Running rough. Any Ideas?

[OrangeAnimal]

I have a strange problem. I decided to spend some more time looking into why I can only get 12mpg. I have check my timing and a few other things. Here is what I found.

At 1500rpm the engine starts running rough random missing. It's hard to tell but it seems to smooth out alittle as the rpms increase. It's the worst right around 1550-1600 rpm. I tried changing the timing to see if that made a difference it did not. I am running a brand new Edelbrock 1406 on the engine. All the ignition parts are new as well. I am thinking it's the carb cause it is so precise as to where the engine runs rough. I don't have a pressure regulator on the carb. I guess it could be over powering the needle and trying to flood but it doesn't smoke or smell really rich. My dad said something scary it had to do with the camshaft but I really don't think that it the issue either. The whole program only has about 600 miles on it and I broke the cam in at 1600-2200 rpms for thirty minutes. Any suggestions on the metering rod and jet settings? Any help is appreciated. Thanks.

[70k52wd]

I'm in the process of trying to figure out a rough idle problem myself. In doing so, I just recently spoke to a speed shop "carb guy". I asked him about the carb you are using, the 1406. He said they work real well for a stock cam motor. Any cam other than stock, they don't run right. They were not designed for anything larger than a stock cam. Holley is your best choice for cams running 260 and up. Hope this helps.

[OrangeAnimal]

Well the cam isn't that big. It's a RV cam so I doubt it's that huge a deal. I think I am going to play with it some more I am almost 100% sure I am getting to much fuel. I checked the pressure and I don't get more than 2psi. So it's not flooding and the bowls aren't running empty either. I pinched the fuel line while it was up at the rpm and I did not notice a change. It has to be in the metering system of the carb. I hadn't had this problem until the temp outside started going up. So I figure this will be a fight to the finish to get it just right.

[Pyrotechnic]

My experience is that Edelbrocks will surge or have a dead spot at around 1500 RPM if they are lean. I don't understand exactly why it's around this RPM, but I've seen this more than one time. If you don't already have it, get the tuning kit. One quick test to see if it's lean is to throw a really skinny rod in there. The problem will go away if it was lean.

[OrangeAnimal]

I changed the rods and it helped alittle. I don't know I may have something else going on. The engine is also leaking at the rear main now. So I guess I will be looking into that. There is no blow by. I also can't get the engine to run cool in traffic. I am probably going to have to try to get a better radiator. I just put a new electric fan on it and it sucks air like no tomorrow but I still have the issue. It's a single 16" fan maybe it's just not enough.

[OrangeAnimal]

Well I made a booboo with the timing and I think it's better now as far as power output. Still has alittle rough idle though. I am going to try and put together the set of MSD wires I have today. I got all ticked off last time I went to put them together. The timing without the vacuum advance hooked up was retarded about 3 degrees. That was no good for sure. So I hooked everything back up with the initial timing set at 4 degrees. With the vacuum to it I get about 15 degrees. It runs decent. Produces good engine vacuum. I really don't have any other ideas.

[Adams74Chevy]

Originally Posted by OrangeAnimal

...I also can't get the engine to run cool in traffic. I am probably going to have to try to get a better radiator. I just put a new electric fan on it and it sucks air like no tomorrow but I still have the issue. It's a single 16" fan maybe it's just not enough.

Do you have a transmission cooler? Mine bearly gets off the cold mark with it but would get close to hot without when hauling.

[Rons86]

I had sort of the same probelm with my truck after changing distributor parts. I have the same carb also. I found out is was the distributor itself. I replaced all the internals, but finally replaced the distributor and it ran great. Just something to think about if you haven't replaced it yet.

[Pyrotechnic]

Retarded timing will cause hot running and poor gas mileage. This was probably a huge part of your problem. Depending on what particular cam you have, I have a feeling you will need more timing. 34 total is a good figure.

Be careful when setting total timing with an HEI. They act like they top out at around 3000 RPM but sometimes they creep in an extra 3-4 degree at around 4000 or more RPM depending on what the application was. If you have a mechanical fan I would advise removing it for this procedure.

[OrangeAnimal]

I installed a new radiator. Still running hot. It still runs rough. I played around with the timing and it just seems to be worse now than before. I can't seem to get it right. The only other thing I can think of is the MSD Street Fire Ignition box. I seriously think Something is wrong somewhere but can't put my finger on it. I have the initial timing (no advance hooked up) at 4* then when you hook up the advance it jumps way up. Around 16 degrees. I think I may have a issue with that somewhere along the line. I am thinking of getting a blueprinted distributor or a programmable one. I didn't really think that I should need all of that to make a basically stock engine run. It runs really well when you step on it but not very good at any other time and rough at idle.

[OrangeAnimal]

Holy crap I am feeling pretty stupid now. I re did the timing and then for &*^$ and Giggles I checked the idle mixture screws. Well needless to say there was a issue. It runs much better. I set the timing at 12* and left the vacuum advance unhooked. I am getting only about 20* without it though. So I hooked it to the ported vacuum and it worked right but gave too much advance. It was over 40* So I am going to have to get a real adjustable vacuum advance to make that work right.

Although that is much much better I still have the running hot at idle. I am running around 215 and it's still climbing that's with no A/C on and I am still waiting on parts from those jackasses. So I am going to try a dual fan setup. I figure 2 12" fans should get the job done.

[OrangeAnimal]

Well I am still having some issues but it is much better now. I am going to change the rods in the carb back out cause I had previously made the mix richer. Now I have to get the advance working better too. I can not hook it up or around 1600 rpm it runs very very bad. It runs really good without it but the fuel consumption is now worse than before. I need to get the advance dialed in.

[Desert1957]

Hey,

Just thought I would ask you again from a previous posting you had. Do you have or can you get the cam card for the Camshaft that's in your motor. this would tell you alot. It would also help us figure out what is going on with your engine.

As far as the overheating problem , you did mention that the engine only has 600 miles could still be tight. Many other things can cause an engine to run hot , vacum leak (causing a lean condition) , Ignition timing mis-adjusted , RV Camshaft , more radical then you think it is , slight miss-fire under load , and the list goes on an on.

One thing to note about overheating , if the temp creeps up in traffic but goes back down at speed this could be , air in the cooling system , temp gauge calibration off, bad fan clutch (if equiped) , no fan shroud installed.

If it goes hot and will not come back down , chances are the radiator is just not up to the job , I know you said you replaced it , Iv'e even seen electric fans mounted on the inside of the radiator , wired wrong pushing air back through the radiator so at speed there was no air flow.

Do not overlook the obvious.

Even removing the Thermostat can make it run even Hotter , because the coolant flows so fast it does not stay in the radiator long enough to disapate its heat.

Also do you know the difference between ported Distributor Vacum and Manifold Vacum? It makes a Huge difference in Performance and Gas mileage the way its hooked up.

Desert

[Desert1957]

PS: Here is a good timing article to read for all....

http://www.netwelding.com/ignition_timing.htm

Desert

[OrangeAnimal]

Desert, I know what the issue is with the temp. I have too small of an electric fan on there.

I cannot use the manifold vacuum for the advance. It simply gives way too much advance. I have found to get the appropriate throttle response off idle it cannot be set more than it is now and I could probably back off a couple degrees and get even better response from the engine. As it is right now I can gun it from a dead stop and leave a 30 foot mark down the road. This is the best the response has been since I installed the engine. This is close to the way I set things from the start. When I put it all together I used 8* initial and no vacuum advance.