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  1. #31
    Senior Member BasicQ's Avatar
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    Quote Originally Posted by LXCHEV View Post
    Thanks for this feedback Geoff. It's pretty clear that these "cheapo" dizzies are certainly decent enough. I'm all for buying quality parts to ensure maximum reliability. I'm definitely interested in trying one of these out. I do need to run a melonite gear for my cam, but that can be worked out easily enough. Stay tuned. I'll do a tiny bit more research before committing.
    There are also upgrades out there too

    https://www.summitracing.com/parts/msd-83647

    https://www.summitracing.com/parts/msd-8225


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  2. #32
    Senior Member BasicQ's Avatar
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    Default SBC - Troubleshooting oily spark plugs

    Quote Originally Posted by LXCHEV View Post
    I love (and hate) this topic! My PCV is a #2072. Brand new from Repco, can't recall the branding. Billet Specialties rocker covers with what appears to be decent enough baffles. No air-oil separator installed. Is this PCV valve correct for my setup - most likely NOT?

    I only chose the #2072 valve as it's a nice right angle fitting which slots into my rocker cover beautifully. Since that point in time, I've spent hours reading endless amounts of PCV threads on the internet (including a lot of yankee sites) and it's amazing just how many people are both for and against their use. Some people have problems with them, others don't. The sheer variety of different style (flow rates) of PCV valves in incredible - but the lack of specifications and information is disappointing. It seems to be a huge guessing game as to which one to use on any particular engine.

    I have no idea what the #2072 is factory fitted on and no idea of flow rates. What I do know is that it seems to suck bloody hard on my engine and I've even heard whistling noises from it too (which might indicate it's likely flowing too much, but I'm guessing). At idle if I remove it and put my finger over the end, it has huge suction. For an interesting read - check this dude out who also had whistling noises from a 2072.

    I ran no PCV on this engine for 8 years straight, with no problems at all. The only reason for finally fitting one fairly recently is to minimise oil smells and make the car as family cruise-friendly as possible. Whilst it has nothing to do with my primary oily thread issue here, it's still an interesting thing to discuss and could potentially make things worse inside the combustion chamber. I'd be up for trying a different valve if this one is clearly incorrect.

    I also wonder if the current valve is contributing to my off-idle stumble (feels mega lean to me). I might piss it off for a while and reset my idle mixture screws as a bit of a test. Again, I need to pull my finger out and get this AFR gauge installed.
    FYI

    This pcv was factory installed on low vac solid cam sbc.

    https://www.summitracing.com/search/part-type/pcv-valves/year/1969/make/chevrolet/model/camaro/submodel/z28/engine-size/4-9l-302/engine-family/chevy-small-block-gen-i

    As the above may be better but not be perfect this will greatly reduce oil into combustion chamber.

    https://www.summitracing.com/parts/mor-85496

    Just like getting ignition timing right before tuning carby so should pcv function.

    I am only going on the shiny look of the plugs in post 1, 2nd & 3rd pic that a bit of oil could be getting in there via pcv, but pictures depending on light etc can be deceptive.


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    Last edited by BasicQ; 19-04-2021 at 06:22 PM.

  3. #33
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    hi

    adjustable// tuneable PCV

    http://mewagner.com/?p=444

  4. #34
    Senior Member LXCHEV's Avatar
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    swampy; I remember looking at that adjustable PCV in other threads previously - it's a pretty cool bit of gear, along with the price tag to match. Since I only see 6" of idle vacuum, I wouldn't be confident spending the coin on that unit, as it's advertised as follows:

    "The low vacuum spring can accommodate engines with idle vacuum levels from 7″-10″ Hg, while the high vacuum spring is used on engines with 10″+ Hg at idle. Regardless, very interesting.

    Basic; I'm going to track down one of those "1969" style PCVs that you've suggested - it must be a much better match for my combo than what I'm currently using. Just on that Moroso air oil separator - is that what you're running on yours? It certainly seems to be the best overall solution (ie retaining a functioning PCV with all it's benefits, yet not introducing dirty/oily fumes into the chamber).

    As I've mentioned on here before - many years ago we did a PCV test on the dyno with a previous 383 combo of mine;

    First test (PCV connected) - air:fuel ratio curve was already very good (consistent) and produced figures in the mid to high 12's (noting it never touched the 13's).

    Second test (PCV removed and plugged, with breather installed) - the curve flattened out (improved) even more (leaning off slightly) and just dipped into the 13's - proving there was indeed a small improvement to the intake charge (cleaner/more pure air). Outright power levels did not change whatsoever. So whilst there was no performance increase, the gains would be in cleaner air/less chance of detonation/cleaner plugs, valves, oil etc and of course improved crankcase pressure.

  5. #35
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    Hi
    LX
    There was a section in the Wagner instructions about running below 7" Hg . Its called Fixed orifice tuning mode .

    http://mewagner.com/?page_id=462

    http://mewagner.com/?page_id=447
    Last edited by swampy; 21-04-2021 at 02:01 PM.

  6. #36
    Senior Member BasicQ's Avatar
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    Default SBC - Troubleshooting oily spark plugs

    Quote Originally Posted by LXCHEV View Post
    swampy; I remember looking at that adjustable PCV in other threads previously - it's a pretty cool bit of gear, along with the price tag to match. Since I only see 6" of idle vacuum, I wouldn't be confident spending the coin on that unit, as it's advertised as follows:

    "The low vacuum spring can accommodate engines with idle vacuum levels from 7″-10″ Hg, while the high vacuum spring is used on engines with 10″+ Hg at idle. Regardless, very interesting.

    Basic; I'm going to track down one of those "1969" style PCVs that you've suggested - it must be a much better match for my combo than what I'm currently using. Just on that Moroso air oil separator - is that what you're running on yours? It certainly seems to be the best overall solution (ie retaining a functioning PCV with all it's benefits, yet not introducing dirty/oily fumes into the chamber).

    As I've mentioned on here before - many years ago we did a PCV test on the dyno with a previous 383 combo of mine;

    First test (PCV connected) - air:fuel ratio curve was already very good (consistent) and produced figures in the mid to high 12's (noting it never touched the 13's).

    Second test (PCV removed and plugged, with breather installed) - the curve flattened out (improved) even more (leaning off slightly) and just dipped into the 13's - proving there was indeed a small improvement to the intake charge (cleaner/more pure air). Outright power levels did not change whatsoever. So whilst there was no performance increase, the gains would be in cleaner air/less chance of detonation/cleaner plugs, valves, oil etc and of course improved crankcase pressure.
    Yes that's the air/oil separator I am using. Neat small unit easy to install with nothing more than in/out hose after mounting. The bottom half screws off to drain. Price one local but I usually find buying things like that from Summit, by the time it lands at your door total cost is almost the same if not less than local. You could get the PCV on the same order. There is also a fixed orifice Fram FV410.

    I am guessing if the same pcv - no pcv test above was repeated with an air/oil separator in line with pcv you may get the same results. Oxygen sensors used for AFR detect oxygen remaining in the exhaust after combustion. Blowby gasses would be very low on oxygen and inert so introducing them via pcv into the cylinder would displace some oxygen. Tuning AFR with pcv in place accounts for this so when itís removed more air containing oxygen takes blowby gasses place. Hypothetically in your case above if you wanted to remove the pcv but maintain mid to high 12s AFR then jetting would be adjusted up. Extra fuel now takes place of extra oxygen. Air fuel ratio is oxygen:fuel ratio. Unburned fuel vapor also makes its way to the crankcase so some of that will also be drawn into the combustion chamber richening the mix. So what I am saying is it may not necessarily been better or cleaner without pcv, just more room in the chamber for oxygen without blowby gasses being part of the equation. Either way pcv or not it can be tuned for the same end result if oil can be kept out of there. Too much oil in there then combustion is compromised, not all oxygen used and lean condition results.

    As for the oily looking spark plug threads, install your afr gauge, get your ignition and pcv functioning right and have fun tuning. I reckon if you reduce the carbon on the plugs you may well reduce the black crap washed up on the threads. As other guys have said they have the same condition so it might not go all together but get better with tuning.
    Last edited by BasicQ; 22-04-2021 at 06:47 AM.

  7. #37
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    LX,
    I 'modify' the std GM PCV to work with low vacuum. I measured the CSA of a PCV in the idle position & it was equivalent to the diam of a 7/64" drill bit. I cut open the PCV, gut it, fit a disc & braze in place. Then drill a hole with a 7/64" bit. Braze it back together. No more worries about whether it is working.....
    I am only concerned with flow at idle because [a] nearly all carbs are calibrated for idle flow with a working PCV & [b] it allows clean air flow through the engine.

    Wagner must have been Ned Kelly in another life.........

  8. #38
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    I read a PVC article a while ago where, to prevent oil vapour entering through the PCV, they recommended fitting a good quality catch can and replacing the internals of the PCV with a disc as GTOGeoff described but before making it permanent, using a gauge to measure vacuum through the other rocker cover at idle and altering the size of the hole to obtain around 1.5 in/hg. This accounts for how much idle vacuum the engine produces.

    One really weird cause I read about was of an engine that had been rebuilt and after run in was oiling the plugs , had low vacuum and was using a small amount of oil yet it had no leaks and the wet/dry compression test was spot on. Eventually it was discovered that it had been decked and heads were shaved during the rebuild but the inlet manifold mating surfaces hadn't been checked and machined to compensate and the lower section of the gaskets weren't sealing properly and oil mist was being drawn into the ports from the lifter valley.
    Last edited by Sneem26; 22-04-2021 at 09:35 PM.

  9. #39
    Do you ever leave? EH179's Avatar
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    Been thinking about this and more questions come to mind.

    1. Is a BP5FS plug correct for a SBC? They are for a 253-308, but dunno about Chev! The Chev "reach" can range from .460" to .708" and possibly further, but which is the correct one for your engine/heads?
    2. Loose fitted plugs can have carbon tracking the length of the threads.
    3. The most common reason for oil to be present on the upper exposed threads is an oil leak, even though we think the engine is sealed up.
    4. As i have said previously, many do not run sufficient initial timing.

  10. #40
    Senior Member BasicQ's Avatar
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    I couldn’t remember where I read about fuel (fuel vapors) getting up in the spark plug thread but I stumbled across it last night. It is mentioned when talking about emissions and ‘crevice volume’. Stick with reading the below and it may go some way to explaining what the oily looking residue is on plug threads

    Designing an emissions friendly, high-output engine

    When dealing with combustion efficiency and the gas exchange process, the most challenging emissions to eliminate are HC (hydrocarbons) and NOx (oxides of nitrogen). These properties are inextricably linked to the means normally associated with increasing engine output: camshafts with excessive overlap and high compression ratios....
    When trying to control HC production, the crevice volume or region becomes highly relevant. The crevice is an area in the combustion chamber that the flame front cannot access, but one that the A/F mixture will. The largest contributor to crevice volume is the area created by the piston and piston rings in relation to the cylinder wall. Other crevice areas are represented by the threads around the spark plug, the space around the spark plug center electrode, the space between the heads of the intake and exhaust valves and the cylinder head, as well as the head gasket cutout.
    As the cylinder pressure rises during compression, the mixture is forced into these regions. During combustion the cylinder pressure rises even more, forcing more HC into the crevices. Since the flame travel cannot access these areas, the A/F mixture waits in the crevice until cylinder pressure is lower than the crevice gas pressure and flows out the exhaust.
    In an engine experiencing proper combustion it has been determined that the ring package is responsible for 80 percent of the hydrocarbon production, the head gasket 13 percent and the spark plug threads 5 percent. All other sources contribute the rest.....


    So let’s say cruising at 3000rpm you have A/F mix getting jammed into the spark plug threads 1,500 times a minute eventually some of that mix will take some carbon with it and condense and hang around. Looking at my longer thread spark plugs the heat is drying it out toward the business end but not enough heat at the hex end for it to burn off.


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  11. #41
    Do you ever leave? immortality's Avatar
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    What are your cruise AFR's like?

  12. #42
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    Interesting read.

    Modern production engines do not seem to suffer the 'wet threads' syndrome with plugs. I suspect this is because they run hotter, as part of the emissions package.

  13. #43
    Do you ever leave? immortality's Avatar
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    No excess fuel except during cold start and when in PE (power enrichment) mode. I don't like how they run them hot as that causes issues later on in life.

  14. #44
    Senior Member BasicQ's Avatar
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    Quote Originally Posted by GtoGeoff View Post
    Interesting read.

    Modern production engines do not seem to suffer the 'wet threads' syndrome with plugs. I suspect this is because they run hotter, as part of the emissions package.
    That and it would have a lot to do with cylinder pressure. Would it be safe to assume dynamic comp ratio would be less on modern production engines compared even to something starting at say 10.5:1 static and 235* @.050” cam? I would also suspect modern engines burn closer to stoichiometric almost all of the time so a heck of a lot less carbon to mix with fuel vapors and give oil appearance. So it may still happen to a degree but no tell-tale black residue.

  15. #45
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    hi
    Modern engines can run live fuel tables
    Modern engines have detonation sensing
    Modern engines have better combustion chamber design
    All above runs leaner and cleaner =more efficient combustion while cheating detonation oh yea clean plugs

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