68 GMC Project Tommy

[T_Raven]

Sweet project. Nice work so far. I like the 455 Olds. I'm a Pontiac guy myself and like most BOP stuff over Chevy stuff. I've got an Olds 455 in my 79 TA, Pontiac 455 in my 72 Firebird, and haven't found the right Buick yet so I can get a Buick 455 lol

[CParnell]

I finally found some more time to get things done. Engine is stripped now and at the shop to get cleaned. Should have time to get the frame welded together next week.

This is the vortec crank next to my original 250 crank (right). Only eight weights on the newer crank.

[skorpioskorpio]

Since you've completely tore down the block, now would be the time to Time-Sert and stud the block. The Atlas is all originally torque to yield on the head and the caps. Also because of that all the head bolts and cap bolts cannot be reused, just FYI. Oh and later Atlas engines have a 58X reluctor on them just like the LS engines, yours looks like the earlier 24X which is kind of an odd ball and may cause challenges if you plan to use anything but a hacked GM PCM.

My engine only has 10K miles on it so I haven't really tore into mine, though if I did I would have Carrillo/CP make me pistons and H beam rods, send the head to Lance at Hayward Performance who I've talked to several times and seems to know what to do with the heads on these engines. There is also a guy on Vortec4200.com that has had harmonic dampers made to bump the harmonic rocking off another 1000 RPM so it doesn't happen until into the mid 7000s and bi metals can push it even further. Some of the guys racing these engines in Altered classes are pushing them past 9K with the occasional slip into 10K territory.

[CParnell]

Thanks for the reply.

It's an 06 engine that's why it has the 7 notch crank trigger. I got the whole engine for a good price and mainly because I knew the head is one of the best as far as flow. I'm looking to order a new 08 crank to get the 58x trigger wheel so I can run the Holley Dominator system. The plan is to stud the head and bottom end and get new pistons and rods. I'm hoping a flat top pistons will bring the compression down close to 9:1 but I haven't measured anything yet.

Right now I just wanted the block cleaned up so that I can mess around with mocking it up and making engine mounts.

Thanks for telling me about the harmonic damper, I'm gonna head over there now and see if I can find that.

[skorpioskorpio]

My engine is an '08, pretty sure the '06-09s are all basically the same except for the crank trigger change in '08. Oh and the '08s on all have totally different connectors on the wiring harness and everything that attaches to it because of the possibility that Delphi would go bankrupt, so '08s and '09s all have different AC compressors, alternators, sensors, etc..

There is also a guy (Limeswap) doing a turbo pipe for the stock exhaust manifold if that's where you are going with it. I don't know what year they changed the exhaust manifold but the later ones flow better if you are thinking about staying with the iron exhaust.

As far as mounts, I'm going to use the stock iron brackets off the block with the C6 Corvette mounts from Hinson Motorsports. They're Poly Hockey Puck style and internally linked, you'll need to space them out from the brackets about a thick washer or twos worth so they don't bind on the bracket, not a big deal.

Anything other than a 4L60(65,70)E trans or a Canyon 5 speed is tricky, I'm doing a 4L80E with a PCS 6 speed valve body and a TCI planetary set. To pull it off I've machined off the bellhousing and am making an adapter plate at the pump to mount it to the 4L60 bellhousing.

So just curious, did you manage to do the tear down without shearing any bolts off? I know it's a common problem with rebuilding one of these.

[CParnell]

Yeah as for as I know 06-09 engines are the same. They changed the head for 06 which bumped up the HP, in 08 they got the new crank trigger. Thanks for the info on the sensors, I still need a wiring harness to work with so I won't look for the 08 and up ones. I will look into the engine mounts, thanks again. I'm going to make a turbo header or use a cast turbo manifold. I don't have the link, but there was a turbo diesel company that made them for the Atlas as well. My plan is to do the same as you, adapt a 4l80e to the bellhousing from the 4l60 from these engines. Although the idea of a T-56 still holds a lot of appeal.

As far as tear down goes, I had no issues with stripped bolts or threads at all, maybe I got lucky.

[CParnell]

Got the engine back from the shop, they did a great job on this one to. Nice a clean and they found zero cracks as well. It's a very neat engine to look at all tore down and clean. I spent a few hours and cleaned up most of the casting flash on the outside of the black and cleaned up all the water ports and oil holes on the top of the block. It was cast using the lost foam process and you can clearly see where the multiple foam parts were glued together for the casting.





And then I painted a good coat of cast coat aluminium on it to keep the oxidation at bay and hopefully help it clean up better in the future.

[skorpioskorpio]

Block looks great, yea don't ever paint one of these engines white unless you want it to look like a Styrofoam mockup .

That turbo manifold you probably saw was made by SteedSpeed, it was a prototype and there will like be no more of those.

So the issue isn't striped bolts isn't bolts shearing off, the engines are torque to yield and aluminum has a tendency to gaul so you end up with a bolt that doesn't have enough strength to overcome the force required to remove it, also the reason 'serts and studs are a good idea, you can apply the same amount of torque and be within the limits of the fastener.

[CParnell]

LOL, never thought of the white, that would look funny.

I will tap all the holes but they looked pretty good to me. I'm gonna spend some extra time with a dremel and clean up the oil returns in the block. There is a lot of casting where the glue came out between the mold pieces.

Yeah the guy (EFI-DIY) that did the templates up for that manifold lives in the same city as me. I'm hoping to meet up with him at some point and pick his brain. If the manifold is a no go, I'm more than happy to do up a header for the turbo.

[kingstrider]

Wow cool thread, subscribed!

[CParnell]

And boom it's a shortbox.

My dad's friend from work helped me weld it all up today, his welds are nothing short of amazing.

[CParnell]

My wife got me a wicked father's day present. It's mint.

[CParnell]

Broke the frame down today. Still have a few things to remove then I will take it to the blaster.

[mcbassin]

Nice work on the frame! Looks great!

[weedoublewide]

Anything new happen to Project Tommy recently???