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Thread: 6.2 Redblock Theory

  1. #1
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    Default 6.2 Redblock Theory

    I really really really want to build a Red Block 6.2 bad! It is like the mythical unicorn of the 6.2 world…

    1. Has anyone ever built-up/modernized a 6.2 Red Block and gave it a lot of power/boost?

    2. Has the higher nickel content theory ever been tested or confirmed?

  2. #2
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    I will watch to see what you end up doing
    I have 3 in my yard
    1 is ventelated
    2 is burnt
    3 is running in a 2wd rustbucket
    The burnt one still rolled over,had antifreeze in the block and is out of the weather
    90 Chev 3500 c/c 4x4,6.2na,400 auto,4:10 gears.DSG Timing gears,main girdle, isspro tach, pyro,boost,oil and trany temp.Dual Tstats, High volume peninsular pump,on shelf, Custom turbo and intercooler 85%complete. Change of plans for the dually, it's going to get a Cummins. Both trucks are Blue 90 4x4 crews

  3. #3
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    Quote Originally Posted by Yukon6.2 View Post
    I will watch to see what you end up doing
    I have 3 in my yard
    1 is ventelated
    2 is burnt
    3 is running in a 2wd rustbucket
    The burnt one still rolled over,had antifreeze in the block and is out of the weather
    You willing to take them apart and see if they are crack free? I would only need one.

    Also would you be willing to take a clean uncontaminated block sample to a lab? I could reimburse you for the lab results.

  4. #4
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    Quote Originally Posted by 2INSANE View Post
    You willing to take them apart and see if they are crack free? I would only need one.

    Also would you be willing to take a clean uncontaminated block sample to a lab? I could reimburse you for the lab results.
    If you want i could break a piece off the ventilated block and send you,no labs anywhere around here that aren't cooking meth not that it's a problem around here.
    The burnt one is out and semi accessible so it could get checked out.But at this time it would have to wait till winter.
    We got snow again last night,and my yard cleaning project has to start i have made a commitment to myself to get rid of at least 22 vehicles by the end of 22.So far i am at 1.
    I did by a truck that was already sitting in my yard,not sure yet if that works against me.But it was one you don't see many oftravel all 2.jpgtravel all 4.jpg
    Attached Images Attached Images
    90 Chev 3500 c/c 4x4,6.2na,400 auto,4:10 gears.DSG Timing gears,main girdle, isspro tach, pyro,boost,oil and trany temp.Dual Tstats, High volume peninsular pump,on shelf, Custom turbo and intercooler 85%complete. Change of plans for the dually, it's going to get a Cummins. Both trucks are Blue 90 4x4 crews

  5. #5
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    Quote Originally Posted by Yukon6.2 View Post
    If you want i could break a piece off the ventilated block and send you,no labs anywhere around here that aren't cooking meth not that it's a problem around here.
    The burnt one is out and semi accessible so it could get checked out.But at this time it would have to wait till winter.
    We got snow again last night,and my yard cleaning project has to start i have made a commitment to myself to get rid of at least 22 vehicles by the end of 22.So far i am at 1.
    I did by a truck that was already sitting in my yard,not sure yet if that works against me.But it was one you don't see many oftravel all 2.jpgtravel all 4.jpg
    Heck yeah! That would be great! And a sample of the head too please! Send me a pm when you got it ready! I swear I read that Simone already had lab results but I can’t find that info anymore.

  6. #6
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    I had one apart back in the mid 80's that some clown had added a turbo to and melted a few pistons trying to make a bazilllllion HP

    Aside from the melted pistons it was solid.

    There were zero cracks in the bottom end......

    The alloy story is one that has circulated around a lot over the years......I can't confirm it though.

    The red blocks were 1982/83 only IIRC.

    The early heads had coarse threaded injectors I believe....which is not a big deal, just something to remember when building.

    The rocker arms were a cast type rather than the stampings that you will see in the 6.5

    I had one of those engine blocks and finally let it go a while back.

    Good luck.....Fun stuff
    (1) 1995 Suburban 2500 4x4
    (1) 1997 Astro
    (1) 2007 Chevy Avalanche
    THIS IS BOW TIE COUNTRY

  7. #7
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    The red blocks and coarse thread injectors were unique to the 1982 M/Y. Original heads had larger valves, as well. A crack-free red block and original heads are more and more rare these days. Certainly a diamond-in-the-rough, if you can find one. However, I wouldn't look for one if huge power is the goal. These, and subsequent years, lived a long, happy life due to the modest power demands of the time, and it had, essentially, no significant competition. A banks or ATS turbo system didn't destroy them if installed in accordance with recommendations. If you're looking for greater power, keep in mind, the block was never the primary weak link.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  8. #8
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    Quote Originally Posted by Robyn View Post
    I had one apart back in the mid 80's that some clown had added a turbo to and melted a few pistons trying to make a bazilllllion HP

    Aside from the melted pistons it was solid.

    There were zero cracks in the bottom end......

    The alloy story is one that has circulated around a lot over the years......I can't confirm it though.

    The red blocks were 1982/83 only IIRC.

    The early heads had coarse threaded injectors I believe....which is not a big deal, just something to remember when building.

    The rocker arms were a cast type rather than the stampings that you will see in the 6.5

    I had one of those engine blocks and finally let it go a while back.

    Good luck.....Fun stuff
    Ooo yes yes! Please tell me more!

    Quote Originally Posted by DmaxMaverick View Post
    The red blocks and coarse thread injectors were unique to the 1982 M/Y. Original heads had larger valves, as well. A crack-free red block and original heads are more and more rare these days. Certainly a diamond-in-the-rough, if you can find one. However, I wouldn't look for one if huge power is the goal. These, and subsequent years, lived a long, happy life due to the modest power demands of the time, and it had, essentially, no significant competition. A banks or ATS turbo system didn't destroy them if installed in accordance with recommendations. If you're looking for greater power, keep in mind, the block was never the primary weak link.
    I just want to build one and do every mod possible to it. Fully modernized and push it to its limits! No idea what I would put it in.

    This Red Block Theory has been a theory long enough! IMO. I am tired of reading about it! I want to be the guy that has hard data about the Red Block and if it does have a higher nickel cast, I want to be the guy to to build it and throw everything at it! I have a formula in my head that I think would turn it into a Duramax Slayer! Call me crazy?

    But finding one with a good block now a days… Seems impossible.


    To get this party started, I will take 2 clean and uncontaminated samples from my 6.5 Optimizer Heads and Block and send them into a lab for testing. First I need to find a lab…

    Anyone have ideas which lab to contact?
    Last edited by 2INSANE; 05-18-2022 at 18:30.

  9. #9
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    The Truth about the early 6.2 engine
    These were built in a time when MPG was king

    The 1/2 ton rigs were capable of pulling down mid to high 20 MPG on the road.

    They were a good runner, grocery getter and such.

    That is what GM built them for....GETTING THE CAFE NUMBERS UP

    As far as power goes....they were a real turd....

    About 130 hp IIRC in the 1/2 ton.

    Dual exhaust and fun to drive...

    A banks turbo kit would wake them up a bunch.....but still.....by today's standards.....A real slug......

    You can do a rebuild on one of these and add a Banks turbo (Seen on ebay off and on) and make 160-180 HP and get a decent little runner.

    A K5 Blazer with one is a good little hunting/camping rig and can easily pull a modest size camp trailer....(READ THIS AS NOT A BIG ONE) 16' OR SO.....

    Have fun
    (1) 1995 Suburban 2500 4x4
    (1) 1997 Astro
    (1) 2007 Chevy Avalanche
    THIS IS BOW TIE COUNTRY

  10. #10
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    Quote Originally Posted by Robyn View Post
    The Truth about the early 6.2 engine
    These were built in a time when MPG was king

    The 1/2 ton rigs were capable of pulling down mid to high 20 MPG on the road.

    They were a good runner, grocery getter and such.

    That is what GM built them for....GETTING THE CAFE NUMBERS UP

    As far as power goes....they were a real turd....

    About 130 hp IIRC in the 1/2 ton.

    Dual exhaust and fun to drive...

    A banks turbo kit would wake them up a bunch.....but still.....by today's standards.....A real slug......

    You can do a rebuild on one of these and add a Banks turbo (Seen on ebay off and on) and make 160-180 HP and get a decent little runner.

    A K5 Blazer with one is a good little hunting/camping rig and can easily pull a modest size camp trailer....(READ THIS AS NOT A BIG ONE) 16' OR SO.....

    Have fun

    Here’s my red block formula I would use if the nickel theory is true… tell me what you think…

    1. Crack free rebuilt 6.2 redblock.
    2. 18:1 coated pistons.
    3. Taper Main Bolt holes.
    4. Twisted Steel Girdle.
    5. Improved Heads.
    6. Brass tube between valves. (Lock n Stitch)
    7. 33 plunger Injection pump.
    8. Compounds
    9. Downpipe straight out of hood
    10. Ho 130gpm water pump
    11. 9 blade dmax fan
    12. Paradox by design
    13. Quadstar upper plenum
    14. Quadstar oil drain
    15. Quadstar Valve cover braces
    16. Light porting of the exhaust ports
    17. Port all burs
    18. Dual thermostat cross over
    19. Innercooler
    20. Fass lift pump

    Anything else yal think should be thrown in?

  11. #11
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    All cool stuff....
    "Splayed mains" are a good idea.....The bad part is the original outer bolt holes must be plugged and the plugs sealed in with Red Loctite.

    Drilling more holes weakens the main webs even more.
    A good girdle on the mainline is not a bad plan...

    The brass sleeves between the valves "Was a stop gap BANDAID" to repair cracked heads....

    A fresh set of either AMG heads or even the Clearwater heads....NEW IRON that has not seen GAWD knows how many duty (Heat) cycles

    Deburing all sharp edges inside the block and a quick hit with a countersink on all bolt hole to remove the stress risers (Just break the sharp edges)

    The cooling mods +++
    Fan blade and clutch +++
    Cleaning up the exhaust ports +++
    Intake air cooler + Really works best if the boost pressure is 15 psi or over

    Heavy boost on these engines is just a bridge too far.

    These engines do not have enough head bolts to really clamp things together well ....Gaskets will not hold for extended mileage

    Adding BIG fuel - - -
    An IDI (Pre cup engine) keeps way too much heat in the heads where the heat can't be easily dissipated into the cooling system.

    A direct injected engine on the other hand (Cummins, Powerstroke or other heavy diesels) have the combustion in a bowl in the top of the piston and the heat dissipates into the cylinder walls and the piston oil spray nozzles get some of it from under the piston head and take it off through the oil cooler...

    About 300 flywheel hp on a 6.5 is about it....at least being able to keep the beast alive for a decent amount of miles.

    The big power that has been made with the 6.2/6.5 has been for marine use...

    Cooling is soooooooooooo easy....You have a huge lake, river or ????? amount of cold water to use to keep the heat down.

    Bottom line.

    The 6.2 is just not the platform to try and build a buttload of power.

    So much could have been done at GM when they hatched these engines.

    Deep skirted block with cross bolted main caps (6 bolts)
    Forged steel crankshaft
    Better head design with more bolts per cylinder
    Direct injection (Common rail)

    The bean counters got after it...

    The 6.2 was a quick fix to get the CAFE numbers across the product line where the company wanted it. And the marketing department sold the public on the idea that these were beasts....Lotsa Torque ......Sort of...

    Mission accomplished......
    The 6.2.."Little engine that could" got great mileage and most of them lasted a lot of miles.

    250K miles was very common..

    Most people do not keep a rig long enough for the mfg to justify worrying about much more life span.....

    I have seen some mid 80's 6.2 light duty rigs go 300K miles....

    Building one of these to do what they were meant to do would be sweet.....As far as making a moose motor......Chasing the wind my friend.....

    Much of the "Fixes" for the 6.2/6.5 are/were BANDAIDS to get the rig going again.
    Back in the hay day of these engines I have seen many really low mile rigs sitting because people were either not willing to or could not afford to repair them.

    This wonderful forum was started to help people (DIYER'S) learn from others, swap ideas and keep their rigs on the road......

    Have fun......

    What ever you decide to do.....SHARE IT....Always interested in wasssup here at the page...
    (1) 1995 Suburban 2500 4x4
    (1) 1997 Astro
    (1) 2007 Chevy Avalanche
    THIS IS BOW TIE COUNTRY

  12. #12
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    Quote Originally Posted by Robyn View Post
    All cool stuff....
    "Splayed mains" are a good idea.....The bad part is the original outer bolt holes must be plugged and the plugs sealed in with Red Loctite.

    Drilling more holes weakens the main webs even more.
    A good girdle on the mainline is not a bad plan...

    The brass sleeves between the valves "Was a stop gap BANDAID" to repair cracked heads....

    A fresh set of either AMG heads or even the Clearwater heads....NEW IRON that has not seen GAWD knows how many duty (Heat) cycles

    Deburing all sharp edges inside the block and a quick hit with a countersink on all bolt hole to remove the stress risers (Just break the sharp edges)

    The cooling mods +++
    Fan blade and clutch +++
    Cleaning up the exhaust ports +++
    Intake air cooler + Really works best if the boost pressure is 15 psi or over

    Heavy boost on these engines is just a bridge too far.

    These engines do not have enough head bolts to really clamp things together well ....Gaskets will not hold for extended mileage

    Adding BIG fuel - - -
    An IDI (Pre cup engine) keeps way too much heat in the heads where the heat can't be easily dissipated into the cooling system.

    A direct injected engine on the other hand (Cummins, Powerstroke or other heavy diesels) have the combustion in a bowl in the top of the piston and the heat dissipates into the cylinder walls and the piston oil spray nozzles get some of it from under the piston head and take it off through the oil cooler...

    About 300 flywheel hp on a 6.5 is about it....at least being able to keep the beast alive for a decent amount of miles.

    The big power that has been made with the 6.2/6.5 has been for marine use...

    Cooling is soooooooooooo easy....You have a huge lake, river or ????? amount of cold water to use to keep the heat down.

    Bottom line.

    The 6.2 is just not the platform to try and build a buttload of power.

    So much could have been done at GM when they hatched these engines.

    Deep skirted block with cross bolted main caps (6 bolts)
    Forged steel crankshaft
    Better head design with more bolts per cylinder
    Direct injection (Common rail)

    The bean counters got after it...

    The 6.2 was a quick fix to get the CAFE numbers across the product line where the company wanted it. And the marketing department sold the public on the idea that these were beasts....Lotsa Torque ......Sort of...

    Mission accomplished......
    The 6.2.."Little engine that could" got great mileage and most of them lasted a lot of miles.

    250K miles was very common..

    Most people do not keep a rig long enough for the mfg to justify worrying about much more life span.....

    I have seen some mid 80's 6.2 light duty rigs go 300K miles....

    Building one of these to do what they were meant to do would be sweet.....As far as making a moose motor......Chasing the wind my friend.....

    Much of the "Fixes" for the 6.2/6.5 are/were BANDAIDS to get the rig going again.
    Back in the hay day of these engines I have seen many really low mile rigs sitting because people were either not willing to or could not afford to repair them.

    This wonderful forum was started to help people (DIYER'S) learn from others, swap ideas and keep their rigs on the road......

    Have fun......

    What ever you decide to do.....SHARE IT....Always interested in wasssup here at the page...
    Thanks for the correction and more info! Now all I need is some redblock samples!

  13. #13
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    So let me ask a dumb question; if I have an engine from '83 with the large valves, is that a red block? This is the one in my '84 G30 RV.

  14. #14
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    If it was the original engine...
    Probably not.
    From what i have read they were a one year only engine,1981.
    There may have been a few that got used in 82.
    GM changed the color of the diesel to black,probably to help dissipate the heat.That was a racing trick out of Smokey's bag so GM would have know about it.
    90 Chev 3500 c/c 4x4,6.2na,400 auto,4:10 gears.DSG Timing gears,main girdle, isspro tach, pyro,boost,oil and trany temp.Dual Tstats, High volume peninsular pump,on shelf, Custom turbo and intercooler 85%complete. Change of plans for the dually, it's going to get a Cummins. Both trucks are Blue 90 4x4 crews

  15. #15
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    The 6.2 made its appearance in the C/K trucks in the 1982 model year.
    The red block was only 82.
    The 83 and later was black....
    The 82/83 had the coarse threaded injectors/heads

    The 82 heads had larger valves and the heads were more prone to cracking......

    Also the 82 heads had an extra water passage and those were prone to leaking at the head gasket....

    A am pretty sure the Early "Red" blocks were 660 castings.....

    The cast rockers were dropped in the 84 model year....
    (1) 1995 Suburban 2500 4x4
    (1) 1997 Astro
    (1) 2007 Chevy Avalanche
    THIS IS BOW TIE COUNTRY

  16. #16
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    I have seen 1981 stamped on a few red blocks.

    https://www.dieselplace.com/threads/do-i-have-a-red-block.340496/

    Still having a hard time trying to find one. :-/

  17. #17
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    Quote Originally Posted by 2INSANE View Post
    I have seen 1981 stamped on a few red blocks.

    https://www.dieselplace.com/threads/...-block.340496/

    Still having a hard time trying to find one. :-/
    They were unique to the 1982 model year. Of course, they were cast in 1981. I would expect, probably most of them were cast in 1981.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  18. #18
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    At 40 years on...there is certainly not the supply of iron out there to choose from that was available back in the early to mid 90's.

    With Red blocks only being made for basically 2 years...82 was RED and 83 was the same block...just painted black...these are gonna be scarce....Not impossible to find but tough...

    The 6.2 did not make a stellar impression on folks so they are not an item that is being hoarded....
    (1) 1995 Suburban 2500 4x4
    (1) 1997 Astro
    (1) 2007 Chevy Avalanche
    THIS IS BOW TIE COUNTRY

  19. #19
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    I hoard them...
    But then all of us way up here are all a little way out there...
    90 Chev 3500 c/c 4x4,6.2na,400 auto,4:10 gears.DSG Timing gears,main girdle, isspro tach, pyro,boost,oil and trany temp.Dual Tstats, High volume peninsular pump,on shelf, Custom turbo and intercooler 85%complete. Change of plans for the dually, it's going to get a Cummins. Both trucks are Blue 90 4x4 crews

  20. #20
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    Waaaaay upppp North

    I can think of a few things to go along with the 6.2 diesels in the hoard pile..
    (1) 1995 Suburban 2500 4x4
    (1) 1997 Astro
    (1) 2007 Chevy Avalanche
    THIS IS BOW TIE COUNTRY

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