Differences between 6.5 GEP NA and turbo

What are the differences between the 6.5L GEP NA and 6.5L GEP Turbo (other than the obvious addition of a turbo charger)?

Is the angle of the intake headers the same and can the turbo with manifold be added to a 6.5L GEP NA engine?

The turbo block has ports on top to supply oil to the turbo.

Action said:

The turbo block has ports on top to supply oil to the turbo.

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Can they be drilled, tapped, or faced without taking the whole thing apart?

The turbo engine has the different heads that are used with GM vans and H1/HMMWV.
If you are looking for an engine for a CUCV and wish to install a GM truck side mount turbocharger, get the NA GEP engine. The HMMWV turbocharged engine will not fit in a CUCV or CUCVII due to the exhaust pipes being routed along the back of the engine, where they will hit the firewall.

NDT said:

The turbo engine has the different heads that are used with GM vans and H1/HMMWV.
If you are looking for an engine for a CUCV and wish to install a GM truck side mount turbocharger, get the NA GEP engine. The HMMWV turbocharged engine will not fit in a CUCV or CUCVII due to the exhaust pipes being routed along the back of the engine, where they will hit the firewall.

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This is NOT for a CUCV but for a M998. Rear mount turbo is what I need. Just wondering whether the turbo plus intake header from the turbo engine will fit the NA block. Again, this question pertains to the GEP blocks.

alpine44 said:

Just wondering whether the turbo plus intake header from the turbo engine will fit the NA block.

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No, the turbo engine has van style heads and the NA does not.

alpine44 said:

Can they be drilled, tapped, or faced without taking the whole thing apart?

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The answer is no.
That kind of work needs to be done with a milling machine, and you better do this after the block was completely stripped, since there will be iron chips and -dust, everywhere and especially inside the oil gallery!

As NDT has indicated your #10163726 (N/A)heads will have to be replaced with the #12556822 (turbo)heads in order to accept the turbo-model, specific intake manifolds.



G.

and a turbo wont fit in your current m998 without a few mods...body lift and tunnel opening reshaping.

alpine44 said:

Can they be drilled, tapped, or faced without taking the whole thing apart?

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Been trying to find the answer to this for a while now. Can not get a clear and definitive answer anywhere.

linhster said:

Been trying to find the answer to this for a while now. Can not get a clear and definitive answer anywhere.

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Read post #7 above.

Thanks all for the helpful info.

If I understand it correctly:

• The M998 would require a 6.5L GEP Turbo engine plus modifications to body, doghouse, and exhaust.
• The 6.5L GEP NA block would be a better candidate for a side turbo setup in a CUCV (with a custom oil feed and return for the turbo).
• Both blocks should alleviate worries about the dreaded cracks at the main bearings.

Action said:

Read post #7 above.

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Sorry, did not scrolled down before posting… Lesson learned. Funny, that I asked the same question about the oil port a few weeks ago with zero reply.

alpine44 said:

Thanks all for the helpful info.

If I understand it correctly:

• The M998 would require a 6.5L GEP Turbo engine plus modifications to body, doghouse, and exhaust.
• The 6.5L GEP NA block would be a better candidate for a side turbo setup in a CUCV (with a custom oil feed and return for the turbo).
• Both blocks should alleviate worries about the dreaded cracks at the main bearings.

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the issue was #8 cyl crack issue on early turbos....amongst others, but that was the #1 fix when GEP took it over.
GM didn't want to bother due to the soon to be released Duramax....no sense in dumping money on an old design.