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1973 C10 "The Purple Truck"

Basic build
Overview Gallery Discussion
what is the vacuum advance number you are using?

Some of those plugs look darker vs lighter. Curious if the lighter ones are partially plugged injectors
 
I have new plugs coming so we'll see what they all look like.

I remember not taking the vacuum advance as far as it would go, because I don't fully understand how it works on the PF4. I want to say it's at 8°.
 
The vacuum advance on the PF4 is one of the few things I don't like about it, because it only lets you add a minimum amount, and it's not available at idle. I max it out. I wish they would let you make it work at idle, and also add a full in setting so you can actually use the way it should work. The way it works is it will only give you the actual setting if you achieve 30 inHg, which doesn't usually happen, if you are at 20 inHg, you only get 2/3, so if you have it set at max 15 deg, you will rarely see more than 10 degrees, and never at idle.
 
Didn't get all that plugs replaced.

20241003_164153.jpg
:doah:

That's actually the first time I've done that. One header tube tweaks the socket just enough that I put too much angle on it.

Here's all of the old plugs.

20241003_164101.jpg

20241003_164036.jpg

20241003_164032.jpg

20241003_145543.jpg
 
Oh yeah she's back! Spark plugs did the trick. I guess when they say 30K mile longevity they're serious.
 
Ah not really necessary.
I ran my 89 350 for 8 years with a tick i suspect was a lifter, never changed the spark plugs, cap. Rotor or even the oil

It still ran like a raped ape and wouldn't die, I did add a quart of oil every year because I noticed the oil was low.
All your overbearing maintenance is causing your engines to not run good and fail.
Remember if it ain't broke don't fix it
 
mrk5 said:
Oh yeah she's back! Spark plugs did the trick. I guess when they say 30K mile longevity they're serious.
Click to expand...
Keep in mind, carbed vehicles we were supposed to start checking plugs once a year

Even though this is injected, it doesn’t use a knock system, so the timing leaves some on the table. Plug life is not quite to the expectancy of a full stand alone system like an LS or LT system


Based on the old plugs, you are burning some oil, and I’d say just a touch lean
 
The modern stuff use precious metal tips to get longer plug life since the tip doesn't wear as fast, but the tip can fall off and cause small scratches and stuff where they shouldn't be.

On anything I build I run the std ngk plugs and just change them occasionally.
 
These plugs were in the engine from day one. I wonder if that had anything to do with their condition.

I'm putting about 12,000 miles a year on the truck. I figure I should at least check them every 2 years at that rate.

I am running the cruise AFR a little lean in hopes to get a little better fuel mileage.

I also ran the vacuum advance all the way up to 15, it was at 9. Didn't notice a seat of the pants difference, but I did see the cruise timing was up at around 44° vs the 40° it was running.
 
You won't feel the seat of the pants thing at that much timing anyway. SOP really has to be a gain of about 15-20 before you actually feel it

The timing at 44 at cruise will do more for the mileage than the super lean
It's worth noting that the 14.7 target is what most newer GM systems try to maintain, but without a vacuum advance
It's set up in the kPA vs spark tables to add some extra

I pull a plug from each bank once a year, air filter and timing check. Tune up, just like it was a carb. I usually find something that needs corrected
 
I'm curious now to check the cruise AFR. I think at one point I bumped it up to 15:1 but I feel like I brought that back down. But then I also think that could be what I did on the old Sniper setup in the crew cab. :doah:
 
mrk5 said:
I also ran the vacuum advance all the way up to 15, it was at 9. Didn't notice a seat of the pants difference, but I did see the cruise timing was up at around 44° vs the 40° it was running.
Click to expand...
Its more of a clean burning efficiency thing than seat of the pants, the moment you punch it, the vacuum advance is zero. You may feel it at part throttle but it won't be night and day, it's more likely to affect your fuel mileage.
 
I'm just going to come out and say it, i messed up the shift kit install in the 4l80. I watched several YouTube videos about it and made the mistake of heeding the advice of a couple of street bros.

They recommended drilling out the hole in the plate for the 1-2 shift even larger than the kit tells to. Big mistake! It's not catastrophic but the ever present tire scratch on the 1-2 shift gets old after awhile.

I like a firm shift but I've learned there is a line and I jumped over it. Am I motivated to change it? Whoa now, I'm still the same lazy guy, remember i said it's not catastrophic....
 
Yeah, just a small difference in size has a quick difference when working on those.
The vehicle and how it's used also makes a difference. My '01 is just about right for me as I normally use it. When I hooked onto about 15K of trailer and load, it got rather brutal.
I can't remember what size that we went with though.
 
mrk5 said:
I'm just going to come out and say it, i messed up the shift kit install in the 4l80. I watched several YouTube videos about it and made the mistake of heeding the advice of a couple of street bros.

They recommended drilling out the hole in the plate for the 1-2 shift even larger than the kit tells to. Big mistake! It's not catastrophic but the ever present tire scratch on the 1-2 shift gets old after awhile.

I like a firm shift but I've learned there is a line and I jumped over it. Am I motivated to change it? Whoa now, I'm still the same lazy guy, remember i said it's not catastrophic....
Click to expand...
Is this at all throttle levels or just too harsh at low throttle?
 
It's all the time. You can adjust shift firmness with the ProFlo trans controller, but I have that turned down. Guess I haven't looked to see if I can make it negative.
 
I would not turn it down above 50% throttle. You don't want to sacrifice holding power for shift firmness at higher loads. At low loads you can tune some of it out, but there is a limit without destroying your clutches.
 
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