CK5
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79' GMC C15 - Spruce Caboose

79 GMC 1500
While i was troubleshooting my alternator charging issue, i ended up with a no crank issue also. I traced the cranking 12v in the yellow wire down the column, and realized the safety neutral switch was acting up. Took it out and cleaned all the contacts, and then reinstalled. No more cranking issues.

I also got re-wired the starting and charging circuit. 80A breaker on the firewall, feeding the relay panel and the bus bar, and the Alternator connected to the battery side. The one wire from the regulator ( load sensing wire / terminal L ) has a 470 ohm 1/2 watt resistor, tied onto the same breaker. The ALT now reads 14.1 with lights and things on.

I went through and rotated the motor by hand and checked the rockers at full lift for any signs of a loose something. Changed oil and seems to run the same.. Seem to have ironed out a good idle with the fuel map. Now its time for more test drives.

My terminator x display issue turns out to be that its not turning off, its just very dim. Traced the wire back to the splitter and no issues. If i wiggle it, sometimes it comes back but will cut out again at some point. Havent contacted holley yet, but planning on seeing if i can get a replacement unit sent out.

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Nothing new to really report except for some progress in the tuning, and my tail shaft leak keeps marking its territory..

It idled pretty good at 13.8-13.9 AFR and i ended up just sorta leaving it there and then addressing timing, and the other idle parameters. It was always a little rough going in and out of gear, and it would stall sometimes. A few looks under the truck and i could see the rear pinion was high a bit, and my test drive had some vibration around 30-45 mph. I installed some 2 degree shims in the rear and it went into gear way smoother. A few test drives later and i had been bumping the timing up in a few regions, and my idle timing ended up around 20* or more in some areas This idled decent at around 45%-55% VE, and at around 825-875 rpm. After another test drive, it seemed to stall going into gear every time.

Once i realized my AFR for idle had been around 13.5-14 , and i was having this issue pop up. I knew i had to go back to my idle timing and start over. I first pulled some plugs. My headers make 2 of them a pain in the dingles, but i pulled enough to see they were running rich, and tried to read the straps for timing indications. Seemed to be too advanced, but im no spark plug critique.

Ive got it idling now at : 14.5 AFR ( steady within .03) / 18.5 degrees of base timing / and about 50% VE / 58 kpa ( average based on the data log i took ) / and 750 Rpm idle. It goes into gear nice and almost seemless now but didnt get any time to move it more than back and forth a few times. I do realize the converter is going to be tight considering the 4l60e came out of a 4.3L astro van, but just another thing fighting me putting it into gear.

Another thing that i hadnt really addressed was the - idle spark - in the holley EFI. I figured i should get the truck to idle without this turned on, as its compensations would throw off me finding its happy point. Now with this on or off it idles almost the same. I do have it on but lowered the P & D terms. In the Holley help section it said it was common to lower these values. I have them set now at 30 and 50 instead of 40-60. No idea what the p and d terms are, but hey.

I was also having some hard start issues sometime and my IAC hold position was set at 50%.. Bumped it down to 30 and also lowered the ramp down time to 3 seconds from the 5 seconds it was auto set to.

I also read up on using the holley efi knock parameters. I have the 2 wire non resonant type. Its measured by the cylinder bore and frequency. the 3.78 bore of this 5.3 on the chart says to start at 6 Khz, and then it has a a sensitivity you can adjust until no actual knock shows up on the data log.

 
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Another thing I want to do is confirm my timing so I can verify what the Holley system is telling me...I did put those parts in myself afterall.. :whistle: Would also be nice to have if I ever advanced my cam timing in the future. After reading a few posts lately from @folkenheath, it seems like not a bad idea if and when the motor gets some speed parts tossed at it.


Picked up a TDC tool, and a timing tab.
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That's a nice tool, but not accurate enough, you also have a high probability of bending it with the wedge style combustion chamber of all 2 valve per cylinder Chevy V8s that I am aware of, as the spark plug is at an acute angle relative to the piston top. Unlike a hemi or DOHC engine where the spark plug goes in from the top through the valve cover. If you are looking for TDC the piston will kind of hover at the top for a few degrees or more, which is not accurate enough.

I use a sold brass one with a hole in it, vents the compression. You set the piston at around 10 degrees before TDC, then screw the stop in until it contacts the piston. Now, rotate the engine both ways by hand until it contacts the stop. Mark each place on the balancer or pointer with a marker or tape. Then the point exactly in between there is TDC once you remove the piston stop. This is much more accurate. Looks like this...

iu


I also have one like this since sometimes that one is rubbing on the valve...

iu
 
That's a nice tool, but not accurate enough, you also have a high probability of bending it with the wedge style combustion chamber of all 2 valve per cylinder Chevy V8s that I am aware of, as the spark plug is at an acute angle relative to the piston top. Unlike a hemi or DOHC engine where the spark plug goes in from the top through the valve cover. If you are looking for TDC the piston will kind of hover at the top for a few degrees or more, which is not accurate enough.

I use a sold brass one with a hole in it, vents the compression. You set the piston at around 10 degrees before TDC, then screw the stop in until it contacts the piston. Now, rotate the engine both ways by hand until it contacts the stop. Mark each place on the balancer or pointer with a marker or tape. Then the point exactly in between there is TDC once you remove the piston stop. This is much more accurate. Looks like this...

iu


I also have one like this since sometimes that one is rubbing on the valve...

iu



ahh gotcha, thanks for the info there. I went for this one because i watched a video where a guy had hit one like you have with his valve, and used that as TDC. Your reasoning makes perfect sense and I can just return this once, since i dont see myself owning a honda at any point in the future or any DOHC engines. Changing out bucket shims on my yamahas DOHC was enough for me to know im not so into the DOHC stuff..
 
That reminds me, important note! I always take the rocker arms off the #1 cylinder if they are on. Although usually I am degreeing a cam or something so I have them off previously. But if you don't that is a risk, especially with the larger brass one. I usually remember that as I am screwing the piston stop in and think, oh crap, I better remove the rockers just in case. I do that to prevent possibly bending a valve, because if you project the spark plug forward and then try to open the valve it won't be good on some engines.
 
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There is another style to use with the head off, which I use more frequently, although I didn't buy one of these, I just use a piece of 1/4"x1" aluminum bar about 8 inches long with an aluminum shim under it if its a flat top or dish piston.

Keep in mind on a 7" balancer each degree is about a 1/16", and .07" on a 8" balancer, so you want to be more accurate than that to be within a degree. I try to make it dead on, within .020" or so I would guess.

iu
 
I used a magnetic dial indicator to find TDC on the piston top with the heads off, while i installed the cam sprocket. So i should assume im close but would like to have it marked on the balancer. Shoulda woulda coulda done it then.. but didnt..

Do you tape the threads with any sort of protectant for when the piston makes contact with the inner set screw? I ordered a comp cams TDC marker like the second photo you had in the first post.

I wouldnt have thought of that, but i will definitely take the rockers off cylinder one when i check for TDC.
 
I like the brass one because it's softer with a rounded end and lets the compression out.

On the steel one I just rounded the end so there are not sharp edges.

And while rotating it by hand I make sure I don't use excess force and mark the piston either way. You can feel the solid stop easier without the plugs in because it's easier to turn over.
 
I also found my battery dead today and see that i have a .6 amp draw with the truck off. I figured id check the alternator since that was the only recent change, and when i unplug my load sensing wire from the ALT, the draw is gone. Does this indicate the ALT isnt grounded properly..? I can kill the connection at the firewall with the breaker in the meantime, since thats where the load sensing wire is hooked up to.



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I also ordered some real chinesium door crank handles but hey, they will at least let me reclaim a pair of vice grips off the regulator cranks. The 3 different kind of adapters they came with didnt work, one sqaure shank, one splined, and one round. I just drilled the round ones out to the thickness of the regulator crank and cut off the splined section of the regulator also. The remaining smooth section of the shaft was the exact length needed to secure the new ones. Easy enough fix for 79 regulators in 74 shells.

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I found the time to weld in my tail pan today. Its nice working from a rolley chair. Definitely burned a few holes to fill on the rear panel, and im going to fill the screw holes with a weld also.

My tailgate got some fresh rods, springs, and handle. Tailagte needs a good buff to get some crusty bubbles off.

Also wondering if i should put the leaf back in the passengers side spring back to compensate for the full tank of fuel "lean".



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Tailgate works Mucho better now... The small things in life like doors that shut well, once i got the doors lined up well, the new weatherstripping didnt give me any closing issues. The tailgate handle is a bit slanted, i forgot to put a wedge in there to align it when i screwed it in.


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You're motivating me to give my C10's tailgate some attention. It doesn't close as nice as yours!
Its not going to fix itself :whistle:ha.

This one was always driving me nuts before, the way it was when i got it was a lottery in terms of what it would do. I picked up a full tailgate kit off rockauto, its well made and didnt cost too much. Comes with the articulating hinge bars also.
 
The biggest problem with mine is the latches like to squeak so I have to lube them up on occasion.
 
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