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GM8 turbo on 6.2 help

muddybuddy

muddybuddy

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im acquiriing a GM8 turbo setup of a '97 3500. what all do i need to make it work? i did a search and found that the 6.5 manifolds wont bolt up to the 6.2 unless you use 6.5 heads. i saw i also need to use 6.5 injectors. what else do i need to maximumize performance? where can i find the mechanical wastegates? thanks
 
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I'm not sure how different GM-8 and GM-3 turbos are. I know for my GM-3 really the only modifications that needed to be done were that you'll need the passenger side exhaust manifold off the 6.5 and to plumb an oil return into the pan. I have successfully installed the return plumbing but don't have the tubing installed yet but if you want I can share a pic with you when it is all done, plus the Ace Hardware part numbers you'll need for the assembly.

Injectors for the 6.2 worked with my setup, but mine (out of a '91 Suburban) had the short van style injectors, which I plan on replacing with 6.5 injectors.

The 6.5 exhaust manifold had no problems mounting on the 6.2 passenger side head, not sure if this is different for your application?

You'll also probably need if you don't have it the modified CDR valve that wraps over the turbo mounting bracket.

Wastegates are something I haven't researched yet. My esteemed colleague, JeremyK5, is a pro at searching CK5 and the web for information, and I couldn't have made any progress on this project without him. He might see this post. If not, he probably wouldn't mind if you dropped him a line. :thumb:

My digital cam charger is MIA but when I find it I can take a couple pics for you. That is, like I said, assuming these two setups are similar.

Good luck!
 
thanks, if you could get me the part numbers from ace and what not that would be sweet!

hopefully he sees this and posts up some info to help me :)
 
These are the parts we used to install the oil return. The engine is not here at my house or I would take a pic for you. We put the return on the passenger side of the pan towards the front of the truck. Hope this helps some. I will try to get some pics soon.


Hardware for Turbo Oil Return
Elbow: 45 deg. 1/2" Ace 4066999 $1.79

Elbow: 90 deg. 1/2" Ace 4007845 $1.49

Flange: 1/2" Ace 4068268 $2.79

Plug: 1/2" Ace 47824 $0.79
 
No problem. Thats probably one of the best diesel sites i have found so im sure that they could help you out on any questions that you have.

Well, I would, but the turbo that I found was sold before I could get to it. I would still love to if I had the money and found another truck with the turbo in it. If you have a donor truck it doesnt seem too hard at all.
 
yea i joined there a couple days ago, appears to have alot of good info
 
Yes, lots of info there:D

The GM-8 will work great. It's the last turbo made for the 6.5L and has all the improvements. Supposed to work markedly better than the GM-3 or GM-5. It has a vacuum controlled wastegate and some prefer mechanical and swap to a Turbo Master controller or fab one up themselves. Fairly straightforward mod.
 
what kind of hp/tq gains do you think i will see? the guy i got the turbo setup from said to run single 3.5" or so. would it be worth getting some 6.5 heads, and porting and polishing them? or maybe just take the 6.2 heads of and port/polish them?
 
Enough to be worth it:D

6.5 heads will help as well but most are of the opinion having the heads polished & ported isn't worth the cost:( Somebody used a gasket as a reference between the exhaust & head and was surprised they didn't line up like he thought they should so he used a dremel type stone to match them up better. I thought that might be worth looking into on my build.

I just got my GM-8 Turbo delivered. The cast iron parts are definately different. The aluminum intake is visibly different inside as there is a greater opening following the intake fins. I'm going to take some pics of the two side by side. Since the rebuild kits are the same for all the GM Turbos I'll assume the impellers, shaft, etc are the same.

As for exhaust there are several 4" systems for trucks which is the optimum price/power size. I'm getting one of those and may have some "modding" to do so it will fit my K5;)
 
so you are going to go with a 4" kit and mod it to work with the k5? then thats what i will do. any idea what the best company would be to with?
 
Heartthrob? Heart-something is supposed to be good and they are cheap:D Can't remember the name of the other one. Less than $300 for a aluminized system.

As for boost, how much do you want?:laugh: 15 is easy, 20 is doable and I think if you push it you can get 25. I'm looking to stay around 15.
 
Well, if I went that route, I would want to keep it at 10 or less for my 6.2. I dont have the money to be going any more than that.

Oh and sorry for the hijack muddy.
 
KGsK5 said:
Well, if I went that route, I would want to keep it at 10 or less for my 6.2. I dont have the money to be going any more than that.

Oh and sorry for the hijack muddy.
Click to expand...

no sweat man! i had heard that 15lb was safe, and with proper mods 18-20lbs was good. im going to stay around 15lbs, as this will be a dd/weekend warrior and i want to maximize performance while keeping it reliable.
 
Really? You can go up to 15 without low compresion pistons? I know that with the low compresion pistons you can go alot higher but I had thought with stock safe was about 10. But i dont know for sure. Just what i heard.

And IIRC low compresion pistons were ~1000
 
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