Hi

Since my firebird has its original engine, should I be adding a lead additive to the gas in the tank. I believe that if you dont have hardened valve seats, then the unleaded gas will wear out the seats? What is true?

My engine builder told me that unless I put excessive workload on the engine then there would be no issue. I always used lead additive in my '69 and when I pulled the heads last spring there was no recession.

Seeing the amount of lead deposited on the valves, I would use a bottle every few tanks, not every tank, for protective purposes.

I've since had hardened seats installed since the heads were due for overhaul already.

It is true. I use Maxlead tetraethyl lead additive to each tank on mine. I have used a lead substitute in the past but switched to the real stuff 2-3 years ago. It helps raise the octane on the 93 octane gas for less pinging on mine too.

I also add ZDDPPlus to each oil change to replace the ZDDP that the EPA has mandated out of oil. ZDDP protects the high pressure wear surface of the cam and lifters.

Many engines (including mine) that don't have hardened seats and last just fine without lead. To the point that I can't think of anyone that adds it.
The risks of valve recession were way overblown. Now, if you're running massive spring pressure, then all bets are off.

And it would also depend on how you treat it too. If you're going to go out and thrash on it every chance yo get, eventually the stress will take it's toll on parts. But if you drive it like you want to protect your investment then you shouldn't have any problems not using added lead. Valve recession does happen though.

When I pulled the heads off of my engine, I was amazed how the valves were pounded into the head.

I know of lots of engines that have come apart and showed no signs of valve recession. YMMV.
That said, I'd put in hardened exhaust seats if I rebuilt.

Many years ago, about when they were changing over to nolead gas, I was sitting on a plane next to a PHD chemist from a major oil products research company who was quite familiar with the issue. (They were developing the processes to make the unleaded gasoline.) We first started talking because I had worked one college summer job with the company.

He believed that with all the miles that I had on the car being run on leaded gas, that there should be sufficient lead that would have permeated the seats to protect them.

That said, I have still used either a lead substitute or real tetraethyl lead with every unleaded tank. It's just my cautious, conservative and redundancy-seeking nature, I suppose. (I need the octane in the 400HO anyway to reduce pinging so the real lead also takes care of that.)

I just use lead substitute in my '68 ford with a small V8.

A former colleague was similarly concerned about his 1960s Mercedes 280 SL designed for high octane leaded gas. He wrote to Shell Oil and asked about lead/valve seat recession etc and received quite a technical package back which he let me read some years ago.

In essence, provided the octane is high enough to meet the compression needs of the engine, and provided the engine is not 'loaded' heavily on a regular basis (racing/towing etc), the degree/pace of valve seat recession should not be an issue to concern a collector car owner; however, hardened valve seats still represent the safest and longest lasting solution.

grant

I do exactly as Jim 2002 does--MaxLead 2000 in the gas and the ZDP in the oil--better safe than sorry.

FWIW, the Shell data also noted that unleaded fuel was particularly 'sensitive' to the addition of tetraethyl lead, meaning a small amount added resulted in a disproportionately larger increase in octane rating.

THAT EXPLAINS IT! Now it makes sense.

I copied a Consumer Reports article back in the days of the demise of leaded premium. They claimed that a 50/50 mix of Shell 89.1 leaded regular (still available then) and 91.6 unleaded premium would yield an octane rating of 91.2, much more than the average of the two.

I use the Octane Supreme additive in my Sprint. I believe that is the new name for Maxlead. When I only burn a 4-5 tanks a year, figure it is worth adding a half a bottle every tank full.