What would cause fouling on just half of the spark plug?

[Grit dog]

I believe @SirRobyn0 was chasing the same or very similar issue and ultimately the intake manifold gasket was the culprit.

 

[SirRobyn0]

@BMac Attack & @Grit dog For me it was one cylinder #7. Those plugs in post #1 are obviously oil fouled. Valve stem seals are the most common cause of blue smoke, but in my case it was the intake manifold sucking oil in. Not common at all but something to keep in mind. If you have a way of running a camera (borescope) down the intake you should be able to see the oil trail where it enters at the gasket. Or if it's the valve stem seals there'd be no oil trail from the manifold gasket.

If it was me the first thing I'd do is run a compression test on all cylinders so you can be sure the engine is worth putting work into. Next I'd scope it if possible. If not pick valve stem seals or intake to do first and see what happens. I think though in hindsight on my own vehicle I have a hard time believing valve stem seals would foul a plug in less than 100 miles. So that's something to keep in mind.

 

[Ricko1966]

If you have a vacuum gauge finding a intake leak to the lifter Valley is simple, but first run the compression test.

 

[SirRobyn0]

If you have a vacuum gauge finding a intake leak to the lifter Valley is simple, but first run the compression test.

It should be and 99% of the time that test works perfect, however my engine passed that test. I think maybe it just didn't seal up well enough at something I didn't think about plugging off like the dipstick tube.....

 

[Ricko1966]

@SirRobyn0 you plug the pcv valve,you put duct tape over the oil fill location and pcv grommet and hook the vacuum gauge to the dipstick tube,if your pulling manifold vacuum at the dipstick tube you have a leak. Didn't want to go this far until he runs the compression test,because if it doesn't pass everything else is pointless.

 

[SirRobyn0]

@SirRobyn0 you plug the pcv valve,you put duct tape over the oil fill location and pcv grommet and hook the vacuum gauge to the dipstick tube,if your pulling manifold vacuum at the dipstick tube you have a leak. Didn't want to go this far until he runs the compression test,because if it doesn't pass everything else is pointless.

Right I understand. I'm just saying at the time I was comfortable that I got a good test, but clearly I must have not had something sealed up.

Completely agree OP needs to do a compression test before moving forward.

 

[BMac Attack]

I really appreciate all the suggestions, I'll run the compression test(s) tonight and advise.

 

[BMac Attack]

Here is what I got after doing my first compression test. It looks pretty good to me, correct me of I’m wrong. So, rings and valves seem to be OK if I understand correctly. I am now leaning toward an intake gasket leak. This motor came with no intake and I installed one. I got a little aggressive in tightening the 2nd bolt back from the front, driver side and stripped it when I was installing it. That bolt is smack dab above cylinder #1 where I’ve been having my issues. I drove it for a few weeks with that bolt messed up, not understanding the apparent significance. I knew it felt funny when it happened and that it wasn’t very tight but didn’t realize how big a deal that was. It’s never run very well since I installed the engine. I’ve messed with timing over and over, springs in the carb, choke settings, fuel regulator, etc etc. After recognizing that I was having a fouling issue I was tightening valve cover bolts, exhaust manifold bolts etc and checking over everything and I was able to clean the threads with a thread chaser on that messed up intake bolt hole and used a slightly longer bolt and was able to get it ‘tight’. I’m wondering if I messed the intake gasket up and that’s been my issue all along.

 

[Ricko1966]

We're you holding the throttle wide open during all tests?

 

[Ricko1966]

We're you holding the throttle wide open during your tests? Why didn't you check all cylinders? Wasn't your problem on 1 and 3? Look at those numbers both are lowest. I'd like to see how they compare to your other cylinders.

 

[Ricko1966]

I'm leaning towards @fast 99 s post,post 4 I suspect your engine needs rings

 

[fast 99]

Those a relatively easy intakes to pull however it would be nice to know for sure the intake gasket is suspect. It's no fun to tear something down and not find anything.

Appears it is somewhat apart already so might be easier to pull it now. Other option is to get it running and check for a leak.

If you don't know how to diagnose an intake leak on the bottom ask, I can explain it.

 

[Ricko1966]

Those a relatively easy intakes to pull however it would be nice to know for sure the intake gasket is suspect. It's no fun to tear something down and not find anything.

Appears it is somewhat apart already so might be easier to pull it now. Other option is to get it running and check for a leak.

If you don't know how to diagnose an intake leak on the bottom ask, I can explain it.

I posted my way on post 20. I'd be interested in knowing your way.

 

[SquareRoot]

I had the exact same problem when I installed the PF4. Junk Edelbrock intake gaskets delaminated and caused vacuum leaks. Switched to felpro rubber gaskets and lived happily ever since.

 

[fast 99]

I posted my way on post 20. I'd be interested in knowing your way.\

Plugged off as you do except leave one side open, never did anything with the dipstick. They usually seal somewhat anyway. Using the palm of a hand cover the remaining hole. Hold for a few seconds usually less than 10. It will either have pressure or vacuum.

I think in this particular case if the intake is leaking it will be quite noticeable.