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Old 08-24-2010, 05:32 PM
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Need help fast with 350. please answer!

Guys i have a sort of emergency. As you might know i've been working on a 78 firebird with a 350 that i just built. The problem is that it starts up fine when cold but once it warm up to about half the operating temp and i shut it off, it is impossible to start. This car needs to be driven tomorrow and i don't know what to do! Is there any tips you may have to help this problem. It's not a fuel delivery problem, it's getting to the carb fine. The carb is a load of crap. It's a 750 q-jet and it is in awful shape. I timed it by ear and it runs smooth with great throttle response. But i can't park the darn thing because it wont start back up. Please help me guys.
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Old 08-24-2010, 06:20 PM
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The usual problem with old Q-jets was the main well plugs on the bottom of the main body would leak flooding the engine and making a hot engine tough to start. I would peen the casting back over both plugs and epoxy over them and that seemed to work for a long time. The plugs extend below the gasket surface and into a recess in the throttle body. I had some kind of special epoxy from Devcon that was for contact with gasoline. I hope I'm not heading you down the wrong path.
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Old 08-24-2010, 07:01 PM
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alright, i think ill just risk it for tomorrow but im looking into getting a edelbrock or holley to replace it. which is more dependable, as in starting dependability? im really getting tired of struggling to start the car.
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Old 08-24-2010, 07:45 PM
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Quote:
Originally Posted by bigdog7373
alright, i think ill just risk it for tomorrow but im looking into getting a edelbrock or holley to replace it. which is more dependable, as in starting dependability? im really getting tired of struggling to start the car.
Be prepared to lose some gas mileage going with either of the other choices . But that is just my experience . Others experiences may be different than mine .
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Old 08-24-2010, 08:50 PM
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I actually picked up a few mpg when I went to an Edelbrock 1406 from a Quadrajet. Though the Quadrajet wasn't tuned and I tuned the Edelbrock with a wideband O2 sensor.
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Old 08-24-2010, 08:59 PM
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Quote:
Originally Posted by Sinister
I actually picked up a few mpg when I went to an Edelbrock 1406 from a Quadrajet. Though the Quadrajet wasn't tuned and I tuned the Edelbrock with a wideband O2 sensor.
Tuning definitely makes a difference . I played with a Q-jet back in about '90 and could make it get anywhere from 8 to 22 mpg depending on what primary jets I put in it . This was in a 4500 lb '78 K-10
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Old 08-24-2010, 09:41 PM
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Bad carb or Timing

Just jumping in after reading your issue with cold starts as opposed to warm no-starts....when you say you ear timed it , did you actually drive it to check throttle response / , or were under hood checking repsonse.. if you were underhood , still could very well be timing..especially after being warmed up..ran into that issue with my Chevelle ...dont get me wrong , still think the quadrapuke needs to go , my recommendation would be a edelbrock , out of the box they seem to be worry free without too much adjustment needed...
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Old 08-25-2010, 07:17 AM
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Quote:
Originally Posted by bigdog7373
Guys i have a sort of emergency. As you might know i've been working on a 78 firebird with a 350 that i just built. The problem is that it starts up fine when cold but once it warm up to about half the operating temp and i shut it off, it is impossible to start. This car needs to be driven tomorrow and i don't know what to do! Is there any tips you may have to help this problem. It's not a fuel delivery problem, it's getting to the carb fine. The carb is a load of crap. It's a 750 q-jet and it is in awful shape. I timed it by ear and it runs smooth with great throttle response. But i can't park the darn thing because it wont start back up. Please help me guys.
If you let it warm up all the way will it restart. It could be as simple as the choke is not opening fast enough or to fast for that matter. I would take a look at it. The choke should be closed on a cold engine after tapping the gas once, should open 1/8 to 1/4 immediately when starting and slowly open the rest of the way as the engine warms. If the choke is still closed and the engine is partially warmed up it can cause hard starts.
Next time it doesn't want to start, try holding the pedal to the floor while cranking, if it is flooded the extra air will usually get it to start.
Does it not start right away, when you turn it off are you trying to restart it immediately or after it has sat for a while.
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Old 08-25-2010, 03:33 PM
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it has no choke. it starts kinda ok when cold but not at all when hot. whil a holley or edelbrock give easier starts?
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Old 08-25-2010, 07:31 PM
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Whats the timing at idle? Is it fighting the starter or just turning without firing up?
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Old 08-25-2010, 07:44 PM
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There is no resistance while trying to start it, it just won't fire. I'm going to order a edelbrock 600 and be done with fighting it.
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Old 08-25-2010, 08:54 PM
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Quote:
Originally Posted by bigdog7373
There is no resistance while trying to start it, it just won't fire. I'm going to order a edelbrock 600 and be done with fighting it.
I ran over a 1/4 million miles on just two different q-jets with no staring problems whatsoever so I don't believe it has anything to do with it just being a Q-jet . If you are planning to use the same manifold with a square bore carb you need to puchase the adapter . I bought a Mr Gasket for about $30 just last month .
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Old 08-26-2010, 07:25 AM
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I have a holley 750, 4160, that needs a good 10 seconds of cranking to start when hot. It was suggested on here that it's rich fuel in the carb from sitting and more air is needed so the 'wot' trick helps in my case. I wonder if you have a similar issue? Unfortunately, mashing the gas while cranking is also dumping gas form the accelerator pump into the carb causing a minor flooding issue.
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Old 08-26-2010, 07:27 AM
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I'm not saying it's bad just because it's a q-jet, i'm saying it's bad because it doesn't work like it should. And i have tried everything to get it started when hot and nothing works except for letting it cool down and starting it again. And i already have a square bore manifold on it, i'm using an adapter to run the q-jet.
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Old 08-26-2010, 08:26 AM
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Quote:
Originally Posted by bigdog7373
I'm not saying it's bad just because it's a q-jet, i'm saying it's bad because it doesn't work like it should. And i have tried everything to get it started when hot and nothing works except for letting it cool down and starting it again. And i already have a square bore manifold on it, i'm using an adapter to run the q-jet.
Sounds like you are good to go then . Just didn't want you to get your new edelbrock and then have to wait for the adapter to be able to run it . As it has been said on here many times . Most always a Edelbrock will run fine right out of the box . Just to let you know , there are calibration kits avaiable for an Edelbrock . I bought one for my 1405 'cause the last owner had it jetted so rich it burned your eyes just being in the driveway with the car. Cough Cough . With shipping,a pack of 5 cover gasket, a kit with 6 sets each of jets , springs , and metering rods was $65 . You probably won't need them unless you want to play around with it . Happy Motoring !
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