What gas should I be using

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keith9291

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I just recently bought a 71 Swinger with 75,000 original miles on it. Car is in fantastic condition and runs great...A/C still blows cold. I am wondering what grade gas I should be buying and should I be adding any lead additives? I dont want to be using the wrong fuel and do any damage. I found this "fuel usage statement" in the paper work i got.

Chrylser supports all efforts to control and reduce vehicle emissions and will continue to design its engines towards this end. As a result, our 1971 "regular" fuel engines are designed to operate in normal usage on 91 octane "low lead" or "low polluntant" gasolines containing at least 0.5 grams per gallon of lead, or the equivalent additive.

such fuels are suitable for use in all 1971 Chrysler Corporation passenger cars, except those cars equipped with engine designed specifically to operate on premium fuels.
These engines are,
340 Cubic Inch Displacement
426 Cubic Inch Displacement Hemi
440 Cubic Inch Displacement High performance
(with single 4 barrel carburetor, 9.7:1 compression ratio, 370 H.P.)
440 Cubic Inch Displacement with 3-2 barrel carburetors.

Chrysler Corporation recommends against continuous use of completely lead-free or clear gasolines which do not contain suitable lubricating additives such as lead or phosphorus. Continuous use of such fuels in normal driving could cause valve seat burning, resulting in excessive emissions, poor performance and possible engine failure.
 
As far as octane ratings go, I think the rule of thumb is that as long as the engine is tuned/timed properly, you can use the lowest grade fuel unless it begins to detonate (especially under load). I am not one for retarding though. As far as unleaded fuel goes, you could go through the cost of installing hardened seats but again, there are just tons of people running these motors on unleaded pump gas. I guess you could pour in some lead additive to lubricate the seats every once in awhile if it makes you feel more comfortable.
 
with saying that I can use the lowest grade of fuel unless it detonates, does this mean by using higher grade I am less likely to detonate? If that is the case would it be safer to use a higher grade to begin with? Will the lead additive actually help the seats? Does the gas of the early 70's have different additives and such as the gas now? I just dont want to be doing and damage to the engine if I can avoid it and later find out I should of been using this octane and this addtive!
 
Hi Keith, what size engine do you have?
Adding a lead additive will not cause any damage to a "no lead engine" (it will damage the atmosphere), as for as octane boosters go, all engines run better with higher octane, you will get higher gas mileage, cleaner burn, less chance for detonation (pinging) and a bit more HP.
If you are going to be using this vehicle for regular driving, not racing, skip the lead. It will take a lot of miles before you chip a valve or damage the valve seats in regular driving.
The only other thing the higher octane will cause, is a slightly higher engine temperature.
 

What engine do you have? With the engines you listed in your post I would use premium. If it is a /6 or 318 I would use regular. As far as the lead is concerned. If you run unleaded fuel the exhaust seats in the head will get beat out if you drive your car daily. I had a '69 Fury III with a 273 that I had as a daily driver. I put a set of rebuilt heads on the car and about 18 months later I was pulling them back off because it was running so poorly. The exhaust seats were all beat in from not having the lead in the fuel. If you are going to drive your car daily put on later model heads or hard seats in your older heads because the seats will eventually go bad.

Chuck
 
sorry guys my engine is a 318 and it will be used as a daily driver.

I have thought about buying a new set of heads for it. I had a flier from Hensley I got from one of the shows they have a kit for around a grand that is prepped heads, intake, carb and cam. Does that sound like a decent price anyone used Hensley in the past?
 
I've bought stuff from hensley and they were great to deal with....I'll buy from them again.
 
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