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  1. 75gmck25

    AC mismatch?

    All the conversion guides suggest a high pressure cutout might be needed, but pressures on my converted ‘75 system (Sanden compressor, parallel flow condenser and custom barrier hoses) never go higher than about 200-225. I also have a problem with a very slow leak, but have not had time to...
  2. 75gmck25

    Bed bolt upgrade?

    If you cut a notch across the head, a helper can use a large screwdriver to stop it from spinning when you remove the nut underneath. Once you get it a few turns loose you can clamp vice grips on the edge of the head and get a better grip. It will be harder to turn as the nut gets farther off...
  3. 75gmck25

    Manual Transmission Swap Options

    GM also offered the A-833 overdrive manual transmission in some 81-86 trucks (MY06 code). I know almost nothing about it, but some did have a 3.09 low gear. The A-833 was very durable as a standard 4 speed and was even used with big block Mopar engines, but maybe it lost some strength when...
  4. 75gmck25

    Pressure Brake Bleeding Question

    I’ve used the MotIve bleeder on my BMW and it worked really well. However, that car has a threaded cap on the master cylinder and it was easy to get a good seal and push brake fluid into the system for a flush. I’m not sure how well the flat plate adapter works to seal on an old style master...
  5. 75gmck25

    All time 4x4 / NP203 Truck Questions, hard to make tight turns

    Ref post #4, you have a light that shows it is in Loc? I have never seen any documentation of a truck that has a sensor/switch and “Loc” light. It would be great to have on my ‘75.
  6. 75gmck25

    Internal engine noise

    Pull both valve covers and check for loose pushrods and rockers. Adjuster nut may have loosened up and the pushrod is bouncing against something.
  7. 75gmck25

    Dual tanks - was not expecting that

    Is the dash switch mounted on the metal dash near the ash tray, and is it a black rocker switch? If both answers are yes, it’s probably a factory switch. Any other type of switch is probably aftermarket, which usually means a dealer-installed auxiliary tank.
  8. 75gmck25

    Original color of my instrument panel?

    There were also multiple different woodgrain patterns, depending on trim level. My ‘75 Siverado panel is black, with a very slim silver trim glued on around the outside edge, and a woodgrain pattern over the center. The woodgrain matches the right side dash and the door trim.
  9. 75gmck25

    Temperature hunting at stop lights

    I’ll list the parts that have worked for my ‘75 K25. YMMV - Original SBC steel fan and shroud, which was part of the factory HD cooling package - severe duty fan clutch - Stewart high flow water pump and 195 degree high flow Robert Shaw thermostat - Champion aluminum 3 row (I think) radiator...
  10. 75gmck25

    Temperature hunting at stop lights

    Assuming the shroud and fan blades are good, it sounds like you need a new severe duty fan clutch, since your air flow is not adequate at slow speeds. However, temps in the range of 210 don’t really hurt anything. The threshold is around 230 before system pressure goes high enough to pop the...
  11. 75gmck25

    quick ratio steering box

    In my K25 I have a Borgeson standard ratio box and the u-joint conversion. Everything works well, but I think I now also need to replace the inner tie rods (this short tie rod is only on a 4wD) to get rid of 100% of the play. I did not notice any change in steering wheel vibration after the...
  12. 75gmck25

    1983 AC Condenser - Best Fit?

    RockAuto usually has the best selection, lists the specific brands, and has pictures of most of them. I would look at their offerings and compare to your old one.
  13. 75gmck25

    Can you pls identify this distributor wiring harness?

    The silver block appears to be just a GM under-hood relay. My ‘75 Camper Special has the same type of relay to control the charging of the auxiliary battery. When my ignition is off it isolates the 2nd battery so that power draw from a camper does not affect the primary battery.
  14. 75gmck25

    Worth purchasing 1976 c10 silverado in fair condition for $2500?

    Can you see the RPO sticker inside the glove box? Having a 454 and TH400 as original in a short bed half ton sounds like a really unusual combination. Maybe they had a sport truck version, but most short beds were light duty run-around vehicles with an SBC.
  15. 75gmck25

    A/C Oil question

    PAG oil can cause corrosion issues, but many new compressors require it to maintain the warranty. However, it sounds like the OP is using the original A6 compressor. POE (ester) is often used for a retrofit application, and it should work fine for this application. The orifice may not need...
  16. 75gmck25

    A/C Oil question

    You are correct, mineral oil was used in older R12 (Freon) systems, but R134a usually uses PAG oil. PAG and mineral oil do not mix. You need to use A/C flush, followed by compressed air, to clean the entire system. You will need to disassemble all the parts, including the orifice and the...
  17. 75gmck25

    Who knows auto insurance? Ins outs loopholes

    When your car is hit from behind by another car, almost 100% of the time they consider the car behind to be at fault. That driver’s vehicle is moving forward and he/she is expected to drive at a speed and in a manner that keeps the vehicle under control and safely away from other vehicles. If...
  18. 75gmck25

    A/C Oil question

    I don’t recall the specific rule of thumb, but if you have flushed the system you need to add more than just the oil in the compressor. Did you replace any other components? A very general estimate is that the system has about 2-4 ounces in addition to the oil in the compressor, but that...
  19. 75gmck25

    Free 383 for Blaze

    I don’t want to sound like a big downer, but the 350/290 hp heads are probably just about one of the worst flowing heads you could find for an SBC build. They are fine for a grocery getter or maybe a plow truck, but you won’t get the power you want when they are used on a 383. However, maybe...
  20. 75gmck25

    Who knows auto insurance? Ins outs loopholes

    I think there is a misconception that someone has to be cited by the police to establish fault. This is not true. A ticket might make it a little simpler, but the insurance companies still do their own investigation. I was rear-ended in my 2021 BMW about 3 years ago and the other driver just...
  21. 75gmck25

    Dim headlight question

    Get a basic cheap voltmeter, and compare the voltage at the terminals inside the connector feeding each headlight. If it’s different, you have a power or ground lead to fix. If it’s the same, you need to clean the terminals on the headlight, or replace the headlight. You can also buy a...
  22. 75gmck25

    Quadrajet Idle Mixing Screws

    Are you sure the anti-tamper plugs that cover the idle mixture screws have been removed? I believe there is a special drill bit that is designed to drill out the plugs, but mine had already been done before I bought the carburetor at a pick and pull.
  23. 75gmck25

    75 k10 wiring harness help. Plz

    Yes, there is a specific power wire, but you need to start at the battery and work forward. Look at the pictures in post #3 - at starter - large cable from battery to the starter post. Make sure you have power at that post, and that the two smaller wires are firmly connected - go to the...
  24. 75gmck25

    Non-stop horn honking

    The final assembly includes a 3 hole plastic piece (made of 3 nylon bushings, connected with plastic strips) that acts an insulator as you reassemble. Are you sure you have it in the right place, so as you put the plate down it does not ground out and activate the horn? It is shown as part...
  25. 75gmck25

    Grounding question

    My error. You are right, the ground toward the center of my truck is from the T-One adapter, not the original truck wiring. My GM wiring diagram shows a black 18 gauge wire on the driver’s side near the left taillight, and it runs to a junction that then grounds all the bulb holders for the...

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