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Discussion Starter · #1 ·
Hello guys its been a few weeks since I last posted but am having problems and need some final advice on things. Engine is a 350 sbc dual plane intake with a hydraullic roller cam etc. Engine and all parts are all new clear down to the last bolt. Problem is engine will run and start up and runs fine some times and other times it does not. When you give it gas and it runs right it will rev nice and fast with no problems. Then when it does its problem that its doing if you rev it it will fall flat on its face and will want to die and will not want to run and you have to like fight it too keep fighting it to keep going. Some times it wants to drop a cylinder or two and then refire up and plugs are getting fowled out cause the engine does not want to stay running and all these problems.

When it is running fine it will stay and idle well then it will slowly want to start to die off and quit like its chocked or something. When you can get it to stay running decent it will seem to want to stall and you have to give it gas to try to keep it going. At a steady throttle it will stay running sometimes other times it does not just depends. Sometimes if you give it gas it helps and other times it wants to kill it. Ok here is a list of all that has been replaced and checked on this thing.

Two Edelbrock carburetors a 600 cfm performer and 750 performer both in excellent running condition.

One Holley Street avenger 670 carburetor brand new and floats and everyting set as it should be and ims screws all tuned right.
Two different Hei's where used and both are in excellent working condition and both have been tested at the autoparts store and everything is fine on them.

Two sets of plug wires and three sets of spark plugs where used and all are new.
Ignition wire to hei where all checked and 12 volts are being supplied
New gas tank and original fuel sending unit installed.
All new fuel line.

Two brand new mechanical fuel pumps where used and have correct fuel pressure of around 5-6 psi.

New alternator has been installed and checked.
New vacuum lines have been installed and all checked out fine and no cracks and carb cleaner sprayed around intake manifold and no leak around carb base or in front or back of intake. There is no hint of a vacuum leak and vacuum is steady at 14-15 hg (performance cam)

Ok guys after all these things have been checked and after all the different things swaped out for the process of elimination it still wants to do this and don't know else to do here. All electriacl stuff and fuel stuff has been checked out and replaced with new stuff to troubleshoot here. Everything is what it's supposed to be and timing was dead on and nothing else was ever messed with.

Any suggestions here? When you can get it out it will run good then bad then good then bad again it will rev strong then will just fall flat and there is no pattern it just happens when it wants too. Hope to hear from someone here. My Dad has worked on cars for over 30 plus years and hes know's it all pretty much and he is just baffled with this mystery.
Thanks guys
Eric
 

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This is just something to check. With the engine running and at idle remove the air cleaner, shine a light down in the carbs throat and see if you see fuel coming out of the boosters. Do this if you can when the car goes to acting up.
 

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Discussion Starter · #3 ·
Hello guys first of all I have looked and the carb is not dripping fuel into the intake at idle and all three carbs are fine with that. Also Fbird do you mean run a battery type ground and drill a hole into the fire wall and screw one end there and then run the end to my frame then run the other ground from my frame to my battery? Currently my ground wire wich is a hefty gauge wire goes from my battery to my passenger side motor mount. So what else would you do for another ground strap? Do I get a another battery ground wire and what gauge should I get? This is a 96 chevy s10. Trust me I am going to do what you said cause I need to rule anything out.

Its funny though with the same setup now with my previous motor it was just hooked up like it is now and never had any problems with my hei running funny or anything so is it really the ground issue cause it ran fine before I had to take my motor out again cause I had to replace the previous new oil pump I had it went bad. My Dad resealed the oil pan and resealed the intake and rear main seal that was all. After we got the motor back into the truck it ran fine for a couple of weeks and was driving it everyday and then all of a sudden all this started to happen and I started to replace everything I could check of. Still a good idea though for the ground stuff hope you will help me on that. Always appreciate your help.


Eric
 

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I would run another ground from block to frame and one from block to firewall, I recommend this be done to all vehicles for starting purposes, however, you can add grounds but it may not be the issue. Have you checked the spark when it goes to running erratic? a friend of mine`s car did this years ago and it was narrowed down to the module in the HEI. Sometimes it ran great other times it ran horrible.
 

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Discussion Starter · #5 ·
Well I have two different control modules and the one is only a year old or so and the other one is prett old but was working good the last engine I had it on. I had them both checked today at advance auto parts store and the both checked out just fine. Will add more ground just to eliminate that but it's probably not that but will add another strap to rule it out.
Eric
 

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Howdy--I think that I would go after a fuel delivery problem. You mentioned correct pressure, hows your volume? What modifications did you make to the original sending unit assy after removing the elec. pump?
 

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Discussion Starter · #8 ·
Hello guys well first of all thanks to everyone who was patient with me as me and my Dad have spent countless hours checking for everything that we can think of and he has worked on motors and cars in general for over thirty years and know his stuff and I have learned a lot from the horrible experience. Well I did what you said Fbird I used a ten gauge wire from my motor back to the fire wall and also have one going from engine to frame and also the main ground going from battery to the motor mount.

Ok after some more of checking stuff today I got a fuel pressure regulator and put it on and still no change in things it would idle better now but would still fall flat on its face after 2500 rpm and then pick back up.

Well after countless hours and over three weeks of changin everything out and putting in all new stuff I found the problem and it was the brand new Holley street avenger carb that I got back in September. My two previous Edelbrock carbs worked fine on this truck but then thing started to go bad at that time and I later on a week later found out I had to burnt plug wires but looking at them you could not tell as they where new and all. I stuck the holley on before I found out this stuff so it only added to the headache.

We stuck a rebuilt holley 600 carb on that my Dad had lying around and we put it on and man all issues went away. I can't believe a brand new holley carburetor would work so crappy that I have to go through all this and was thinking it was not the carb cause it was brand new. I adjusted the float bowls like was stated and it did not help anything at all. The fuel bowls kepy running out of fuel very fast after you would rev it and it just kept falling flat and would pick back up and man just too much to tell. This is the second time I have bought a brand new holley carburetor and straight from the box it would not work period regardless what you did to it. I did not take it apart I just am shipping it back to jegs and am trying again.

If this ones bad then I will call holley and tell them to stuff there crap if they can't have better carburetors then that. It seems to me quality control went out the door a long time ago. I bought a barry grant carb two years ago and the fuel transfer slots on the base plate was not machined right and it ran too rich on one side and lean on the ohter :mad: O well here we go again at least this time if I have any issues what so ever I know its the carb period.

At least I have a brand new fuel tank and lines, plugs wires again with extra's and the right amount of ground wires to make things work good now. Take care guys and thanks for all your help much appreciated.
Eric
 

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Discussion Starter · #10 ·
Hello guys I got my replacement holley street avenger carburetor today and I did my basic idle mixture tuning and idle setting and man my engine runs excellent again. Thanks to all who helped me out I appreciate it a bunch. FBird, techinspector, Ericnova 72, and all others who are regulars on here I thank you a bunch for sharing your knowledge with me and others so we can learn to do the same things as well and gain confidence in doing so.

Thanks again
Eric
 
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