter blocks started. For the most part, 506's with sae bellhousing bolts are a losing gamble. 506's with metric bellhousing bolts are gen 2 blocks and improved. The rest breaks down to production date and where it was cast.
FellowTraveler
Well-Known Member
Perhaps a custom billet block could be had for a reasonable price these days with all the new machining tech.......
Will L.
Well-Known Member
Reasonable is a relative cost. The first one or two parts made from billet are never useable. Its like a learning curve to get the part made exact os something so complicated. Even if there is someone THAT good they get it on the first try, all the cad time into it will still put the first one or two made over $10,000. The only reason you see some in the $6000 range is they can do repeated runs and make it up in some volume. No one is going to lay out the cash for that in a 6.5.
For just a moment lets pretend you could do a p400 billet block and full girdle for $8,000. How many here would buy just that for that much money? I say not one. Because how many people bought complete running p400 for about the same?