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Opinions needed - Performed Optical Bump

Well I got out there today and pulled the air cleaner and found that there is no snorkel in the fender but I discovered something that I don’t particularly like. I was spinning and playing with the turbo impeller and found that the shaft has some side to side movement. Not sure how much movement is considered to be ok but I can not only feel the movement but can see it also! It’s also coated in oil from the cdr valve.
 
Oil from cdr is normal. Gm says it ok, but all other manufacturers say oil spray (or anything else) shortens turbo life.

As to freeplay- NONE. If you feel it move- it is done. If you let it go to far it may kill the engine. As turbo man says:
ITS TURBO TIME!

If the turbo lets loose worse case scenario- it can grenade and actually kill you. The parts could go in and stick in valves destroying them, piston if it gets through valve. With the shaft out of the way, all that oil normally lubricating the turbo can feed the engine as unrestricted fuel and cause a run away.

What else- maybe it just rattles doesn’t make proper power (sound familiar?) and eventually just stops spinning.
 
Is the compressor wheel rubbing the housing? A picture of the turbo inlet will help. You can feel a little play in turbo's as the oil pressure comes up and zero's it out. But the clear wear limit is the wheel rubbing the turbo housing. The compressor side oil seal letting go is an engine oil fed diesel runaway.
 
Here’s some photos of the compressor wheel and data tag. I really thought it had a GM-8 but I see the tag shows GM-4
 

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It doesn’t really look like the wheel is touching the housing but by me just using one finger in the wheel spinning it round and round I can feel it seem to catch tension and then free up but not on every revolution, it’s more at random.
 
Anyone recommend a good place to get a GM-8 turbo from that won’t break the bank? Even if someone has a good used one laying around! Looking at the differences between the 4 and the 8 I think I’d probably benefit by going that route and not having to do much in terms of modifications
 
dbrannon79 said:
Anyone recommend a good place to get a GM-8 turbo from that won’t break the bank? Even if someone has a good used one laying around! Looking at the differences between the 4 and the 8 I think I’d probably benefit by going that route and not having to do much in terms of modifications
Click to expand...
And then, You never know what condition a used GM8 turbo would be in after You receive it. I dismantled and installed a rebuild kit into my GM8 and also a wicked wheel compressor wheel. After I got the turbo tore down and dismantled, there is a big crack in the one housing on tje exhaust side. I know that cant be doing a bit of good as far as performance but its what I had to work with.
Do the smart thing, go to Leroy Diesel or to Quadstar Tuning and buy a good turbo and a tune to match Your driving preferences.
 
I’ll definitely look at the thread and see what’s for sale. I’m actually afraid of getting a big turbo like an A-team or others because (correct me if I’m wrong) I think I’d have to pull the heads and spend a bunch of money which this motor isn’t worth, doing the head studs and such, but for a reliable and beneficial upgrade from a GM-4 would a GM-8 be the way to go? I’m not looking to make a power house out if it, just get back the power it should have without all the major changes that cost bigger bucks. One day (when I win the lottery). Dreaming of course, I would want to invest into an AM general optimizer engine. But that’s a day I’ll probably never see
 
Is the compressor wheel rubbing on the housing? I can't tell from the picture.

Less back pressure with a big turbo is easier on the engine. You don't need to pull the heads off. The QSV or stall converter would help off the line from a light as big towing turbo's don't light off until around 2000 RPM. With 18 PSI or less boost I made the same power as a HX40II at 24 PSI. Other turbo's are available today aside of the huge towing turbo's.

ATT run vs. HX40II

Statistically the power output on the 1986 6.2 Military engine is the same for both turbo's. There is bragging rights if I was selling an air filter. Except one turbo wins torque while the other wins HP. Yet, the numbers are so close - less than 5% there isn't a clear power winner IMO. Driving...
www.thetruckstop.us
 
Ok- lottery is p400 heads not optimizer.

But NO. Bigger turbo is easier on the heads, gaskets, engine as a whole than gm turbo if ran at same boost. Pay attention to what does the bigger turbo at same boost pressure do. No more stress- exactly the same. But it is pushing more air volume and therefore less compressed heat. So same on ‘abuse’ to engine except less engine heat to deal with.

Having more volume of air at same boost means more fuel can be used. So more power at that boost level.
All that without a tune.

But to do it way better and get the improvement in power, mpg and heat- get the tune.
 
Youtube and look up gingersnap customs. He does a turbo change and posts the EGTs and the exhaust pressure it takes to run the GM X turbo and also whichever turbo it os that he installed.
Cant remember what the exhaust pressure is called, but, it was a very significant amount amount less with a different brand of turbo.
I dont onow if it is right for us to post the videos or else I would do so.
I also dont understand why he doesnt come in here and post his findings. Most of the time He works with Quadstar tuning to test new equipment and tunes that Quadstar comes up with.
 
Courtland and John had a big falling out. He didn't use any Quadstar parts on the blue truck he did. ALOT of guys are unhappy with John hiding out and not giving people specs for his parts. Hell we never hear from him on here and he's a vendor. I asked for specs on the S60 years ago and he threw a temper tantrum on me🤣. Then there is the "Custom Beast pump" which is just an off the shelf 6033.... anyway when it comes to tuning I can't say anything bad about what he does there. So anyone looking to run a DS shouldn't think twice about using his tunes. I personally won't buy ANYTHING from John... but thats for different reasons.

FB is where all the younger kids hang out, it would be cool to get people like Courtland on here. But I doubt that will happen.

Back to the original post. The GM8 runs a 2:1 boost to drive ratio. So 10psi of boost is 20psi on the turbine side. Thats what kills these engines. Upgrade to a hx35 with a 14cm housing and you can drop that ratio down closer to 1:1. That will improve performance and take stress off the engine. Pair that with a tune and it will be a whole new truck.
 
@Rockabillyrat

Thats the numbers I was looking for and could not think of. The drive pressure to the boost ratio.
The videos that Courtland has out there has some impressive results on what He gas done to his 6.5 systems.
 
I went ahead and installed a Spectre cone air filter in place of the stock filter. I’ve noticed a decent difference even with a turbo that showing signs of failure. Pickup is better and getting higher boost on light acceleration. Y’all guys are right. It’s time for a bigger turbo. I’ll post a photo if it in a bit
 
Here’s the photo. One thing I noticed while I was out on a drive, I took an on-ramp that has a decent incline and it boosted almost immediately to 12 psi and stayed there, I was at 60mph in no time :)
 

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