3 and 4 are right next to each other in the firing order. If the lifters are good, I'd suspect ignition.
Head scratcher
- Thread starter L31MaxExpress
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L31MaxExpress
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It may actually be something ignition due to parts availabilty in the country and rushing at the time failing to lookup all the details. It has 0.708" reach taper seat NGK TR6 plugs in it. AFR that uses the same cylinder head casting for their Enforcer calls for a 0.750" reach gasket seat plug. My local Oreilly's has some NGK 6988s on the way for me. Those are a 7 heat range, 0.750" reach Iridium with a projected tip and a 0.044" gap out of the box. Before I dig into it more I am going to try simply installing. The #4 cylinder and #3 cylinder as well as a couple of others all show evidence of fuel glazing. Like they were fouling with fuel and started firing at heavy throttle and baked the fuel and additives on it. Reading about fuel aka high speed glazing it can cause misfiring as well.
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L31MaxExpress
I'm Awesome
#4 was the only plug that looked this way but I have a feeling I know why.
The PCV valve vacuum port dumps nearly on top of the #4 intake runner opening in the intake manifold. Any oil from the PCV gets a near straight shot into cylinder #4s incoming air.
Maybe @Supercharged111 or anyone running the same intake manifold can reply back if they also see signs of additional oil burning on cylinder #4. I want to say I remember the old 350 showings signs of higher oil consumption in cylinder 4 and assumed it was a somewhat hurt cylinder or bad valve stem seal at the time. Might be time to put a PCV catch can in line and see if that prevents the oil use. That or use the vacuum fitting in the front of the manifold where the trucks would have the EGR tube for the PCM. My aftermarket valve covers have a factory style baffle setup but still seem to allow oil past them.
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The PCV valve vacuum port dumps nearly on top of the #4 intake runner opening in the intake manifold. Any oil from the PCV gets a near straight shot into cylinder #4s incoming air.
You must be registered for see images attach
Maybe @Supercharged111 or anyone running the same intake manifold can reply back if they also see signs of additional oil burning on cylinder #4. I want to say I remember the old 350 showings signs of higher oil consumption in cylinder 4 and assumed it was a somewhat hurt cylinder or bad valve stem seal at the time. Might be time to put a PCV catch can in line and see if that prevents the oil use. That or use the vacuum fitting in the front of the manifold where the trucks would have the EGR tube for the PCM. My aftermarket valve covers have a factory style baffle setup but still seem to allow oil past them.
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L31MaxExpress
I'm Awesome
Had to test fire it briefly after changing the front 4 plugs. Smooth as can be and very responsive to throttle. Rear 4 are a more of a pain and about to climb under it and fight them. Learned a lesson here, check the plugs first even if you had recently changed them. Kind of makes me wonder if the cylinder 4 misfire was falsely triggering cylinder 3 misfire detection or maybe it had some misfiring on its own.
Supercharged111
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Your timing is pretty good, I am about to regap the existing plugs and swap in some new wires.
That plug looks like crap, all those specs of junk on it too. I dunno what the NGK deal is. Been running just some plain ol AC delco's in stuff for ages. No problems, the problems usually came when someone put in some fancy pants spark plugs.
The LS is factory, but haven't built an engine that I didn't just vent to atmosphere. There was a PCV thread awhile back. Pretty sure I came across as a planet killing heathen, but its ok.
The LS is factory, but haven't built an engine that I didn't just vent to atmosphere. There was a PCV thread awhile back. Pretty sure I came across as a planet killing heathen, but its ok.
L31MaxExpress
I'm Awesome
Ended up putting Rapidfire 5s in it. They only had 6 of the NGKs show up. NGK makes many of the OE AC Delco plugs. #5 is the AC Delco recomeended replacement for the late 80s and early 90s aluminum head TPI 350. Looks to be a cold plug temperature wise which I need anyway at nearly 11:1.
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L31MaxExpress
I'm Awesome
I meant to also say the #3 plug had some tacky feeling gunk on the plug body, the wire boot and the heatshield cover. Best I can relate it to is varnishing fuel or indian head gasket shellac. I think #3 plug was not fully seated in the head and the fuel was building up on it causing the varnish like shellac substance. It was some nasty sticky stuff.
L31MaxExpress
I'm Awesome
I ordered an oil seperating catch can that looks nice. It has an actual seperator in it and can be disassembled for cleaning opposed to some that are just a canister with two lines on it and a drain.
So much healthier back on all 8 cylinders.
Funny that it was a plug getting somewhat fouled causing this issue, but glad it is on all 8 and again. Will drive it around some tomorrow to verify the repair fixed it. I also noticed it wants some more timing off-idle without a load, so I will add a bit there too.
So much healthier back on all 8 cylinders.
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Funny that it was a plug getting somewhat fouled causing this issue, but glad it is on all 8 and again. Will drive it around some tomorrow to verify the repair fixed it. I also noticed it wants some more timing off-idle without a load, so I will add a bit there too.
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Yes you do. More than you might realize. And so do I, for 40+ years after using one of these daily for
a couple of years I miss having such an unfair troubleshooting advantage at my fingertips. :0)
When they were new the price of admission was such that only a pro mechanic doing this for a living could
justify the investment. But as an apprentice I felt so lucky to be using a Sun 1115 on a daily basis. It was
so easy to perform a load balance test to quickly figure out which cylinder(s) weren't contributing their fair
share towards spinning the crank.
And the 'parade of sparks' was so high resolution that you could actually see voltage & burn time
variations on the same cylinder (as long as you cared to watch) due to slightly burned valves, etc. With
practice, it was so easy to differentiate between the steady firing cylinders vs the intermittent/weak ones.
You really gained an appreciation for the fact that a V8 is 8 individual single-cylinder engines sharing a common block.
Of course this was a big realtime analog monster, so there was no data storage or graphing capability,
but even so you could really get a feel for what was going on in the engine. And after using it to diagnose
literally 100s of different customer cars, both good and bad, it was like using a Hasselblad camera - the limits
of the data displayed was the gonkulation power behind the eyes, not what was displayed on the screen. :0)
For what it's worth, the new Pico scopes look to give the same sharp display quality plus deep data storage,
but alas I'm afraid that I'll only get to admire them from a distance because they are so spendy.
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