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Old 07-30-2009, 05:15 PM
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Faulty spark plug wires, poor cylinder combustion and oil consumption ???

I won't go into much detail but as some of you know I have had to bring my car back to my engine builder after 500 miles and excessive oil consumption. He has been looking at it for 3 days and has run tests including compression, leak down both to rule out the rings. He also went ahead and swapped out all the valve seals (swapped out during rebuild) just to rule out the heads. I know the first day he suspected the PCV not operating correctly but 2 days later he has troubleshooted the oil consumption to in part or mostly due to faultly wires (currently running Accell 8.8MM spiral core with not many miles on them). Appears that a few of the cylinders were not getting hardly any spark and the rest possibly weak or intermittent spark causing a varying degree of spark fouling and lack of combusition in the cylinders allowing oil to get past the rings. Just wanted to get other's opinions on if really bad wires can be the cause of such oil consumption ? Maybe not getting enough spark/heat/combustion in the cylinders to fully seat the rings ? Any insight would be appreciated. Thanks.
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Old 07-30-2009, 06:27 PM
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The scenario described is very possible, I've seen a dead or partially dead cylinder due to valvetrain damage turn into a oil pumping cylinder in just a few minutes run time. Your machinist may be right.

Accel has a poor reputation in the last 10 years, and I personally would never use the 8.8 wires, too many better choices out there(Moroso, Taylor, MSD, Pertronix, etc.)

What has been your break-in driving style?? You need to drive it like you stole it, DON'T baby it too much, you got to force those rings against the cylinder walls to get them broke in, and that takes combustion pressure. 3/4 to full throttle, up to 80% or so of your redline rpm repeatedly a dozen or more times.
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Old 07-31-2009, 08:19 AM
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I agree, anything with accel written on it should have a destination to the trash. Usually anything with weak spark will have other signs as well. Busting, missing, popping, etc. Even so it don`t always show itself at low to middle RPM as it does on high end. So yes it could well be the issue. My last build I used Moroso spiral core blue max 875 ohm wires and they performed excellant. I`ve also used the cheapy summit wires without issue.
In the past I used accel I got a HEI super coil, it was no good. Got another, it was bad as well. My brother ordered 8 injectors for his TPI and 3 of them were bad. I`ve had high resistance right out of the box also with accel wires.
A used to be friend and I, along with his cousin, we all got a accel HEI cap and rotor kit for our SBC`s, all 3 caps melted in the center in the first week of use. After that I won`t go near accel stuff.
You can do a spark test and if the spark is yellow it`s weak. Good Luck.
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Old 07-31-2009, 08:23 AM
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Wires

This is some good info.

My engine builder has the same thoughts on accel. Has a brand new set of wires in box that are N/G. He did a spark test and few of the cylinders he noticed spark a faint yellow spark if that. I believe he is going to replace with MSD or taylor, but if it was me I would just of threw on a new set of 8.0MM which are way cheaper. Hopefully I will know today if my "issue" is solved.

Last edited by y2k600f4; 07-31-2009 at 09:00 AM.
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Old 07-31-2009, 05:07 PM
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Quote:
Originally Posted by y2k600f4
I won't go into much detail but as some of you know I have had to bring my car back to my engine builder after 500 miles and excessive oil consumption. He has been looking at it for 3 days and has run tests including compression, leak down both to rule out the rings. He also went ahead and swapped out all the valve seals (swapped out during rebuild) just to rule out the heads. I know the first day he suspected the PCV not operating correctly but 2 days later he has troubleshooted the oil consumption to in part or mostly due to faultly wires (currently running Accell 8.8MM spiral core with not many miles on them). Appears that a few of the cylinders were not getting hardly any spark and the rest possibly weak or intermittent spark causing a varying degree of spark fouling and lack of combusition in the cylinders allowing oil to get past the rings. Just wanted to get other's opinions on if really bad wires can be the cause of such oil consumption ? Maybe not getting enough spark/heat/combustion in the cylinders to fully seat the rings ? Any insight would be appreciated. Thanks.
A compression test and/or a leak down test is not a definitive test for oil consumption getting around the rings.

Yes, in most common cases compression and leak down have a significance to oil consumption because the rings, pistons and bores are worn out or damaged and can't control compression nor wipe oil from the bore walls.

But situations exist where for reasons of improper bore finish or damage/improper installation of the oil control rings, that the oil control rings cannot, or do not, wipe oil from the bore walls. This will show as excessive oil consumption, but the engine will be pressure sealed and will appear normal in compression and leak-down tests.

Another bottom end oil consumption problem unrelated to the quality of the rings, pistons and/or bores is excessive throw off from the crank. This is often the combination of narrow and/or low tension rings along with loose clearances and a high volume oil pump. In this situation there is just so much oil, the rings just are overwhelmed.

Up on the top end issues with oil consumption can be related to excessive valve stem to guide clearance, or missing/failed stem oil seal. The intake stem to guide clearance is always exposed to manifold vacuum and this will really pull a lot of oil given the chance. Another possible point is a failure or inadequate seal of the intake manifold to the heads, if the seal allows a vacuum leak into the valley area a lot of oil can be pulled into the intake tract. Sometimes, with engines that use Positive Crankcase Ventilation (PCV), if the oil separator in the rocker cover is inadequate or missing, the PCV valve will pull over a lot of oil. Except for the possibility of a manifold to port fit that is bad enough to show unexpectedly low manifold vacuum readings on a gauge, it is unlikely that these failures will show up on the usual tests.

There are also the screw-ball failures of leaks past bolt threads, porous castings, breakthroughs under the rocker studs into the intake ports. Stupid things like that which prove to be pretty hard to find until all the reasonable fixes have been attempted to no improvement.

Yes a miss-firing cylinder will be encouraged to draw oil over, but this shouldn't show up as noticeably bad oil consumption unless some of these other basic problems are also present.

Bogie
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Old 08-01-2009, 07:04 AM
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Quote:
Originally Posted by oldbogie
A compression test and/or a leak down test is not a definitive test for oil consumption getting around the rings.

Yes, in most common cases compression and leak down have a significance to oil consumption because the rings, pistons and bores are worn out or damaged and can't control compression nor wipe oil from the bore walls.

But situations exist where for reasons of improper bore finish or damage/improper installation of the oil control rings, that the oil control rings cannot, or do not, wipe oil from the bore walls. This will show as excessive oil consumption, but the engine will be pressure sealed and will appear normal in compression and leak-down tests.

Another bottom end oil consumption problem unrelated to the quality of the rings, pistons and/or bores is excessive throw off from the crank. This is often the combination of narrow and/or low tension rings along with loose clearances and a high volume oil pump. In this situation there is just so much oil, the rings just are overwhelmed.

Up on the top end issues with oil consumption can be related to excessive valve stem to guide clearance, or missing/failed stem oil seal. The intake stem to guide clearance is always exposed to manifold vacuum and this will really pull a lot of oil given the chance. Another possible point is a failure or inadequate seal of the intake manifold to the heads, if the seal allows a vacuum leak into the valley area a lot of oil can be pulled into the intake tract. Sometimes, with engines that use Positive Crankcase Ventilation (PCV), if the oil separator in the rocker cover is inadequate or missing, the PCV valve will pull over a lot of oil. Except for the possibility of a manifold to port fit that is bad enough to show unexpectedly low manifold vacuum readings on a gauge, it is unlikely that these failures will show up on the usual tests.

There are also the screw-ball failures of leaks past bolt threads, porous castings, breakthroughs under the rocker studs into the intake ports. Stupid things like that which prove to be pretty hard to find until all the reasonable fixes have been attempted to no improvement.

Yes a miss-firing cylinder will be encouraged to draw oil over, but this shouldn't show up as noticeably bad oil consumption unless some of these other basic problems are also present.

Bogie
Thanks for the detailed info Bogie. Very informative. I don't know the latest results of my "issue". Been with the builder over 4 days and after compression, leak down, removal of PCV (replaced with breather), new plugs and wires, new valve seals again (replaced during rebuild)...from what I am reading if the problem is not solved a tear down is in order to investigate futher. Thanks.
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Old 08-01-2009, 10:00 AM
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I do not see removing the PCV valve and replacing it w/a breather helping anything, unless there was an issue w/the PCV inhaling oil. But that would call for baffles, not removal.
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Old 08-01-2009, 01:27 PM
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I do not see removing the PCV valve and replacing it w/a breather helping anything, unless there was an issue w/the PCV inhaling oil. But that would call for baffles, not removal.
My thoughts exactly !! Actually I was trying to cover all my bases during the rebuild and I had him custom make brackets (actually he insisted he do due to warranty and paid him some extra in labor) to mount a pair of SBC stock baffles in my aluminum valve covers, since he had everything apart already. He claims that he tested out the PCV and it was not operating correctly.

My best guess he is tackling one thing at a time and attempting to at least rule out some things e.g. valve seals, wires, pvc and now he is doing an oil consumption analysis. So far he has run it some miles with an old set of wires and all smoking at idle has stopped, however if you "crack" the gas at idle you get a puff of smoke on the one side (exhaust pipes are already hot)..however the smell and appearance is different and his thoughts is it is burning oil laying in the exhaust pipes etc. Also it appears the oil use has decreased. However he plans on installing some good wires and doing an oil consumption analysis over the next 100 miles. If the engine needs to come out that is what he says he will do since he stands behind his work. I guess I will let him do what he needs to do in the next few days and take if from there. I am guessing his thoughts now was some of the rings may not of seated due to the lack of spark/heat in the cylinder at least contributing to the oil issue...but I guess only time will tell to see if this is true or not.
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