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  1. 75gmck25

    Replacement Option Code Glove Box Label for my 86 GMC High Sierra

    For an ‘86 you might be able get original build info from the GM heritage center. Based on that info, and looking at some other examples of ‘86 glove box labels, you could fabricate one for your truck.
  2. 75gmck25

    Nasty parasitic draw from plow

    I’ve never measured voltage, but I know there are solenoids that are specifically rated for continuous duty, and some are not. For example, the common Ford external starter solenoid works fine for a starter (short engagement) , but will not last if used for something like switching a dual...
  3. 75gmck25

    Need advice on Tuning a Quad

    You can buy a piston stop from summit, or make your own from an old spark plug. General process ( from memory) for finding TDC is: - Remove plugs and turn the engine over until you are a little short of where you think TDC is. Check rotor to make sure you are on #1, not #6. - screw piston stop...
  4. 75gmck25

    Need advice on Tuning a Quad

    Every engine is different, but a common guideline is that base plus mechanical should not exceed about 34-36 degrees for a mild build, usually measured at about 3000 rpm. However, this is just a guideline. It’s common for mechanical advance mechanisms to add about 20 degrees, so 12 degrees base...
  5. 75gmck25

    Under dash air box hvac.

    That actuator on the back is hard to reach with your hand, and IIRC, the plenum has to come out to remove it. However, you should be able to reach the lines after you remove the glove compartment and the vertical plastic plenum piece behind it. I also think that on my truck it’s the one...
  6. 75gmck25

    1986 Engine Wiring Question

    I don’t mind reading the diagrams. However, unless I understand what the functions are for each component, it hard to know what to disconnect or bypass. For example, if the AIR pump has been removed, what is the AIR module trying to do with the feed to distributor?
  7. 75gmck25

    Disappearing coolant

    Also check the bolts for the intake manifold . I used the bolts from my iron intake on a new aluminum intake, and never noticed that at least one bolt bottomed in out in the hole before the intake was tight. It was leaking slightly in the back passenger side corner between the intake and the...
  8. 75gmck25

    Broken hearted kid and fuel system

    Please start a new thread with your question . This one is already 7 pages long.
  9. 75gmck25

    Need advice on Tuning a Quad

    Good point about every engine being different. My aluminum heads seem to tolerate my timing setup on regular gas with no issues, but I also know that my compression ratio is probably no more than 9.2-9.4. I believe my GM 350 crate with 74 cc smog heads probably had only 8-8.2 compression when...
  10. 75gmck25

    Need advice on Tuning a Quad

    I also rebuilt and tuned my Quadrajet with a kit from Cliff Ruggles. Mine shows similar AFR readings as yours, and it seems to run fine. Not sure why it goes so lean at cruise. I’ll have to disagree on 4 degrees being enough base timing. 4 degrees made my engine really lethargic. When I had...
  11. 75gmck25

    Defroster not working

    In my experience, that 3/16” rubber line works well for splicing the old hard line. It pulling vacuum, so it doesn’t take a lot to seal if the fit is tight.
  12. 75gmck25

    recommend some tough seat covers

    There are new synthetic materials that are as durable as vinyl or leather, but don’t feel like hot plastic. I would think an upholsterer would have a catalog to get them from, if you are getting custom made covers.
  13. 75gmck25

    AC Confusion-Need Help

    The big compressor in the picture is the long, heavy A6, and the smaller pancake compressor is the R4. Both are generally not too reliable. I’ve never seen the compressor mounted on a squarebody on the passenger side. Where is the alternator mounted? Extending the compressor lines should...
  14. 75gmck25

    Defroster not working

    As suggested, check that line under the hood for vacuum as it comes out of the ball, and then find the same line where it comes through under the dash and check it again. It’s probably the thin GM hard vacuum line. I always hate to cut it just for testing, but you can easily splice it again...
  15. 75gmck25

    K20 Wheel/Tire Confirmation

    I also had similar tires and wheels on my ‘75. I found the cheapest solution for wheels was to go to pick and pull and get 8 bolt 16” steel wheels off a 3/ 4 ton GMC or Chevy. I paid $25 each for one I pulled myself. For tires I just looked for the best price on 245/75R16E tires with a decent...
  16. 75gmck25

    Holley sniper cable routing

    Drivers side - If you have dual tanks, there is a grommet for the wiring just to the passenger side of the brake booster. Look up under the dash where it comes through, and pick a good spot nearby to make a new hole for the EFI harness to come through. Passenger side - there should be a...
  17. 75gmck25

    Hiya Folks, new owner, battery, oil, and filter recommendations

    Since you like Mobil 1, they sell classic car oil with the high zinc levels (usually about 1200-1300) you need for a flat tappet cam. I know they have the high zinc in 15w50 and 0W40, and I can usually find it’s in stock at the local stores (even Walmart). There are other brands of high zinc...
  18. 75gmck25

    ac control vacume line source

    I believe all with A/C have the same basic design, although the vacuum ball may be shaped a little different, and I’ve seen one mounted so the vacuum connections go sideways toward the drivers side. All that canister does is provide a reservoir for vacuum, so when you accelerate and engine...
  19. 75gmck25

    ac control vacume line source

    This is the picture of my ‘75. The larger vacuum line coming out of the bottom of the reservoir/ball runs over to a manifold vacuum tree on the intake. You can also see the small vacuum line that runs across the plenum, and through the firewall to the dash controls. Your vacuum ball might be...
  20. 75gmck25

    Blower fan/relay

    If you have A/C there is a blower motor relay mounted on the A/C plenum under the hood. I’m not sure of the setup on a non-A/C truck. On my ‘75 there is also a blower resistor pack/assembly on the plenum. The resistors are used for lower speeds, and high speed is a direct 12 volts.
  21. 75gmck25

    Question about headers

    I’ve alway been interested in whether the old style (straight down outlet) 2 1/2” rams horn manifold can be used on a squarebody without doing a lot of cutting or re-engineering to get them to fit. They have a good reputation for flow, and there are both original and aftermarket versions...
  22. 75gmck25

    Q: AC Vacuum Accumulator

    If you have a vacuum canister on the drivers side near the firewall, I assume it’s probably for cruise control, which I don’t have.
  23. 75gmck25

    Q: AC Vacuum Accumulator

    This is a picture of the vacuum canister on my ‘75. The larger hose coming out of the bottom runs down and over to manifold vacuum. You can see the small line that comes out of the bottom, across the plenum top, and then over and through the firewall. That small line is connected to the HVAC...
  24. 75gmck25

    Alternator cable routing

    Original routing on my ‘75 was with the BAT wire in a plastic loom, clipped to the top of the valve cover, down the back of the engine through the metal tube, and with a fusible link where it connected to the starter lug. There is a 2nd power wire connected to the starter lug, and it runs up...
  25. 75gmck25

    Q: Trick to Reattaching Speedo-Cable

    You also need to push firmly but carefully until the flared end of the cable gets by the spring clip and is held in place. The speedometer might initially work if it’s not fully seated, but it will eventually pop back out, or make the needle bounce later.

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