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Thread: To turbo a low compression 6.2?

  1. #1
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    Default To turbo a low compression 6.2?

    Good day!

    I just did a compression test on a customers very beautiful 1985 Chevy 6.2 n/a truck. It runs a lot better after I put a manual glow plug override on it and adjusted the injection pump timing. Starts right up after 8 seconds of glow plug time, not plugged in.

    However, it has excessive Blowby coming out of the oil fill tube and has some whiteish smoke from the exhaust.

    I just did a compression test:

    Cylinder #1=325 at 17 puffs
    Cylinder #2=355 at 15 puffs
    Cylinder #3=320 at 13 puffs
    Cylinder #4=355 at 16 puffs
    Cylinder #5=325 at 13 puffs
    Cylinder #6=345 at 17 puffs
    Cylinder #7=320 at 15 puffs
    Cylinder #8=365 at 17 puffs

    Customer wants to add a 6.5 turbo to the 6.2.

    What are your thoughts?

    How long would his low compression 6.2 last with a turbo?

    Would it be ok to turbo a low compression 6.2?

    Would a take out Navistar or Navistar optimizer be a better candidate for a turbo?

    Customer does not want spend a ton a money on a motor. Just wants something reliable with a little bit more power.

    He loves the old 6.2 and 6.5 diesels and would rather keep it a diesel.

    Any advice from you gurus would be helpful for the customer.

  2. #2
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    Turbo it and he'll be needing a motor sooner....
    1993 Chevy K3500

    owner - Twisted Steel Performance

    porting, ceramic & powder coating

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  3. #3
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    6 puffs on a warm engine is the compression value you need. By the looks of your compression results, heed the above post.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  4. #4
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    Quote Originally Posted by DmaxMaverick View Post
    6 puffs on a warm engine is the compression value you need. By the looks of your compression results, heed the above post.
    At 6 puffs, the compression results would have been much much lower. The motor was hot. Your thoughts on putting a turbo on it?

  5. #5
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    If he was my customer he would need to find someone else to do the work, I'm not going to damage my reputation for anyone... can you guess my answer ???
    1993 Chevy K3500

    owner - Twisted Steel Performance

    porting, ceramic & powder coating

    like us on Facebook

  6. #6
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    Quote Originally Posted by sctrailrider View Post
    If he was my customer he would need to find someone else to do the work, I'm not going to damage my reputation for anyone... can you guess my answer ???
    Understood. Customer has already been advised.

  7. #7
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    I run into this with some customers building motors, I won't do something I know is not good to do just because they want it, they either follow my advice or go somewhere else...
    1993 Chevy K3500

    owner - Twisted Steel Performance

    porting, ceramic & powder coating

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  8. #8
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    Quote Originally Posted by 2INSANE View Post
    At 6 puffs, the compression results would have been much much lower. The motor was hot. Your thoughts on putting a turbo on it?
    6 puffs on a warm (or hot) engine is the standard. The values you posted are marginal at best, under the best of conditions. If the actual values would be much lower, the engine needs a refresh before asking it for more. The engine is tired. If it runs well like it is, I'd suggest running it until it doesn't. Or, replace or overhaul it.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  9. #9
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    Ok thanks for your input gentlemen!

  10. #10
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    Very good bet that the rings are all stuck and skunked up.

    Yank the heads off and the pan....Get the pistons/rods out...
    Do a bottle brush hone job and fresh rings....New head gaskets and bolts and a fresh set of Squirts .

    It will run like a scalded dog.....
    (1) 1995 Suburban 2500 4x4
    (1) 1997 Astro
    (1) 2007 Chevy Avalanche
    THIS IS BOW TIE COUNTRY

  11. #11
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    Quote Originally Posted by Robyn View Post
    Very good bet that the rings are all stuck and skunked up.

    Yank the heads off and the pan....Get the pistons/rods out...
    Do a bottle brush hone job and fresh rings....New head gaskets and bolts and a fresh set of Squirts .

    It will run like a scalded dog.....
    All the diesel shops in Gallatin Valley that rebuilds motors recently went out of business or they don’t want to touch a 6.2 or 6.5. Also the cost to rebuild an old 6.2 is close to about the same as a good newer 6.5 block.

    Customer decided to get a 6.5 optimizer reman. Same as what I have. Cost wise and longevity wise it just makes sense.

    I found a donor truck at the junkyard with all the serpentine and turbo parts needed. Parting it out right now for the customer. He is going to have a badass Squarebody!

  12. #12
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    Sweeeeeeet....

    Keep us in the loop
    (1) 1995 Suburban 2500 4x4
    (1) 1997 Astro
    (1) 2007 Chevy Avalanche
    THIS IS BOW TIE COUNTRY

  13. #13
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    There's an engine builder in Hamilton Montana that knows the 6.5. He's the one who did the machine work on the block and rebuilt the heads used in Sarah's Blazer 6.5L. Sarah and I re-assembled the engine and installed all of the bearings and seals, but he'd probably do it for you.

    Engine Rebuilders (Greg, owner)
    217 Fairgrounds Rd
    Hamilton, MT 59840
    (406) 363-6748

  14. #14
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    Quote Originally Posted by 2INSANE View Post
    Good day!

    I just did a compression test on a customers very beautiful 1985 Chevy 6.2 n/a truck. It runs a lot better after I put a manual glow plug override on it and adjusted the injection pump timing. Starts right up after 8 seconds of glow plug time, not plugged in.

    However, it has excessive Blowby coming out of the oil fill tube and has some whiteish smoke from the exhaust.

    I just did a compression test:

    Cylinder #1=325 at 17 puffs
    Cylinder #2=355 at 15 puffs
    Cylinder #3=320 at 13 puffs
    Cylinder #4=355 at 16 puffs
    Cylinder #5=325 at 13 puffs
    Cylinder #6=345 at 17 puffs
    Cylinder #7=320 at 15 puffs
    Cylinder #8=365 at 17 puffs

    Customer wants to add a 6.5 turbo to the 6.2.

    What are your thoughts?

    How long would his low compression 6.2 last with a turbo?

    Would it be ok to turbo a low compression 6.2?

    Would a take out Navistar or Navistar optimizer be a better candidate for a turbo?

    Customer does not want spend a ton a money on a motor. Just wants something reliable with a little bit more power.

    He loves the old 6.2 and 6.5 diesels and would rather keep it a diesel.

    Any advice from you gurus would be helpful for the customer.
    The first 6.2L diesel I owned was rebuilt because of a collapsed lifter. As a consequence of the rebuild process, I had an opportunity to look at the pistons and rings in this 240,000 mile engine. The oil control rings were quite packed with carbon, and the compression rings were significantly deteriorated due to flaking chrome plating on the faces of the rings.

    If on the cheap, this engine could been returned to service with just a good de-carbonization, new rings and new lifters.

    After it was rebuilt, I added a new Banks Sidewinder turbocharger system. I then ran this truck for another 40K before it was traded. There was no negative to having the turbocharger - it was a big plus.

    Non-turbo 6.2's are pretty dirty, and produce more carbon deposits than a turbo'ed engine. This tends to cake the soot on the pistons and rings unless the engine is used in ways that produce higher combustion temperatures.

    The listing of the compression pressures are fairly uniform, though a little low. GM considers 275 psi after 10 puffs on a warm engine as the lowest acceptable. Could be that the pistons just need decarbonized along with fresh rings and new head gaskets. While you're in there, I'd install a new timing chain, and give the heads a good look.

    Jim

  15. #15
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    Quote Originally Posted by More Power View Post
    The first 6.2L diesel I owned was rebuilt because of a collapsed lifter. As a consequence of the rebuild process, I had an opportunity to look at the pistons and rings in this 240,000 mile engine. The oil control rings were quite packed with carbon, and the compression rings were significantly deteriorated due to flaking chrome plating on the faces of the rings.

    If on the cheap, this engine could been returned to service with just a good de-carbonization, new rings and new lifters.

    After it was rebuilt, I added a new Banks Sidewinder turbocharger system. I then ran this truck for another 40K before it was traded. There was no negative to having the turbocharger - it was a big plus.

    Non-turbo 6.2's are pretty dirty, and produce more carbon deposits than a turbo'ed engine. This tends to cake the soot on the pistons and rings unless the engine is used in ways that produce higher combustion temperatures.

    The listing of the compression pressures are fairly uniform, though a little low. GM considers 275 psi after 10 puffs on a warm engine as the lowest acceptable. Could be that the pistons just need decarbonized along with fresh rings and new head gaskets. While you're in there, I'd install a new timing chain, and give the heads a good look.

    Jim
    That is very good to know! Could you pm me his name and number?

  16. #16
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    Quote Originally Posted by 2INSANE View Post
    That is very good to know! Could you pm me his name and number?
    The engine shop I mentioned earlier was identified in post #13 above. He runs a small shop, but appears to do a good job. It's becoming harder to find engine shops that'll work on the 6.2/6.5, which seems odd to me, given that the same engine machining technology is used for any gas V8.

  17. #17
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    Quote Originally Posted by More Power View Post
    The engine shop I mentioned earlier was identified in post #13 above. He runs a small shop, but appears to do a good job. It's becoming harder to find engine shops that'll work on the 6.2/6.5, which seems odd to me, given that the same engine machining technology is used for any gas V8.
    Sorry… It was a long day… Thanks man! I contacted them and got quotes!

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