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Need som engine Info

Discussion in 'Chevy Trucks' started by 81GMDump, Aug 31, 2003.

  1. 81GMDump

    81GMDump Junior Member
    from Canada
    Messages: 8

    HI new here I picked up a 1981 GM C3500 Dumptruck back in march I got it with a 454 Hi perf BB Ran great (still kicking myself) but I traded it for a 366 BB out of a 1978 5 ton dump It barley ran when I got it( I found out recently it has a 750 Holly Dubble pumper from a mustang) in has a bad oil pan small hole. I'm trying to hook it up so I can use my guages I have no temp/oil pressure . I also have no other info on it. . So I was wondering if anyone has any knowledge of this engine.
     
  2. Chuck Smith

    Chuck Smith 2000 Club Member
    from NJ
    Messages: 2,317

    I am sure Chris will be able to give you specifics. The first thing you need to do is lose that carb. A double pumper will do you no good in the long run, other than suck down fuel. A carb with vacuum secondaries would be better.

    From what I have heard from friends, it is a good motor. They are in a lot of school busses down here in the US. Lots of torque.

    ~Chuck
     
  3. John DiMartino

    John DiMartino PlowSite.com Veteran
    Messages: 2,154

    The 366 isnot much different that the rest of the big blocks,it does have a thicker wall casting,and a tall deck block,so the intakes are different.Also they have sodium filled exhaust valves for better heat transfer under high loads. The 366 isnt a powerhouse by any means,but it will get the job done.Like CHuck said,you may lose mpg with that carb,but if it runs good id be tempted to leave it(being the power junkie i am) but Holleys have been problematic IMO,and a Qjet or big 2bbl would be more reliable.I dont know what RPM the stock 366 is safe too,the valves are heavy,and I think the overspeed safety kicks in at 4000RPM,so id keep it below 4000 to be safe,unless you know the valves/springs can take more.The stock carb had overspeed protection,it would cut the power if you overrevved it,literally you'd have to pull over and idle for about 15 seconds,before it would run above idle again.This was to protect the engine from abusive drivers.My Dad had a 366 in his Coca Cola truck for 10 yrs,he bought it brand new,he put about 300K on it,and it never had to be rebuilt.He ran at 30,000-35000 lbs daily with it.It was a C60 or 70 if i remember right.
     
  4. wyldman

    wyldman Member
    Messages: 3,265

    I think John explained most of it.I'd also keep the double pumper,as on a big heavy dump truck,with a manual trans,you need a big pump shot to get it going.
     
  5. 81GMDump

    81GMDump Junior Member
    from Canada
    Messages: 8

    Thank for the input the carb is a 4 barrel it has vacuum secondary's with a gov. I'd like to hook up the temperature and oil pressure but I can't find where to hook them up to it has a mechanical temp sensor from what I can see and I have no Idea where to hook it up. I also don't know where the oil pressure sensor is or need to be hooked up to.
     
  6. John DiMartino

    John DiMartino PlowSite.com Veteran
    Messages: 2,154

    oil pressure tap port should be at the rear of the block,an 1/8" NPT next to the distributor.If not there,then usually above the oil filter on drivers side there is a port you can tap into for oil pressure. SO your carb has a governor on it,goo deal,id make sure its hooked up,those big vlave stems are heavy,they float valves easy.You should be able to get the water temp from the intake manifold,or possibly the cyl head.You dont want to get it from the t-stat housing,if the stat sticks shut you'll think its running cool,meanwhile its overheating.
     
  7. 81GMDump

    81GMDump Junior Member
    from Canada
    Messages: 8

    well I've got a few pics of the engine bay and one of the interior I've pointed out where I believe the temp sensor is but have no idea how to hook it up so it sends to the cab guage.
    [​IMG]
    [​IMG]

    these are the "extra" connectors I have
    [​IMG]

    and for the heck of it here's most of my interior
    [​IMG]
     
  8. John DiMartino

    John DiMartino PlowSite.com Veteran
    Messages: 2,154

    The top connector is the water temp connector,just slip it over the water temp sender .They slide on from the side.The bottom is the oil pressure sender wire. It looks like a single wire type.thats should be easy to hook up as well. The one in them iddle i cant see the pattern on the connector.Im not positive of what it is.Maybe Wyldman will know.
     
  9. wyldman

    wyldman Member
    Messages: 3,265

    In the connector pic,the top one is the temp sender (as shown in the first two pics).It slides on at a right angle,from the top.The bottom is the oil pressure.The middle one looks to me like the blower motor resistor,which plugs into the blower housing below the blower motor.If that's what it is,you blower probably doesn't work,or has high speed only.
     
  10. 81GMDump

    81GMDump Junior Member
    from Canada
    Messages: 8

    Thanks for all the info Got oil and temp. hooked up now had to get a new oil pressure sending unit didn't have one on engine.Downside is my carb blew up it was in bad shape. have to get a new one. Where is the blower motor connection usually on the firewall? or elsewhere. the center connector (in my pics) allows for 2 prongs. and then there's a big square gap on it.