GM-8 Turbo change over info help!

[chestatee]

Need some knowledge/experienced based feedback about changing over a GM-4 to a GM-8 on a 1994 6.5;

1) Is there any performance or benefits with going from a GM-4 to a GM-8?
2) It seems physically that the GM-8 has a larger chamber and exhaust neck prior to the downpipe flange? Is there any other difference?
3) If I do make a change over on my 94, what will I need to do as far as operational or set up changes. It seems to be a straight change over, but what about the vacuum set-up, add-ons or alterations or anything else?
4) Best way to determine the quality of the turbo? i.e shaft play etc.

Thank you
MDS

[arveetek]

I was contemplating the same thing a few weeks ago. I came into the possession of a GM-8 and thought about replacing the GM-4 that is on my 95. However, after doing some research, most folks said there really wasn't much of a gain in the swap. The exhaust elbow is, in fact, better on the 8, but the A/R ratios are the same otherwise. I have a Turbomaster on my GM-4, and it won't work on the GM-8, so I would have to buy a new one.

Some have reported better power with the 8 over the 4, but I decided it wasn't worth the hassle of swapping it out. I did replace my EGR intake with a non-EGR style, and installed a free-flowing downpipe, crossover pipe, and 3.5" exhaust sytem.

Casey

[Kennedy]

Like Casey said the gains are so minimal it's really not worth the hassle for most.

[HH]

I noticed a difference from my -3 to the -8 when towing. IMHO I think the swap was worth it, but then again, my turbo needed replacing and the 8 was available. It was not much of a hassle to change.

[chestatee]

Thanks for your input with this matter: which assisted me with a conclusion.

MDS