Does a 1966 Buick engine need this?

[Guest Teamsterdug]

Is a lead additive necessary for a 1966 Buick 340c.i. engine? Thanks in advance for any help!

[NTX5467]

Theoretically, any cylinder head without hardened or hard valve seats needs some kind of valve recession additive for the fuel. But, there are other variables involved in that deal too (i.e., how hard the vehicle is driven, valve rotators or not, other anti-wear fuel additives in the fuel already).

From what I understand, it takes about 1 gram of lead per gallon to give minimal protection from valve seat wear with non-hardened seats. In the days of 100 Research Octane fuels, there were about 4 grams/gallon. Lead was also the main octane increase additive back then too.

GM changed all of their engines to unleaded fuel capability in April of 1971. This included induction hardened valve seats in the cylinder heads. In later years, some engines actually have hardened valve seat inserts in the heads (cast iron included) as all aluminum heads already have.

A competent machine shop can install the hardened seat inserts in heads which didn't come with them or did not have the induction hardened seats. I don't believe that valve seat recession has been quite the big deal it was originally suspected of being, so you might be better off driving the car on existing fuels (without additives) as octane would probably be a more critical issue than a lack of lead.

The lead additives on the market will not supply even 1 gram per gallon unless you dump a whole case in the tank at each fillup. Not all fuels respond to that deal to increase octane either.

NTX5467

[Guest]

I have 180,000 miles on my '65 Skylark since 1991 without any hardened valve seats. Drive it!

[Guest brh]

I too have been weighing pros and cons on this on my 65 Skylark. This summer I drove a total of 1000 miles. I put lead additive in it was only 1.98 at pep boys. Before this I was not using an additive. My attitude is when the engine needs a rebuild I'll worry about it. At 1000 miles a year its going to be a long time before this is a consideration. Drive it.

[Guest 70 Electra]

Short answer: NO.

Long answer: One of my buds is a prominent GM research engineer for fuels/lubes. He spent the first half of his 35 year career at Ethyl Corp, the company that makes fuel additives, including the tetra-ethyl lead that was in fuels for decades. This guy is also a big-time car collector/enthusiast/restorer.

His advice? He says that only sustained heavy loads would be cause for concern over valve seat recession due to the absence of lead. By sustained heavy loads, he means trailing, racing, etc. (And by "racing", he doesn't mean an occasional WOT run through the gears!) In other words, 99% of us don't need to worry about this.

[YellowLark]

Don't worry about lead additive. Worry about octane additive.

If you have the 340 MB engine with 10.25:1 compression, you can expect pinging without an octane booster.

[Guest Teamsterdug]

Thanks everyone. All are informative opinions and a lot of help. Looks like I gas and drive!

[NTX5467]

I concur Greg.

Along about '73, I found an article in Chilton's "Automotive Industries" magazine that reviewed what Chrysler did in some testing. It wasn't until about the '74 model year that Chrysler's engines were fully unleaded fuel compatible (with induction hardened valve seats) so they recommended switching off between leaded and unleaded fuels (one tank of leaded for each two of unleaded) at that time.

What they did was take a New Yorker station wagon with a 440 equipped with their heavy duty trailer equipment package and hooked it to a trailer that was "full rated capacity" for the vehicle. They ran it on the proving grounds at something like 75mph under that load with unleaded fuel only just to see how far it would go before problems happened.

Valve seat recession had completely ruined the heads in about 10,000 or 12,000 miles. Again, this was heavy loads and higher speed conditions. I rather doubt that was all on level roads too. At that time, the only anti-wear additives in the fuel typically was the tetraethyl lead.

During these earlier times, Amoco marked a high octane unleaded fuel. There were no issues with valve seat recession or it would not have been on the market as long as it was. If they'd been buying cylinder heads, it would have been different. There were other fuel additives that would do the same as tetraethyl lead would do with respect to valve seat wear, just that lead did double duty as an octane booster and wear preventative. Unleaded fuel also takes about 5% more crude oil to refine than did leaded fuel, so you can see the economic implications of using tetraethyl lead.

I agree that few of us will drive our vintage cars at full rated load and higher speeds on a regular basis. I also concur that having a fuel of sufficient octane to work in our older engines (without clattering too much) is probably more important in day to day or other occassional use than worrying about valve seat wear.

As long as the valve guides are in good shape, the valve will seat squarely and not typically cause any problems. It's when the guide and valve stem pairing get some wear on them that the valve might wobble and not seat squarely each time it closes. This will lead to oil consumption (from too much clearance and further wear the valve stem seals) and "burnt" valves.

In retrospect, I haven't observed the unleaded fuel in engines originally designed for leaded fuels to be the big issue it was suspected it would be in passenger car use engines.

Just some additional thoughts,

NTX5467

[Guest Reatta1]

The biggest problem I noticed in my 340 was severe pinging with the low lead fuels. I used to use regular gas with no problem till the switch to low lead, after that I had to us premium and still add an octane booster. I am in the process of restoration on my convertible and haven't driven it in some years. I have done a complete rebuild on it and am curious to see how it will run on currently available fuel. I don't know if hardened seat were installed or not. Failure on my part to discuss that with the shop. Has been several years since the rebuild as it was the very first thing I did when I decided to restore the car. I will have to research my receipts and see what exactly was done. I always expected I would have to use a lead and an octane additive when I start driving her again. The 'Green Dream' will ride again.

[Philippe Racicot]

I recently blown the 430 engine of my 67 Riviera and when I took off the heads of this 77 000 miles engine i noticed that most valve seats were recessed. I had this car for two years and had done 12 000 miles with it. This car was stored between 1990 and 2000 and had done fewer than 400 miles during that period. So I guess that previous owner still used leaded fuel when the car was stored. I have no idea if the wear was normal or if it was due to the unleaded fuel but I asked my rebuilding shop to harden the valve seats while they rebuild my "new" 51 000 miles 430. On that engine that was also stored many years the valve seats were much better but the camshaft, lifters and main bearings were not better than those of my 77000 miles engine and it had no oil pressure. I was surprised to see that on both engines, timing covers were still good!

[The Old Guy]

I have driven my 40 Buick over 90,000 miles in the thirty years I have owned it, and have never used an additive. I also pulled an Airstream trailer all over the country with a 57 Buick wagon, and never had any problem with valve recession. The Buick block had a higher nickel content than most engines,and does not seem to suffer like many other engines from this particular problem.

[Guest Teamsterdug]

Thanks again everyone. I'm getting so smart reading all of this I may have to quit my day job!In summation....high octane, drive, drive, drive.