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  1. 75gmck25

    Rag joint replacement difficulty

    The jeep steering shaft conversion will not work with ‘79 and early squarebody trucks if you still have the original steering box. I installed a new rag joint on my ‘75 (easy job) and it helped quite a bit, but there is still a fair amount of play in my steering box. There is also an adjuster...
  2. 75gmck25

    Anyone ever make/crimp their own high pressure hoses?

    Another thing to watch out for is that many of these hoses only work well if the fitting orientation is correct. For example, if a shop crimps a 90 degree fitting on and it’s pointing in the wrong direction/orientation it cannot be corrected later because you can’t rotate the fitting once...
  3. 75gmck25

    Front indicators alternating when headlights on

    On my ‘75 GMC they always alternate.
  4. 75gmck25

    83 K20 GEAR RATIO

    Based on my references, the 4.56 was only a factory option for the K30, and 4.10 was the lowest ratio for a K20. However, it may have been swapped.
  5. 75gmck25

    Newbie Vortec Cam Question

    Do a search for the Engine-masters video where they compared intake manifolds and how well they worked. Don’t get confused about high rise vs. low rise, which is not the same as dual plane vs. single plane. You do not want single plane with a carburetor and a relatively stock engine. From...
  6. 75gmck25

    Fuel mixture screws

    Since you already have the plugs out, I would pull the valve covers and adjust the valves. You might also find that you have a really loose or bent pushrod, or other problems in the valve train. Rerun your compression test, but squirt a little oil in the low cylinder. If compression comes up...
  7. 75gmck25

    Heater not working but blower motor working just fine.

    The lower blower speeds go through the resistor pack, and the high speed is a direct connect through a separate fuse. The separate high speed fuse is in a wire that runs across the top of the firewall from the junction next to the brake booster over to the blower relay. My ‘75 GMC kept frying...
  8. 75gmck25

    Recently acquired 1977 K20. I want an original-ish truck.

    Do you know what thermostat is has? Stock would be a 195 degree, but many guys get the idea that a 180 or even a 160 would work better. This is not true for a relatively stock engine. If your cooling system is bad/inadequate, changing to a lower temp thermostat willl not fix overheating. GM...
  9. 75gmck25

    Carburetor on my 82' C20

    California 17080513 vs. 49 state 17080213 version of the same carburetor. It should work fine, or maybe even better.
  10. 75gmck25

    Rear Bumper 1986 K10

    My Dad sold Ford trucks in that timeframe, and they seldom ordered the factory bumper. His rationale was that farmers and ranchers often wanted a specific type of rear bumper (or none at all), so it was easier to keep a few standard models in the parts room. I do recall one bumper style that...
  11. 75gmck25

    thoughts on low vacuum?

    Most big cams need more timing to operate effectively. I would advance base timing to at least 12 at 650 rpm, but not more than 16. Then check all-in timing (base plus mechanical) at about 3500 rpm to verify it does not go higher than 34-36. Also check the vacuum advance to see what it adds.
  12. 75gmck25

    Front posi-traction differential

    In general, if you expect to drive it on pavement, you need a limited slip, selectable front differential. Some use switches that are electrical and some are air switched.
  13. 75gmck25

    Want to build a good horsepower, good fuel economy engine for a 1978 c20 with stock 350. I don't know much and need help.

    I had a similar goal for my 1975 K25, so I can provide my input. - original smog era 350s and GM replacement crate engines are seriously hobbled by low compression and poor head flow. Compression ratio with typical 76cc heads and dished pistons is about 8-8.2. - switching to an iron Vortec...
  14. 75gmck25

    Left Turn signal . doesn't work

    Most likely to be either a bad bulb, or the ground at the turn signal housing. Also check the bulbs to make sure they are oriented correctly (one has two contacts), and are not corroded in the socket.
  15. 75gmck25

    Gas smell

    I had a similar problem, and they gas mostly went onto the exhaust manifold and burned off. Gas smell, but no visible gas residue. Just replace the pump and be done with it. They aren’t expensive, and not that hard to replace. The only challenge is to get the pump lever up under the rod...
  16. 75gmck25

    Heater Core question

    There is one bolt that is very hard to reach because it’s down behind the edge of the inner fender. You can unbolt the inner fender to get space for a regular wrench, or some folks have used various universal joints to get in there. You will need an assistant when you bolt the housing back in...
  17. 75gmck25

    Vacuum hose routing for brake booster

    With a Quadrajet or Edelbrock 4 barrel there is a threaded port on the back of the carburetor base. From the factory there is a metal line (6” long?) threaded into that port and it runs back and over to near the brake booster. From there you have a short rubber line connected to the brake...
  18. 75gmck25

    Vacuum lines where do they go

    The identifying number will be something 17080213 for a newer Quadrajet carburetor, or 7045583 for an older Quadrajet (this is rhe number from my original 1975 carb). Your carburetor has been worked over by a brainless mechanic at some time. It’s missing pieces from the old hot air choke...
  19. 75gmck25

    Electrical Issues 1973 c10

    Check the fusible link where the wire from the alternator connects to the power junction that is next to the brake booster. If you squeeze the wire you may find it is burned inside (it will easily compress), but you can’t really see the burned area on the outside.
  20. 75gmck25

    Black Fuse-like Electrical Connector?

    It’s one of two fuses for the ammeter. The 2nd one is over on the other side of the engine compartment.
  21. 75gmck25

    shift indicator

    It’s also common that the little plastic piece the wire slides on may have broken. It’s molded as part of the plastic cluster housing, so you have to replace the housing to fix it properly. Not real expensive from LMC, but it requires quite a bit of time to pull the cluster and swap everything...
  22. 75gmck25

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

    I have another question. When you look at the squarebody GM emissions stickers they all (I think) have a large two letter code at the top, like AM, XC, etc. I assume this code can be matched to a year, engine and vehicle combination, but I’ve never seen a table that listed the codes. Is...
  23. 75gmck25

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

    It collects vapor from the gas tanks and periodically vents it into the carburetor. In general, the venting is usually controlled by engine vacuum, but the exact setup ( canister with built in purge valve, separate purge valve, etc.) varies by year.
  24. 75gmck25

    350 water pump studs

    I’m confused. What options don’t you have? Dorman or Help! branded parts are sold at almost all parts stores. If they don’t have them on hand, you can usually order them for free store delivery. The link I posted was for Amazon, and I don’t know anywhere in the US that they don’t deliver...
  25. 75gmck25

    1976 C20 Burb: 3/4 ton fuel system and EVAP

    I have the GM repair manuals for my truck, but they are not very specific about emissions equipment and what was included with each powertrain combination. I got my truck in about 2002 and it looked like the 350 engine was relatively unmolested; however, it had been in my wife’s family for...

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