chromekilla
New Member
Well I was just gonna mark the compressor and turbine housing, shaft, nut, and wheel so that way they go in the same way they come out. That way some semblance of balance is done.
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Rebuilding a GM8 turbo,show and tell
- Thread starter bison
- Start date
geotracker
New Member
- Messages
- 1
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- 0
how did you take of the end plate? the plate behind the compressor turbin, witht the three counter sunk srews
bison
Well-Known Member
Some of them can be tight(glue'd down from the silcone).
You can try rotating it with hammer and punch till the hold breaks.
the-schmidtshow
New Member
Hoping someone is still around here that can answer a couple questions for me. I'm rebuilding my GM-4 turbo off my 95 K1500 suburban. Everything has gone pretty smooth until I went to put it back the housings. I'm attaching pictures, I feel like the blade on the exhaust side isn't seating deep enough but after several times apart and back together I can't see how this would change. Additionally once I have the housing around the intake side the turbine no longer spins, is this normal? First stab at something like this rebuild so I appreciate the insight.
NVW
Well-Known Member
Did you lube the bearings?
the-schmidtshow
New Member
Yes, everything got a nice coat of fresh oil.
ak diesel driver
6.5 driver
Been awhile since I had one apart but it sounds like the wheels aren't seated on the shaft fully.
MrMarty51
Well-Known Member
X~2
Might have to remove the wheels and compare the new components to the old to make sure that all the parts are exact and precisely what the old components are.
Make sure that there is not something that is keeping one or both wheels from seating on the shafts.
Also, I believe there is a gasket between the housing and the ends, make sure the gasket{s} are of the proper thickness.
the-schmidtshow
New Member
Thanks guys, I did check the old and new parts against each other to confirm sizing. The bearings both spin smoothly and seat to the same spot on the shaft as the originals when not installed on the turbo and are sitting locked in the right spots internally so I will have to pull everything apart again and see if there is something I am missing.
NVW
Well-Known Member
bison had mentioned tapping each end with a mallet to seat everything
Big T
Well-Known Member
What’s so great about a GM8?
Will L.
Well-Known Member
@Scholioso First, welcome to the forum!
Second- why rescue a gm4? Sell it to the honda 4 cylinder guys as rebuildable for $300 then spend the $300 you were gonna spend anyways along with $200 more from the tooth fairy money and get an ATT on there.
Don’t worry, the mpg savings will replace the tooth fairy money and the rest soon enough. And the extra power, lower egt, cooler running and longer lasting engine are all freebies for the effort.
Second- why rescue a gm4? Sell it to the honda 4 cylinder guys as rebuildable for $300 then spend the $300 you were gonna spend anyways along with $200 more from the tooth fairy money and get an ATT on there.
Don’t worry, the mpg savings will replace the tooth fairy money and the rest soon enough. And the extra power, lower egt, cooler running and longer lasting engine are all freebies for the effort.
Big T
Well-Known Member
@Scholioso First, welcome to the forum!
Second- why rescue a gm4? Sell it to the honda 4 cylinder guys as rebuildable for $300 then spend the $300 you were gonna spend anyways along with $200 more from the tooth fairy money and get an ATT on there.
Don’t worry, the mpg savings will replace the tooth fairy money and the rest soon enough. And the extra power, lower egt, cooler running and longer lasting engine are all freebies for the effort.
Are Honda guys using GM4s on their 4 cylinders?
Will L.
Well-Known Member
@Big T , I haven’t paid attention in last few years honestly, but up till 2014/15 all the 6.5 gm turbos except centermount were on their desired list.
It turns out the GM choke monsters are wonderfully sized for the 4 cylinders, especially the vtecs. 1.6, 1.8 were both way popular hot rod ricers here.
My phone number gets passed around Vegas as someone willing to help mechanics in shops on the 6.2/6.5 platform- probably had an honest 500 calls from them over the last 25 years for trucks. Because of that I bet I have had 100 honda guys and a few Toyota guys wanting to turbo their gassers calling me hoping I could help with their questions- All I could say is sorry and good luck. On the puckup guys upgrading their turbos Craigslist adds just added Honda in the keyword.
After mentioning to a guy at a yard I became buddies with that owned a 6.5 truck, he started asking customers and said every one sold that he asked about was a Honda guy.
Not surprising when you think about it...Figure this:
6.5x2000rpm =13,000. 1.8x7,200rpm =12,960.
They are almost perfect for them. The restriction on exhaust at low rpm means a quick spool, and wastegate control dials it in really well. Inner
Cooler eliminates the rise in egt/iat that fights the turbo, and even the 3” exhaust matches the turbo design.
It turns out the GM choke monsters are wonderfully sized for the 4 cylinders, especially the vtecs. 1.6, 1.8 were both way popular hot rod ricers here.
My phone number gets passed around Vegas as someone willing to help mechanics in shops on the 6.2/6.5 platform- probably had an honest 500 calls from them over the last 25 years for trucks. Because of that I bet I have had 100 honda guys and a few Toyota guys wanting to turbo their gassers calling me hoping I could help with their questions- All I could say is sorry and good luck. On the puckup guys upgrading their turbos Craigslist adds just added Honda in the keyword.
After mentioning to a guy at a yard I became buddies with that owned a 6.5 truck, he started asking customers and said every one sold that he asked about was a Honda guy.
Not surprising when you think about it...Figure this:
6.5x2000rpm =13,000. 1.8x7,200rpm =12,960.
They are almost perfect for them. The restriction on exhaust at low rpm means a quick spool, and wastegate control dials it in really well. Inner
Cooler eliminates the rise in egt/iat that fights the turbo, and even the 3” exhaust matches the turbo design.
@Scholioso First, welcome to the forum!
Second- why rescue a gm4? Sell it to the honda 4 cylinder guys as rebuildable for $300 then spend the $300 you were gonna spend anyways along with $200 more from the tooth fairy money and get an ATT on there.
Don’t worry, the mpg savings will replace the tooth fairy money and the rest soon enough. And the extra power, lower egt, cooler running and longer lasting engine are all freebies for the effort.
Ok, so heres my story. I moved from CO to CA (worst mistake) about 2 years ago. In the process, I left my truck in good hands at a reputable diesel shop to have them store it/we were talking about doing a 12v swap. Anyways, that never happened, & the truck has just been sitting. Well, the day has finally come that I need my truck back in my life. So I'm flying out to go get it. However, before I left, I knew it had a boost leak. Would only push around 2 psi. On startup, exhaust would exit through the turbo intake. So I know it needs a new turbo/rebuilt.
Well I was in the junkyard & I found a 6.5 gm4. I'm going to rebuild this one to throw on my engine to hopefully fix my boost issue. The shop said it does have an exhaust leak though so I will have to fix that as well. But until then, this is just to get it from CO to CA as cheap as possible till I can actually tear it down & fix it how I want it.
I also still want to do a 12v swap. No offense to the 6.5 at all. I love em. Especially the way they sound. Now, before I get hung on the cross, I've done research as far as getting a new or used military block, better heads, etc. The cost to me just isn't worth it. I can pickup a decent 12v motor for much cheaper & have the same reliability. Granted, the swap will still run more initially, but long term, I'm hoping it'll just be a reliable workhorse.
That's why I'm rebuilding a GM4. I do have a question with that though. I tore the turbo down as per the T.O. (this thread) & I believe the turbo I got has been rebuilt. The brass trust plate isn't star sorta shaped like the one in the pictures. It's just a metal(aluminum? its definitely not brass color) circle with holes drilled in it. Not sure if this is factory or not, but the rebuild kit I purchased (according to pics) has the same star shaped brass trust plate. To me, it looks like the one that I have would restrict oil flow? Or maybe it's designed that way to keep oil in that spot particularly? Not sure, I will get pics. Just would like to get ya'll thoughts on that. Any thoughts or ideas?
On that same truck, I found a relocated gray PMD on the front bumper with a heat shield too so I snagged that so I'll be putting that on as well to help make it back. Hopefully nothing goes wrong!
Will L.
Well-Known Member
Yeah, if you know he 6.5 is coming out, I get doing the rebuild then. And understand the 12v decision, won’t hound you on that provided you find a good home for the 6.5 when it comes out.
Ok, so I got my rebuild kit in today. Took all my old turbo main parts (core, snails, blades, bolts, etc.) to work today to use the clean tank, gonna let those sit overnight in the solvent. As for the replaceable parts... what is the differences? Apart from the brass bushings (one has a lip & is taller, the other is flat & shorter), what are the differences in the trust plates? In the picture, the two on the left (top) are new & included with the kit. What came out of my turbo is on the right (bottom). Does the full circle hinder oil flow? Does the half circle hinder oil flow? Does the star shape hinder oil flow? I don't know what the reason in different shapes is other than oil flow/control. I would go with the star shape for better oil flow would be my guess but maybe I'm wrong. Ideas? 
ak diesel driver
6.5 driver
top one looks like the ones I've used. that was on a gm6
Any idea as to design differences? I haven't found much guidance in the ways of changing which bushing to use, but as far as trust plate design, I'm leaning more towards the middle. Obviously someone didn't machine that piece out for no reason compared to the others. The others (to me) look like someone just said "meh, it's good enough" & shipped it.
As for the bushings, I'm going to use the same style as what came out of it, the bushings with the lip on the edge & not the flat ones. Anyone else have advice on this?
Also, the kit came with a bunch of small screws. From Really short, to short, to medium, to long. They are all the same size, just length is different. Looks like they are all for the trust plate depending on what screw length you need? These new screws are philips though & not torx. Any advantage to either? I find torx aren't as likely to strip but from what I've read, these torx screws are prone to strip? I can replace the trust plate torx screws, however the aluminum end cap will get the same torx screws put back as the kit did not come with the bigger size screws (not sure if it was supposed to or not).
Also, anyone have the torque values for the screws & bolts for turbo reassembly? Any military diesel vehicle mechanics with access to a HMMWV Tech Manual to check? My Chilton's owners manual doesn't have nearly anything on the diesels.
As for the bushings, I'm going to use the same style as what came out of it, the bushings with the lip on the edge & not the flat ones. Anyone else have advice on this?
Also, the kit came with a bunch of small screws. From Really short, to short, to medium, to long. They are all the same size, just length is different. Looks like they are all for the trust plate depending on what screw length you need? These new screws are philips though & not torx. Any advantage to either? I find torx aren't as likely to strip but from what I've read, these torx screws are prone to strip? I can replace the trust plate torx screws, however the aluminum end cap will get the same torx screws put back as the kit did not come with the bigger size screws (not sure if it was supposed to or not).
Also, anyone have the torque values for the screws & bolts for turbo reassembly? Any military diesel vehicle mechanics with access to a HMMWV Tech Manual to check? My Chilton's owners manual doesn't have nearly anything on the diesels.