Current status plug #4

Current status plug #4

 

Glad to see you are enjoying your vehicle.
Were these new plugs after the heads were done?
They look like they are burning OK but not sure of the black deposits on the metal shell. A hotter plug may help.

What is the quality of the gas you have available in your country?
I would put a few cans of dry gas into the tank to see if it helps with the twitch.

Could be carb related. Possibly the fuel is not atomizing well or the when the carb transfers from the idle circuit to the primary jets there is a problem because of the idle mixture screws are not set properly. As discussed previously there is something wrong with the idle mixture system if you turn the idle mixture screws in all the way the car still runs.

Have you tried opening the idle screws up to where the idles speed is at the maximum? If not, I would. Then turn the throttle plate idle screw if needed to set the proper RPM.

Your other comment on finding debris in the bowl coming from the fuels lines could also be contributing to this. I would have expected the filters you showed in the previous post would have prevented this. Make sure you have a least one filter at the carb as you previously did.

 

Yeah, I drive it every chance I get 😉.

The plugs are “old”, as in they were put in in April and ran with the bad valves… spark plugs are expensive here, but I will replace them if that would solve my issue.

I will try to adjust the mixture screws later today and see what happens. Ultimately I will replace the carb, thinking of a fuel injection system…

I will update with results later

 

We have ok-quality gas here, 95 and 98 RON Octane, equivalent to 91 and 93 octane at the pump in the US. I have been using 95, but after reading a bit more about it, I think it’s better to run 98… expensive though, $8/gal…

also, fuel filters, I have one before and two after the fuel pump. I haven’t had any problems since I added them. I looked at them today, and it’s probably about time to replace the first one…

 

You are looking at big money for EFI. This will improve the drive ability hot and cold and may improve mileage.

Unless you are having problems with pre-ignition or the lower octane is less quality, I doubt higher octane will help. Increasing the timing may help assuming it does not cause pre-ignition. If increased timing runs better but causes pre-ignition, then you may consider higher octane.

If increasing the timing runs better but causes hard cranking issues, then turn the timing back and consider changing the advance springs in the distributor to provide more advance above idle. Spring kits are cheap in the states. Plot the advance curve (RPM vs degrees) with the old springs then install the new ones and do the same. The total advance should not change but the rate at which the degrees increase should with a weaker spring.

Adding a lead substitute may help prolong the valve life unless the seats were replaced with hardened seats at some time.

https://www.autozone.com/diy/fuel-sy...ead-substitute

 

Yeah, the money will be fine, eventually… not in any hurry .

the 98 octane fuel has less added biofuel in it, about 3% compared to 10% in the lower octane fuel, so I think it might make a difference…

I have adjusted the mixture screws, opened them up a full turn, and it seems to be better. Next is new fuel, so we’ll see what that does .

 

Well, about 1 1/2 year after last time I had trouble, trouble is back... The engine is either eating valves, or I have piston rings going bad... plus all the twitchy scetchy driving characteristics are back... Oh well, I guess I'm checking everything again.

Compression (cold enginge) is waaaay down again:

Right bank no oil/with oil
1- 83/90 psi
2- 70/75 psi
3- 70/77 psi
4- 70/75 psi

Left bank
5- 95/105 psi
6- 120/130 psi
7- 95/100 psi
8- 90/110 psi

 

Welcome back! Here is some questions to help better us understand your issue and a few items to look at-

Did you check the compression after you did the work previously and was it OK then?

How many miles on the spark plugs?

There is a lot of oil on the plug threads but most plugs look like they are burning clean. Plug 4 looks like it is oiled fouled while plug 3 looks like it has raw fuel on it. Make sure the oil drain port in the rear of the head is not clogged.

Do you have external oil leaks which are causing the wires to arc out?

I would also check the distributor cap for cracks. Is your ignition coil good?

How about the points? A bad capacitor can cause the engine to run poorly. Cheap to change but there are a lot of defective new ones. This is why I converted the system to electronic ignition.



Issues which could cause burnt valves-

Is the cooling system connected properly including thermostats, heater hoses etc? The fact one head has higher compression could be an indication of poor coolant flow through the engine.

Does the engine reach operating temperature as it should and not overheat?

Do you have a reliable temperature indicator on the engine?

Running unleaded fuel with heads designed for leaded fuel can damage the valves but I would expect this to take time. I suggest you to put in a lead additive if you are using unleaded gas.

When the valve job was done, did they properly grind the valves and seats or just lap them?

 

I did another test with warm engine. A bit better…

Right bank warm

1- 95 psi

2- 100 psi

3- 85 psi

4- 90 psi



Left bank

5- 115 psi

6- 130 psi

7- 100 psi

8- 105 psi

I have flushed the whole cooling system, and both thermostat and waterpump are new. I only have gauge on the dash to go by, but I have never had any indication that it was running warm.

will check the oil return tomorrow!

The ignition parts all look undamaged. I can’t check the capacitor, suppose I can replace it and see.

I re-gapped the plugs too… they had opened up to twice the gap for some reason.

 

I would replace plugs 3 and 4. 4 is fouled and 3 could have a cracked porcelain keeping it from firing.

I would install an aftermarket gauge set since what you have may not be accurate due to age which can result in serious engine damage. Temperature and oil pressure.

Was the throttle open when you ran the compression check? It should be.

Do not block of the heater hoses if you are not using the heater since it can alter the cooling flow through the engine.
Some of the new thermostats have a safety feature built in- you overheat the engine and they lock open, then need to be replaced.

I would also check the centrifugal advance in the distributor to verify it is free (rotate the rotor by hand and verify it springs back) and verify the vacuum advance is working.
While you are in there check for excessive side play in the upper bearing which can cause erratic opening of the points.

 

Ok, I am getting a couple of new plugs to replace those two you mentioned.

I have an aftermarket "multi-gauge" that shows water- and oil temp, oil pressure and battery charge. It's currently in a car I'm not using, so I will go ahead and move it over to the pickup.

Yes, the throttle was wide open, I think I have some worn out rings. Might also be that the lapping of the valves was insufficient, so that might have to be redone...

No water hoses are blocked off. I use the heat even in the summer, Sweden can get chilly on summer nights. I checked the function of the thermostat recently, and it seems to open just fine.

The distributor works as far as I can tell, both mechanical and vacuum, and the side to side movement of the axle in there isn't very much at all.


I was messing about with it the other day, replacing my water pump. It was starting to sound pretty bad, very loud and rattl-y. After that I had the engine running up to temperature, and as I was sitting there, I was trying different scenarios. I tried pressing the gas pedal down slowly. At first it would start to rev up. At about 1/4 throttle it started to sputter, almost die - this I notice sometimes when driving also. If I just held it steady at that point it sputtered on, but didn't clear up until I went past that point. The carb is 50 years old, and although renovated, it's still old... I ordered a new aftermarket one :-)

 

I looked at spark plug pictures prior to your previous overhaul and #4 also shows sign of oil residue but it is not that bad. You maybe passing some oil past the rings but it is not bad enough to consider a ring job.

If you are not using a PCV valve, adding one may increase the vacuum below the piston and reduce the flow of oil past the rings. When we rebuilt my son's 390 we had a slight amount of smoke at idle. When we reinstalled the PVC system, it went away.

Were your valves properly ground then lapped or were they just lapped when you did the overhaul? If just lapped, you may not be able to achieve the full compression you would achieve doing a multi angle grind first.

You are likely zeroing into the problem as being a fuel issue caused by the carburetor.

The ports which feed the small slots (about 0.5mm wide by 2mm long) in the throttle body bore just above the throttle plate which allow additional fuel between the idle and power stages may be partially clogged.

If you look down the bore while idling and see fuel dripping out of the venturi, you may have a problem with fuel passing past the vacuum operated power valve (if you have a conventional Ford carburetor). This can cause an over rich idle and stumble as you come off idle.

I successfully rebuilt an old carburetor (69 Mustang 390 4 barrel) after failing the first time. To do it correct I had to use piano wire and clean out both air and fuel passages. Using carburetor cleaner does not work when corrosion is present. Just because you see some cleaner coming through does not mean it is cleaned enough for the proper amount of air or fuel flow.

Good luck with your new carburetor!

 

I have a PCV valve in the passenger side valve cover, with a hose connected to a plate underneath the carburetor. On the other valve cover there is a vented cap, but no hose to the air cleaner..

 

This will work good.

 

the gasket underneath the carburetor is soaked… that doesn’t seem right?!