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  1. 75gmck25

    Which ground do I start with?

    IIRC, the cargo lamp housing is insulated from the truck with small spacers to stop it from being grounded. It always has power on the orange wire. If the interior lights are on, and the cargo light switch is on, then for correct operation the cargo light has a ground through the door switch...
  2. 75gmck25

    Rochester Quadrajet Woes

    Take a close look at the throttle linkage side of the carb and get the Quadrajet number. This tells you which carb you have (original or later), and you will need it to get the right rebuild kit. For example, my original 1975 Quadrajet is 7045583, which is an older version, but I am currently...
  3. 75gmck25

    Big block running hot. Can’t figure out the issue

    Not to nitpick too much, but stoichiometric (best) AFR for gasoline is about 14.7. 14 is slightly rich, but that should actually help with cooling.
  4. 75gmck25

    Tool for adjusting idle

    Original Quadrajet idle screws are usually a double-d shape, and there is a flexible carb tool that has that special end on it. When I rebuilt my Quadrajet, the kit came with new idle screws with a hex end that has a screwdriver slot in it. Your carburetor also had factory caps or casting over...
  5. 75gmck25

    Steering Help

    One simple check - make sure all the air is out of the system. GM book says to jack it up with both front wheels off the ground. Then start the engine and slowly turn the steering wheel full lock to lock at least ten times. At the same time I would have someone else turn the steering...
  6. 75gmck25

    brake pedal has no pressure

    All good suggestions. If the seal is torn or damaged inside the master cylinder it will not seal against the cylinder, and the pedal goes to the floor. Seal often gets damaged while bleeding an old master cylinder that has built up a ridge inside. Ridge is buildup where the seal has stopped...
  7. 75gmck25

    82 Sierra Grill alternatives

    When you start swapping grills, remember there are sometimes also differences in mounting brackets. I have about a ‘79 grill on my ‘75, and I had to swap the metal mounting brackets for the grill. Not hard if you have a donor vehicle. I would like to have a true ‘75 grill so it would have the...
  8. 75gmck25

    First real drive! Not tragic but not good. I think I need carb advice.

    One strong recommendation is to immediately convert it to HEI ignition. It is very reliable, and does not require periodic adjustment like you will need with your points ignition. Lots of large cap HEI distributors available from aftermarket, or you could even get one from pick and pull...
  9. 75gmck25

    First real drive! Not tragic but not good. I think I need carb advice.

    Also get number off the side of the Quadrajet. For example my ‘75 Quadrajet is 7045583 YZ.
  10. 75gmck25

    A/C Question

    I do not have a write up, but I have a lot of pictures and a list of everything used. This could motivate me to write it all down in one place.
  11. 75gmck25

    A/C Question

    The old A6 compressor is a true boat anchor, and it has heavy brackets to keep it supported. It’s also now old and not very reliable (do a search on A6 Black Death). It uses R12 and mineral oil, while current systems are usually R134 and PAG oil. A complete explanation of how to convert or...
  12. 75gmck25

    First real drive! Not tragic but not good. I think I need carb advice.

    The air cleaner has a thermostatic valve in the snout to control heated air, and it’s connected to vacuum at the carburetor. No reason to have that hose if the heat stove and tube to the air cleaner is not mounted on the headers. If your carburetor is like my ‘75, it has an extra (larger...
  13. 75gmck25

    LMC headlights/harness kinda wonky

    Bought one of the LMC kits many years ago. Wiring seemed a little chintzy (not really HD) at the same, but it’s lasted a long time. Since it did not include fuses, I added a power point on the fender near the battery and connected the relays into constant 12 volts at the battery using a...
  14. 75gmck25

    Found the oil leak - front oil pan seal or timing cover gasket?

    IIRC, to get a good seal you have to install the timing cover first, and then the oil pan. Someone may have pulled the timing cover, but only loosened the oil pan just enough to get the timing cover off, and then tightened it all down. Sometimes it seals fine when you do that, but many times it...
  15. 75gmck25

    First real drive! Not tragic but not good. I think I need carb advice.

    I believe that vacuum hose is for the HVAC recirculate function. It has a T because it connects to a vacuum motor in the cowl, and another one in the passenger kick panel. I think the rubber fitting is probably around the line that goes up to the cowl. There is a round vacuum canister next to...
  16. 75gmck25

    First real drive! Not tragic but not good. I think I need carb advice.

    Your truck is nearly identical to my ‘75 GMC K25, except that in ‘75 they made HEI ignition standard and tweaked a few other minor things. The ‘74 Quadrajet is one of the older designs, since the truck carburetors got upgraded later than cars. It will work fine if rebuilt properly, but later...
  17. 75gmck25

    Help with starting 79 k20 400SBC

    I’m a little confused about where you are at in your installation. You said it ran with the Quadrajet, but not very well, so you installed the Edelbrock. Then you later said on you stabbed the distributor with it set at about 0 degrees. Did it start and run with the Quadrajet, and then you...
  18. 75gmck25

    LMC Dash Pad Supplier

    If you want a different color than black for the AMD pad, can you dye it another color, or does that not work with black? My original GMC dash pad is a real dark brown that coordinates with the lighter colors on the saddle tan interior. I’d like to go original color if it’s possible.
  19. 75gmck25

    New stater not catching

    Did you measure the clearance between starter gear and the flywheel, and use shims to adjust it?
  20. 75gmck25

    How far do long tube headers hang down

    I went with the Sanderson headers because they fit better with my Blueprint heads. However, they are shorty headers that only come down about as far as the stock iron manifold does on the passenger side. This means that the flange and bolts are really close to the bell housing, so it's a PIA...
  21. 75gmck25

    No dash lights suddenly, just the small gauges, on the 77.

    There aren’t really that many bulbs in the cluster. Maybe 5 white dash lights, and the rest are turn signals and high beam indicator. IIRC, on that left side there is one bulb near the top, between the two upper gauges. There is a 2nd bulb near the bottom, just to the right of the clock. You...
  22. 75gmck25

    Engine Block Heater for SBC 350

    One risk with a dipstick heater (but also maybe an old wives tale) is that you have a heated electrical probe running down into the oil pan. If you have managed to flood out the engine you may also have gas that ran down into the pan and it’s floating on top of the oil. There is a small...
  23. 75gmck25

    Big block running hot. Can’t figure out the issue

    I had radiator issues, and replaced it with a Champion all aluminum radiator from Jegs. I have a stock v-belt system and an HD fan clutch with the stock fan, and I could leave it idling in the driveway in 90 degree weather with the A/C on and it levels out at about 200-205 degrees. My ‘75 used...
  24. 75gmck25

    Engine Block Heater for SBC 350

    I grew up in ND, and freeze plug (or block) heaters were installed on just about every carbureted vehicle. You can put it on a timer for a few hours, or if you aren’t worried about the electric bill you can run it all night. A 1500 watt heater element will never be able to heat the antifreeze...
  25. 75gmck25

    Rear disc conversion

    14 bolt FF should be a direct bolt on to the springs, but the driveshaft connection might be different. Many of them are also 4.10 or even 4.56, so it might not match your front axle. My ‘75 K25 8400 GVW has 4.10 gears and a 14 bolt FF with 13” drums. Front axle is a Dana 44 HD. If you look...

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