Re: Sullii the 72 GMC 1500
 

Looks good. Nice to have helpers :)
Definitely black walls

Re: Sullii the 72 GMC 1500
 

Really good stuff in here man. Truck looks good. I plan to hopefully do the same on mine for the frame work!

Re: Sullii the 72 GMC 1500
 

Thanks everyone!

Yeah, it should work out if you're still looking for the budget minded approach. I thought a long time about how I could get really low in the rear without dropping a ton on aftermarket suspension parts. I wanted to retain most of the factory components which you cannot do with a rear frame weld in step notch. Even though I committed a sin by cutting a rust free original shortbed frame in half, I think the end result is going to get me right where I want the ride height to be.

Re: Sullii the 72 GMC 1500
 

I felt like I learned everything I needed to with the engine test fit, so it was time to pull it back out. With the engine out, it really emphasized how bad the engine bay looks. My friend and motivator convinced me that it was worth taking the time to clean up the firewall and other engine bay components, so we rolled the truck outside for a proper cleaning. (Note this is before cleaning!)

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After cleaning, we primed the firewall for a fresh coat of 510 Medium Blue. The final results will have to wait until the paint arrives, but it already looks better than it did.

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With the engine bay on hold, it was time to divert attention back to the motor. I wanted to get the engine and transmission mated for good, so it was time to actually install the clutch components. I spent quite a bit of time researching and agonizing over what components I should use to marry these two together. Ultimately, I used all stock components with the addition of a slave cylinder shim kit to make it all work. On the engine side I used all 2002 Silverado components, and on the transmission side I used 2001 Blazer parts. With the addition of the shim kit, it all came together perfectly. For those curious or trying to research this for your own build, here's what I used:

Silverado Parts

-2002 GenIII 5.3 from a Silverado
-GM 11569956 LS Flywheel Bolt M11X1.5 x6
-Pressure Plate Bolt M10x1.5 x6
-LUK 04205 (04-205) Clutch Kit (includes clutch disk, pressure plate, pilot bearing, and alignment tool)
-SACHS NFW1050 Flywheel

Blazer Parts

-2001 NV3500 from a Blazer Xtreme
-LUK LMC444 Clutch Master Cylinder
-SACHS SH6133WB Clutch Slave Cylinder

Holley 319-204 Release Bearing Shim Kit

As far as functionality goes, I have not been able to actuate this clutch yet, but assembly and clearances all checked out. I will update once I am able to test this combo.

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Once I paint the firewall, I will be able to drop the motor/trans back in for what should be the final time. Until then, all I can do is admire how it's all coming together.

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Re: Sullii the 72 GMC 1500
 

Looking good!

Re: Sullii the 72 GMC 1500
 

Quick update with the completed firewall paint. I used Automotive Touchup basecoat/clearcoat and the match was pretty close considering all I did was give them the correct paint code. The current goal is to have the engine bay completely clean while retaining the OG patina on the exterior.

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Re: Sullii the 72 GMC 1500
 

Just wondering if the chrome bumpers and the full wheel covers were added after the purchase? This is the lowest option truck I have even seen. I see someone added a radio.
I was under the impression the 6 cylinder was still the base motor? Must have changed by 1972? I have also read where the GMC's had leaf springs stock and this one has trailing arms. I't more likely the GVW had everything to do with the spring type and nothing to do with a Chev or GMC. A lot I don't know and some of what I thought I knew is wrong.
Love the patina. Should be a blast fixing it up.
Cheers

Re: Sullii the 72 GMC 1500
 

Thank you! Yes, it's definitely a low optioned truck. I believe a few things were added to it over the years including the sport bumpers, full wheel covers, and white top. I have reverted back to the original style "dog dish" hubcaps and white wheels, but I will leave the white top and bumpers because I like the look. As for the engine, as far as I can tell it was an all original 307. I was surprised as well to see this one was a trailing arm truck as I also heard most GMCs were leaf spring. For me, I actually like low optioned simple trucks so this one had to come home with me!

Re: Sullii the 72 GMC 1500
 

Looking awesome:metal::metal:


As far as the leaf spring debate goes. I believe that only GMC’s were available with leafs but they were also available with trailing arms. Up here it still seems to be predominantly coil spring. I’ve had about 10 or so 67-72 GMC’s and only 2 were leaf spring trucks.

Re: Sullii the 72 GMC 1500
 

Thank you!

Re: Sullii the 72 GMC 1500
 

I took a big step forward to getting this truck back together. I was able to get the motor mounted for what should be the final time. Since this was the second time installing the motor, there were no surprises. With the front fender on it is clear that I will have to do some clearancing for suspension travel. I won't be running inner fenders at first but eventually plan to add some that allow for a big drop. I also cut the hole for the harness to pass through the firewall. I ended up going with a 2" hole and PN 63595K35 from McMaster-Carr for the grommet. I haven't pulled the harness through yet but it looks like it should work.

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With the weight of the motor the truck is close to its final stance. It should drop about 1/2" more in the front when it's fully back together. In its current state the frame is completely level. I was hoping for about a 1" rake when done, so I may need to take 1/2" off the rear blocks. I will wait on that until the truck is complete and I have a chance to put some miles on the springs since they are all still new. It's definitely motivating to get an idea of how the truck will sit!

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Re: Sullii the 72 GMC 1500
 

I've been slowly working my way through a number of items recently. At this point, there's so much left to do that I sort of get scatter brained. I'll work on one thing for 10 minutes and then get distracted and work on something else. Overall, though, it's still progress. Lately I've been focused on engine items. I installed new valve cover gaskets and used the opportunity to inspect (all looks good!). The water pump was in need of installation, so I got that cleaned, painted, and installed as well. I was also going to install the alternator mount but decided the stock 5.3 mount is too obnoxious to put back on. I will wait on the alternator and get a low mount kit later.

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Next I got distracted by the wiring harness again so I started to lay that out how I wanted it. I'm finally at a point with it that I can start to finalize the layout and add all the external connections. I am also working on rewrapping the harness with adhesive cloth tape.

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With the help of a friend, we also got the inner fenders clearanced and painted to match the firewall. The shape of the cutout on the fender was slightly modified after this photo since the rear corner still came pretty close to the tire. With the fender installed, it starts to give a pretty good indication of what the engine bay will look like. I was originally going to run with no inner fenders but the bay is starting to look too good to let it get ruined again by road debris. I will have to find an economical solution to inner fenders because I can't stomach upwards of $1k for some of the aftermarket options.

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With all the work going on up front, I realized I still have quite a bit left to do out back. I decided it wasn't worth the hassle of crawling around under the truck, so the bed came back apart. The time spent removing the bed will be worth the aggravation avoided. Checklist for the rear includes relocated fuel cell, fuel lines, relocated battery, crossmember cutouts, and exhaust. I'm starting to think I won't finish this thing by October for the C10 Revival!

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Re: Sullii the 72 GMC 1500
 

Beautiful work as usual doc. Check out Vanatta Fab for some cheaper inner wheel tub options.

Re: Sullii the 72 GMC 1500
 

Thank you! I'll have to check them out. I've started to also think about how to make some of my own. The biggest thing is I like the stock appearing inners, so I was trying to think of a way to maybe modify the originals. I know for the 73-up trucks it's fairly straightforward to just raise them, but I've not seen anyone do a 67-72 like that.

Re: Sullii the 72 GMC 1500
 

I hope you figure something out with the factory inner wheel wells. I think I'll be in the same situation soon.

Re: Sullii the 72 GMC 1500
 

Well I'm hoping you beat me to it, haha. You're doing an awesome job on your build and I've been using your thread for inspiration and ideas!

Re: Sullii the 72 GMC 1500
 

Since my last post I have been working away at several different tasks. The truck has been on and off jackstands several times as I work my way through my checklist. I have it taped to the window to remind me whats left, yet I feel like I never have anything completed enough to actually check it off the list!

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The most significant progress I've made is on the exhaust system. I had several requirements for this system that I wanted which were 2.5" mandrel bent duals, fully tucked in the frame, and an x-pipe. I knew this was going to be tricky to accomplish but I came up with this vision in my head that I was able to make a reality. I started off with some Summit Racing exhaust manifolds. These were actually very nice quality for the price, and they had the 2.5" collector unlike many of the cheap manifolds on ebay which are only 2 1/4". From there I worked with a 2.5" universal exhaust kit I got from Amazon. I took a chance with it and it turned out to be very good builder quality tubing.

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In order to stay above the bottom of the frame rails and make it over the trans crossmember, I had to come directly out of the collector flange with a bend. These manifolds are 26 degrees from vertical, so my first bend is 64 degrees to get me horizontal straight back along the frame rails. This is where integrating the x-pipe gets tricky.

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I knew I didn't really have enough room to snake the exhaust down under the driveshaft behind the trans, and then back up with enough room to get through the cutouts I made in the trailing arm crossmember. Others more skilled than I have tried and it's just not very feasible. This is where my lightbulb went off. Why not utilize all that extra space I created for myself when I raised the bed floor and retained the stock truck arms? So, just behind the cab I turned the exhaust up with a 90 and then towards the middle with another 90. This got the two sides pointed at eachother and gave me the opportunity to squeeze in an x. Since I needed to get my mufflers in there and pointed at the rear axle, I had to do my x at a custom angle. This gave me the ability to go straight back from the x, through the mufflers, over the axle and sneak past the corner of where my fuel tank will be mounted.

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At this point, the whole exhaust has been finalized except for the tail pipes. I will have to wait on these until the bed is on so I can position them perfectly. I plan to have them just barely sticking out behind the wheels with turn downs at the end. I also do need to remove the exhaust and final weld everything and clean it up.

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That's it for now, but first, back on the ground again for some motivation!

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Re: Sullii the 72 GMC 1500
 

Exhaust looks great!
A lot of hours in it

Re: Sullii the 72 GMC 1500
 

I agree great looking exhaust.
Looks like Black Widow Mufflers?
I really like the sound.
Cheers

Re: Sullii the 72 GMC 1500
 

Thanks guys. Yeah, I guess I forgot to mention what mufflers I went with! They are Black Widow Venom 250s. I watched videos for so many different mufflers, but it's hard to know for sure what it's going to sound like on your own setup. Black Widows have made a big splash in the muffler world over the last few years so I figured I'd give them a try.

Re: Sullii the 72 GMC 1500
 

One thing I've discovered (and and maybe others can chime in) is the exact same exhaust system on a small block chevy sounds different the newer LS engine.

Re: Sullii the 72 GMC 1500
 

It's the firing order. Your truck is coming along nicely.

Re: Sullii the 72 GMC 1500
 

I am using Black Widows on my LS. I like the sound. Your cross over it better done than mine so maybe yours will be different. Not too loud at idle, and just above, but I am not leaving the neighborhood without everyone knowing. No drone at all. I would be lying if I didn't say they are loud with much throttle. The best part is the sound when it starts up and on cold choke. Really a great sound for a cam with only 212/218 duration. Mine smooths out substantially after it warms up.

Re: Sullii the 72 GMC 1500
 

Sweet! Do you have any videos of yours running? I would eventually like to put a cam in mine, but for now it will be a stock '04 5.3.

Re: Sullii the 72 GMC 1500
 

No videos but I will attempt to get one I can post.
I am using the BTR Stage II truck cam. I am really happy with it. The LS1 is all stock with the exception of the LS6 intake the cam and headers. Made 354hp at the wheels.
It works with the stock converter. But you will be leaving some acceleration on the table without a converter. Simply put the converter get the motor into its power-band quicker.
Smaller tires with harder compound do the same thing as they spin easily so the motor reves into the power band. However, it just makes the spin worse. It's a balancing act with our trucks. Lack of traction because all the weight is on the front is a huge issue. If you don't have a posi HP becomes an effort in futility. I had a stock 06 Corvette and one just punched it and you will in the low 13's without effort. My LS1 has more engine HP than the LS2 in the Corvette. The C10 the tires are narrower the weight is more and the weight on the tires is less. It is way harder to drive fast. The advertised 0-60 time with the 06 Corvette is 4.6. Best I have been able to do with the C10 is 6.2 seconds.
I have a set of slicks I need to try as traction is such an issue. Especially in the winter.
Rambled enough.
Cheers.