350 does not want to idle correctly

[zap387]

Just got a new to me 78 camper special with a 350. It does not want to idle correctly it idles rough and shakes a little bit and sometimes stalls out. Someone poorly wired in an electric fuel pump and its pushing about 3.2 PSI for fuel. It does well revving but it wont idle well, it has a new Edelbrock 1406 600 carb. It has a single plane weiand 7546 intake and all new vac lines. I checked the vacuum and it bounces rapidly between 16 and 19 inches of mercury. According to all my research it looks like i might have worn valve guides, but i am not sure. I have some experience with LS stuff but this 70s small block is far off from what i usually work on. Any advice would be appreciated.

[Richard2112]

Bad valve guides will tend to make the engine use/burn oil. One way to check that is look for blue smoke at the exhaust, and your oil will smell like gasoline, although that isn't conclusive. Pull the plugs and look for heavy/oily deposits. A compression test is helpful also. If the guide is leaking oil into the cylinder, it can cause a higher than normal reading.

Also, check the cheaper/easier stuff first, timing plug wires, dist cap/rotor...

[Bandit130]

[zap387]

Thanks for the help and the welcome, I forgot to mention it does have a new cap and rotor, new plugs, new wires, and it doesn't smoke or anything, but I also went out and checked the oil and it smells like gas for sure. The speedo cable doesnt work either so i dont even know for sure how many miles are on this truck. Looks like i could get the heads done, but probably going to do a motor swap on her now maybe a ls engine or a 454.

[geezer#99]

How did you check the fuel pressure?

[Richard2112]

Oil that smells like gas could also be a carb problem. If the needle doesn't seal in the seat the float will over run causing flooding when idling. Gas will also run into the manifold after the engine is shut off, and down into the cylinders. As it sits there, it can seep past the rings into the oil. I suspect the carb.

[zap387]

geezer99 ...i have a vac gauge that will also do low fuel pressure as well, i just took the fuel line off the carb and used a hose clap and clamped it to the vac/fuel pressure gauge and turned the electric fuel pump on and i got 3.2 psi.

Richard 2112 I also think it could of been the old carb being an issue right before i got it the previous owner changed the carb to this new edelbrock one. I am still fighting to see why the manifold vac pressure keeps changing so rapidly. Next i am going to be rewiring the fuel pump correctly with a relay and a oil pressure switch and then i am going to do the same for the electric choke the wiring is terrible.

[geezer#99]

Did you adjust the mix screws?
Have you checked the timing?
Have you looked in the carb while it’s surging?

What air cleaner?

[zap387]

I have not touched the idle or the mix screws yet on the carb.
I have not checked the timing yet. I still need to get a timing light and find the mark on the balancer and see if i can see where the base timing is.
I have not yet looked into the carb while its idling yet i will do this tomorrow.
The air cleaner is a edelbrock PRO-FLO its 10 inches in diameter and its maybe 2 inches tall with a new paper filter. Thank you for all the help geezer and everyone else. i will continue to work on these issue and try and get it worked out all i want to do is drive it.

[geezer#99]

I mention air cleaner because sometimes if the lid is too close to the vent on the top of the carb, it will surge like that.
You might need to test without it for a short period.

[Dead Parrot]

New Eddy carbs are bad for poorly adjusted float levels out of the box. Possible the PO adjusted(if it can be adjusted) the electric pump trying to compensate for a too high fuel level in the carb.
Stock cam or was that replaced with the new intake?
If the electric pump winds up being weak, might consider going back to the mechanical pump.

You should be able to download the manual for the carb from the Edelbrock site.

Stock 350s like a lot of timing advance. If the PO adjusted to what the EPA sticker shows, probably not enough. Somewhere around 12~16 initial seems to be what most of us wind up with. Start with less and work up in case your timing mark doesn't exactly match your true TDC.

[Richard2112]

It's been said that 90% of carb issues are timing problems. You may have a bit of each. Either way, they're not a deal breaker. A little patience with the right tools and procedure will go far.

Geezer is right about that air cleaner also. I run the same style air cleaner on my Rochester (10 inch diameter/2 inch filter) and though it idles and runs well, I can feel it choking the carb at cruise.

[truckin 79]

I would ask more questions of previous owner like why a single plane manifold. Is your 350 really a 383 stroker and is that why there is a single plane manifold. Most stock or street engines idle/run better with a dual plane manifold. Also if oil smells like gas adjust the floats on carb probably to high

[zap387]

I did download the carb manual and I will look at the carb float levels, The fuel pump doesn't even have a fuel regulator on it so you cant adjust the flow or anything, but at 3.2 psi its so low i don't think i need a fuel regulator. I am debating going back to stock fuel pump. Its got stock heads on it and stock rockers and springs etc in the head. It doesn't sound like it has an after market cam either but who knows whats in it. Its not a 383 as far as i know its gutless and slow. I do agree that the single plane does not make sense at all for this motor so i don't know why its on there either. i am guessing it will work for now just want it to run and drive so i can use it to make dump runs and stuff. I still need to get all the gauges working as well so far the volt meter works and the gas gauge and thats it.

[geezer#99]

I know you measured it but 3.2 psi doesn’t seem right.
Look in the carb. If you see fuel at all then it’s a float or too much pressure.
Careful buying a new pump. Spend a little extra for one rated near 5 psi or a cheaper one and a regulator. Eddy carbs don’t like more than 5 psi.

[zap387]

I will look into the float and the carb. I was thinking the same thing with the fuel pump it seemed that 3.2 was pretty weak as well but at higher RPMS it doesn't seem to have any trouble running there so its not running out of fuel. But can wire so i am going to make some relays and have them go live when the ignition is in the on position and then i am going to get a better pump and then run a pressure regulator with a return line to the tank on it.

[nonstop]

Sounds like the carb as well! Do yourself a favor and find a good used dual plane intake first even if it is stock. The single plane is not helping you at all. Throw that on and adjust the carb to that. I say that because the distributor needs to be pulled to replace the intake, and idle and the mixture settings will be different between the two. The other thing with the single plane is that the ports might not be lining up correctly, which could cause problems/leaks.

[kwmech]

What else is known about the engine other than it is a 1978? Mileage? Compression? valve adj? what do the spark plugs look like?

[zap387]

non stop you are right about the single plane should be using a dual plane for sure on this stock engine.

kwmech I haven't really got into tearing into the engine yet, The odometer says 87,000 miles but the speedo cable snapped so i know that's not right, I have not done a compression test yet on the cylinders, valves have not been touched yet, i did pull the covers and made sure there weren't any broken springs, I pulled the plugs to check them but they are brand new, so are the wires, cap, rotor PO did all that right before i got it apparently.