Section : Engine

unleaded 

Posted By : Peter Coleman, 02-Sep-2005, 04:34pm

• unleaded 

  Posted By : Daniel James, 05-Sep-2005, 01:13pm

  I expect the people to talk to would be hart racing:
  
  http://www.hartrace.demon.co.uk/
  
  if you want my opinion (go on, you know you do)
  
  it's not worth having an old engine swapped over. first of all valve seat recession will only occur if you put the engine under sustained load (towing on the moterway, drag racing etc) at high revs. Even then the damage will be minimal. it'll take many 10's of thousands of miles to seriously damage the engine...at which point you just get a new head. To change the valve seats now is to assume that nothing else will go wrong that would require new valves/valve seats/head/engine anyway before the seats receed due to lack of lead in the petrol....that's a big assumption.
  
  put another way...how much are you spending, and how much will it save in the future?
  
  http://www.canleyclassics.com/infodatabase.asp?art...
  
  p.s. I run my Stag on shell optimax, i don't even know if it has harderned seats or not!

  • unleaded 

    Posted By : Nigel Gibbins, 05-Sep-2005, 01:56pm

    I completely agree... getting the valve seats done can be a case of if it ain't broke don't fix it. Just use the unleaded stuff anyway and keep a 'ear' on the tappets. Valve seat recession will only occure above 3000rpm in anycase and you will find you have to do 1000s of miles before you'll see/notice it.
    
    Keep adjusting the valves until you begin to run out of adjustment, then get the head done, afterall they would have to grind out the valve seats to fit the insterts anyway. You'll just have less to grind away .
    
    Of course, if the head is off for other 'work' anyway then you may as well get them done as it will only add a few quid to the price of the other work.
    
    If your engine has done 1000s of milea already then all that running may have hardened your seats for you already and after reading the Canley article you'll wonder why you were so worried in the first place.

  • unleaded 

    Posted By : Colin Wake, 05-Sep-2005, 05:07pm

    <Snip>
    Even then the damage will be minimal. it'll take many 10's of thousands of miles to seriously damage the engine...at which point you just get a new head.
    <snip>
    
    My only thought on this is what will another stag head cost??
    
    OK to do it on a spitfire ( I have!), there are shed loads of old heads about. Stag heads tend to warp so may be a bit thinner on teh ground.
    
    Colin

    • unleaded 

      Posted By : Nigel Gibbins, 05-Sep-2005, 10:30pm

      I suppose the theory is that the damaged parts will be ground out and replaced with the new valve seats anyway..

      • unleaded 

        Posted By : Chris Taylor, 06-Sep-2005, 07:30pm

        If I recall correctly, this issue was raised on this messageboard last year. Dave Pearson of Canley Classics posted a reply, which if I recall correctly, said that original Stag heads were fine for unleaded (designed for the American market) and there's precious little difference (if any) in today's so-called lead free heads.
        Even if you do get valve recession, there's no way you're going to damage the head irreparably. Because the head is alloy, it must have steel inserts already. IF they need replacing, they will be machined out. The engine will have ceased to run (*zero compression) LONG before the seat is burnt away.
        Fill up with unleaded, check for pinking, and then just forget, apart from checking on valve clearances from time to time.

        • unleaded 

          Posted By : Peter Coleman, 15-Sep-2005, 09:53am

          thanks for all your replies guys I will leave well alone now as I wont be doing excessive speeds or mileage in the new beast. incidently fitted a new fuel sender last night in the stag as the guage was not registering at all, ok now but the little darling refuses to turn over at all. sounds like either starter motor solenoid bad connection or battery is buggered as just get dimming of interior lights and strange noise from starter motor !! recharged battery but volt meter only showing 11 volts which I dont think is enough to turn the pig over. I will try spare battery and jump leads tonight any suggestions would be welcome .
          
          regards. pete.c

          • unleaded 

            Posted By : Chris Taylor, 15-Sep-2005, 06:43pm

            If your battery is only showing 11volts when fully charged, I'm afraid it's dead. It's probably lost one cell.
            (I'm assuming that you are measuring the voltage with the battery disconnected? If there is a bad current drain then that could account for a low reading, but you'd probably see smoke from the wiring loom with that sort of volt reading!!)