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unleaded gas vs non hardened valve seats

Discussion in 'The Hokey Ass Message Board' started by Rustytoolss, Aug 27, 2013.

  1. Rustytoolss
    Joined: Jul 27, 2009
    Posts: 252


    Just how bad is it to run unleaded fuel in a car WITHOUT hardened valve seats ?
    I've read that at the peak of leaded fuel the was 3% lead. And by the end of leaded fuel it was .1% lead.
    Also read that you would have to drive like 70mph 24hrs for a heck of a long time before harming a engine that did not have hardened valve seats. If its a huge deal , I'll update. but for a daily 5,000 mile a year ride, is it all that important ??
    Joined: Jun 28, 2011
    Posts: 388

    from Dinuba

  3. F&J
    Joined: Apr 5, 2007
    Posts: 13,223


    most people don't recall that the old Amoco stations were once called American, and those stations were always lead free, and bragged about it. Back in those days, a lot of car owners stuck with one brand for life, and I never heard of a problem back then.

    American stations; That is where people also bought lead free "white gas" for their camp stoves and mantle camping lights.

    If towing heavy loads, or fighting massive headwinds with a motor home, or lugging the motor on hills while never can get recession.
    Joined: Nov 10, 2005
    Posts: 846

    from Holly

    If the vehicle is used as a "working " unit. You will need at least a fuel additive. Best to have seats installed.

    I have been in the engine business since the sixties. Many engines are not bothered by unlead gas. By design or they use better iron alloys.

    Then others won't last 5000 miles. Snug valve guides help also. V8 Chevies tend to eat the center exhaust guides/seats if worked.

  5. hoop98
    Joined: Jan 23, 2013
    Posts: 1,362

    from Texas

    Joined: Jun 6, 2007
    Posts: 3,559


    I also do not think hardened seats are necessary. In a car that sees moderate use you will not have a problem. This is based on my personal experience with a collection of hotrodded engines and also much dynamometer durability testing on unleaded fuel in my 31 years as an engine performance development engineer at Ford.
  7. R35J1S
    Joined: Jul 20, 2012
    Posts: 141

    from Missouri

    I will tell you this. Back in the early 90's I worked in a machine shop. I pulled down a lot of engines that didn't have hardened seats. ,most had some degree of seat set back from being hammered away. Most were not totally shot but some were. Some had the seats hammered in more than a 1/8th inch and the valves tulliped or cupped out like a flower. Now that being said, who knows how many miles it took to do that. It will happen, just a matter of how long will it be. Is it worth the cost to change them now or wait until you do a rebuild.

    Posted using the Full Custom H.A.M.B. App!
  8. steel rebel
    Joined: Jun 14, 2006
    Posts: 3,604

    steel rebel
    Member Emeritus

    I don't have anything to back this up but I think the gas today is as good as it ever has been. I base that on I can't get any of my cars to ping however I time them up and one is a '48 Ford with a '50 Cad engine with 11 1/2 compression and I put regular in them. I wish I could and then I would know where they were at. and back it off a little and it would be ring. As it is I just have to try to get it to run the best I can.
  9. are hardened seats necessary? here is a head i recently took off a 283

  10. oldwagonlover
    Joined: Jul 5, 2008
    Posts: 233


    A buddy of mine uses Nav gas and does not have any problems.
  11. steel rebel
    Joined: Jun 14, 2006
    Posts: 3,604

    steel rebel
    Member Emeritus

    Piedmont? I used to have a girlfriend there. What is Nav gas?
  12. drptop70ss
    Joined: May 31, 2010
    Posts: 1,179

    from NY

    Maybe RPM has to do with it? I had a 350 in a 69 chevelle that would run 3000 RPM at highway speed, after two years of doing that regularly the engine was torn down for updates. Exhaust valves were hammered into the heads, turned them into trash.
  13. Engine-Ear
    Joined: Jun 12, 2008
    Posts: 706

    Alliance Vendor

    My daily driver for the last 10 years has been a '62 Bonneville with a junkyard 326 (separate story)...the engine is underpowered for the car but after 30,000 miles, it still starts every day karts my arse to where I need to be, including on multi-state trips.

    IMO, metallurgy is a factor, as are driving habits and engine loading.

    Unless you're pulling a trailer and/or live in the mountains, I wouldn't sweat it. Drive it.
  14. Hemiroid
    Joined: Nov 6, 2011
    Posts: 135


    Have you put any thoughts into running a lead additive?
  15. Don's Hot Rods
    Joined: Oct 7, 2005
    Posts: 8,319

    Don's Hot Rods
    from florida

    I asked the owner of the shop who does our machining that question. He said on an engine you drive every day and lots of miles it might be important, but on an engine in a car we drive occasionally or lightly, it really isn't important. That has been my experience too.

  16. classic gary
    Joined: Sep 24, 2009
    Posts: 497

    classic gary

    ive been using stock SBC double hump heads with stainless valves since the 70's no problem with the valves "sinking" yet.
  17. stimpy
    Joined: Apr 16, 2006
    Posts: 3,547


    most of the early chevy motors I have done work on its important , as for the other Gm brands , never seen a problem , but like somone mentioned I think it had to do alot with the alloys used by the OEms , as Chevys alloys are like butter compaired to a Olds or Ponitac , and Ford and Mopar are like Diamond . the shop I use for my engine work loves working on Mopars and Fords as they can cut bores and not have problems like they do with Chevys , and I know a so called shop that complains if you bring them a non chevy block , they will charge you extra as its "hard on there tooling" they say , IMO they are a bunch of tools anyways over there . also several Oems started induction harden there seats in the late 60's , but I remember my grandfather and my dad talking about they used to valve jobs on there 40-50 era cars almost every 2-3 years when they had lead in the gas .
    one of my Ponchos has 260K on it and was a unleaded car since the late 70's when they outlawed it here in Illinois , it was a daily driver apx 100 miles a day , in a old 72 bonneville , the heads have a little recession of the valves , one has micro welding of the valve itself , it still sealed ( 100 PSI) and ran when I pulled it out of the rusted out body .
  18. 327-365hp
    Joined: Feb 5, 2006
    Posts: 5,418

    from Mass

    Yeah, I put lead additive in the tank when I think of it. Maybe every 4 or 5 tankfuls. And I put zinc in my oil. Call me crazy. :p
  19. Hemiroid
    Joined: Nov 6, 2011
    Posts: 135


    Some peeps don't get it, that's fine.

    I want my ride thinking it is still living in the 60's. A few bucks for cheap insurance does not make you crazy...

  20. 48stude
    Joined: Jul 31, 2004
    Posts: 1,177


    I worked at an Amoco station in the late sixties, The man that owned the station had a 64 Buick Wildcat that he bought new. He would only run Hi-Test American white gas in it.
    In 68 or 69 they had to do a complete valve job, it had 38,000 miles on it. Bill
  21. leaded or unleaded, cars of the30s, 40s, & 50s needed more frequent valve repair.
  22. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,524

    Rusty O'Toole

    This was a big deal in the seventies and eighties. I don't think you will have any trouble with a car used gently for moderate miles.

    There are different factors involved. One is that metal loses strength as it gets hotter. At some point, a critical degree of heat is reached where valves and seats wear rapidly.

    The harder the engine is working, the hotter the combustion chamber is going to get. A truck or heavily loaded car, on a long uphill pull in the mountains can get very hot.

    Another factor is, that seventies cars were set up very lean for emissions reasons. This meant higher combustion chamber temps especially exhaust valve temps. These were the cars that burned valves and seats the fastest especially Chevs.

    You can also add some type of upper cylinder oil, Marvel Mystery Oil, or 2 stroke oil to protect the valves. These things will not add lead but will add lubrication to the top end. These additives were popular when your older cars were new and they did make engines last longer.

    The upshot is, add a little MMM or Redex, don't drive too hard or fast for long periods and you should have no trouble.
  23. Truckedup
    Joined: Jul 25, 2006
    Posts: 4,074


    The seats are slowly destroyed by micro welding.The red hot exhaust valve transfers heat to the seat for the brief time it's closed.The lead in fuel helped the heat transfer so valve gear was designed for use with lead.When the lead disappeared,micro welding occurred when the exhaust valve touched the seat eroding the seat. Eventually the manufacturers solved the problem with different materials.
    People often mention stainless steel exhaust valve as a fix....I've taken apart Chevy engines as old as 1937 and they had stainless exhaust valves. I assume other engines used stainless ....
    Not all engines are affected the same....

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