Engine/Sparkplug Question

[soule64]

New guy here, so please bear with me on my question. I did do numerous searches within the site and got some relevent information, but a second or third opinion never hurts. I have started the tear down of my 68 SWB. I am to the point where I have to make a decision on what to do about the motor (350 - rebuilt by the PO back in '99 - I have the receipt for the work). When I bought the truck, the PO said that he fouled the plugs every couple of months, but I really wasn't concerned because I had intentions of putting in a crate motor from the start. I drove it back from Nashville and it's been parked since. Lately I have been tossing around the idea of putting on one of the Edelbrock top end kits rather than going with the crate engine because it really does run pretty good - it starts with just a bump of the key every time. Tonight I pulled all of the plugs (AC R45s) and did a dry compression test (WOT and around 4 turns on the motor). Every cylinder had nearly identical readings - between 120 and 130psi, but all of the plugs were jet black, shiney, some with noticable build up of carbon and some with wet oil on the threads . Not real sure if it is burning oil or way too rich on the gas or both. So, my question is this - should I consider this motor a candidate for surgury with the top end kit or write it off and transplant it with a crate? (I'm thinking ZZ4) I am not in a big hurry to get this truck done, but I want it done right - I have no intentions of rebuilding the shortblock if that is necessary. Not going to be a daily driver but I want to be able to if necessary and when I step on the gas, I want it to run. I am going to attempt to enclose a photo of the plugs. Thanks in advance for any help or opinions you can provide. Wow, I just previewed and the picture is huge. Sorry about that...

[Sinister]

That looks like oil to me, I don't think I'd waste the money on a new top end, but I'm sure someone else will have something to say...

[Longhorn Man]

if you have ZZ4 money... do it up!

[tsetsaf]

You've got oil! May be sipping by the valves or up past the rings. Do you belch any blue smoke? What is the top end now? Stock?

As for your question, the spark plugs alone do not answer. How does the oil look? Does it burn any? You have sufficient compression.

It sounds like you are looking for an excuse to get a new one so pull the motor sell it on craigslist for $500 and put the money towards a new one.

[soule64]

I am not sure about what is stock internally on the motor, heads are cast iron, intake is stock GM and the carb is a newer looking Edelbrock. I havn't driven it enough to tell if consumes oil, but there is no smoke when it starts which leads me to think that it may not be the valve guides/seals so much as the rings. And yes, I am sort of looking for a reason to justify the crate. I have liked the idea of the ZZ4 since it was called the ZZ3. The turn-key package/serpetine setup sounds like a good deal - for a grand more you get quite a bit of accessories. This would also allow for a turn-key CL sale of the existing motor.

[Gray Ghost]

I never rebuild part of any motor, it's a recipe for disaster.

As far as crate motors go....save a ton of cash contact a local builder to rebuild your motor. You can also usually come out way ahead HP and torque wise over what GM offers.

I ordered a GM 350 HO with roller cam and roller timing chain [350hp] back in 2000 and wound up being very disappointed with the power. The engine alone cost me $2850 back then and my locally built El Camino SS's motor [325 hp according to the PO] with a 3.08 posi would run circles around the Monte Carlo SS with it's 3.73. That was my last crate motor. I have had two built for that same $2850 since [in two different trucks].

Another local guy had a ZZ4 in his C-10...spent $4200 on that one and while it was a good running truck, no one else in the club thought it ran good enough to warrant the price or the hype the crates get.

[Andy4639]

I'm not really a internal engine man but the oil showing on the plugs dosen't look like the thing to be concerned with. You stated the PO said it fouled plugs every couple of month's. What kind of distributor does it have? Coil size? What gap setting are the plugs? Is the timing off? You said it runs good, but fouls the plugs every couple of months...
Does it have the HEI in it are the old style points & condensor? Compression test showed good also.
It may need a good tune up.

[soule64]

Thanks for all of the responses - this place is really a great place for information and knowlege. The distributer is a nearly new looking HEI. I never checked the timing or the plug gaps, never even crossed my mind (should have thought of that but I was pre-occupied with the thrill of the tear down), but it ran very smooth at idle and seemed to work just fine through the RPM's, but the PO said that it fouled plugs every couple of months. I never drove it enough to confirm that.

[jgrh64]

Take that motor to the re-builder- it's a seasoned block and maybe the PO rebuild never broke in the rings since it fouled the plugs often.CHECK REFERENCES there are some shoddy re-builders out their and some fantastic ones too. A good re-builder is worth their weight in gold and will do better for you in the long run than a crate motor

[PanelDeland]

If I was going to replace it,it would be a toss up between the ZZ4 and a GM383 short block with the Edelbrock top end.
There's no telling what internals were used when the engine was built.The plugs are fouling but I would do a major tune-up and drive it a while to see what exactly was happening before throwing a new engine(unless you just want to be sure of what you got.

[CCCC]

You have reeceived some good info and advice here. I would not give up on this engine quite yet. If the oil is on the plug threads ONLY, the oil is not necessarily coming past valve guides or rings, particulrly if you have no smoke or significant oil consumption. Is the side of the block or are the plug recesses wet with oil externally?

If the plugs are fouled by feathery carbon - or even somewhat cooked carbon - and you cannot confirm that oil is going into the combustion chamber in any significant amount, you may be mostly suffering from a rich fuel mix and/or some ignition weakness that is leading to the fouling. I would make certain that the external block is clean and dry near the plug holes (and keep it dry), put in some new plugs, check all timing and spark issues for good specs, check the fuel mixture at carb, and then run the new plugs for at least 1k miles. Then pull them and inspect. If the plugs are wet with oil, it is internal. If they are not, but still fouled from carbon, keep working with the ignition and carb mix.

Somebody said "do not rebuild only part of the engine" - leads to more trouble. I agree wholeheartedly. Somebody else said "find a local rebuilder who has been doing it locally for a long time and has a good rep" - I agree again.

[soule64]

Thanks again for all of the great advice - I really appreciate all it. When I started this build I did establish a budget and so far I am right where I want to be with it. I did contact a couple of local engine builders yesterday about producing a 383 shortblock out of the core. One place wanted $3k and the other wanted 1,700. Even the smaller number seemed a little high since a 'BluePrint' shortblock was the same price at Jegs. Not sure of the quality of 'BluePrint' though, nor do I have any idea of the quality of work from the local guys (I am still kind of new to Huntsville). I guess for right now I will heed some of the advice given so far and stick with it, clean it up and replace the suspect components. Worst case - if it continues I can always transfer the new stuff to a good shortblock - same stuff that I would have bought for it anyway. Thanks again for all of the advice. Hopefully in the future I might be more of a 'provider' than an 'asker'. Also, I am taking lots of pictures as I go for a sort of start-to-complete-finish build thread for anyone that might be interested.

[El Jay]

Originally Posted by Gray Ghost

I never rebuild part of any motor, it's a recipe for disaster.

As far as crate motors go....save a ton of cash contact a local builder to rebuild your motor. You can also usually come out way ahead HP and torque wise over what GM offers.

I ordered a GM 350 HO with roller cam and roller timing chain [350hp] back in 2000 and wound up being very disappointed with the power. The engine alone cost me $2850 back then and my locally built El Camino SS's motor [325 hp according to the PO] with a 3.08 posi would run circles around the Monte Carlo SS with it's 3.73. That was my last crate motor. I have had two built for that same $2850 since [in two different trucks].

Another local guy had a ZZ4 in his C-10...spent $4200 on that one and while it was a good running truck, no one else in the club thought it ran good enough to warrant the price or the hype the crates get.

Mr. "Old Skool" here,

Mr. Ghost is correct.
Never rebuild part of a motor.
If you just do the top end, you'll just end up beating the crap out of the bottom end/bearings because of the "new" compression.
Do it all, or do none.

As for oil on the spark plug threads, you'll find that on all of my vehicles. I put a little oil on the threads to lubricate them before installation.

Personally, I'd do a full electric tune up & run it.
Then in a few thousand miles I'd pull the plugs & "read" them.

If they're "oily", it could very well be time for an overhaul.
If they're just "sooty", start looking @ the fuel system, or maybe you need a hotter plug because of your particular driving habits.

And, just as an aside, I love building motors. Just don't get to do it often enough.

I hoped this helped a bit.

El Jay