68 GMC Project Tommy

[CParnell]

25 years ago my grandparents gave me this truck. Even at a young age I loved fixing things and they must have figured this was a good outlet for it. She has some good war wounds, but she worked hard as a farm truck. Life got in the way and even though I always found time to go and visit my grandparents and the truck I didn't have the means to do anything with it. Well some time has past and I finally have the time/money to make this dream finally come true. This isn't going to be a fast build but I hope you will enjoy it. Plans are to keep the six if it isn't cracked and add a procharger and some other fun bits. For now enjoy the pictures.

That's me in the back of the truck with my brother in tow about the time I got the truck.


And on the trip home from the farm.




And the progress today. Also it is almost exactly 25 years to the day that I got the truck.







I'm keeping the end of the box for a shop seat like I have seen on here.

[Hardesty454]

Good lookin truck. What are the main plans? Make sure to not bite off too much. Most get bored and quit that way. :/

[CParnell]

The current drivetrain plan is to run the 6 if it's not cracked. With that I would like to run a small Procharger for about 15 pounds of boost. There is also a couple aluminum heads I'm looking at along with EFI. I would then back that up with a Holinger SMG transmission.

If the 6 is actually broke then It will be an LS7 and T-56 combo.

Haven't decided on a colour yet. White or blue just dunno. Will lower it some and run 18's. I have a million other ideas but It depends on which engine is under the hood. I will be keeping it 68 GMC though and getting copies of the 910 badges from the original truck made.

[CParnell]

[thelonerife]

Nice project!

[Hardesty454]

Nice plans! Hope you got the spare coin if that I-6 is busted. Ls7/t56 ain't cheap!!!

[BigDaddyV]

Nice truck and start, I would love to see the procharged 6 rollin! Rock on, I'll follow along

[Cash3481]

Love seeing GMCs stay on the road. And that red is a bonus. I just sold that exact same colored 68 GMC to a friend. Good luck with the build as you have a great clean truck to start with for sure.

Mike

[CParnell]

More progress today. The six is looking good so far no visible cracks or breaks. Found all my seat foam. Most was in the heater, but some unlucky bastard of a mouse made a nest in the clutch. It didn't end well for them.








And the assistant sleeping on the job.

[SuperC10Tex]

Good start to a 4-eyed !!! Keep the pics coming.......

[CParnell]

Well I got the cab gutted today and pulled it off the frame. Not much left to take apart. What's the best way to remove the frame rivets?

[BigDaddyV]

Looking Good!
as far as the rivits, Cut an X in the top of it with a grinder and use a chisel to knock them loose, or you could try a hammer chisel if you have one handy.

[CParnell]

So I stripped the engine down today. The amount of crap in the bottom of the pan was shocking. I had fun taking it apart, I have built a few engines before but no inline sixes. Dropped it off at my machinist to get cleaned, check for cracks and let me know how much needs to be cut to get the bores back in shape.

[Molberg]

Nice start!... sub'd

[BigDaddyV]

Please share what you learn, I've built every V8 I can think of but never a I6 either. Keep up the good work

[mcbassin]

Looks like a nice project. That cab also looks to be pretty solid. subscribed.

[CParnell]

Well 6 days all on my own and the major disassembly work is done. Next stop is shortening the frame.





Engine is at the machinist and the cab is crated up to take to the body man. Everything is going faster than I thought it would.

[BigDaddyV]

I was holding my breath as I went threw the cut pics...
and when I got to the second section removal, my heart dropped til
I realized you had the back half flipped over.... LOL, (its to dang early)
Awesome work! Looking forward to seeing that Olds engine runnin!

[CParnell]

So a few things have changed again. I really need to nail down a plan so I don't spend too much.

I have decided to keep the 455 for my 74 cutlass. I picked up a new straight six. I wanted to keep it 6 cylinder like when I got the truck but I wanted it to be more modern. So I picked up a 4.2L Atlas engine. I stripped a bunch of it today, it's very different from the engines I have built in the past and I'm looking forward to building it. Will have to go turbo on this one for sure.

The 455 and the original 250 six.


And the new 4.2L Atlas.

[CParnell]

I dug a little deeper into the Atlas today and I thought you might like to see what it looks like.

[mcbassin]

Very nice job on the frame. You made it look too easy

[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.