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  1. 75gmck25

    Are these vacuum ports?

    AFAIK, my my Edelbrock intake came with a choke stove block off plate, and I think they sell aftermarket replacements. My aluminum heads don’t have an exhaust crossover, so it I don’t think it would do anything anyway.
  2. 75gmck25

    EFI rated fuel plumbing solution

    Amazon and other vendors sell SAE J30R9 fuel hose, which is rated for high pressure EFI and modern gas. Local stores also carry it, but it’s usually much cheaper to buy lengths of it (20 feet?) from online. They also have EFI hose clamps, which are made like band clamps, so they don’t cut...
  3. 75gmck25

    Ever dealt with GM crate motor warranty replacement?

    Do some simple troubleshooting first. Pull the valve cover and check pushrods and rockers. Maybe have someone crank it over while you watch the valve train. You may also want to pull the intake and check for collapsed lifters, antifreeze leaks, etc. If no problems are visible in the valve...
  4. 75gmck25

    PCV manifold or ported vacuum?

    What is the number on the side of your Quadrajet? Mine is a 1980 model, and it does not have that #4 connection. PCV hose definitely does not go to the charcoal canister, but it is possible that the canister vent is T’d into the PCV line. PCV hose is connected to a 3/8” fitting on the...
  5. 75gmck25

    New crate engine oil priming/ ignition timing impact if the distributor is mis-installed

    Does your new engine have a a flat tappet cam or a roller cam? Flat tappet cams require break-in, and if you have never done it before it can make you very uncomfortable. Standing next to an engine that is running at 2500 rpm for 20 minutes to break in the cam is really noisy, and it feels like...
  6. 75gmck25

    74 k10 going 55 mph is at 3,500 rpm

    My similar ‘75 K25 with 4.10 gears, np203 and TH350, and stock height tires (245/75R16E - about 31”) runs at about 2800-3000 rpm at 60 mph. I doubt I’m getting much over 10 mpg. You should be able to fit up 33” tires with no lift or fender trimming on a K10, and that would help. Also make...
  7. 75gmck25

    Air conditioner compressor wires

    IIRC, on my compressor the black wire is grounded to the body of the compressor.
  8. 75gmck25

    Timing light recommendations

    I’m using an Innova light with setback dial and a tachometer readout, and IIRC it was about $100-110. It seems to be good quality, and it has all the info I need in one package (both timing and rpm) to check my vacuum and mechanical advance. I first tried buying a similar light from Harbor...
  9. 75gmck25

    Dash/radio lose power on ignition wires

    It may be the ignition switch out of adjustment, or the rack and rod mechanism has broken. Some of the switch contacts may be only making a partial connection. The actual electrical switch is mounted on the column about where it goes through the dash. The key switch has a toothed gear on the...
  10. 75gmck25

    Fixing vapor lock now that I barely made it home, experience with 3 port filters?

    I’ve never see a filter with a return port, so I don’t know how well they work. However, the mechanical fuel pump with a return line was used on many GM vehicles, and the pumps are not expensive. I would go with the OEM solution. Rubber gas line will work to add the line, but you want to use...
  11. 75gmck25

    AC temp control wire

    I’m not sure it’s that wire, but on my ‘75 controls there is an extra wire and two indents on the temperature slider. If you slide it left to the first indent, almost all the way to the left, and the truck is on A/C, you get normal operation of the blower. If you slide it fully to the left...
  12. 75gmck25

    LED headlight upgrade

    It also helps quite a bit to install a headlight relay kit that provides direct battery power to the headlights. It’s a simple plug and play harness and two relays, and the headlight brightness no longer depends on the old wiring running to your headlight switch. The kit I got from LMC had a...
  13. 75gmck25

    GM Delco CB Radio

    Just connect a CB antenna. CB needs a good antenna that matches the frequencies, but an AM/FM radio is so simple that it could get by with an antenna made of just about any wire you found around the garage.
  14. 75gmck25

    Better illumination of gauge cluster possible?

    I wasn’t sure the #168 bulbs would help that much. I decided to repaint the metal back of the cluster white, and then ordered new dimmable led bulbs from an online store (Super-bright LEDs, IIRC). They are dimmable, but not exactly like an incandescent. They dim to about 1/2 brightness, and...
  15. 75gmck25

    Steering Box Screw

    If you read the GM shop manual, it is definitely an adjustment point. However, there is at least one other adjustment you do before you touch that allen screw. It’s all explained in the repair manual. And when you adjust the Allen screw the steering box should be disconnected from the...
  16. 75gmck25

    Steering Box Screw

    It should have an Allen wrench fitting in the middle, and a locknut around the outside. You put the Allen wrench in to hold the adjuster, and then loosen the outer locknut. If you want to take a little play out of the steering you would turn the center adjuster portion clockwise a very...
  17. 75gmck25

    1977 C20 hd emissions vacuum lines

    GM didn’t put the emissions diagram and other info on the core support until sometime in the late 70’s. AFAIK, for my ‘75 the diagram was on the side of the air cleaner, and it’s long gone.
  18. 75gmck25

    Deleting emissions,read this article.

    Rules for compliance also differ for each state. My ‘75 GMC is 8400 lbs GVW, so it’s original HD emissions equipment was minimal , and it never had cats. It now has antique plates, but I considered getting full inspections and regular plates like I used to have. The guy at the inspecting...
  19. 75gmck25

    Auxiliary trans oil cooler

    If you buy a separate external cooler, look for a stacked plate design, not a serpentine tube if you want best cooling. Long Mfg Low Pressure Drop (LPD) and the B&M coolers use stacked plates, and I’m sure there are others.
  20. 75gmck25

    1977 C20 hd emissions vacuum lines

    I have a similar carburetor on my truck right now - a 17080213, so maybe you will find these pictures useful. - I use full manifold vacuum for the distributor, but you could use ported instead. Whichever you use, the other small port must be plugged. - The large threaded port on the back is...
  21. 75gmck25

    CNC machined emblems

    Great looking emblems! What CAD program did your student use? If you use something like SolidWorks, the initial file created is usually a common file type that many different machines can use. It’s translated by the machine software to a set of commands for the specific machine. With a...
  22. 75gmck25

    1980 C10 backfires through carb under load

    Also buy a spring kit for the carburetor and try swapping to higher rated springs. Stock step-up springs on a 1406 are 5”, so the carburetor goes from cruise to power mode when engine vacuum drops to 5”. The kit will also have 6”, 7” and 8” springs. For example, when you use a 7” spring it...
  23. 75gmck25

    Anyone use edelbrock universal EFI fuel sump Kit w 2 tanks

    I have looked at using an EFI sump for my dual tanks, and the only question I have is how to handle the fuel return lines. I already have return lines on my mechanical fuel pump, and a six port solenoid that switches them. It would still work as designed for the mechanical pump. If the...
  24. 75gmck25

    fuel tank swap

    The tanks all interchange (although 87+ are supposed to have internal baffles for EFI), but sending units and filler pipes differ from year to year. It would require some body work to add a filler door, so you might want to look for the fillers from an older truck. I’d get a bunch of...
  25. 75gmck25

    Dead battery

    When you find dual batteries in a gasoline squarebody, it’s because they have the camper special package, maybe trailer towing package, or have added a plow or winch. The main battery and the aux battery then have totally different uses, so they are seldom identical.
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