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  1. #1
    JimK is offline Diamond
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    I have no experience running older gasoline engines on today's unleaded gasoline.

    By older I don't mean ancient, I mean car and truck motors that wre in production when lead tetraethyl was dis allowed in gasoline.

    I see gasoline additives sold for the engines that ran leaded fuel, Are they required?

    I understand that when runing gaseous fuels that engines need stellite valve seats and valve faces. I can't imagine Ferds and Chevvulay's with that kind of sophistication.

    What gives? Can I run a 1960's motor on today's gas without having troubles mit?

  2. #2
    C9
    C9 is offline Aluminum
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    You shouldn't have any problems.

    Lead is a requirement for engines under a constant heavy load.
    Boats, trucks, race cars etc.

    One of the back east oil companies sold unleaded gas for many years prior to the federal requirement for unleaded gas.

    Studies they did showed that during normal passenger car use there were no problems.

    You shouldn't have any problems running unleaded in a 60's era car.

  3. #3
    johnoder's Avatar
    johnoder is offline Diamond
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    The lead did in fact act as a lubricant - especially in the valve seat area. In my 1930 Packard I ran a little Marvel Mystery oil to compensate. Also known as "top oil".

    John

  4. #4
    metlmunchr is offline Diamond
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    The "lead substitute" and "octane booster" stuff is just snake oil. Tetraethyl lead is so deadly in the hands of the average person that there's no way its going to be in any of these concoctions in adequate quantity to have any real effect. There are a number of slow burning alcohols and petroleum based hydrocarbons that would give a slight increase in the octane rating as measured by knock resistance, but these would not replace the mechanical effect which the lead had. Somehow it "softened" the valve closing, something I've never quite understood. Undoubtedly it worked though.

    If you run an old engine on unleaded, in the long term it will have valve seat problems. How long it might take is dependent on the particular engine according to several things I've read over the years, but its not an overnight thing in any case. If you were rebuilding an old engine, it would definitely be worthwhile to install hardened seats, but IMO its not something so critical that you'd want to tear down an otherwise good running engine just to add the seats. I've put about 40K miles on an old corvette since leaded gas went away, and it hasn't shown any signs of valve related problems so far.

  5. #5
    steelhead is offline Senior Member
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    Besides the valve seat issue there is also the issue of octane. Depending on the compression of the engine the newer unleaded fuels that are commonly available at the pump may not have enough octane to prevent pinging. This would only apply to some of the high compression 60s v8 muscle car motors. Granted there are high octane unleaded fuels like cam2 available for race vehicles but the price is high and the availability scarce.

  6. #6
    Michael Az is offline Senior Member
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    I also use Marvel mystery oil. Not sure how much it helps, but makes me feel better. If I were rebuilding an old engine I would update the seats.
    Michael

  7. #7
    jim rozen is offline Diamond
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    I run many old motors on unleaded fuel.

    The sign that somethings 'up' is that the
    valve clearances tend to tighten up over time.
    This means that the valves or seats are wearing
    a bit.

    The octane issue is important especially in
    motors with large hemispherical heads and two
    large valves in the center, and plug way offset
    to the side. Heads like that are quite prone
    to detonation and pre-ignition and there are
    pretty much two ways to deal with the issue -
    either by dual-plugging, or by lowering the CR
    overall.

    Jim

  8. #8
    JimK is offline Diamond
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    Re: Marvel Mystery Oil

    Reciprocating steam engines had steam cylinder oil added to the incoming steam by a displacement lubricator.

    More modern steam engines had mechanical lubricators that injected the steam cylinder oil.

    Sooooooooooo-

    Cylinder lubrication throgh the inlet has been standard practice for quite a while.

    Marvel made a lubricator that infused their Mystery Oil through the intake manifold without losing manifold vacuum.

    Nice Piece! I haven't seen one in years and years.

    It seem that this would be the way to go since the Mystery Oil would be less diluted compared with putting the raw stuff in the gas tank.

    Machts nict now. The EPA and the GRU and the KGB and the the FBI and fourteen other three-letter agencies would be down your shirt collar if you had the timerity to add top cylinder lubricant to the incoming air stream.

  9. #9
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    My understanding is this...the tetraethyl lead actually was a lubricant of sorts for the exhaust valve seat and valve.

    Not that there's that much scrubbing going on there but it tends to accumulate cycles pretty fast.

    As Jim Rozen pointed out, when the clearances start to change there's an erosion of the seat going on.

    It will even happen in a modern cast-iron head engine with induction hardened seats when run Wide Open Throttle, max rpms for 400 hrs. Although the valve clearance issue is masked by self-adjusting(hydraulic) lifters.

    I always ran the lead substitute in old engines with the thought it was an exhaust valve seat lube, and helping to prolong the life of the seats more than having anything to do with octane modification. Run premium 93 or avgas 102 if knock is a problem.

    -Matt

  10. #10
    Peter S is online now Titanium
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    Jim,

    NZ removed all lead around 10 years ago, so there was no choice. The petrol stations all supplied additives for those who had old engines (ie valves seating direct in head). Everyone used them for a start, then the additives dissapeared within a year or two, maybe the odd person uses them.

    I ran a 327 Chev from before the unleaded came in until quite recently. It was an engine I rebuilt myself, and then clocked up around 175,000 miles without touching it. I ran it without additives (and without hardened, or any, valve seat inserts).
    My reasoning was this - for many years before petrol went unleaded, NZers' were running their cars on LPG and CNG - no lead in that stuff. My father had run his Chev for years on LPG with no seat problems.
    No scientific proof...but I can say that the old valve seating in cast iron head was ok for me for a good long mileage.

  11. #11
    The Doctor is offline Cast Iron
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    Well, I've got some experience running a car that was designed for leaded gas on unleaded. Back in the 80s I bought an old VW 412, which was built back in 73. It had a 1.7 L engine, port fuel injection, and an automatic transmission. The engine had quite a bit more power than the typical beetle, but it was not a big, relaxed V8 like most American cars ran. It was a small, rather highly stressed engine. When I bought the car it had a bout 48,000 miles on it. When my health quit me from driving it in 98, it had 210,000 miles. The owner's manual for this car specifically suggested regular or low leaded gas, and did not recommend the use of unleaded. I can also assure you the car did not have a pampered life, as it had just enough acceleration to keep me happy. So, flat to the floor every light until it got up to speed. I worked 40 miles away from home at this time, and quite often was cruising around 75 or 80 miles an hour on 295. Believe me, that engine is turning some serious revs at that speed. I can tell you that even with this treatment, I do not have valve problems at all on the engine. Recommended valve adjustment interval was 6000 miles, I did an oil change and valve adjustment every 5000. I can tell you that the exhaust smells are usually very slightly tight at least every other adjustment, which would tend to indicate that some valve seat recession was occurring. However, the engine never lost compression or developed any kind of performance problems. I think a big lumbering V8 turning half the RPMs and a lot less throttle opening would have even better results. As long as you do not experience knock on the older engine, run it and be happy.

    Ed

  12. #12
    Avanti is offline Cast Iron
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    Dr:
    That 412 came with pretty hard seats in it originally, or did you think the seat was aluminum? It is normal for VW exhaust clearance to tighten up as they run. When it it becomes a problem it usually means that the stem and valve head are getting ready to part company.

    Valve seat recession can be a problem with older motors IF they are run at high loads at high RPMs. This means your MG Midget will have problems, but you 350 Chevy probably won't unless it is in a dump truck or other heavy duty application.

    Aftermarket hard seats are problematic. I have seen WAY too may of them fall out to ever hard seat a good head.

  13. #13
    Avanti is offline Cast Iron
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    Dr:
    That 412 came with pretty hard seats in it originally, or did you think the seat was aluminum? It is normal for VW exhaust clearance to tighten up as they run. When it it becomes a problem it usually means that the stem and valve head are getting ready to part company.

    Valve seat recession can be a problem with older motors IF they are run at high loads at high RPMs. This means your MG Midget will have problems, but you 350 Chevy probably won't unless it is in a dump truck or other heavy duty application.

    Aftermarket hard seats are problematic. I have seen WAY too may of them fall out to ever hard seat a good head.

  14. #14
    Avanti is offline Cast Iron
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    Dr:
    That 412 came with pretty hard seats in it originally, or did you think the seat was aluminum? It is normal for VW exhaust clearance to tighten up as they run. When it it becomes a problem it usually means that the stem and valve head are getting ready to part company.

    Valve seat recession can be a problem with older motors IF they are run at high loads at high RPMs. This means your MG Midget will have problems, but you 350 Chevy probably won't unless it is in a dump truck or other heavy duty application.

    Aftermarket hard seats are problematic. I have seen WAY too may of them fall out to ever hard seat a good head.

  15. #15
    Avanti is offline Cast Iron
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    Dr:
    That 412 came with pretty hard seats in it originally, or did you think the seat was aluminum? It is normal for VW exhaust clearance to tighten up as they run. When it it becomes a problem it usually means that the stem and valve head are getting ready to part company.

    Valve seat recession can be a problem with older motors IF they are run at high loads at high RPMs. This means your MG Midget will have problems, but you 350 Chevy probably won't unless it is in a dump truck or other heavy duty application.

    Aftermarket hard seats are problematic. I have seen WAY too may of them fall out to ever hard seat a good head.

  16. #16
    Avanti is offline Cast Iron
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    Dr:
    That 412 came with pretty hard seats in it originally, or did you think the seat was aluminum? It is normal for VW exhaust clearance to tighten up as they run. When it it becomes a problem it usually means that the stem and valve head are getting ready to part company.

    Valve seat recession can be a problem with older motors IF they are run at high loads at high RPMs. This means your MG Midget will have problems, but you 350 Chevy probably won't unless it is in a dump truck or other heavy duty application.

    Aftermarket hard seats are problematic. I have seen WAY too may of them fall out to ever hard seat a good head.

  17. #17
    ENGINENUT2 is offline Aluminum
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    yes, valve seat recession is the common way that modern heads show the absence of lead.I've been messing with engine valves since 1958-grinding my own heads/valves since 1967 so I've gone through the transition of lead to none.We used to see white tail pipe deposits on a clean running engine-no more.We saw when cleaning up the heads/valves for reseating the inlet seating area would be shiny with no deposits while the exhaust was not.It's coating was a hard white or reddish material that when removed with wire brush revealed pits and gouges that had not shown up before and the engine many times had shown no signs of valve leakage.Since the elemination of lead the exhaust seats are now also not coated like the inlet and many times the valve will have worn quite deeply into the head.The lead formed a protective coating on the faces that lubricated the relative rotary movement between valve face and head seat area and it constantly renewed itself.Things they did to reduce this face and seat wear on lightly loaded engines like passenger cars and light trucks were induction hardening of the head seat area.This is shallow and can be ground away if regrind is excessive.Addition of rotation inducing spring retainers helped stem and guide life but may have even hurt by increasing the valve face abrasion against the seat--any way we got them.If repair seats are PROPERLY installed they work well but add considerably to the cost of a valve job.IMHO for light use, not industrial or continious duty, standard integral seats should serve well with non leaded fuels.There are engines that need all the help they can get and they will already have some drastic changes built in if they were originally specked for this service.

  18. #18
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    Ralph_P is offline Stainless
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    If spark knock (pinging) is a problem on older engines, add an EGR system from the 70's or early 80's.

  19. #19
    The Doctor is offline Cast Iron
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    Avanti, yes I am aware that the engine used valve seat inserts. I don't suspect it would last 50,000 miles if the valves were seating directly in the aluminum, with or without lead in the gas. But the fact that the owners manual recommends against unleaded gas tends to suggest that neither the valve material nor the seats were designed for lack of lead. My point was that this was an engine not designed for unleaded, running at higher load and higher rpm than the average car engine of the day, and it still did not self-destruct.

    Ed

  20. #20
    scphantm is offline Cast Iron
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    the answer to this depends on the type of engine and more importanly the oiling system of the engine. all flatheads need fuel additives. the main reason being the valve guides are lubed by the fuel.

    rule of thumb, late 50's - 60's on, no problem. earlier than that it goes by engine. flatheads need Marvel Mystery Oil, no option. other engines depend.

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