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Old 03-24-2005, 04:52 PM   #1
shifty
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67-72 engines leaded?

Are the stock engines that come with our truck supposed to use leaded gas? Are the parts hard enough on our trucks that it won't matter if unleaded gas is used? Should I get a lead additive for my gas, or does it not matter?

Just curious...
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Old 03-24-2005, 05:00 PM   #2
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Yep, they were designed for leaded gas. I would suggest using the additive
until the heads are replaced with hardened heads that can use regular gas.
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Old 03-24-2005, 05:00 PM   #3
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Depends on year of engine. I think starting in 71 all engines got hardened valve seats to compensate for lower lead/unleaded gas.
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Old 03-24-2005, 09:20 PM   #4
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Quote:
Originally Posted by CPNE
Depends on year of engine. I think starting in 71 all engines got hardened valve seats to compensate for lower lead/unleaded gas.
I think you are right. My owners manual for my 72 states "unleaded fuel only".
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Old 03-24-2005, 05:44 PM   #5
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Both of my engines are stamped with 1968, so I'm assuming they're both from 1968.

I'll buy some of the additive tonight and fill up this weekend. I don't think the previous owner actually knew the engine was leaded, so it's been driven for 16-18 months on the weekends with unleaded gas. Dunno if this is the case with the new engine. I know the engine I just put in had a lot of work done on the heads. Not sure about the rest - but it was a pro rebuild, so ...
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Old 03-24-2005, 05:50 PM   #6
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I would guess the heads were replaced with hardened heads if the engine
was professionally rebuilt.
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Old 03-24-2005, 06:34 PM   #7
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How expensive is the additive? You might be better off running without the lead additive and then just adding hardened seats when you start getting exessive valve seat recession. Your intakes should be fine so you would only be looking at replacing the exhaust. Buying the additive could add up in no time and when you are talking about installing 8 seats it doesn't cost that much.
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Old 03-24-2005, 06:54 PM   #8
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^what he said. Save your $ for later.
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Old 03-24-2005, 08:13 PM   #9
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Talking

Me too on the above posts.

The engine in your truck will last a long time without the additives unless you drive in such a way as to run the engine at elevated temperatures as in towing. Short trips and occasional driving should not cause the recession as it happens when the seats and valves get hot and the seat welds to the valve breaking it away. If you are going on a long sustained trip, additives might be a good idea.

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Old 03-24-2005, 08:41 PM   #10
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I have been told by a trained GM mech not to worry about it. Original engines, if the seats have not been re-ground, have enough lead build up on them to protect them.
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Old 03-25-2005, 01:59 AM   #11
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3 on the tree's tech has it right. You wouldn't need lead in an older motor unless you used it for all out towing or racing or the like - if it had been run for years on leaded gas. As others said, '72 was definitely built to allow unleaded. I don't know exactly what year that started though.
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