New motor/1050 dominator won't idle

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RockinRobin

RockinRobin

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Started my 5.7 hemi based 414 stroker for the 1st time today in 45 degree weather. The 1050 Dominator from Pro Systems carbs did eventually startup, but the motor won't idle. Have to run the idle screw all the way in to get the motor to run at 3000rpm. If I back out the idle screw even a little bit it dies. I'm thinking I need to try opening up the idle mixture screws since the temp is 45 degrees. There is NO vacuum port anywhere on the carb or the intake, so I guess I'll have to go by ear/rpm.
Any other suggestions? Does it seem like I'm on the right track?
 
Not knowing the particulars of your combo, I have to say your dead lean for some reason. The possibility of a big vacuum leak would be the obvious first thought? Must be a pretty serious combo for the need to use that carb.
 
OldmanRick said:
Not knowing the particulars of your combo, I have to say your dead lean for some reason. The possibility of a big vacuum leak would be the obvious first thought? Must be a pretty serious combo for the need to use that carb.
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Only place I can think of would be at the carb base. Would adding a 2nd gasket help??
 
I have a hard time believing a base gasket would cause that big of a issue. My first thinking could be wrong. Does it seem like it's lacking fuel when it dies, or is it loading up? Possibly too much fuel.....Meaning floats too high or too much fuel pressure? I assume you're using a pretty decent sized electric pump.


P.S. Robin, I have to say that my thinking is in general terms. I've never worked on a late model conversion, and don't really know about the ignition requirements involved, if the problem could stem from that.
 
OldmanRick said:
I have a hard time believing a base gasket would cause that big of a issue. My first thinking could be wrong. Does it seem like it's lacking fuel when it dies, or is it loading up? Possibly too much fuel.....Meaning floats too high or too much fuel pressure? I assume you're using a pretty decent sized electric pump.


P.S. Robin, I have to say that my thinking is in general terms. I've never worked on a late model conversion, and don't really know about the ignition requirements involved, if the problem could stem from that.
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Carb has glass bowl plugs, they do seem a little high, esp. the back one, but since the cold weather I thought maybe it needed a little more. I really think it's fuel, the ignition is MSD 6-Hemi, pretty straight forward.
 
If you run the idle screw all the way in you will completely expose the transfer slots and start pulling fuel from the main circuit. No more than .020" of the transfer slot should be exposed. As stated earlier, check for vacuum leaks, float levels, fuel pressure and if you have adjustable air bleeds, make sure the restrictions are appropriate to rule out any problems in those areas. If you're running a 45 power valve you've probably got a pretty snotty cam I would imagine! Lol! Personally, I would plug the power valves and up-jet accordingly. Depending on your idle vacuum, the power valves could be dumping extra fuel into the mix as well. The next step would be to crack open the secondary throttle plates. The adjustment should be on the underside of the carb (it is on a 4150 anyway). Again, don't expose any more than .020 of the secondary transfer slots. Once all that is done and you still can't get a decent idle you can drill holes in the primary throttle blades. Obviously, you want to make sure your idle screw and throttle plate adjustments are correct then start small and work your way up in drill size until you achieve acceptable idle quality. Be careful not to go too far all at once because once the holes are drilled you can't go back. Not easily anyway!
 
Update: next day-noticed back bowl was filling too much. Adjusted.
Adjusted fuel pressure to 10 PSI (it was much lower)
Idle mixture screws backed out to 2 turns each.
Now starts clean and will idle at 2000RPM, but any attempt to turn mixture screws in results in engine slowly dying.
Idle RPM screw is all the way out, RPM will go up if I tighten it but won't come down.
Vacuum leak??
 
RockinRobin said:
Update: next day-noticed back bowl was filling too much. Adjusted.
Adjusted fuel pressure to 10 PSI (it was much lower)
Idle mixture screws backed out to 2 turns each.
Now starts clean and will idle at 2000RPM, but any attempt to turn mixture screws in results in engine slowly dying.
Idle RPM screw is all the way out, RPM will go up if I tighten it but won't come down.
Vacuum leak??
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try to turn them out to richen it up 1/8 turn at a time.
 
I run mine at 8psi. And am going to set it lower about 7.i can drive it with one foot all day.
 
Fast01 said:
I kinda think you're pushing past the needle and seats as well.
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Me too. Needle and seats vary on what they can handle. Some will take as much as 9 but generally you shouldn't go over 7-1/2 psi at the most or you risk blowing the needles off the seats.

RockinRobin, why so little timing? By the sounds of the low rate power valve requirements and huge carb your in the territory of generally having to run A LOT more timing than 6 degrees initial, and 24 total sounds pretty low unless your running a healthy shot of NOS. If you could post your engine specs it sure would help give us more of an idea what your even working with. I don't know new Hemi's so maybe I'm off base here but IMO the engine would have to be extremely efficient to only require that little timing advance
 
UPDATE 12/16/13:
The motor now idles at about 1000 in neutral, 800 in gear.
It wasn't a vacuum leak.
It wasn't fuel pressure.
It was......operator error :-o
A quick call to the carb. builder Monday morning to let me know that their are separate idle screws for the primaries AND the secondaries. I thought the one on the secondary side was just to operate the accelerator pump. Live and learn. Also, this carb likes the mixture screws out a little further, 2 to 3 turns to start rather than the standard 1 1/2.
 
Glad you got it sorted out....Reading your original post I was going to reply "call the guy who built the carb" and go from there.
 
mshred said:
Glad you got it sorted out....Reading your original post I was going to reply "call the guy who built the carb" and go from there.
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Yep, it's still rough, but I'm being told that dominators don't idle too well anyway. I'll keep tinkering with it and see if I can smooth it out a little more.
 
fishy68 said:
Me too. Needle and seats vary on what they can handle. Some will take as much as 9 but generally you shouldn't go over 7-1/2 psi at the most or you risk blowing the needles off the seats.

RockinRobin, why so little timing? By the sounds of the low rate power valve requirements and huge carb your in the territory of generally having to run A LOT more timing than 6 degrees initial, and 24 total sounds pretty low unless your running a healthy shot of NOS. If you could post your engine specs it sure would help give us more of an idea what your even working with. I don't know new Hemi's so maybe I'm off base here but IMO the engine would have to be extremely efficient to only require that little timing advance
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Here you go:
Gen III Hemi (5.7 based) stroked out to 414
Eagle heads that have been ported, etc.
12.5:1 Manley pistons
dual plug coil packs, Brisk plugs gapped @ .042"
Drag pak intake manifold
1050 Dominator carb
Comp cam (don't have the specs handy)
MSD 6-Hemi ignition control (no MAP sensor, just runs the timing), stock timing curve: 0-2000 RPM is 10 degrees, then it ramps up to 24 degrees @ 3000 RPM, then level up to 5000RPM, then tapers back to 20 degrees the rest of the way up.
Everything I've read so far says the gen 3 Hemis don't take much timing advance.
 
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