regular gas vs unleaded? - Pontiac GTO Forum
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post #1 of 14 (permalink) Old 01-08-2013, 05:03 PM Thread Starter
 
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regular gas vs unleaded?

What's your guy's thoughts on using reg unleaded in these old cars that were meant to run Regular leaded? Is it a big deal to run unleaded in my 68 lemans if the valves or seats haven't been changed out?
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post #2 of 14 (permalink) Old 01-08-2013, 05:48 PM Thread Starter
 
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I should add, all I have is a 350 with a 2 barrel....... wasn't the whole lead deal more to do with high performance engines?
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post #3 of 14 (permalink) Old 01-08-2013, 07:23 PM
 
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As long as you use high octane(91 or 93), you'll be fine.
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post #4 of 14 (permalink) Old 01-08-2013, 09:17 PM
 
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I use the regular with lead substitute in my '55 and it does fine. The GTO needs high octane and I put lead substitute in hat too, but not sure if it is necessary.
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post #5 of 14 (permalink) Old 01-08-2013, 09:43 PM
 
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Premium grade (high octane) and you should be fine unless you push it really hard frequently.
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post #6 of 14 (permalink) Old 01-09-2013, 06:06 AM
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I am using Lucas Ethanol Treatment.

I add 1oz per every 5 gallons at every fill. I noticed improved detonation. The car ran great before, but since using it, I noticed improved firing.

If your car begins running like $hit after years of using this junk gas, check the rubber in the carb for cracks and replace with ethanol friendly ones.

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post #7 of 14 (permalink) Old 01-09-2013, 08:58 AM Thread Starter
 
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Thanks for the info guys, I appreciate it....
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post #8 of 14 (permalink) Old 01-09-2013, 09:41 AM
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Originally Posted by poncho power View Post
I should add, all I have is a 350 with a 2 barrel....... wasn't the whole lead deal more to do with high performance engines?
It's my understanding it had to do with the valve seats. To run unleaded you wanted hardened valve seats. If the seats haven't been changed, I would run a lead substitute too....



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post #9 of 14 (permalink) Old 01-09-2013, 11:05 AM
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The general consensus in the industry is that lead is needed for these cars IF they are running under constant high load: above 3000 rpm for extended periods or trailer towing. The lead is needed to prevent valve seat recession. Hardened valve seats aren't deemed necessary if the car is a cruiser/not pushed super hard. I have seen valve seat recession in some of my own cars over the years running unleaded fuel and stock valve seats, and these cars were not driven super hard and had mild camshafts. I re-did the heads on my '67 about 5 years ago (6-10k miles ago) with stock soft seats (all I could find for my small valve heads). I'll let you know down the line if I have issues, as I drive the car a lot.
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post #10 of 14 (permalink) Old 01-09-2013, 01:16 PM
 
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I used to work with a guy that built Pro Stock Oldmobile engines, he said that BOP used a better grade of metal than Chevy heads. When I asked him if I should put hardened seats in my engine, he said that it wasn't neccessary. He also claimed that if the seats aren't installed right, they can push out and destroy your engine. I can't say if any of that is true or not though just food for thought.
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