# regular gas vs unleaded?



## poncho power (Nov 28, 2012)

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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## poncho power (Nov 28, 2012)

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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## etewald (Dec 27, 2011)

As long as you use high octane(91 or 93), you'll be fine.


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## skurfan (Sep 19, 2012)

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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## 69ra3 (Dec 29, 2012)

Premium grade (high octane) and you should be fine unless you push it really hard frequently.


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## GTO JUDGE (May 14, 2005)

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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## poncho power (Nov 28, 2012)

Thanks for the info guys, I appreciate it....


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## 68greengoat (Sep 15, 2005)

poncho power said:


> 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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## geeteeohguy (Feb 2, 2008)

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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## 68GTO4004Spd (Jun 19, 2008)

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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## geeteeohguy (Feb 2, 2008)

I have heard the same thing from machinists. That said, I have personally experienced valve recession within 30,000 miles of normal use, and had a valve seat drop out of a head that was not installed correctly on another car. The "soft" seats in my '65 GTO have held up fine so far for 32 years and 50,000+ miles, and that car has been driven _hard_. Anybody else out there have any real world results of hardened vs oem valve seats??


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## BearGFR (Aug 25, 2008)

Lead in fuel served two purposes. One was to raise the octane rating, the other was to provide lubrication for the exhaust valve seats.

Like many things in the car hobby, this is one of those topics where you'll find people who are passionate about one position or the other: meaning whether or not hardened seats are necessary.

It's true that Pontiac "iron" is of better quality than bowtie iron. Also, unless you're spending lots of time under very heavy load (like pulling a trailer, or constant racing) it's not likely that you'll have a problem with "old" seats and unleaded fuel, in my opinion. It's also true that if you have the seats replaced and it's not done right, there's a risk there as well. (In addition because of that "joint" in the metal the seat inserts are going to tend to run hotter than they would if it was all continuous metal.)

In short, there's some degree of risk in both choices. Me, in my car and how I drive it, I'm sure I'm fine without replacing the seats. 

Everyone has to make that decision for themselves though.

Bear


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## danthepontiacman (Jul 5, 2008)

if your 350 is in good shape you should be ok, my dad had my cars original 326 2v engine rebuilt around 1982, phs papers state 9'2 compreshion for the 2v and frome that point to now it always gets reguler 89 octane put into its tank and never gets any additives. its been 0ver 30 years and 50'000 miles and has had to trouble. car gets driven liek a modern car meaning 70-75 on the highways, 60 on backroads, heavy takeoffs from time to time and even some 120 plus joyrides and still no trouble. pontiac designers had a very strong engine design that has proven durible even by todays standerds. with all that said i think your 350 be fine as long has your not drag raceing.:cool


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## poncho power (Nov 28, 2012)

thanks guys, this helps a bunch...... my car is just a cruiser, so there won't be much heavy foot action.


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