Mid '70s cars and lead gas requirements

bcubed72

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.)

andre1969

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.

Mr_Shiftright

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.

blh7068

"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.

Mr_Shiftright

Of course you can always retard the ignition timing a bit and run on regular, but then you'll lose power.

blh7068

"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!

71chevyc10

:surprise: 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. :sick:

Mr_Shiftright

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.

dweezil

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.

andys120

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..

IIRC my '89 Accord hatch had no Cat. Honda used a stratified charge lean-burn system called CVCC (Compound Vortex Controlled Combustion) to control emissions.

I won't pretend to know how it worked.

dweezil

Wow. All the way to 89. I didn't know that.

Honda started with that in the 70s and offered both CVCC and non CVCC Civics as well. Something to do with a 3rd valve, I think or a pre combustion chamber. I remember there were a couple of articles in Motor Trend at the time with lots of info and cut away drawings.

Apparently GM has developed something that ignites the fuel with out spark plugs, just using pressure. This eliminates a lot of emissions devices, runs cleaner, and imp[roves gas mileage. There's no unburned waste. It's in today's Car Connection.

texases

I thought that (CVCC) was during the '70s, with pretty much all cars switched over to unleaded and cats. They're listed for '89 Accords.

71chevyc10

ok so i have moved it back to about 10 degrees instead of 14 where i had it before. and it does run much better especially on the highway. so compression on the whole engine is about 120 per cylinder and about 95 on the 6th cylinder with the tapping noise. tapping meaning its probably the valvs. so it idles at 700-800 rpm and under load is abot 550- 600 rpm, is this normal? and it has good power from about 0- 30mph and even better power on the highway, it cruises at about 2700-3000 rpms on the highway going 60mph varing on the roads hills. so do you know if the rpm are ok at that speed. i drive about 20miles to school so about half hour on the roador more depending on traffic. :confuse:

Mr_Shiftright

It idles a bit high....you might check for a vacuum leak somewhere. The noise + lower compression could also be a worn camshaft lobe. I think that engine has hydraulic lifters but you may be able to snug them up a bit. You can also sometimes clean them by adding a cup of automatic transmission fluid to the oil, then run the car hard and change the oil out.

71chevyc10

so would a cam kit be a good idea right now or not. pull the heads and change everything out, valves and all. im going to try that trany oil thing u talked about. what it there is alot of carbon build up on the pistons and the heads. then what. clean it myself or take it in, cause yesterday me and my uncle bought a 63 chevy c10 and the heads looked like some one put mud on the pistons and alover the spark plugs. really bad. :surprise: ok so my truck now, the idle is lower at around 600 to 500 rpm at idle and under load about the same just lower , man it run really good at night with that cold air coming in, is that how its supose to run during the day??? really ballsy :shades: with just regular gas from chevron. ive tested all other ones and chevron seems to last me longer and better performance out of it? :shades: Hey thank alot for helping me out. really do appriciate it> Ben.

fezo

I had an 8o Accord and later an 85. Both were capable of running on leaded fuel in that they didn't have catalytic converters but the last year that Honda had a filler neck that would allow the leaded gas nozzle in was 1979.

I believe they changed the filler neck due to federal regulations kicking in. That's what the Honda service guy said - at the same time he was suggesting ways around it if I wanted to do that.