Rebuilt 350 not running under 1500 rpm

[aruss99]

Hi all,

I recently rebuilt my 350 in my 1971 C-10, it has a mild cam in it as well as and Edelbrock Performer intake and Edelbrock 1406 carburetor. The problem I am facing is I cannot get the motor to idle under 1500 rpm. I have adjusted the idle screw so that the truck will still run without my foot on the gas. I then tried to lower the rpm that way but once the rpm got below 1300 rpm, the motor would start to die. I then tried adjusting the idle mixture screws at 1-1/2 turns out and tried adjusting the idle that way but no matter which way I turned the screws, no audible difference happened as well as no rpm change. I have not tried turning the screws super far out because I do not know much about carbuertors and didn't want to mess anything up anymore than it is. If anybody could shed a little light on what to do in order to get it to idle lower that would be great

Thanks

[geezer#99]

Could be flooding.
Look in the carb. Any raw fuel says it's flooding.
Eddy carbs don't like more than 5 psi fuel pressure.
You might need a fuel regulator.

[DillonGMC]

Torn carb gasket sounds like. Just dropped my brothers new engine in his camaro a couple weeks ago. Did the same thing. It had a washer on one of the studs under the gasket. I recomend one of the thick gaskets with the lead bushings in them. Also, if you are running an electric choke make sure it is hooked up. I've ran into that before. It sounds like Its drawing air from somewhere, you can spray ether around your carb base, intake gaskets, and any vacuum lines to find the leak.

[RodnRudy]

Sure sounds like a vacuum leak to me. Check for missing vacuum plugs on carb and intake manifold.

[aruss99]

Thanks for all the advice. I will check for vacuum leaks as soon as I can and let you guys know what I find.

Thanks again for the help

[aruss99]

Hi all,

I was unable to find any vacuum leaks on the motor. I checked all the vacuum plugs as well as sprayed starter fluid around the carberatour to no avail. I am stumped on what I should check next.

geezer#99 said that my fuel pressure may be too high. Could the different cam have changed that? I don't know if that is a stupid question but I figured it is better to ask than just assume. Any explanation would be appreciated

As usual, thanks for all the advice.

[geezer#99]

Originally Posted by aruss99

Hi all,

I was unable to find any vacuum leaks on the motor. I checked all the vacuum plugs as well as sprayed starter fluid around the carberatour to no avail. I am stumped on what I should check next.

geezer#99 said that my fuel pressure may be too high. Could the different cam have changed that? I don't know if that is a stupid question but I figured it is better to ask than just assume. Any explanation would be appreciated

As usual, thanks for all the advice.

Eddy carbs are known to be fuel pressure sensitive. THey don't tolerate more than 5 psi. Higher pressures keep the needles off the seat and it floods.
Simple way to check is look in the carb.
Should be no raw fuel visible while idling.
Your mild cam plus other mods also need more timing.

[RatPwrd72]

Need to check the timing when it's at a point it'll run as well as look for vacuum leaks.

[aruss99]

Originally Posted by geezer#99

Eddy carbs are known to be fuel pressure sensitive. THey don't tolerate more than 5 psi. Higher pressures keep the needles off the seat and it floods.
Simple way to check is look in the carb.
Should be no raw fuel visible while idling.
Your mild cam plus other mods also need more timing.

Thanks for the help, I went out to check the fuel and whenever it started to run it started shooting fire out of the carb which leads me to believe that it is indeed getting too much fuel. Is that a correct assumption or am I wrong?

[geezer#99]

Originally Posted by aruss99

Thanks for the help, I went out to check the fuel and whenever it started to run it started shooting fire out of the carb which leads me to believe that it is indeed getting too much fuel. Is that a correct assumption or am I wrong?

THat means your timing is retarded!
Forget the fuel right now.
Loosen the dizzy and rotate it ccw about 1/2 inch. Then try it running. If it gets better keep advancing it. When it will idle and not backfire, lock the dizzy down and check for fuel, adjust the idle down and adjust the mix screws.

[GASoline71]

Then get a timing light and adjust the timing properly.

Gary

[DillonGMC]

X2 on a timing light.

[aruss99]

Okay thanks for the advice. I will get to it as soon as possible and let everyone know what I find.

Thanks for the help

[aruss99]

Originally Posted by geezer#99

THat means your timing is retarded!
Forget the fuel right now.
Loosen the dizzy and rotate it ccw about 1/2 inch. Then try it running. If it gets better keep advancing it. When it will idle and not backfire, lock the dizzy down and check for fuel, adjust the idle down and adjust the mix screws.

Thank you for your help. I was able to advance the timing enough to get it to idle under 1k rpm, so problem solved. I appreciate your insight as I'm only 15 and have not had the opportunity to learn these kinds of things yet, but you learn something new everyday.

Again, thanks for the help

[geezer#99]

Not solved yet!
You need to get the idle below 800rpm. The mechanical timing in the dizzy kicks in at 850 ish.
You're likely still not idling on initial timing yet.

[aruss99]

Originally Posted by geezer#99

Not solved yet!
You need to get the idle below 800rpm. The mechanical timing in the dizzy kicks in at 850 ish.
You're likely still not idling on initial timing yet.

Okay, I'm sure I can get her there. I stopped lowering the idle around 900 rpm because I had to manually keep the dizzy from moving as it wasn't tight. Ill lower it to around 700 rpm since that was what the motor ran at before the rebuild.

[geezer#99]

You're doing good for a 15 year old!!
When I was your age I was helping the hotrodder next door put a new timing chain on his 427 Ford S.O.H.C.!!
Now that's a timing nightmare!! LOL!!
If you don't know what that is, google 'Single Over Head Cam for a 427 Ford.

[aruss99]

Originally Posted by geezer#99

You're doing good for a 15 year old!!
When I was your age I was helping the hotrodder next door put a new timing chain on his 427 Ford S.O.H.C.!!
Now that's a timing nightmare!! LOL!!
If you don't know what that is, google 'Single Over Head Cam for a 427 Ford.

Thank you, and will do

[snipescastle2]

might have been said already, but did you check the intake manifold for leaks? I'd try to retorque the intake just to make sure, maybe spray some carb cleaner there too.....
HTH,
Ben

[MagmaJct]

Originally Posted by aruss99

Thanks for the help, I went out to check the fuel and whenever it started to run it started shooting fire out of the carb which leads me to believe that it is indeed getting too much fuel. Is that a correct assumption or am I wrong?

I am reminded of the animated fire in that in the Lego movie.

I can say that in the 20 years I've been working on my own carbureted vehicles, I have NEVER had a fire of any kind. With that being said, as others have mentioned, apparently the timing can cause this. Although, I'd find it hard to believe the engine could even run with it that far out.

My advice to you, coming from someone who was once 15... Take some automotive classes in high school. I took it for two years. Then, take a college course or two. I took one semester.

I hope they at least teach carburetor theory still. Fuel injection makes so much more sense if the carburetor theory is taught well, including the limitations of carburetor metered engines.

Regards,
Mike