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Old 08-31-2011, 01:49 AM
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HP Chevy 350 wont idle

Hello, thx for the forum. Recently I bought a 73 010 4 bolt 350 and set of 625 vette 2.02 1.60 heads polished ports. Stripped it down. Replaced bearings, oil pump, cam ( Crane Cams Blueprinted 350 hp 967251) lifters and double roller timing chain. engine had been rebuilt before. Pistons were letter stamped. No ledge and could still see cross hatches from honing. So I didnt go as far as replacing the rings. Old engine already had new Edeldrock performer intake and 1406 carb and headers. Mallory Ignition, Comp 9000 Unilite distributor, Promaster coil and ballast resister. Installed it in a 1987 GTA Trans Am.

OK, so have to hold throttle wide open and crank for 30 seconds or so before it will start. Doesnt change hot or cold. Once started it revs nice, but refuses to idle and very rough at low rpm. Has NKG race plugs gapped at 45 Mallory sidewinder wires. Plugs are black soaked with gas. Everything ran fine on the other engine. Parts were stored in clean safe place and didnt set but 2 weeks.

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Old 08-31-2011, 04:15 AM
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The writing is on the wall. Anytime you have to hold it wide open to start it means it`s flooded and by holding it wide open is the only way it can pull enough air in to ignite the fuel charge. Check the float height, the needle and seat, make sure it don`t have trash in it and is sticking open, check the fuel pressure. If all these check out good then I`d say you don`t have enough base timing and the throttle is too far open as a result which causes it to draw from the main boosters instead of the idle circuit.
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Old 08-31-2011, 08:23 AM
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Thx DV, ill take carb off now check it all out.
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Old 08-31-2011, 05:07 PM
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Ok, I took carb apart and bought rebuild kit for safe measure. You were right floats were way out of wack and some junk in it. So I rebuilt it, reset the floats according to spec 7/16 and 15/16 - 1". With no luck... Coil has 12.5 volts seems to fire fine and timing is nuts. So friend said "well how good you feel about your valve adjustment" hmm. So I took valve covers off adjusted the valves. He had told me only go 1/4 turn past lash. To my surprise it starts alot easier, still have to hold throttle open get it fired though but it will run at 1200 now. I havent a fuel pressure gauge working on that one, but I did swap out the fuel pumps with no change. Its stock mechanical not electric like would normally run in the 87 TA. So now my attention has turned to valve springs not strong enough as well. It was my understanding the cam didnt need any over stock mods really, as the cam has 485 lift max I was told you can go on stock. Im really not wanting to put anymore cash in this. To the point where im about to have to sell to let somebody else deal with. which I really dont want to do, but im about out of options. Also I may be able to trade Edelbrock with lil cash for 650 Demon carb.
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Old 08-31-2011, 09:56 PM
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Weak valve springs won't have anything to do with hard starting.

It still sounds like a rich fuel problem, like you're dumping excess fuel into the motor at idle and when shut off. After sitting for a spell, are the fuel bowls empty?

Did you follow what DV said about the butterflies being too far open at idle, drawing fuel over from the primary side?
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Old 08-31-2011, 11:08 PM
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What 68 said is the gospel, but also If you don`t have a fuel pressure gauge you are doing what I call "Flying blind" so by all means Get one. It`s imparitive for all performance engines to have a fuel pressure gauge. It don`t matter the fuel pump is stock. I had a stock pump on my cutlass and it was putting out 15 psi and I was blowing carbs apart. My problem proved to be a tank venting issue. the pressure would build up in the tank with no place to escape except the fuel line going to the carb so it created a huge mess, fuel would be shooting out of the boosters pushed so hard it looked like fuel injection at this would be at idle. Edelbrock carbs don`t like anything over 5 psi fuel pressure. I wouldn`t swap the carb for a demon, but I`d swap it for a Quadrajet in a second. I used to have a demon. It wasn`t a bad carb, but I wouldn`t buy another one. I don`t like Edelbrock carbs at all and pretty much won`t fool with them. The rear fuel entry on them makes for a mile of fuel line on top of the engine, I don`t like that idea very much as it makes it that much less safe. I also don`t like you have to shave metal off the secondary tang to set the vacuum secondaries, if you remove too much metal you can`t put it back so you have to get creative with it.
As myself and 68 said, get a fuel pressure gauge and look into how far open the secondary butterflies are.
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Old 09-18-2011, 12:33 AM
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Thanks guys. I haven't had a whole lot of time to get into the car. Lifes in the ****ter atm working ton of hours. Anyhow, fuel pressure is good to go. I adjusted the valves out to 0 valve lash and to my surprise it fires right up and runs easier and acutual runs decent. So I contacted the guy I bought the cam from, instead of it being the Crane Cam he had thought, he is now saying he made a mistake that it is a 350 hp cam for corvette. It was new never used, i used the lube that was in the box installed it ran it at 2500 rpm for half hour to break in the cam. so it wouldnt grind out. So now im torn, I read in most corvettes back in the day ran solid lifters ( hense my reason for adjusting the back to 0 lash ). So then I tore the intake off pulled a lifter out took apart to check to see whether I have solid lifters or hydraulic, since this guy changed cam story, it has spring piston inside. So do I have a solid lift cam operating with hyd lifters ? Im still having vacuum issues at low rpm and high rpm misfire and wont idle way down like it should and carb loads up will die under 1100 rpm. Adjustments on the carb have no effect what so ever. I been through the timing over and over. Took compression test and all cylinders are right at 165-175. To the point im just going to pull the engine tear it apart and redo it with all new with parts that I know for fact are right. Dont have the cash to do it though.
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Old 09-18-2011, 09:08 AM
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Tight valves can cause hard starting and inconsistent vacuum. You really need to know what the cam is. Guessing will just get you into trouble. Once you have the specs for the cam you can start tuning from there. As stated above you just may need more initial timing or a multitude of other things.
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Old 09-18-2011, 11:35 AM
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Quote:
Originally Posted by Shfty937
Hello, thx for the forum. Recently I bought a 73 010 4 bolt 350 and set of 625 vette 2.02 1.60 heads polished ports. Stripped it down. Replaced bearings, oil pump, cam ( Crane Cams Blueprinted 350 hp 967251) lifters and double roller timing chain. engine had been rebuilt before. Pistons were letter stamped. No ledge and could still see cross hatches from honing. So I didnt go as far as replacing the rings. Old engine already had new Edeldrock performer intake and 1406 carb and headers. Mallory Ignition, Comp 9000 Unilite distributor, Promaster coil and ballast resister. Installed it in a 1987 GTA Trans Am.

OK, so have to hold throttle wide open and crank for 30 seconds or so before it will start. Doesnt change hot or cold. Once started it revs nice, but refuses to idle and very rough at low rpm. Has NKG race plugs gapped at 45 Mallory sidewinder wires. Plugs are black soaked with gas. Everything ran fine on the other engine. Parts were stored in clean safe place and didnt set but 2 weeks.
If it is a Crane Cams Blueprinted 350 hp 967251 cam, it uses flat tappet (solid) lifters. You should readjust them to the recommended valve lash that came with the cam/lifters, usually around .022

Last edited by S10 Racer; 09-18-2011 at 11:50 AM.
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