Build thread for the 72 GMC, finally. Thanks John!

In reply to tuna55 :

What's different about those (Toyota, Subaru, etc) paint jobs is that they're non-metallic.  Glossy color without metal flake in it.  Personally, I love it.  I'd call it timeless but not many folks look to me for fashion advice ;)

It's definitely a current trend, but it's not the first time it's been popular.

My dad would always refer to these as "housepaint blue" (or insert color of car) when we were at street rod shows.  That was his way (and I presume he didn't coin the term) of describing a non-metallic paint job on a nice car.

Spark plug wires

New wires fix the miss?

NOHOME said:

New wires fix the miss?

No that is me just documenting something from weeks ago finally. New cap and rotor are coming from DUI this week. 

Well this is annoying

Apparently the problem was elsewhere in the rotor, I played with it a bit tonight and finally got everything to go. I started a briefly but it only served to annoy wife and child alike. Hopefully tomorrow I can spend a little bit of time in the driveway tuning.

So a more complete story, The weights were hitting the rotor, so it would not advance when I tested it. I played with it for a while before figuring out that it was hitting that boss. I trimmed it with the Dremel and cleaned it up. Then I cranked it over, remembered that I had not hooked up the distributor, then cranked it and it fired up on the first crank. Then I annoyed everyone in my house because it was eleven. 

Have you ever seen such a strange juxtaposition?

It started on the first try again. That's pretty great. The brakes got pretty spongy, and I will have to address that. Shifting still seems really sketchy, and I will have to address that too. The emergency brake wouldn't hold it on this hill, and I'll have to address that. 

I drove it out of the garage, which made the kids very excited. It's really only running on six or seven cylinders though, and that makes nobody very excited. I checked for spark at each cylinder with the timing light and found it everywhere, the timing is about 10° , but the idle screws don't seem to be doing anything. One of the very short pipes I'm using as a temporary exhaust points straight down, and there was tons of soot beneath it. That side measured about 10 to 1 on my wide band, the other side was a little higher. I'm pretty sure I had a miss on both banks, and I think that invalidates the wideband readings. The strange thing is that it ran extremely smoothly right before I ran out of gas. So obviously this thing is pig rich, but I don't know why the idle screws would not tame that. Thoughts?

Idle mix needs to be set with the throttle closed or only open a tiny bit like maybe 1 turn.

If you close the idle mix jets and the engine does not shut off, then the throttle plate  is open too far and is into the transition slots. It will be rich and stumble when accelerating

I may be preaching to the choir, but this was breakthrough stuff for me when learning basic carb tuning.

Check float level. Might be high 

The choke was stuck on

Having the choke on meant I needed the idle screw for advanced which meant that the idle screws were not engaged because the idle circuits weren't doing anything. I got that figured out, now I got it stuck in first gear in the driveway while trying to put it back in the garage. It idled pretty smooth but it still probably missing a bit.

1: adjust rear brakes for emergency brake function

2: bleed brakes for proper brake function

3: install dash and get a tach at least for now

4: buy timing tape so I can see and set the timing curve. As I recall it was too aggressive.

5: install mirrors for now so I can back it into the garage without annoyed tunawife

6: install coolant overflow

7: design battery hold down

8: get the truck to a tree to fix the weird bow in the bed side

9: make sure I can't over travel into reverse

10: adjust clutch take-up. It's pretty high. 

I adjusted the clutch and shifter with tunakid 1. I adjusted the rear brakes with tunakid 2. That takes care of 10, 9, 2 and 1. 

Super fun to work with my kids during daylight by the way. Video coming

That was awesome.  I thought for a second he was going to drop a column shifter into gear!

No doubt that will happen soon enough.

Pete

NOHOME said:

That was awesome.  I thought for a second he was going to drop a column shifter into gear!

No doubt that will happen soon enough.

 

Pete

Well the column shifter is long gone, of course. He has driven (briefly) a manual transmission before (ye olde Catywompus) but not this yet. I don't see any reason he couldn't, though with unassisted brakes and steering, maybe a parking lot would be better than pulling out of a garage 90 degrees to the driveway facing a retaining wall.

Parental flashback time.

Tunakid 1, in the video above, helped me adjust the shifter rods. This is an external rod shifter, which I am just now realizing that many of you have not played with. The deal is that each shifter fork (1-2, 3-4, and R) has its own lever. Each lever is actuated by a corresponding gate/lever at the shifter. They are connected with rods. They can over and under travel if improperly adjusted and the transmission can accidently be put into two gears at the same time. This is nontrivial. Unlike a Hurst Super-Competition shifter, there is no "stick a 1/4" rod in these holes" element, it's just a "Hey here are these threaded rods. Have fun!". I was under the truck with wrenches while the kiddo was in the cab with the shifter. He was careful not to chop my fingers off. We went back and forth and figured out that the reverse rod was way out of adjustment. I got it handled and he took off to go play.

Tunakid 2 showed up and it was time to address the brakes. First I was in the cab and he was spinning wheels. We found, rather easily, that the back two wheels were not really doing anything on hydraulic or emergency brakes. I took the wheels and drums off and showed him how they worked. We had a good time (Mechanics like to name things really creatively. You see how this looks like a drum? They call that a drum brake. See how this one looks like a disc? You'll never guess what they call it) and eventually switched places after fixing the adjusters. He hit the brakes, I adjusted and reinstalled. Repeat. Now both brake systems work well.

I had a flashback. TunaDad was absent for a lot of my early adolescence. There was actually a restraining order against him taken out by TunaMom, with Tunasister and I named. We didn't see the guy for a couple years. It was probably better that way, even though it was really rough. When we finally got the legal permissions to have overnight visits, the three of us were all packed in a one bedroom basement apartment. For the first few visits, we actually shared the same bed. I was perhaps 12 and Tunasister was probably 10 or so.

So the flashback. Tunasister and I had fallen asleep (on our own ancient cots in the living room at this stage) and it was late. I didn't know how late. No clocks in the room, just a "furniture grade" TV set, old green couch/loveseat, and a tunnel ram. I know it was dark and I was very groggy. I awoke to something like "Hey Tuna, get up and meet me in the parking lot. I need a hand." TunaDad was a Mac dealer at this point, and parked the big truck in the parking lot behind the apartment building. It was Saturday (or Sunday morning) and he wasn't racing the next day, so there really wasn't any urgency that I could think of. Anyway I got there and he's in the front under the hood banging around and yelling at inanimate things. "get in the seat at pump the gas" OK. This seems pretty simple, for you who are awake, are not twelve, and have maybe started a car before once in your life. At this point I don't think I had ever been in the drivers seat of a car. I knew which one was the gas, at least, so I pumped it, which probably meant "ON/OFF/ON/OFF" at the time. I was yelled at for doing it wrong. I tried again, was yelled at again, then sent back to bed. To this day I have no clue what he was fixing, why, or why pumping the gas was needed. It was just a carb 454, so he could have just done it himself I think.

Anyway in the video I told Tunakid 1 to pump the gas. You could see the smile he tried to hold back, in typical teenage style. In that instant I had this flashback. I really hope that my kids have awesome memories to tell the GRM forum of the future someday about helping their Dad. Especially the part where he never yelled at them for doing it wrong.

Tunakid 2 pulled the rear tire off himself, remember he's 11. It bounced and hit the bed a bit. He apologized a few times. All I could say "Hey bud it's okay. No harm. I get it, it's really heavy."

So I guess I'm asking if there are good wheels I can get inexpensively for the truck that are a big bigger diameter and a bit lighter. They are 5x5 pattern.

Thanks

I have 15x8 truck rally's with decent tires and center caps here. Even gmc center caps!

Probably not what you want, but figured id offer. 

Edit for picture:

The thing only gains like ten degrees of timing, but it's all in around 1500 RPM. That seems all wrong. Seems like twenty degrees around 2500, am I way off?

An advance kit is like $10 from any auto parts store near you.  Comes with a wack of springs and a couple weights to set the timing you want.  Just use the springs, not the weights.

I added a weight limiter so mechanical advance actually "stops" where I want it, and I tailor the weights to set how quickly it comes in.

General rule of thumb for a SBC is to be around 36° all in by 2500.

Assuming I'm reading correctly what it is you are doing.