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I pulled these out of my dent today and wanted to get some help with diagnosing any trouble seen in them. I don't do this much so not sure what I'm looking at. #4 and #5 look a little suspicious. Truck has been running fine, I noticed it seems to be a little rich (gassy exhaust).
Kind of depends on how many miles on the engine.... At first look, I'd say the engine is just getting tired. If it is a big concern to you, just run a compression check to see if you have a bit lower compression on #4 and #5....
Perhaps try some of the after market spark plugs to help with better burn..
Motor doesn't have but probably 5,000 miles on it, I didn't do the rebuild but it's a stock 400 (2 barrel carb, etc.)
I am planning to put new plugs, wires, coil, rotor and cap on it to see if that does anything. I was wondering if #5 was a bad spark, carbon or oil fouled... So your compression check is a good idea to rule that out.
Rebuilt means a lot of different things. some of them look a little rough if they only have 5k on them. looks like oil.
Could be valve seals or guides. what was done to the heads ? does it smoke or use any oil ? actually it would take very little oil to mess up a plug or two . it's also possible you're pulling a little oil in at the intake gasket . where is your PCV hooked to vacuum ?
new plugs and related items aren't going to change anything but I would replace them.
agreed - no telling what was done on the rebuild. Truck runs fine, just a little concerned that the plugs didn't all look similar and whether something internal is lurking.
Doesn't smoke or lose any noticeable oil (I never need to add over the course of a year between oil changes)
I'll have to verify on the PCV but I'm pretty sure it goes to the back of the carb (if not it goes to the vacuum "tree" on the back of the manifold). PCV is new-ish (<5 yr, 1,000 miles)
If it goes to a vacuum tree that could explain it. all of the PCV could be going into one or two runners. by putting it into the carb base it spreads it out.
If you're not smoking or burning oil I wouldn't worry about it too much. keep driving and if there's a problem you'll find it later.
@440 sixpack - I did confirm the PCV runs into the carb base as its supposed to.
I swapped in some new plugs, wires, cap, rotor and coil today - seemed to pep the old girl up. It was idling high so I put a Vacuum gauge on the manifold and tuned the idle mixture till I was getting max vacuum of 18 at idle (I'm at ~500 ft above sea level).
I stomped around on it this afternoon and it felt peppy and idled smooth in/out of gear.
I didn't do a compression test yet but read that if there is a compression issue somewhere the vacuum gauge needle will flutter a bit - I did notice that when I dialed it up to 18 it would move back and forth between 17.5 and 18 - wasn't sure if that was a sign or just normal for a ? rebuild.
That's good vacuum. fluttering can be valve timing , ignition timing will cause issues too. you're fine.
I wouldn't bother with a compression test but it won't hurt anything. unless you're willing to pull the engine it doesn't matter at this point really . the oil you're getting on a plug or two is almost certainly from a guide or seal and it doesn't sound like you have any other issues that's good. unless it gets bad enough you want to tear into it I'd just drive it and keep an eye on #5. the only easy fix would be a new valve seal and there's no guarantee that will fix it . watch for a puff of smoke when you start it , that's a tell tale sign. but with just one cylinder it may not show much .
a little STP or power punch can help too. everyone thinks they're old school snake oil but they really do help a bit.
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