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Lead additive

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DonJ

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In older Jags such as mine I believe that the lead in the gas provided some lubrication to the valves, or valve seats, I don't remember which. What is the opinion of running a lead additive through an occasional tank of gas? A waste of time and money or does it do some good?

Thanks,
dj
 
In the 50 yrs. I have been running the older Jags, I have never used an additive, except fuel conditioner. I have always used higher octane fuel with no valve problems. The older cars were run in an era of white gas ( no lead ) in the 50s and then lead was added. Then the lead was supposedly removed from fuel in the 70s. If you are going to race the car, be it track, solo, etc., definitely add the additive. My 50s Jags use premium fuel, no additives without problems. If you can find a non-alcohol fuel from a reputable dealer, by all means use it. Alcohol will be the worse on carbs and hoses and fuel sending units than the no-lead of the fuel.
 
My primary marque is old flathead Fords. I have never used an additive in them, one engine (I rebuilt it in 1972 or 1973) went 300K, rings wore out, guides loose, I can lap and hone, new rings and it will be fine. NEVER had an issue with seats or valves.
My Jag (2.4L, but same head design as 3.4 and 3.8)...PO provided me with some hairball additive, used it twice, drove it 40K without, engine had a problem, but it was clueless mechanics last rebuild....two bent vales (camshaft advance), oil pump, rings....but I replaced two valves, lapped them all...and no problems.

Are there issues? Yes....cars "of the era" when they dropped lead sometimes had cast iron heads and integral cast iron valve seats.....and yes, you could and did. Have issues.
Almost every Flathead Ford has insert valve seats, and with aluminium heads (like on XK Jag engines), you probably better have something stronger than aluminium seats...which they do.
 
I agree - no additive in my E-Type. I do carry a bottle of octane booster in case I am forced to get regular gas somewhere (remote areas of AZ may only have one grade available).

On my TR with a cast iron head I did experience valve recession, the final time was after an 8 hour high speed (80ish mph) run from CA to AZ. I just figured I'd drive until the receded to the point where I could not adjust them, then get hardened seats. I did and it did and all has been fine since.
 
To tell you a story on this.....my Jag, when I got it and checked it over...the exhaust lash was perfect...inlets were zero lash.
You could turn the pucks, but a .0015" would in no way, shape or form fit.
I thought, maybe, I was starting to sink some valves through the seats....but they were all exactly the same.
So, I drove it...for 40K...and they never, ever changed.

Morons set them to zero as the inlet valves were hitting the pistons and they were clueless (apparently) as to how to fix it...like, oh, maybe set the cams to the gear properly?

Then to get some power out of the pig (remember 2.4L), they put Mercedes Pontoon carbs on it...welded the advance plate shut (well, brazed it in 3 places) and it was still a pig...but, since I had exactly zero experience with any Jag 2.4L, I thought that was it.
Boy, was I wrong.
Once I got carbs, then breaker plate cut lose, advance working...then the cams done....it does move now.
 
Hmmmm, I have always been the antiadditive, such as zinc guy and always get hammered so at last I gave in and got a case of lead additive on Amazo. Drive it about 750 miles a year, 25 or so each time aloong PCH at rarely over 4K rpm. Also have been doing these cars for over forty years and never change brake fluid, the usual every 10, years or so seal replacement, that wheel gets bled. Daily cars up to 80,000 mi before replace and never touch brake fluid, Subaru for cabin in WY 14 yrs old, 92000 mi fluid still up, all is well. Go ahead, let me have it. What no one can let me have is solid data on brake fluid end of life. other than mythologies such as lead, zinc or car will blow up.
Jay, '67 Etype convt.
 
Only main problem with brake fluid is the absorbing of water. As the pipes heat and cool the internals drip moisture, as brake fluid is a good absorber of water. * note on fluid container, unsealed can absorbs moisture. Regular bleeding, bi-annual, at all bleed points pushes the moisture out and prevents the seal leaks and soft pedals. Sure you can go 80,000 without touching fluid, but, how much corrosion is in the system from the moisture? Like the rusty master cylinder bowls. I, myself, would rather know I can stop, rather than hope I can. I have cars from the 50s, 60, 70s and newer, and all are bled every 2 years, no matter what, Same as cooling systems. Another story. As for lead additive. Been a mechanic for 52 yrs., never used the additive, never saw a street problem without it. The 50s to early 60s cars were run on white gas (as it was called) non-lead fuel. Lead was introduce in early 60s ( note fuel price increase for the additive) the eliminated in the 70s ( another price increase to leave it out). Unless you race a car or drive it hard you don't need it. Like the Jags, they used hardened seats because of the racing by the factory and just put them in all the XK engines ( might get an argument here ) but, my good machine shop noted that the Brits knew about hardening steel and said it is not needed. I drove a Triumph GT6 hard for 200,000 miles with only a burnt valve, not a seat problem. My XK engines are driven, not cuddled, and still not problems, except the carboning from todays fuels.
 
Hi Larry, yes brake fluid absorbs some water but also most contain a rust inhibitor,a difference that makes no difference is no difference. a well sealed used can will only absorb water from the open space inside the can, I would expect an amount that simply does not matter. I do not understand how your changing schedule is relevant as to whether or not you would have damaged the system by not changing and how long you have been a mechanic etc. is irrelevant unless you have kept a log and have data on cars with rust damage brake systems and those without and the owners fluid change pattern. I expect during manufacture, the whole process of making the fluid and then filling is not done in a vaccum chamber.
Jay '67 Etype
 
Okay...you can believe that if you want to.
When you work on motor vehicles for a living, and see puddled rusty water in wheel cylinders that are now locked up...well...that's one issue. Wait until you get puddled water and get the brakes really hot in some spirited mountain driving and the water boils. And you have zero brakes.

Bleed them once a year at least (not sure twice is needed, but who knows), and if you go with DOT5, you need to make sure the seals work with DOT5...all my suppliers scream "NEVER use DOT5 in a MK2!" as the seals aren't designed for the stuff.
Rather that try to prove them wrong, I just use 3 or 4.

Hydroscopic DOT3 or DOT4 absorbs water...until it won't. In other words, when you have exceeded the amount of water in the system taht the fluid is designed to absorb, it no longer absorbs the stuff.
 
TOC :encouragement:
 
https://www.crashforensics.com/brakefailure.cfm

"The typical generic "normal driving" temperature range for well balanced vehicle brakes is 100 to 200 degrees. A controlled mountain grade descent can produce brake temperatures between 200 and 400 degrees. Carlisle reports that a brake resin odor is produced at about 550 degrees and visible smoke is produced at 850 degrees."

And the boiling point of water is.....

"Fluid Fade
Cars and trucks from Class 1 to Class 6 commonly use a hydraulic brake systems. A hydraulic brake system works by using a non compressible fluid (brake fluid) to transmit the force of a driver pushing on the brake pedal to the brake linings. Air and vaporized fluid are compressible and, if allowed into a hydraulic brake system, the brake pedal will feel spongy and the force transmitted to the lining will be reduced. Just like water, brake fluid can boil and change to a vapor if it gets hot enough. Fluid Fade is the overheating of brake fluid causing it to vaporize. The vaporized fluid will have to be compressed before the system can transmit pedal force to the lining. In most cases, there will be insufficient pedal travel to do both.

The brake fluid used in cars and trucks typically has a boiling point of around 401degrees at sea level. Brake fluid is also hygroscopic, a characteristic which allows it to absorb moisture. Over time, brake fluid will become contaminated with moisture. As this happens, the boiling point of the brake fluid will be lowered, since the boiling point of water at sea level is only 212 degrees. Wet brake fluid has only a 3.5% water content and the wet boiling point of brake fluid drops to 284 degrees. I have tested the boiling point of brake fluid many times and have tested samples that boiled at temperatures as low as 260 degrees. For this reason, brake fluid maintenance recommendations are that it should be flushed about every 4 years."
 
How about STP, yuk yuk yuk, I am just amazed however at how many owner do not preheat their oil before going off on a Sunday afternoon run.
 
I've used STP for 49 years after I tore down a Mustang and saw how clean the engine was. The parts had a coating on everything, sticky smooth, but with the oil pump breakdown the coating saved the bearing surfaces and did not require machining. Not good for everything, but I use it in my XK engines religiously. As for warm up. Start, move, drive thru town, if temp is at normal warmth, we are gone, over idling puts too much fuel into the cylinders before engine gets to temp.
 
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