leaded gas

[bronco stuff]

do the early years 68 to 74 have to worry about using leaded gas or is it ok to run unleaded

 

[AZ73]

68-74 was designed to use leaded gas but will run fine on unleaded. There were basically 2 changes for unleaded - the addition of a catalytic converter, which would be destroyed by leaded gas - not a problem for 68-74, and hardened valve seats since the lead was used to "cushion" the valve when it closed. Running unleaded in a motor without these seats will lead to pre-mature wear of them, but any motor that's been rebuilt since the late 70's typically has the hardened seats added during a valve job or re-build. If you have your original valve seats (congratulations!) you can use an additive to help protect them, else just run it and when you're ready for a valve job, modify the seats then.

http://www.essentialhardware.com/product_detail.php?pid=141026&gclid=CJ-Q2J-C7LoCFaZ7QgodWSAApA

 

[broncnaz]

I really doubt that most engines that have been rebuilt have had the exhuast seats replaced. I know mine werent when it was rebuilt back in 86. Biggest issue there is cost. For the most part unless you have some rare heads I wouldnt really waste the money on getting older heads upgraded you can install newer heads for way less money. While it is desired I dont think its a huge problem unless you were going to run EFI on said engine. Carbed engines just dont last as long as EFI engines and will usually need to be rebuilt before the valve seats become a issue.
Additives will help them last longer but the actual issue compared to the cost of using additives over that time makes using the additives kind of a waste of money. IMO. Overall valve recession doesnt seem to be a big issue. I ran my 73 as a daily driver for many years with non hardened seats and unleaded gas no problem. There are still a lot of people running older vehicles with no issues.
Of course it wont hurt to use the additives but I would probably only use them every once in awhile. If the engine has a lot of miles on it already well Id just run it and not worry it will need a rebuild soon anyhow.

 

[Broncobowsher]

Most of these engine have been running the past 30 odd years on unleaded. So really a none issue. If it was going to be a problem, it would have shown itself in the past 30 years.

Lead was helpful in a couple of ways. Octane improvement was the biggest. Valves were the other. But the valves were typically only an issue on engines that were run hard. You still find lead in aircraft fuel since so many of the planes are old and the engines are typically run at near full power all the time. About the only other engine that gets that kind of use would be marine applications. My 52 year old boat has never had the engine opened up, that gets av-gas for a little lead and stability while in storage.

But for a typical old passenger car application, the absence of lead is not a problem.

 

[baddad457]

I don't see where you get the idea EFI motors last longer than one with a carb.

 

[Broncobowsher]

I don't see where you get the idea EFI motors last longer than one with a carb.

Well known fact. Carbs don't have as refined fuel delivery. You get a lot of fuel contamination in the oil, washed down cylinder walls from excessive fuel at startup. Most carbed engines will have noticeable cylinder wall wear by 100k. Maybe not enough for rebuilding, but noticeable wear. With no change to the actual engine but a good factory refined EFI that same engine will probably still have visible cross hatch on the cylinder walls.

 

[baddad457]

The reason you see little to no wear in today's EFI motors is due to the use of low tension piston rings. This almost eliminates bore wear. I think you're confusing bore wear causes here. EFI's also suffer from mixture problems, as much as a carbed motor does. Run the cheap gas with no additives and it won't take long before you get wild variations in mixture due to dirty injectors. I've taken apart enough EFI motors to see this, some cylinders rich, some lean. The computer will enrichen the mix to try and compensate for the lean cylinders to the point where you get what you descibe happens in a carbed motor. I've seen plenty of EFI motors with excessively worn bearings too, something that can be attributed to thinned engine oil from too much fuel washing down from the cylinders. (in addition to many other causes of worn bearings) EFI is not perfect when it comes to keeping the fuel mixture "right".

 

[broncnaz]

EFI May not be perfect but it is a whole lot more precise than many of the older carbed engines. Sure sometimes EFI F's up. Yes most of the EFI engines run lower tension oil rings but the oil rings are not what makes the ridge at the top of the cylinder anyhow. The top and 2nd ring are slightly thinner than the older carbed engines so there is some reduced friction but in the end less carbon and less unburnt fuel washing the cylinder walls in EFI engines that make for less cylinder wear. Of course theres other factors involved as well like piston materail, better machine work ect. That all help make the EFI engines last longer than the older carbed engines.
Heck most carbed engines will have black oil by 3000 miles where a EFI engine may take over 5000 miles and it still wont be no wheres near as black as the carbed engine.

 

[bknbronco]

My answer is simple.....use whatever the closest station sells. I have never used anything in my 68 289 except regular old 87 octane that every station sells. And my motor is stock 68

 

[roundhouse]

I'd be more concerned about the lack of zinc in the motor oil

If you have an older engine without a roller cam you need use a zinc additive since the fedgov outlawed it being added to the oil when the oil is manufactured

 

[baddad457]

EFI May not be perfect but it is a whole lot more precise than many of the older carbed engines. Sure sometimes EFI F's up. Yes most of the EFI engines run lower tension oil rings but the oil rings are not what makes the ridge at the top of the cylinder anyhow. The top and 2nd ring are slightly thinner than the older carbed engines so there is some reduced friction but in the end less carbon and less unburnt fuel washing the cylinder walls in EFI engines that make for less cylinder wear. Of course theres other factors involved as well like piston materail, better machine work ect. That all help make the EFI engines last longer than the older carbed engines.
Heck most carbed engines will have black oil by 3000 miles where a EFI engine may take over 5000 miles and it still wont be no wheres near as black as the carbed engine.

The low tension rings include the whole ring package, not just the oil rings. I can show you heads pulled from both carbed and EFI motors and without telling you which is which, you'd be hard pressed to tell the difference in the mixtures. And as for oil turning black after 3000 miles on a carbed motor, come look at the oil in my 331 after a year's service. It's still clear and it's got THREE carbs on it. The bore wear is hardly due to carb vs EFi. It's all in the low tension rings. Excessive engine wear is directly attributed to poor mantenence, not the fuel delivery method. The late model engines are put together with better materials (gaskets,etc) and tighter tolerances than the old engines, that in itself also lengthens their lifespans. I've seen more than my share of EFI motors that had short lifespans due to poor maintenence and were just as nasty inside as some carbed motors I've torn down in the past.

 

[bknbronco]

I'd be more concerned about the lack of zinc in the motor oil

If you have an older engine without a roller cam you need use a zinc additive since the fedgov outlawed it being added to the oil when the oil is manufactured

I skip that part also%). Its bad enough I gota change the oil every 3000 miles.