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#1 of 17 Mid '70s cars and lead gas requirements
Feb 25, 2007 (9:56 pm)
I'm looking for an affordable, domestic, older car. Since aging boomers have driven the late-60's/early 70's cars beyond my price range, I'm looking at 75+, probably up to the introduction of smog equip (I recall from experience as a kid that early smog stuff wasn't very efficient and took a big performance hit).
I'd appreciate having a few "leaded gas" questions answered.
1. My understanding is that cars went from "soft valves/lead required" to "hard valves/lead or UL okay" to "catalysts installed/UL required." What's the yearly breakdown here? Same for all the big three? Where do I find this out?
2. If I get a leaded car--since you can't buy "regular" these days--I see three options: run UL for as long as possible, buy a lead additive, or use something like 100LL aviation gas.
a. what's cheapest?
b. Is it legal to run 100LL in a car? What would be the penalty if caught?
c. 100LL has 2g lead/gallon. What's the min requuired (i.e. can I "step on it" to save $$$?)
d. 100"octane" avgas calculates octane in a different way and its octane is higher than (R+M)/2 octane. Any ideas what it works out to?
4. I know aircraft that can run auto gas CAN'T run ethanol blends due to rubber in the fuel line that'll deteriorate. Modern cars are equipped for this, but will running ethanol blends in an older car cause rubber bits to clog the carb? (I see the "ethanol" page but didn't want to start a new thread just for this.)
#2 of 17 Re: Mid '70s cars and lead gas requirements [bcubed72]
Feb 26, 2007 (6:02 am)
In a rare moment of anticipation, the Detroit auto makers saw the coming of stricter emissions requirements and phase-out of leaded gasoline, so they switched over to hardened valves several years in advance. I think 1969 was the year that cars started switching over to hardened valve seals, but they may not have all done it at once.
Once they started putting catalytic converters on cars, you couldn't run leaded fuel anymore, because it would eat out the converter. The catalytic converter started showing up on cars in 1975, but I don't think it was mandatory. Some cars were able to get by legally without it. I think mainly imports, but back in college I had a friend who had a 1976 AMC Hornet wagon that didn't have a converter. Her parents had bought it new, and the car actually came with documentation stating that it was exempt from a converter requirement. I don't know what the story was behind that, but it did pose a problem years later, when she got a notice to bring it in for emissions testing and they tried to fail her for not having a converter. Her parents had to fish around for that documentation to prove that it left the factory that way!
So I'd say, as a general rule, you're probably fine with unleaded fuel in anything from around 1969-74, but should use a lead substitute/additive in anything earlier that hasn't been rebuilt (and I'd imagine that any engine that was rebuilt in recent memory would have been done so with hardened valves), and anything 1975 and later would be unleaded-only.
Any car that requires unleaded fuel will have warning labels on it. Usually there's a label at the fuel filler, along with a restricted opening that keeps you from putting too big of a tube down there (the old leaded pumps had a larger nozzle). And most 70's cars would have a label somewhere on the dashboard too, usually on the face of the fuel gauge.
#3 of 17 Re: Mid '70s cars and lead gas requirements [bcubed72]
by Mr_Shiftright HOST
Feb 26, 2007 (9:48 am)
I think that unless you are buying a very high compression car, that you can run unleaded in any old car as long as you aren't racing it or towing with it.
So in other words, any worries about the lack of lead in the fuel is related to high engine stresses....for cruising around town or freeways I don't think an old engine would mind unleaded fuel at all.
If you really want to 'get on it', then use additives as fintail suggests.
#4 of 17 Re: Mid '70s cars and lead gas requirements [andre1969]
Mar 16, 2007 (9:12 am)
"I think 1969 was the year that cars started switching over to hardened valve seals, but they may not have all done it at once."
Actually it was 1971. Yeah, 1975 was the first year for the catalytic converter, that required the use of unleaded fuel.
My 71 firebird is basically bone stock and runs on unleaded...but requires 91 octane. It lets me know if it doesnt get it, lots of spark knock.
#5 of 17 Re: Mid '70s cars and lead gas requirements [blh7068]
by Mr_Shiftright HOST
Mar 16, 2007 (9:14 am)
Of course you can always retard the ignition timing a bit and run on regular, but then you'll lose power.
#6 of 17 Re: Mid '70s cars and lead gas requirements [Mr_Shiftright]
Mar 16, 2007 (10:33 am)
"Of course you can always retard the ignition timing a bit and run on regular, but then you'll lose power"
Actually shifty, Ive got it advanced, so I throw a little octane boost in. The 2.73 rear end bogs it down at it is!
#7 of 17 Re: Mid '70s cars and lead gas requirements [blh7068]
Aug 12, 2007 (10:26 pm)
HEY, SO I GOT THIS 71 CHEVY C10 WITH AN ENGINE FROM A 72 C20. V8 350 I BELIEVE. WITH A TH350 TRANS 4BARREL CARB Q-JET. RUN COOL AND IT HAS LOW COMPRESSION. TIMING IS SET AT ABOUT 13-14 BTDC. RUN GOOD AND I HAVE TRIED ALL OCTANES AND SOMETIMES THEY FEEL THE SAME. COULD IT BE BECAUSE OF THELOW COMPRESSION. I CLEAN MY PULGS EVERY WEEK, I HAVE MSD SUPER CONDUCTOR WIRES AND AN hei DISTRIBUTOR. WITH LIGHT SPRINGS. SHOULD I USE HEAVIER SPRINGS OR HOW DO I GET IT TO RUN BETTER. ITS THE RINGS THAT ARE BAD AND ON ONE CYLINDER THE VALVS A BAD CAUSE IT HAS THE LOWEST COMPRESSION OF THEM ALL WITH MINIMAL OIL ON THE PLUGS.
#8 of 17 Re: Mid '70s cars and lead gas requirements [71chevyc10]
by Mr_Shiftright HOST
Aug 13, 2007 (9:41 am)
If you mean 13-14 degrees at idle, that's too much.
Also with low compression you can't expect much--a cylinder needs a minimum of about 85 psi to fire. MSD wires and HEI only matter for very high HP engines.
Why don't you do a cylinder leakdown test and figure out exactly what you need? If it's just a head freshening, that's not too hard to do. If it's rings, you might think about buying a crate engine and just dropping that in there. Instant, cheap HP and a warranty for maybe $3,500.
Aug 25, 2007 (6:09 pm)
If you are worried there are additives out there. STP makes one,though it may be dropping the product as the latest batch I found [STP Unleaded Fuel Substitute], I found at Big Lots for 1.00 each.Some other companies offer it too... "101" something with all the octane boosters.
I use it in my 63 Valiant, though the engine isn't original. It may very well may have been from a 73 or later car which would have had the hardened valve seats or the upgrade at rebuild as the "new" engine was installed in 1988.It's only covered some 15,000 miles since then and my adding the lead subsitute has been erratic, but there have been no problems so far.
At this rate I will be worrying about finding any fuel derived from dinosaur squeezins by the time any problems might arise from using the unleaded.
CA phased out leaded fuel completely not long after that. Arco offered something called EC 1 that was made for cars that required leaded gas. Don't know what additive was in that.
You'll be fine. Just about everyone had gone to unleaded gas by 1975
and made the proper mechanical revisions, though Subaru and Honda IIRC had emissions controls that would allow a driver to use either leaded or unleaded to no ill effect. They had engineered them in such a way they didn't need catalytic converters to meet Fed standards.