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New engine, new problems

Discussion in 'The Garage' started by Cornfield creations, Jan 17, 2007.

  1. Cornfield creations

    Cornfield creations 1/2 ton status

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    I just got my new 350 HO crate in. I used my old quadrajet carb and put an electric choke conversion on it, removing the old stove pipe choke. Now when I start it up it seems to take a while to engage the choke. Then after it warms up the high rev won't disengage.

    I ran the power wire for the choke to the alternator hot wire. Could that be a problem?

    I tried adjusting it and it got slightly better but not great.

    Also it seems doggier than it should considering I more than doubled the power of my blazer.

    Also my last question. Do they make 600 cfm jets for a quadrajet? If so where can you get them? They recommend a 600 cfm carb for this engine but I wanted my quadrajet as it ran awesome on my old engine, but I believe it's a 650??
     
  2. gmc4cw

    gmc4cw 1/2 ton status GMOTM Winner

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    how long was the carb of the motor? did you drain it when you stored it? I run my choke hot wire off an ignition on circuit. That much money in a new motor and a used carb? I tried to reuse my carb when I swapped motors. it didn't run right.

    spent the money on a truck avenger. it runs great.
     
  3. Cornfield creations

    Cornfield creations 1/2 ton status

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    Well it was partially that I didn't want to spend the money, but also I loved how that carb. ran on my old engine and never had any problems with it. I have a brand new holley on my 327 in my 63 Impala, and I have had nothing but problems with it. If I have to I might change out the carb, but right now I am gonna try to work it out.
     
  4. 1977k5

    1977k5 3/4 ton status Vendor

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    Your Q-jet is probably 750 CFM (the 800 CFM versions usually came on big blocks). Don't worry about it being too big. Jets do not change the CFM (air flow) of the carb, just how lean/rich it runs.

    A bigger carb will always make you more power on any size engine (less restriction). If you run a carb that is bigger than recommended it will not run well on the street and at part throttle.

    Q-jets are one of the exceptions to this rule. They have small primaries and huge secondaries. This allows them to operate well during normal driving (part throttle) and still flow enough air to power big engines. The secondaries have vacuum secondaries that open more as more air is required.

    Stick with the Q-jet, if you are willing to put a little time into tuning it you will be very happy with your setup.

    Now as for your problem with how it runs, you need to tune the carb. I doubt you need to tune anything on the primary circuit (general driving, part throttle). How does it run there?

    Your lack of power is probably because you are running WAY lean on the secondary circuit. More horsepower requires more fuel, and without it, you aren't making the power. The secondary jets are not replaceable but the secondary metering rods are and are really easy to change (that's what you'll need to do).

    Finally, its possible in your motor swap that some dirt got in the carb or fuel lines and has clogged a passageway in the carb. They are pretty sensitive to that. Try searching on how to tune Q-jets, I could write a novel on this but it has all been said before. Feel free to post back with any more questions.
     
  5. big dan

    big dan 1/2 ton status Premium Member

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    yeah I run a 750 q-jet on my 350 and love it. I know that my motor wont ever turn enough rpms to need that many cfms but it runs great. I hooked my choke up to the hot wire that runs to the ignition switch. it sounds to me like your choke needs to be adjusted. if it doesnt open all the way then the fast idle cam wont disengage and you will also have a lack of power. or at least thats what happened when mine didnt open all the way.
     
  6. HarryH3

    HarryH3 1 ton status Author

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    The alternator hot wire goes directly to the battery, so it's hot all the time. So your choke coil is always heated, which defeats its purpose. That wire should get voltage only when the key is in the "run" position.
     
  7. JEBSR

    JEBSR 1/2 ton status

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    exactly, so if you have adjusted the choke with power to it, then it isn't going to come off of high idle because it is as far open as it will go. You should also check the coil spring in the choke due to the fact that it has been on every since you connected the battery and may have burnt out.
     
  8. Cornfield creations

    Cornfield creations 1/2 ton status

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    OK I'll check that. Last night I played around with the adjustment of it and it runs a lot better than it did. But it still hesitates after being warm while accelerating. The secondaries open now too but I need to adjust my tranny kick down.

    I was told to pop up the lock on the kickdown, turn throttle wide open and push it down. After checking it that does nothing for the spring mount. It seems I have to play with the spring to get any sort of effect? Can anyone confirm or inform me on the kickdown adjustment?
     
  9. Cornfield creations

    Cornfield creations 1/2 ton status

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    OK I got things checked and still palying around with the carb adjustment. Thanks guys

    Another problem I have been having issues with. Driving down the road the temp will go past the HOT on the gauge, then quickly drop back down to the line above the cold or down to the cold, it will slowly rise again, then suddenly sky rocket to the HOT again. I got the laser themometer out and it keeps saying about 210 on the sensor, the block, the radiator is even colder yet, and nothing is boiling or anything. I took out the thermostat and the gauge never left the cold mark.

    I put in 3 different thermostats, and 2 differnet sensors, which are now AC delco. Still does it.

    I never had a problem with the gauge so I am unsure if thats what it is. Plus the temp never showed high when I had the thermostat out of the engine and ran it.

    Anyone have any related issues or anything?
     
  10. JEBSR

    JEBSR 1/2 ton status

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    Alot of times when they just suddenly jump up and then come right back down and don't appear to be actually overheating, there is air in the cooling system creating hot spots. Try starting it (cold) with the radiator cap off and letting it warm up till the thermatstat opens. Once the thermastat is open and the water is flowing top it off real good and test drive it.
     
  11. Cornfield creations

    Cornfield creations 1/2 ton status

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    Yeah but since the cap is so high on these I always thought it to be very difficult to get an air lock inside these trucks?
     
  12. JEBSR

    JEBSR 1/2 ton status

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    Not when you just installed a new motor that hasn't had water in it in a while. It will get air trapped in the block on occation. Once it is all out the first time it is a little harder than most to get air trapped though, unless you pull the block plugs and drain the block again anyway.
     

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