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  1. 75gmck25

    76 gmc sierra

    RPO sticker is nice to have, but in that timeframe they were not very specific. My ‘75 lists the Silverado trim (nice to know, but no big deal) and Camper Special package (but there are metal emblems also) . Nearly all the other key options on my truck are visible by inspection, even if the...
  2. 75gmck25

    Fuel gauge grounding location on frame

    When you check prices at the yard, make sure they understand that gas tanks are not that expensive. From RockAuto you can get a new Dorman 20 gal fuel tank for about $84, and a new sending unit for $30-$55. Junkyard price should be way lower, since the used sending unit is probably shot.
  3. 75gmck25

    Fuel gauge grounding location on frame

    I also alternate using the two tanks. For example, one is down below 1/4 now, so I’ll go fill it up and then switch to the other tank. I’ll run that one down and then fill it and switch back to the first one. I don’t drive the truck a lot, so it may take me 1-2 months run one tank near empty...
  4. 75gmck25

    New to me truck/ what should i go through and look at

    Coqngratulations! I’ll assume your ‘74 is very similar to my ‘75 K25, but the option label on the inside of the glove box door will tell you more detail. For example, mine has Silverado trim, so that adds some convenience items. I also have the camper special package and 8400 lb GVW, G80...
  5. 75gmck25

    Towing with a 305 V8?

    If you plan to change gears, check the specs carefully to make sure what will work with your current axle. Some axles have two different carrier assemblies, usually one for low gears (maybe 3.73, 4.10, 4.56) and one for higher gearing (2.73, 3.07, etc.).
  6. 75gmck25

    78 scotts wants to die when leaving a stop

    We need to know the know the exact carburetor, but they all work similarly. Also verify that ignition timing is at factory settings (probably 4 or 8 BTDC, or up to about 12 BTDC if you want more power). This simple change might fix your problem. Moving the vacuum advance to full vacuum port...
  7. 75gmck25

    steering box adjustment

    The redhead boxes are in a price range I would consider ($406) since it would really help the overall feel of the truck if I could tighten up the steering. Another question - My ‘75 K25 truck is too old to use one of the jeep steering shaft replacements, so I’m stuck with the rag joint. I...
  8. 75gmck25

    Towing with a 305 V8?

    You need to verify the transmission, but it’s probably a 700R4 four speed. Then take a look at the rear axle ratio and tire height. Some of these trucks had a crazy high rear axle ratio (like 2.73) that sucks for towing. With a 700r4 the preferred ratio for towing would be about 3.91 or even...
  9. 75gmck25

    Fuel gauge grounding location on frame

    On my ‘75 the ground wire comes down through a hole in the frame and is grounded to a screw/bolt on the inside. It’s not on the top of the frame.
  10. 75gmck25

    steering box adjustment

    On a related topic, has anyone found a reliable new replacement brand steering box? I’ve seen complaints here about a new Borgesen box loosening up and being just as bad as the original box. I would be willing to consider a brand new box if it would properly tighten up my steering. From...
  11. 75gmck25

    steering box adjustment

    That is the type of spring scale you use, and from what I recall you use it to measure the turning resistance of the box arm.
  12. 75gmck25

    steering box adjustment

    The GM manual says to adjust the gearbox slack first and then the small free play adjuster on top. The catch is that the gearbox is adjusted before you mount it in the truck, and the free play is adjusted with the tie rods disconnected, using a spring scale to measure the tightness. Bottom...
  13. 75gmck25

    77 C10 Silverado Longbed spring rates

    Look it up on RockAuto.com and you can usually find the options for stock springs.
  14. 75gmck25

    74 k10 bed not level

    I was able to replace the cab mounts on my ‘75 in the driveway using a small hydraulic jack for support and hand tools to remove the bolts. I was lucky and none of the bolts were fully rusted in place. The one pair of PIA to remove bolts were the two at the radiator support. There was no good...
  15. 75gmck25

    Have to start in neutral or hold the shifter.

    When I replaced the cab bushings on my ‘75 K25, all of a sudden the truck could then be started in neutral and park. Getting the cab properly aligned also put the shift linkage in alignment. YMMV.
  16. 75gmck25

    Options for tuning of Gen1 TBI in 2023

    Another choice is Megasquirt, which has a programmable ECU that can be used to replace the GM ECU. I thought they once had a direct drop-in ECU box, but all I found was this article on how to make one. Lots of tech understanding required, but it’s well documented...
  17. 75gmck25

    Charcoal / vapor / evap canister, how it should be set up and other information

    I assume your ‘73 may have used a purge system like my ‘75 with 3 port sending units. The vacuum canister does not have an separate purge valve, but my original Quadrajet has a dedicated port for a canister purge line. I don’t know what throttle position or condition opens that port on the...
  18. 75gmck25

    fresh air duct

    On max A/C there are two vacuum motors that change it to recirculate mode. The vacuum line has a T in it and you should be able to access it if you remove the glove box door. The actuator on the passenger side kick panel is easy to see, and it pulls air in from inside the truck. There is a...
  19. 75gmck25

    A/C hack for non A/C Vehicles

    In the original GM systems the evaporator is much bigger than the heater core, and it’s usually so large that it’s in a housing that extends out under the hood. However, newer cars downsized the evaporator and fit it behind the dash, so maybe it works fine when it’s smaller.
  20. 75gmck25

    C20 to C10 suspension spring hanger holes.

    My ‘75 K25 has 52” HD (7 leaf?) springs. I have not checked to see if there is another set of holes for the longer springs.
  21. 75gmck25

    Replacing intake manifold+gaskets

    I’ve always used the same oil resistant RTV that I used on the end of the manifold, but Teflon tape may also work fine. I know they sell an HD Teflon tape (grey color) that is thicker and may work better.
  22. 75gmck25

    Fuel tank switch valve

    AFAIK, the 6 port single wire valves are no longer available new. I’m just glad mine still works. However, there are several articles out there about how to switch to the newer 6 port that has multiple wires. If mine fails, I’ve also considered using two 3-port valves, since they are still...
  23. 75gmck25

    Removing bed bolts

    I have had goodl luck with dimpling the area on two sides of the bolt head, and then pushing down and clamping on vice grips vertically. . I then use a large crescent or pipe wrench to hold the vice grips, and turn the nut from below. I have also slipped a piece of metal conduit over the pipe...
  24. 75gmck25

    Qjet fuel drainback information

    If you do an online search you can find the check valve as a separate part, and fit it into any stock filter. The built-in Quadrajet filter has somehow gotten maligned and screwed up by many shade tree mechanics. They get the filter in backwards, leave out the spring, cross thread the housing...
  25. 75gmck25

    Blue Print or GM Performance

    If you are going to buy a new/rebuilt engine, I have two very strong suggestions. - make sure it has Vortec or better flowing 64cc heads that have at least 9-9.5 compressions. Good performance heads are the foundation for reliable 350 power. If you start out with poor flowing smog-era heads...

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