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  1. 75gmck25

    Bed Support "Cross Sill" Options

    I have a 1975 Truck Specifications document in PDF that might have some of the measurements you need. However, when I tried to attach it to my post it was too large. I’ll see if I can compress it or create a zip file that can be attached. On my iPad right now and I don’t have the...
  2. 75gmck25

    Carb vacuum cap blowing off

    PCV line to carburetor is also missing, so did you also remove your PCV system? The PCV system prevents crankcase pressure build-up and also removes moisture. Keeps the engine healthy. No idea if it could be related to a blowing the cap off a vacuum port.
  3. 75gmck25

    Trying to get fuel to my engine, a novice's saga...

    When you buy fuel line, consider upgrading to EFI rated line, because it holds up much better to modern fuel with ethanol. Line that meets SAE J30R7 standard is a more flexible general purpose fuel and emissions hose, while SAE J30R9 is for high pressure fuel injection systems. J30R7 is...
  4. 75gmck25

    Stock 350 getting hot, but only on the highway with AC on

    In my experience lower hoses I’ve purchased no longer have a spring inside. The molded design is supposed to prevent collapse.
  5. 75gmck25

    New wiring harness difficulty

    I agree with fast 99. Don’t replace the entire under dash harness unless it’s really needed. Those wire are usually in good shape (compared to underhood wiring), but have been butchered during a radio installation or an attempt to fix a dash gauge. It’s ironic to me how many times “it’s too...
  6. 75gmck25

    Stock 350 getting hot, but only on the highway with AC on

    I worked through a similar issue with my K25 and the final fix was a new aluminum radiator. Due to the 4.10 gears and higher rpm, mine was apparently generating a lot more heat at 65-70 mph. It never overheated, but did run hotter on the highway. It really liked about 40-45 mph a lot better...
  7. 75gmck25

    Cup Holder

    I assume the end might fit in the ash tray area. Maybe ?
  8. 75gmck25

    77 K10 Cab swap questions

    On my ‘75 K25 the trans hump is bolted in, so it would be easy to remove it and use it as a pattern for cutting out the area in a newer truck. Not sure about a ‘77. FYI- I also found out that the cab hump in my ‘75 is really close to the drivetrain. When I installed new cab bushings it...
  9. 75gmck25

    Help with identifying please

    They are fusible links. IIRC, the 16 on the side means it is designed to protect a 12 gauge wire (link is usually 4 AWG sizes smaller than the wire it protects).
  10. 75gmck25

    Trying to get fuel to my engine, a novice's saga...

    Is this a dual tank truck? In ‘77 I think the main (or single) tank was still the passenger side tank (in later years they changed to the drivers side for the single tank). The switching valves are old, and you will find many posts here about trying to get them to work right. Also, how many...
  11. 75gmck25

    Trying to get fuel to my engine, a novice's saga...

    The old rubber lines deteriorate inside (small pieces fall off) and also crack on the outside (develops holes that are hard to see). It sounds like there is a piece of junk that drops into and plugs the line, but blowing air into the line dislodges it and lets the fuel flow.
  12. 75gmck25

    AMC 258 HEI conversion timing issues.

    One item to check is to make sure the idle is very low (maybe 600-650 or lower), with vacuum advance disconnected and plugged when you measure base timing. Some aftermarket distributors start mechanical advance early and it ramps up quickly. A small difference in idle speed might be enough to...
  13. 75gmck25

    383 Stroker

    What transmission and rear end ratio does it have now? You can buy or build a 700r4 that will survive, but it’s easier/cheaper to build a TH350 if you don’t need overdrive. TH400 will also work if you get one for a good price, but it’s probably overkill for a 383.
  14. 75gmck25

    Fan clutch resistance question

    it’s full of fluid, which might have settled/gelled when it got completely cold. You might try starting up the truck, let it run for about 5 minutes, and then recheck the clutch to see if it loosens up a little. Howeve, it sounds like it is probably working correctly.
  15. 75gmck25

    AC settings/fan blower

    I’m not sure when GM started using continuous blower flow on the low speed all the time, but AFAIK it’s a stock feature. Blower high on Max A/C was also standard on my ‘75, even though my control panel is made differently. FYI for others - on my ‘75 I do not have a max A/C position, but the...
  16. 75gmck25

    1979 Chevy C10 Coolant Leak

    You mentioned that you “filled” the expansion tank. Did you just fill it up to the cool line with the engine cool? Most of the time with a cool engine the tank is only about 1/3 full, and then coolant fills it more as the radiator gets hot. As it cools it will pull coolant back into the...
  17. 75gmck25

    1979 Chevy C10 Coolant Leak

    Since you don’t have a temp gauge, I recommend buying a mechanical gauge similar to this one and mounting it under the dash. https://www.summitracing.com/parts/atm-2333 You could also buy an electrical gauge, but then you have two parts to worry about. Sending units go bad, wires gets shorted...
  18. 75gmck25

    1976 C30 Trailer Brake Controller

    My error. You are correct, the fourth wire is running lights, not a separate brake wire. I also clarified that the turn signal/brake bulbs are a dual duty circuit. I think they stopped connecting into the truck’s hydraulic vehicle brakes to measure braking a long time ago because it was...
  19. 75gmck25

    1976 C30 Trailer Brake Controller

    I’ve considered this upgrade to my K25, and it seems that one of the marine-grade fuse/relay boxes might be a good choice to hold everything. They are mostly waterproof, so I could locate it a variety of places. Something like this seems like it would work. https://www.amazon.com/dp/B08KHVHLL5/...
  20. 75gmck25

    Automatic transmission newbie asking basic questions

    The 700R4 depends on proper adjustment of the TV cable (it runs parallel to the throttle cable at the carburetor), along with transmission fluid pressures, to determine how it shifts. A mis-adjusted cable can lead to eventual transmission failure. If you are going to use a 700R4 for towing...
  21. 75gmck25

    Timing mark ???

    They also sell a piston stop to verify TDC. Similar process as above, but you cycle back and forth until the engine will not turn. The point on the balancer halfway between the stopping point in each direction should be TDC.
  22. 75gmck25

    exhaust manifold "air" ports sealant

    Many years ago I just cut each pipe and removed the fitting. Then I fit a steel ball bearing into each fitting and screwed it back in place. It was still fine when I sold the car.
  23. 75gmck25

    bolts or studs for stock exhaust manifolds

    You may also need an exhaust manifold spreader if things don’t quite line up correctly. Cheap tool, but it can really help if holes in manifold don’t quite line up with the head. I got mine from NAPA. https://www.amazon.com/dp/B0009OR94W/
  24. 75gmck25

    Carb to brake booster hard vacuum line, why can’t I find it!?!?

    The original hard line on my truck was shaped so it curved over and was supported by a grommet in the bracket for the throttle and the TH350 kickdown. Then there was a fairly short rubber line from there over to the brake booster. Very stable, but a PIA when you pulled the Quadrajet off. I...
  25. 75gmck25

    Carb to brake booster hard vacuum line, why can’t I find it!?!?

    This is one source, but since it’s a site for Corvette parts it’s probably overpriced. https://www.zip-corvette.com/78-81-power-brake-booster-vacuum-line.html
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