Lead substiute

[allrightmike]

I'm wondering if anyone who has been using MOTOR MEDIC lead substitute and on disassembly noticed a black buildup on the back of the intake valve. At 1,000 miles an unrelated condition required heads off and that is when I noticed this. Seems sort of sticky and resists removal with a wire wheel way more than a carbon or oil buildup would. I may have overdosed because I did not actually measure fluid ounces but just took a guess (figured not too important). I'm using the stuff because my exhaust seats are factory cast iron. Also, do I really need this additive?

[Heo]

I dont use any leadsubstitute but, i have noticed that black sticky buildup in engines.
When i was a kid in the 70s we had a lot of old small twostroke motorcycles where
you mixed oil in the gas. We used just regular 10/30 motoroil or whatever dad had in the shop.
If you mix regular motoroil today in the gas on an old twostroke engine in a short time
it is full of black sticky buildup to the degree where it wont run. the rings stuck to the
pistons. plug fouled, hard to turnover due to sticky sirup in the cylinder.
So the oil formulas seems to be changed somehow i dont know ???and the gas defenitly changed

[randomologist]

I've used lead substitute in my engine for 15,000 miles. I have not noticed any sticky buildup and I had a head off the engine last year. I didn't see anything amiss.

As far as whether or not you need to use it, probably not.

Lead was originally added to fuel as an anti-knock compound; however, the soft lead also helped non-hardened valve seats by providing cushion to the valves when seating during operation and preventing micro-welding under high heat. Micro-welding is the theory behind "valve seat regression" where the valve comes into contact with the seat under high pressure and high heat which forms a very tiny "weld" bond. The valve is then opened and a tiny piece of metal is broken away from the head, sticking instead to the valve.

Valve seats naturally work harden through heat cycles. A NOS or super low mileage cylinder head without hardened valve seats would be far more likely to have an issue with micro-welding on the exhaust valves than an original engine which has seen hundreds or thousands of heat cycles. Most people seem to have no issues with micro-welding. The quality of the head casting material, the number of duty cycles, and how much heat the engine generates will determine whether or not a lead substitute is actually necessary.

For me, my 427 is a bit of a family heirloom. It's basically a stock 1963 "R" code. I daily drive it for extended periods on the freeway under low load where the power valves aren't open in the carbs so the engine is running leaner there. That means more heat on an engine with a cam that naturally generates a like a volcano. The engine was completely gone through and rebuilt including the heads so the seat material wasn't work hardened anymore. It now has 15,000 miles on it and it's probably work hardened, but considering how rare and important the engine is to me, how much heat the engine generates naturally and the way I drive it, which further increases the heat, I've decided to run lead substitute just in case. I use one bottle per tank whenever I fill up (about 16 gallons per fill up). I never add any extra. I just keep a couple bottles in the trunk so I can toss it in at each fill up. I could see any fuel additive becoming an issue if it was used too heavily.

[Falcon67]

Only crud on the back of the intakes that I've had to deal with came from 93 super unleaded and possibly a little oil getting past the valve seal.  I run VP110 at the track = no pump fuel - and have no buildup behind the intake valves.  I think most of that comes from the crap in pump fuel. 

[cjshaker]

I use a 50/50 mix of 93 Premium and 110LL, which is a low lead fuel designed primarily for airplanes. My engine needs the extra octane kick if I'm going to play, and it's the only available high octane fuel around my parts. It also prevents run-on when shut down. All iron 427, iron heads, no seats.

The lead will leave a gray coating on stuff, not black. What you're describing sounds like a minor oil issue mixing with the lead in your additive, which will leave the black residue you describe. Other than making it really hard to read plugs, the lead won't cause an issue, but the oil/lead mix will eventually cause problems with that gunk building up.

As for needing lead, I can't say that I've ever seen an FE engine sink the valves. Maybe some here have. I HAVE seen it plenty of times on small blocks, primarily from the mid 70's up. That's a known issue with the cast iron and heat treating on those engines, when they were still figuring out the whole 'no lead' thing. I've built and used some hard working FE's in trucks for towing use. A couple I had hardened exhaust seats put in, a couple were bone stock, never had an issue with any of them. If it worries you about your keepsake engine, I wouldn't second guess your desire to be safe and use the additive, but I'd figure out where the oil is coming from. Sooner or later, that is what will cause an issue.

I also think that a bit of lead helps the fuel system in storage times, like over winters. Modern fuels aren't friendly in storage, but lead seems to deter gelling and gunk buildup from the alcohol in them, at least in my experience.

[preaction]

Tetraethyl lead is available on line 2oz raises 1 gallon of 93 to 98 octane.

[preaction]

Tetraethyl lead is available on line.

[allrightmike]

Thanks guys, very helpful info here. I will be looking into the oil control issue. I will say that the exhaust seat angles are still well defined and do not seem to be deteriorating. I am using press on valve seals. The heads are old C4 Big H low riser heads.