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  1. 75gmck25

    roof rust "paint?"

    I’m not a body & paint guy, but could you use POR-15 and then paint over it later? It’s used a lot to prevent rust on the chassis or in the engine compartment, but I don't know if you can use it under a body paint job.
  2. 75gmck25

    Turn signal troubles

    Most turn signal issues are due to poor grounds or missing grounds at the light housings, the wiring loom up under the rear bumper not grounded, or one of the two-conductor signal bulbs is inserted with the wrong orientation. Also check your instrument panel ground up under the dash.
  3. 75gmck25

    Vintage air vs. stock dilemma???

    I bought mine from Summit, and IIRC they were listed as Vintage Air parts. Put a good coat of paint on the brackets or they quickly get surface rust. I would have to track down the receipt to verify, but I think this is the bracket set I used. Had to measure and experiment a little to get the...
  4. 75gmck25

    Are my gears to high for the setup?

    I have 4.10 gears and 31" tires in my K25, and it's a great combination unless you like to drive over about 70 MPH (about 3100 RPM) on the highway. You could use 4.56 gears and be at about the same RPM.
  5. 75gmck25

    alternator upgrade

    You don't need a resistor or dash light for an alternator that works like the original 10si or 12si in a square body. However, you need to check the documentation for your new alternator. It's my understanding that an alternator built as a CS130 clone does need either a resistor or a dash...
  6. 75gmck25

    K10

    AFAIK, HEI became standard in 1975 on square-bodies.
  7. 75gmck25

    Can the heater core be turned off?

    I found a vacuum-controlled heater bypass valve, and set it up so when I put the A/C in Max recirculate mode it also bypassed the heater core. Bottom line - it didn’t really seem to make much difference.
  8. 75gmck25

    GVW

    Using Visa to pay is an easy way to pay for it in US$ and let your bank convert it to NZ$ for your account. I do it frequently the other way around when visiting GB (pounds) or Europe (euros). I think Mastercard also works the same way. In my experience, the bank conversion rate is usually...
  9. 75gmck25

    Modern center console rear a/c and heat

    Many newer cars have heat/AC ducts that come off the main plenum into the console for A/C or under the carpet area to get heat to the rear seats. Not easy to retrofit to your truck.
  10. 75gmck25

    GVW

    If you look through the GM document posted, you will be able to get an idea of what you have. Standard K20 (6000 GVW) should have 5 leaf rear springs, 3.23 ratio axle standard, and will have load range C or D tires C6P option (8600 GVW) should have 8 leaf rear springs, usually 3 leaf front...
  11. 75gmck25

    Small Block choices: A feller has too many

    I used Mahle .026 head gaskets with my crate 350 and 64cc Blueprint heads, to try and make up for the low compression of the stock crate engine. I only used a 213/217 @ .050 retrofit roller cam, so it’s set up for low end torque. Runs smooth and has been that way for several years.
  12. 75gmck25

    In need of a space to work for a short time

    I appreciate your motivation, but that’s a long distance and lots of gas for a 4WD squarebody . Why don’t you let the military ship your squarebody at their expense as part of the move, and then drive or fly yourself across the country? They only pay for one vehicle if you are active duty, so...
  13. 75gmck25

    1973-1980 Tailgate Trim

    I have the original ‘75 tailgate with a narrow band and centered GMC, and I have a complete 80’s bed on the truck, with a wide band that has the offset GMC. I once tried fitting the narrow band to the newer tailgate, but the mounting holes definitely did not line up, and it seemed like the...
  14. 75gmck25

    Gas tank pressure problem

    Go back to basics and check your sending unit and fuel pump fittings. The optimum solution for fuel flow and venting is a three port fuel pump (feed from tank, line to carburetor, return line back to tank), and a 3 port sending unit (feed to carburetor, return line in, vent line to canister)...
  15. 75gmck25

    Another Blower fan switch/relay/resistor thread

    On my ‘75 with A/C the high speed relay and the resistors are mounted on the big evaporator plenum under the hood. I’m not sure where they are located if there is no A/C.
  16. 75gmck25

    Tilt Steering Column

    Has the ‘75 transmission been swapped with something newer? There was no 4 speed auto in ‘75. I’m also confused about your mention of a replacing the gearbox. Do you mean the transmission or the transfer case?
  17. 75gmck25

    Edelbrock 750 cfm or 600 cfm carburetor for 454 stock engine.

    As already mentioned, first make a couple of checks of the existing setup. - Is it a 3 port fuel pump with a return to the gas tank? The return helps keep fuel cooler when the carburetor float dead-heads the flow. With dual tanks you should have a six port solenoid that switches both fuel...
  18. 75gmck25

    in tank fuel pump with Edelbrock carb

    Does your block have the option of installing a stock mechanical pump? They are really cheap, and generally reliable once you find a good supplier. Using an in-tank electric pump is a way more expensive option to feed a carburetor.
  19. 75gmck25

    Storage tray

    Why is the top edge of the back piece so uneven? Is there a piece of trim that goes over it to hide the edge? My truck has holes in the metal, which I assume were used to hold the top of the tray, but if there was trim there it’s long gone.
  20. 75gmck25

    Which A/C compressor do I have?

    I had to do some more research, but then determined there is an A6 (which my '75 had), a DA6 (used in late 80's), and then a later HR6 (known as the Harrison redesigned model). It seems the OP probably has a DA6. I don't know if the later models were more reliable than the A6, but it was the...
  21. 75gmck25

    Which A/C compressor do I have?

    The one in the picture looks like an A6, but it’s the strangest set of mounting brackets I’ve seen. An A6 is usually mounted much farther back, parallel to and outside the valve cover, with the front even with the PS pulley. It’s really heavy, so it has multiple brackets. I think your truck...
  22. 75gmck25

    Inconsistent fuel pressure

    I also recommend you find a good new or used large cap HEI distributor (coil is in the cap) and make the swap. There is no reason to run (or try to fix) points ignition on an SBC, since the HEI has been standard for Squarebody trucks since 1975.
  23. 75gmck25

    Ignition Timing for First-Generation GM V-8 Engines

    If you want to measure timing beyond what shows on the pointer, you can install a timing tape on the balancer, which will have degree marks all the way around. However, the easier solution is to use a dial-back timing light. - You can just set the dial on the light to the timing you want (for...
  24. 75gmck25

    Battery / charging isolator.

    The original setup on my '75 Camper Special had a relay (silver body, similar looking to the blower relay on the A/C plenum) mounted on the driver's side fenderwell. There was a three wire plug for the relay (mine is still on the truck): 1 - charge wire (10 gauge?) that ran from the power...
  25. 75gmck25

    Vortec heads

    I used these heads on my SBC, and they are a complete assembled head. They don’t claim to be a Vortec clone, but have similar performance, and 64 cc chambers. They are drilled for both Vortec and older SBC intakes. I also used thinner head gaskets, since unless you change pistons you still...

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