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Discussion Starter #1
Does the 1970 vette, 350/350, 11 to 1 compression need leaded premium or will it be okay on unleaded premium fuel ??
 

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I don t think you will find any leaded premium anymore...you can run unleaded .. the lead was to increase octane and provide some lubrication for valve seats. the octane of 91-93 premium is fine if you don t use to much timing advance..and you can add an upper cylinder lubricant like Lucas or similar.
 

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it's even getting hard to find leaded race gas.....
 

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In 1970 (if it is still original) it was using leaded fuel. You might try using a lead additive or mix with leaded race gas (I have heard of guys mixing in aviation fuel) If the the heads have been reworked and hardened valve seats have been installed, then you can use unleaded. In any case, with 11:1 compression you will probably need the highest octane gas sold today. I have 11.4:1 in my 427 and I mix race gas with 93 octane.
 

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lead additive is going to be extremely hard to find, unless someone has old stock.. the best you can do is Lead Substitute, which is basically an upper cylinder lubricant. If you try mixing AV-Gas with your unleaded, you will need to re-jet the carb as AV Gas is less dense and therefore lighter ,and will run lean....it requires larger jetting, causing less MPG and at $5 /gal, will get expensive to use.
 

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Discussion Starter #6
Didn't think about top cylinder lube. Lead substitute will work fine. The engine has not been torn down, head numbers and dates are correct. Needs valve cover gaskets anyways as they where leaking. Took it out for a romp and ran okay. Has a ticking noise from the right rear, not the brake, that goes away when you get below 10 MPH. When on the lift, I could not get it to make a noise nor detect any slop in the halhshafts or drive shaft. Will change out the ujoints as they look to be the original ones.
I did not beat it, took it up to 4,500 RPMs in 1st, 2nd and 3rd. ran good except for one handling issue that I will address in a seperate post. He went with me and we BS about the car on the ride. When we got back, he said,"lets ride and this is what it can do". Pulled out of his shop and he hammered it, lighting up the tires, got 2nd gear rubber and 3rd was a chirp, but speed was only 45 MPH when he hit 3rd. Don't like to abuse an original car like that. Glad he did it and not me.
 

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Tetraethyl lead was added to the old gasolines to provide cushioning to the exhaust valve faces and seats. When they went to unleaded fuels (1973?) they started "induction hardening" the exhaust seats. That helped reduce "valve seat recession" (the sinking of the exhaust valves into the head). The problem is once a valve job is done the seats aren't as hard as they originally were as some of the hardness is cut away during the valve job. So after a lot of miles the valves will sink into the heads a little bit. The cure is to have "stellite" seats installed or buy a set of aluminum heads as they come with hard seats installed. My cast iron Dart heads also have the hard seats installed. Valve seat recession takes a long time to occur so if your heads don't have hardened seats right now I wouldn't worry about it too much. Just have hard seats put in when you have a valve job done. But quite frankly it's fairly expensive to put hard seats in so I would consider replacing them with a set of aftermarket heads.
 
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