I have read that unleaded gas can be hard on the valve seats of older engines like my 292. Can some kind soul explain this for a newby such as myself? Is there something i should be doing to my engine?

 

This question has been asked before. Years ago I used the lead additive, then got away from it. Some resident experts here and elsewhere have said you don't haul heavy loads or drive consistanetly at high revs or high speeds then you don't need the lead for trucks that do not have the hardened valve seats.

Haven't added lead in my '54 239 for probably 15 years and I have seen no problems.

abe
abe

 

Hi Dave,

Here's my $.03:

The lead content in gasoline was used (among many other reasons) to lubricate valve seats, primarily the exhaust, in engines made before the mid '70s. When lead was removed, many magazines predicted dire consequences for older engines, and talked about using lead substitute additives, installing hardened seats, water injection to (again, among other things) cool the combustion process, and probably others that I've forgotten now. It's become folklore, now.

Now that 25 years or so have gone by, we've had a chance to look at this...and found, for the most part, nothing.

Let me expand on this a little. I can tell you from personal experience, in the engines/cylinder heads I've torn down since 1980, waaay over a hundred at this point, I've found 3 (three) that had seat problems (possibly) traceable to unleaded gas. All of them were used in RV/heavy continual towing or marine applications, which mean continuous running under heavy loads with higher exhaust temps. All three were from the mid-late '70s, with two having the primitive emissions controls and lean mixture calibrations of the time. The marine engine was, to be blunt, owned by someone who abused it.

In the average everyday grocery getters, and hot rods, I've never found a problem, and in talking to others who are actually in the repair business, that seems to be the general consensus. I have been told that some of the early-mid '80s 302/5.0s & 460s had issues, due to poor metallurgy, but I did not personally run across that in the few I've looked at.

Nowadays, if I rebuild an older engine, I have new seats fitted as a matter of routine- but for the most part, that's because they have recessed seats due to high mileage, or previous work. Under certain circumstances I might choose not to, but for the most part I file it under "Well, as long as I'm already in there...."

I can tell you that I currently have two '50s vintage engines, unrebuilt, that use unleaded gas without a problem. Will they have problems with the seats? Maybe eventually, but I doubt in my lifetime.

If your 292 has valve problems, it'll be due to old age, not unleaded gas. Now, let the dissenting opinions begin

 

The only thing Id add to that is what about this grain alcohol mix thats being used in the midwest? B35 or some such designation.

Ive several pre smog drivers here from bone stock I6 to a 400 or so HP 396 Chebby and have had zero problems with todays winter/summer blend changes. However I have to back off the advance a bit on the 396 when the summer stuff is at the pumps or drive 20 miles North to a different EPA zone!

 

Great topic...and response from Homespun91.

Based on what you've all said, I'll probably quit dumping "lead additive" into my two pre-1970 cars. Putting Supreme into them is already expensive enough!

 

Hey Rob,

The other thing that some (probably not all) additives do...which isn't always mentioned by their manufacturers (shockingly enough )...is that they can leave deposits in the combustion chambers, which sometimes can cause detonation.

Separately, but related: One sign of detonation is, when using a viewer, you can see tiny purplish "*****" on the plug porcelain. When using additives, these specks are noticeably bigger. Stop using the additive, the specks go away, or decrease in size. Note: the specks are an effect, not the cause; but I think the additives can exaggerate the problem, at times. Not exactly scientific, I know.

Carl, that E85 stuff isn't too common here yet; the only station in Illinois south of Chicago is 40 miles away from me. E85 is pretty much a nightmare for anything older than the late '90s IMHO. My '98 F-150 is set up for it though, & I have been told that most Fords were since '97-'98, though Ford made no big deal about it.

Rob, depending on what you drive & how often, you might consider getting some 100LL at the local airport. There are restrictions on its use, but you can usually find a helpful soul. A few gallons mixes nicely with pump swill & works well for engines that get, um, exercised.

 

I've seen the 100LL trick. I was filling up an airplane once in NM when this guy pulled up in a drag car and patiently waited his turn. I think he was headed to the local strip. The car was unbelievably loud!

100LL is 3-4 bucks a gallon these days...

 

everyone seems brain washed on the valve seats.i thought i needed them as well until i asked around.not one rebuilder said to bother unless you are going to work the hell out of it.

 

The other thing to consider is that, unless the machinist knows what he/she is doing, & quality seats are used, you can have some big problems. It's not the easiest process in the world; not the most difficult, either.

Around here for a while in 2005, 100LL was virtually the same price as pump swill! It's still only about .90 more; & mixing 20% is cheaper than buying premium.

 

just for the record, my 66F250 352 has run 140,000 and no valve problems yet, 1966 Mustang, stock 289, 102,000 and no valve problem....rebuilt my 1960 223 six and didn't add hardened seats, now has 60,000 on the engine and no problems yet, I did change them in my other 66 Mustang that has a built 302 and gets run in the ground

 

Thank All for the information. Thanks also for not beating me up over using the list search option first, I'm still new enough to this forum that "searching" doesn't occur to me before i hit the post button.

Dave

 

Do a search in this forum and you might find some threads on this subject....