Old Automobiles Running On Unleaded Gasoline (vehicle, fuel, octane, valve)
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I saw an early 1960s Ford Thunderbird on the freeway yesterday and I wondered, if the engine's specs are exactly what they were when the car came out of the factory. I know that unleaded gasoline will shorten the life of the valves in engines that were made before unleaded gasolne became available in the mid 1970s, since lead will cool the valves. I also know that many classic automobile enthusiasts prefer to keep all of the components as original as possible to maintain the performance the vehicle was designed to have.
It's been over 20 years since I worked on rebuilding an engine, which was on a 1961 Chevrolet heavy-half truck, and I'm curious, what are some of the ways to build old engines so that they'll run on unleaded gasoline, besides putting stainless steel valves? Does modern unleaded gasoline have something in it that allows you to use it in pre-mid 1970s automobiles? Do you also need to add a catalytic converter in the exhaust system?
When most people rebuild an older engine they add in hardened valve seats as the lead in the gasoline would help cushion these and without the lead the seats are beat to death. The lead also boosted the octane rating. Pretty much all older cars will run on modern 93 octane without issue and they also sell lead additive for these cars as well. People go back and forth in the classic world about how necessary it is. Basically it comes down to what you are using the car for. More performance oriented cars that are driven harder can really use the lead additive. Regular older cars driven casually will do just fine on modern unleaded gas.
When it comes to emissions, you are only required to meet the emissions criteria of the model year car you have. If it didn't come with cats, you don't need to add them and there is no benefit from doing it.
I rebuilt a '68 472 a few years ago and had the heads redone and updated for newer gasoline. The primary difference being hardened valve seats. Also did away with the old umbrella style valve seals and went with neoprene collar seals and installed a performance shaft rocker setup.
Having worked in a RR/Bentley restoration clinic and fussing over the most microscopic detail concerning originality I am fairly strict about keeping things original however there are just some components that are much better off upgraded. If it is a performance upgrade and can be hidden from a judging eye then I say go for it.
I would add that more important than the lead content in gasoline is the lack of ZDDP (zinc dithiophosphate) in modern engine oil. It is very important for the longevity of older flat tappet cam configurations. I won't run one of these engines without the additive.
Last edited by Lux Hauler; 09-02-2010 at 09:22 AM..
As NJGOAT says, when most people rebuild the motor they used hardened valve seats. But most of the guys I know, including myself, don't bother unless you are driving the car hard or driving it a lot. My 62 T-bird is a cruiser, I don't get it out as much as I'd like. Still it's got the original motor in it and probably has a good 20,000+ miles since leaded fuel was phased out. The motor still runs strong and doesn't smoke, so I'm avoiding tearing down the motor at all. I haven't even had the valve covers off in the two and a half years I've owned it.
As far as octane level, most pre-70s cars are low compression in comparison to modern motors, so even running on 89 octane fuel is fine. No need for premium, which is primarily needed for high performance modern (high compression) motors.
And no smog equipment is required. It varies from state to state and even county to county how old is old enough, but as a general rule anything over 25 years old is exempt from smog equipment and testing.
BTW - there is something missing from modern oils as well - zinc. Zinc helps lubricate the camshaft lobes where they contact the lifters. Most really modern motors (90s +) have roller cams and don't need it. Most cars from the 80s and before don't, and really need zinc for longevity of the cam and lifters. Some oils (Amsoil, Rotella and some diesel oils) still have zinc, so you either need to use those or a zinc additive for older motors. I use Rotella.
BTW - there is something missing from modern oils as well - zinc. Zinc helps lubricate the camshaft lobes where they contact the lifters. Most really modern motors (90s +) have roller cams and don't need it. Most cars from the 80s and before don't, and really need zinc for longevity of the cam and lifters. Some oils (Amsoil, Rotella and some diesel oils) still have zinc, so you either need to use those or a zinc additive for older motors. I use Rotella.
No oils contain the necessary amount of zinc anymore due to emission reasons. Only source is from additives.
I don't get to see many older cars these days, but I had the idea sodium cooled valves were a common cure for the exhaust valves as well as hardened seats.
And i agree if a vehical was oem with no cat it needs no cat, and the cat would likely harm the exhaust valves too.
I don't get to see many older cars these days, but I had the idea sodium cooled valves were a common cure for the exhaust valves as well as hardened seats.
I think the sodium valves are bit cost prohibitive Mac!
Std equipment in cookie cutter cars in the mid 70's, Yeah they cost more than solid steel but weren't that bad over all for a good solid built engine. Times no doubt have changed.
Just never cut or grind one to be exposed to air. Things go boom then.
The only cars I've seen in normal driving that have had issues with the unleaded gas where older Brit cars where the heads didn't have inserted valve seats ... like old MG's. The cure is simple ... R&R the head and have stellite seats installed. From time to time, we'll add a bit of Dexron or Marvel Mystery Oil to the fuel ... not enough to see visible smoke, but the motors do seem to run a bit smoother for quite awhile after the tank of gas with that in it.
The materials in the old BMW's and MB's I work on don't seem to have any problems.
We do use Rotella T in just about every vehicle, and Lucas oil additive in all the heavy duty motors. I used to use the BGMOA or DOC in every oil change for my customers ... and that combination eliminated the cam/follower wear in those OHC motors, including the diesels. I assumed that the BG formulations contained a lot of TCP and zinc.
I've got neighbors with sizable collections of 1950's-60's farm trucks, domestic cars ... one fellow with a collection of Dodge/Chrysler/Plymouth cars of the 40's-60's. While none of these get a lot of mileage, the trucks do see some heavy service during harvest season each year ... and all run fine on the cheapest unleaded fuel they can buy. I see a number of summer driver cars around here ... 60's era mustangs and corvettes ... which also seem to be doing fine on the available fuels.
FWIW ... in this area, we use a lot of farm tractors from the 1940's-50's ... 8N/9N/2N Fords, IHC Super A's ... and similar small farm utility tractors. Mine get heavy use with bushhogging, grading, raking, manure spreading service ... a neighbor uses his 8N's in a landscaping/concrete business ... and these tractors don't seem to suffer any problems with the unleaded fuel. The 8N motor is essentially a Ford Model A motor with a governor; the biggest problem I've ever had with it mechanically was the intake/exhaust manifold warping and disintegrating at cylinder #4, fixed by an inexpensive new replacement ($88).
Last edited by sunsprit; 09-02-2010 at 11:46 AM..
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