Vintage Mustang Forums banner

1 - 13 of 13 Posts

·
Registered
1967 GT500
Joined
·
567 Posts
Discussion Starter #1
I am about to purchase my first Shelby. I had a 1969 Cobra Jet 428 where I added octane booster to gas. I was told no need to add lead additive as 1969 Cobra Jets had hardened valve seats. For a 1967 PI, what is recommended? Octane booster and lead additive? Thanks.
 

·
Registered
Joined
·
1,077 Posts
Most don't get driven enough to need lead additive ! Octane boost will depend on many things---elevation,octane,timing,compression etc. try it without and see how it goes.
 

·
Registered
Joined
·
35,852 Posts
No, you do not need "lead additive" for either engine. Hardened valve seats completely eliminate any possible need for "lead additive". If you drive your CobraJet daily for the next 15-20 years, there might be a few thousand miles difference. Instead, put $4 in a cookie jar every time you buy gas. 20 years from now, use the money for a valve job.

Of course, if you aren't driving the car to work every day, then the valve seats will most likely never wear out. Fun cars are like that. I haven't needed to adjust the points in my "other" car in nearly 20 years.

Nor is "octane booster" needed. If you get ping under acceleration, use a better grade of gasoline.
 

·
Registered
Joined
·
406 Posts
Just had my heads redone on the 69 351w. I was adamant about adding hardened seats. The machine shop said they havent seen exhaust seats getting hammered like we were told they would by unleaded fuel, and said they would only replace them if they were excessively worn(which they were).
 

·
Registered
Joined
·
9,215 Posts
Amoco started with the lead-free gas in 1966. If this was a big issue, we'd have seen all kinds of problems by now. If the engine sees severe duty use,
I'd do the hardened seats for sure though.
DO NOT use octane booster. It leaves stuff behind in the combustion chamber which then increases your need for more booster or higher grades of
gas. (like a dog chasing its tail)
 
  • Like
Reactions: j persons

·
Registered
Joined
·
21,011 Posts
Hardened seats came out for the 75 cars when unleaded gas was introduced. The CJ wouldn't have them unless a shop added them.

Actually the only reason lead was added to gas was to boost octane. Back in the late 20's typical compression was about 5.5:1. Automotive engineers were looking at ways of boosting octane such as adding alcohol. They were also dealing with exhaust valve seat erosion. What the engineers discovered is if the engines detontated, they had exhaust seat erosion from micro welding. If the engine did not detonate, there was no exhaust seat erosion. Lead was added to raise octane as it was a very cheap way to raise octane and higher compression, more power and better fuel economy with a side benefit of reducing valve seat erosion since the engines wouldn't detonate.

Even back in the 1920 the dangers of tetraethyl lead was known. Maybe people because seriously ill including Thomas Midgley, who was the driving force of lead in gas.

I never worried about the lack of lead in gas. I grew up in the time of leaded gas. No detonation, no exhaust seat erosion. Today's octane rating system is different from the way octane was rated in the 60's. It would have a lower rating my today's standards .
 

·
Registered
Joined
·
125 Posts
Ford first used induction hardened valve seats on 1972 on the 360 and 390 FE engines. The head castings are D2TE-A. This was long after the last 428CJ was built.
Do you need hardened valve seats? No, but they are the only good way to repair worn valve seats. If your heads are not worn out then don't worry about it. Use the best unleaded premium that you can find.
 

·
Registered
Joined
·
35,904 Posts
Amoco started with the lead-free gas in 1966. If this was a big issue, we'd have seen all kinds of problems by now. If the engine sees severe duty use,
I'd do the hardened seats for sure though.
DO NOT use octane booster. It leaves stuff behind in the combustion chamber which then increases your need for more booster or higher grades of
gas. (like a dog chasing its tail)
Actually, Amoco Premium NEVER had lead, and TEL (tetraethyllead) only became common in the thirties as an anti-knock compound. Amoco used aromatics instead. Lead (and lead-substitutes) and just about any OTHER fuel additive cause deposits on spark plugs and valves. Lead, in itself, is corrosive and leads to premature exhaust system failure. Lead IS an effective element for preventing valve seat recession, particularly on air-cooled, constant load engines, like aircraft, medium-to-heavy duty trucks and stationary engines... ones that spend the vast majority of their time under load with high cylinder head and exhaust gas temperatures.

Ford (nor any other automaker to my knowledge) never warned its customers to NOT use Amoco gasoline or any other lead-free gasoline. In fact, I knew of folks back in the sixties that would ONLY use Amoco.
 

·
Registered
Joined
·
9,215 Posts
Here's one of the lead free magazine ads from 1966. (actually has the date on it..... tiny white typeface, very bottom to the right of the sign post)
My Mom worked for Standard Oil back in the day.


744273
 

·
Registered
Joined
·
35,904 Posts
Here's one of the lead free magazine ads from 1966. (actually has the date on it..... tiny white typeface, very bottom to the right of the sign post)
My Mom worked for Standard Oil back in the day.


View attachment 744273
While the AD was from 1966 it was nothing "new".

"While most oil companies were switching to leaded gasolines en masse during the mid-to-late 1920s, American Oil chose to continue marketing its premium-grade "Amoco-Gas" (later Amoco Super-Premium) as a lead-free gasoline by using aromatics rather than tetraethyllead to increase octane levels, decades before the environmental movement of the early 1970s led to more stringent auto-emission controls which ultimately mandated the universal phase out of leaded gasoline. The "Amoco" lead-free gasoline was sold at American's stations in the eastern and southern U.S. alongside American Regular gasoline, which was a leaded fuel. Lead-free Amoco was introduced in the Indiana Standard marketing area in 1970.[9] The Red Crown Regular and White Crown Premium (later Gold Crown Super Premium) gasolines marketed by parent company Standard Oil (Indiana) in its prime marketing area in the Midwest before 1961 also contained lead. "
 

·
Registered
Joined
·
2,399 Posts
Unocal published a paper in the SAE journal in 87 testing various conditions and combinations. Those were then compared to other studies at the time. The conclusion of that test was largely in line with the others. The difference in the conclusions of each test was down to the amount of lead/TEL per gallon of fuel that lead to recession of the valve seats. The primary factors in the amount of wear are duty cycle and duration though wear happens at lower duty cycles and duration just not to the degree of the more demanding conditions. Bottomline is that a minimum of .02 grams of lead/TEL per gallon of gasoline is required to prevent recession on non hardened valve seats particularly head built in the 60s. IOW using unleaded fuel over an extended period of time in your unmodified 60s Mustang heads will indeed lead to valve seat recession.

Croudace, Michael C., and Tim Wusz. “The Effect of Low Lead Gasolines and Some Aftermarket Lead Substitutes on Exhaust Valve Seat Wear.” SAE Transactions, vol. 96, 1987, pp. 423–432. JSTOR, www.jstor.org/stable/44469157. Accessed 12 Feb. 2020.
 
1 - 13 of 13 Posts
Top