running lean - intake manifold ? or carburetor ?

Discussion in 'Chevy C/K Truck Forum' started by otgdy, Jul 20, 2013.

  1. otgdy

    otgdy New Member

    I just rebuilt the 454 in my Big10 and although it runs strong the idle is rough and it runs hot. 230-240 with a 160 thermostat.

    A friend (master mechanic) said the carb was too small (rochester quadrajet). This carb was
    rebuilt at the same time as the engine and I fully trust this builder. Translation.. not fully convinced.

    So here is my question...
    The 454 has a mild towing cam, Rochester QJ, Edelbrock Performer 2.0.. new radiator/thermostat/hoses/flushed cooling system.
    Someone stated that the performer 2.0 is good for the peanut head .. my engine has bigger valved heads
    than that. Has anyone heard this about the 2.0 and the peanut heads ? Could the manifold be leaning out the engine ?
    Interesting thing is I have fully opened up this engine and it runs strong up to 100mph. No missing/bucking/back firing.

    If this doesn't pan out what carb could I use that would be bigger than a 750 Rochester QJ ? and a spread bore to boot ?

    PS .. no the head gaskets are not leaking.

    Thank you
  2. Sirwriter

    Sirwriter New Member

    Hey OTGYD,

    First thoughts: Not the size of the carb necessarily. What is it jetted at?
    Next, why the 160F thermostat? Why not a 190-195?
    Next, a biggie for me, do you have a stock size water pump on there instead of a kick butt tsunami wave water pusher?
    The intake is not leaning out the carb.
    A Holley double pumper would be a nice alternate. That's a nice sounding set up.

  3. otgdy

    otgdy New Member

    I am not sure what the jetting is. I purchased it from a place in Florida as a stage 2 rebuild.
    Had it rebuilt again locally not long after I got it from Fla. (place really sucks in their RQJ rebuilds)
    When I pull the radiator cap the fluid flows fine and you can tell that the thermostat opens/closes.
    The water pump is fine. I swapped the 190 with the 160 just to see what happens. Same old story here.

    Holley would be an option except this is a spread bore. Last I heard the Holley spreadbore is a POS and don't talk to me about the Edelbrock POS. I have a shelf full of them. I have been looking at the Street Demon 750. Don't know about that one as an option. It fits both square and spread bore manifolds.

    Interesting thing I forgot to mention... When the outside temp is around 80 degrees the engine runs around 200 degrees. When the outsidetemp is around 90 the engine runs at close to the red line 220-230 degrees.

    just a thought.. putting a bigger more manly water pump on it?
    Wondering how that helps.. Push more water .. thermostat restricts the flow so the water waits long enough in the radiator to cool. If you move enough water than the thermostat will close and stop the flow. If I want to move more water then I would remove the thermostat and it would over heat due to the increased flow and decreased cooling time delay. Interesting thought but lets not continue with it.
    Last edited: Jul 21, 2013

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