What did you do to your NBS GMT800 Tahoe/Yukon Today?

[Tonyrodz]

I am with these guys. My guess is that the side or spider gears are damaged. The good thing is, I don’t see G80 on the RPO which means that parts are not too expensive if the ring, pinion and bearings are ok. Time to pull the cover.

I wonder if it'll be cheaper to fix it or replace it totally.

 

[George B]

I wonder if it'll be cheaper to fix it or replace it totally.

That depends on whats wrong. If you replace it yo will want to swap your brakes over. Hopefully you get one with good backing plates for the brakes or the axle shafts need to come out.

I would take the cover off and inspect after confirming the fill plug comes out.

 

[Rocket Man]

That depends on whats wrong. If you replace it yo will want to swap your brakes over. Hopefully you get one with good backing plates for the brakes or the axle shafts need to come out.

I would take the cover off and inspect after confirming the fill plug comes out.

Dorman makes two-piece backing plates that don’t require the axles to be removed in order to replace them. It’s one of the few parts made by them I actually recommend.

 

[George B]

Dorman makes two-piece backing plates that don’t require the axles to be removed in order to replace them. It’s one of the few parts made by them I actually recommend.

Good to know! I have pulled too many axles up here in the rust belt.

 

[Walchit]

Hopefully they're not Castech 862 heads. I think one on my van is cracked. Got a pic of the logo on them? Castech logo looks like a battery.

Unless I'm blind neither set I have are castech. I am willing to bet the 706 heads in the truck are, because I've seen a little moisture on the inside of the oil cap. Idk if that indicates castech problems for sure though.
I will take some pics of the heads here in a minute

 

[iamdub]

Oh, and these are the updated valve covers right? I picked them up for 50, came with a set of 862 heads, rocker arms and 15 pushrods lol.

Gonna have to flip that driver side cover over. If it has the circle hole in the baffle, it's the older style. You're looking for a square hole.

 

[iamdub]

Unless I'm blind neither set I have are castech. I am willing to bet the 706 heads in the truck are, because I've seen a little moisture on the inside of the oil cap. Idk if that indicates castech problems for sure though.
I will take some pics of the heads here in a minute

If it's a little moisture, it could just be normal condensation.

 

[Walchit]

Gonna have to flip that driver side cover over. If it has the circle hole in the baffle, it's the older style. You're looking for a square hole.

Geez! Guess I'm still looking for a valve cover then, lol
@Tonyrodz no castech that I can see on these

 

[Tonyrodz]

Geez! Guess I'm still looking for a valve cover then, lol
@Tonyrodz no castech that I can see on these

Nice.

 

[iamdub]

Geez! Guess I'm still looking for a valve cover then, lol
@Tonyrodz no castech that I can see on these

Well, dammit.

You gonna do any work to them heads? They're actually a bit of an underdog and just need some mild porting and maybe some stock intake valves from the 799/243 heads. Good for low- to mid-range torque.

 

[Walchit]

Well, dammit.

You gonna do any work to them heads? They're actually a bit of an underdog and just need some mild porting and maybe some stock intake valves from the 799/243 heads. Good for low- to mid-range torque.

I was just lapping these valves in now. I'm a complete noob, and did a little research on porting and decided against it. Mainly because I thought these were designed more for torque, and I didnt wanna mess anything up.

This lap look alright? I also had found conflicting info on valve lapping so I just went for it, lol

 

[Scottydoggs]

I was just lapping these valves in now. I'm a complete noob, and did a little research on porting and decided against it. Mainly because I thought these were designed more for torque, and I didnt wanna mess anything up.

This lap look alright? I also had found conflicting info on valve lapping so I just went for it, lol

looks good to me. i went and used a drill to lap em in a older engine i freshened up. ported the heads too. something ill never do myself again. way to much work and time. id rather just pay for it.

 

[Rocket Man]

looks good to me. i went and used a drill to lap em in a older engine i freshened up. ported the heads too. something ill never do myself again. way to much work and time. id rather just pay for it. View attachment 367512

I agree on the porting. I still remember how much work I put into a set of 427 Cobra Jet heads for the 460 Ford I was building for my boat and that was 40 years ago. I’ll never do it again.

 

[Scottydoggs]

I agree on the porting. I still remember how much work I put into a set of 427 Cobra Jet heads for the 460 Ford I was building for my boat and that was 40 years ago. I’ll never do it again.

sad part is i actually did a good job. that was for a blown 3800 v6 that i used a na bottom end with. most top swaps as they call it make 8 psi min on the stock blower pulley, i was making 6 psi. less boost= more flow. ended up putting 13 psi through it after a ic and a 2.8 pulley.

 

[Rocket Man]

sad part is i actually did a good job. that was for a blown 3800 v6 that i used a na bottom end with. most top swaps as they call it make 8 psi min on the stock blower pulley, i was making 6 psi. less boost= more flow. ended up putting 13 psi through it after a ic and a 2.8 pulley.

I ended up putting a Weiand blower on that engine but I had a friend help with it. I was out of my knowledge zone by that time. I have no idea how much boost or HP it was throwing down but somebody told me at the time it should bave been about 800-900 tq and 1000hp. I was in my early 20’s and drinking and drugging heavily. I only got to run it with the blower for one summer because I lost pretty much everything due to my bad habits. My truck was zebra striped so the popo would know I was a habitual offender and pull me over on sight. My license was taken for 7 years. The boat sat at my sisters and there must have been water left in the block over that winter because it cracked; all the freeze plugs were blown out. But that was one fun summer. That jet boat would literally jump out of the water and onto a plane instantly, threw 100’ rooster tails. I even got a ticket for recklessly endangering in it by the marine police but when I went to court they didn’t even know what to do with a marine ticket so it was dismissed. Back then you could drink and drive on the water too. Since cell phones weren’t even invented back then, the only pics I had were actual pics that I kept in an album. I lost all my belongings a few times during those years including all my pictures. All I have left are memories and a lot of those are pretty hazy lol. I lived pretty hard and fast during my younger years, I was pretty wild.

 

[Walchit]

I think I did it boys!
@Scottydoggs I used the suction cup on my drill, Idk if I went too far, or not enough, or just right. I guess we will see.
@Rocket Man I've lost a good amount of shit due to drugs and alcohol also, nothing that bad ass though.

 

[Scottydoggs]

I think I did it boys!
@Scottydoggs I used the suction cup on my drill, Idk if I went too far, or not enough, or just right. I guess we will see.
@Rocket Man I've lost a good amount of shit due to drugs and alcohol also, nothing that bad ass though.

once you see the sides of the valve and the valve seat are both a polished match your all set. your pic looked perfect.

i closed the chuck on the top of the valve and pulled on it lightly. slow and light pressure.

 

[Walchit]

I'm gonna regret starting this in a few hours I bet...
Practiced on one of the rockers I got the other day, and the cast iron pan didn't break! Lol

 

[iamdub]

I'm a complete noob, and did a little research on porting and decided against it. Mainly because I thought these were designed more for torque, and I didnt wanna mess anything up.

Better safe than sorry! Are those the heads you got for $50? Are you sure they're not cracked or warped?

This lap look alright? I also had found conflicting info on valve lapping so I just went for it, lol

As the others said, you're good. You've got a lot of matched surface there

 

[Walchit]

@iamdub
No these are the heads that came on the used engine from the junkyard, 294k, pressure tested at the machine shop. I only got those other heads because I thought I was getting an updated valve cover. Lol

I gave up on cleaning these rockers and putting the trunions back in.