'84 oil fouling on all 8 spark plugs

[Lube]

Hey all,

Last year I bought my first mustang, my first domestic car, and my first V8.
The car
I bought this '84 convertible from the PO who had most of his work done by "a friend with a shop" so I have no idea of the qualifications of that party.
PO claims he's put about 15k miles on the engine before sale. Yes, I do assume those were all very hard miles.
It is equipped with BP Engines 306 crate (https://blueprintengines.com/product...block-bp3060ct)
Mechanical fuel pump (unknown pressure)
Had a very rough looking eddy 750 carb on it which seemed like it was too big and also needed a rebuild.
The PO had the wrong type of spark plugs installed, as the threads were too short (.460" i believe, whereas the aluminum heads need a .750") PO also had a baggy in the trunk with what i assume were the previous plugs which were also the same wrong size.
PO also never hooked up the electric choke on that big 750 carb so he would crank the thing for 30 seconds until it started.

All of this above combined for me to bring the car home and find that the breather caps smelled like gas. I knew the oil level was high, but my inexperience didn't raise a flag.
I drained the oil which also reeked of gas, changed filter. Cut open the filter and didn't see any glitter.
I pulled the spark plugs, discovered that they were fouled with oil, and then also found that they were the wrong size.

My theory was that with all of the PO cranking with no choke, the carb being too large, or the carb being in poor condition led to fuel leaking down the cylinder walls into the crankcase. This leaned out the oil and raised the level, and the lean oil was making it's way into the combustion chamber.

Now, I have replaced the carb with an eddy 1905 (https://www.edelbrock.com/avs2-650-c...-egr-1905.html)
Replaced the plugs with proper size and heat range.
Fed it some pennzoil platinum 5w/30 synthetic and new motorcraft filter
Installed wideband 02 sensor/gauge.
Properly set choke and am currently testing some different rod/jet combos.

I checked the spark plug on cyl5 (easiest access) and found that the plugs are still fouling with oil.
Compression seemed ok across the board with lowest cylinder reading between 150/155 and highest cylinder reading 165ish (COLD ENGINE TEST)
I do not have a leakdown tester, and it seems the cheap ones are all horribly reviewed.

If any of you have experience with all 8 plugs fouling with oil, is it usually always worn rings?
I'm really hoping that someone has had a different experience and can give me some optimism to look elsewhere.

Thanks,

[graphicdesigner80]

Sounds like a a few issues to sort out. Gota love 'modifications' previous owners make.

You're on the right track with the compression test. I'd go a step further and squirt a small amount of oil or marvel mystery oil in each cylinder and repeat the compression test, see if the #'s improve. That will indicate issues with the rings. If that doesn't improve the #'s much, the only other way to tell what's going on is with a leak-down tester. That'll give you the best idea of your weak points (rings, intake, or exhaust valves). I bought my tester from amazon and it's done a good job for 3 different engines i've tested. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

I'd keep an eye on the oil level and if it starts to rise again, or smells like gasoline, that usually indicates a ruptured fuel pump diaphragm that's leaking into your crankcase.

Good luck and congrats on getting the car. Hopefully you can get things sorted out soon.

[ashley roachclip]

Check the PCV system , ensure the pcv valve is correct , also look into the valve cover where the valve goes , and make sure the baffle is in place .

[emerygt350]

Yeah, is the pcv even hooked up? When fools work on engines things like that are thrown away.

[Lube]

Thanks everyone--much faster replies than I expected...

The current PCV situation is this: https://www.summitracing.com/parts/sum-g3400
Two of these breather caps--one on each valve cover.

If I'm honest with myself, I will probably be driving this car maybe once every other week on average, so environmentally I feel less bad about myself than the dipstick I watched toss his trash out of his car on the way into work this morning...

That said I am unfamiliar with the effectiveness of these. The PCV vacuum ports on the manifold and carb are plugged and that's the way that I received the car.
I'd be happy to look into modifications there if you suspect they are not as effective at releasing pressure/condensation.

Unrelated rant
I'm 99% sure the same dipstick PO had the thermostat removed also as this car takes a frigging year to warm up, and on a cool night it never hit full operating temp. Unfortunately I see no way to get the housing off without removing the water pump/timing cover as the bolt is long enough that it will interfere.
End

I don't remember looking for baffling in the covers, but can check that out tonight.
Funny, that STAR is the same tester that I had been looking at. I'll likely pick one up.
Also had wondered what the interface between fuel pump and block looks like. I've never had to crack one open before.

[306gt]

Sounds like the plugs are fouled with fuel not oil. Install new plugs after doing a compression test. Make sure the choke is wide open. Start the car and see how it runs. Go from there. If the choke was never hooked up and was closed.The cylinders could be fuel washed. That explains the fouled plugs and the fuel soaked oil in the crankcase.

[emerygt350]

I would return the pcv to stock. Just to be safe. If you have pressure building in the crankcase, a little vacuum help pulling it out can't hurt. Besides, venting those fumes to atmosphere is what caused all the emission crap we have to deal with today.

[erratic50]

Oil that’s too thin will not be controlled properly inside an old engine designed for heavier oil.

I would switch to 10W40 high detergent conventional oil. Mobile or Valvoline or similar.

You need to fix the thermostat issue ASAP. Fuel atomization is very poor when an engine is cold all the time. Hot pistons expand into their bores and tighten up ring tolerances — keep running it cold like this as wear is accelerated like you would not believe!

make sure your ignition timing is around 10-13 degree before TDC. You don’t need more but if there is less it will be lazy and you will likely dump raw fuel out the exhaust for lack of burn time

Look at the plug type and temp and make sure your gap is correct. Put a wideband on it and make sure your edging towards lean while cruising down the road under light load

I would put some seafoam in the oil and in the fuel and run it easy for a couple of hours. After that I would re-test the pressures on each cylinder and make sure it’s up to snuff. plug the fuel line off and run it out of fuel. Remove the rotor out of the distributor. When you check pressures do it with the carb wedged to hold it at wide open throttle.
I agree entirely on the PCV comments! Be sure to fix it.

[KevinK]

Fouling plugs, be sure to use good quality plugs. I picked a 79 long ago in pieces. Put it together and it ran ok for a short time. Plugs fouled, cheap plugs did not last breaking in the engine. New Motorcraft plugs and it ran great.