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  1. 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...
  2. 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...
  3. 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...
  4. 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...
  5. 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...
  6. 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...
  7. 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.
  8. 75gmck25

    New stater not catching

    Did you measure the clearance between starter gear and the flywheel, and use shims to adjust it?
  9. 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...
  10. 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...
  11. 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...
  12. 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...
  13. 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...
  14. 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...
  15. 75gmck25

    CARBURETOR DATED

    I have a Quadrajet with a four hole spacer and it’s tuned the best I could do myself. If it’s only been sitting a couple of days I just pump it twice, and hit the switch and it starts right up. If it’s been sitting for a week or more I may have to give a 2nd round of two pumps, probably because...
  16. 75gmck25

    Tire size confusion.

    After GM switched from 16.5” to 16” tires, the standard size for HD trucks was usually 235/85R16E or 245/75R16E. Your glove box sticker should list the tire size for your truck. My ‘75 8400 GVW truck had 9.50x16.5/D tires when delivered, and they were 31” in diameter. The 245/75R16 is about...
  17. 75gmck25

    What headers will fit a Blueprint 454 in a 1987 K10/V10

    I have Blueprint heads on my SBC and it was a PIA to fit spark plug wires with stock iron exhaust manifolds because of the difference in port spacing. Not easy to grind for clearance once the manifolds are installed. I just swapped to Sanderson headers for my SBC and they definitely fit better...
  18. 75gmck25

    Carb gasket comparison question!

    Check to see what passages those holes line up with in the carburetor. If the carburetor plate is solid in those areas, then the gasket is fine. If there are holes that line up, then you need to get the matching gasket.
  19. 75gmck25

    87 receivers

    Some of the older hitches were designed in three pieces so they would fit multiple brands of trucks. There was a standard crossbar and receiver, and it bolted into left and right brackets that were unique to the truck brand. It seems like that design might be modified fairly easily to fit the...
  20. 75gmck25

    Gas hog

    My '75 K25 has a 350 with aluminum heads, 213/[email protected] retrofit roller cam, Edelbrock Performer intake, and a Quadrajet that has been tuned to run a little better with the cam. I have stock 31" height tires, 4.10 gears, and my NP203 is still full time 4WD. RPM is about 2800-3000 at 60 MPH...
  21. 75gmck25

    Non EEC fuel tank vent

    My ‘75 has three port sending units, and both sides go to a T fitting. That fitting connects to a metal line that runs up to the engine compartment. At the engine compartment it connects to the vapor canister, and that originally vented into a dedicated port on the carburetor. In the engine...
  22. 75gmck25

    73 C10 Rear End Small Lift Needed

    Shackles are easy, but not good for stability and load carrying unless they are really stiff. Blocks are probably a better choice, but more work to install.
  23. 75gmck25

    Coolant Hose Popped Off the Thermostat

    First thing I’d do is to replace the radiator cap. If the pressure release is bad it might let it get too high. I think the stock cap is rated at about 16 lbs pressure for most SBC’s. Also make sure it pushes coolant into the overflow when hot, and then draws it back in as the engine goes...
  24. 75gmck25

    RETRO-Mod: Jeep intermediate steering shaft

    I bought the Borgeson steering shaft and thought I had a similar problem. Turned out to be a non-issue, so maybe the solution will work on yours. Called them and they told me to pull that black rubber bellows down the shaft to expose the slip joint underneath. On the bottom of the shaft there...
  25. 75gmck25

    Help With Parking Break Dash Light Staying On

    Check the small switch on the parking brake pedal mechanism. It may be broken, or not screwed on tight. Proportioning valve can also turn on the light, but it usually only happens when you press the power brake pedal.

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