VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc non-detergent oil and lead additives

My '39 with 216.5 engine was rebuilt approx 20 years ago and was driven just 700 miles until a year ago when I acquired it. I immediately changed all fluids, including crankcase which now runs 10W30. The vehicle has since been driven an additional 1,100 miles. Should I have used non-detergent oil and if so, should I drain the crank case & replace with non-detergent?

Also, I have no idea whether hardened valves were installed 20 yrs ago -- should a lead additive be added with each tank of fresh gasoline, as a precaution?

CDP

Keep with detergent oil. That is what Chevrolet recommended after detergent oils were introduced in 1946. It is not only the detergents but the other aditives that are in modern 10w-30 oil

Your 1939 Chevrolet engine does not need hardened valve seats ot an additive for the valves. In 1939 regular grade of gas did not even contain lead. + the additives do nothing but take your money.

your prompt reply is appreciated; as a pensioner, I feel guilty not being a VCCA member and am considering joining

Gene, new guy here and I have been reading many of your answers and respect the knowledge you have for the old chevys. Your note about a lead additive for the gas, do you use a higher grade of gas than "regular"? I googled up when lead was added to gas and the answer was 1922 and it was used to increase the octane level of the gas.. Would my 35 chevy run better on a higher octane gas??? I does not have the hardened seats or valves.

Regular gas will work fine.

When your car was new, the octane in fuel was very low (maybe 60's? going by memory) so they built the engine with low compression for this reason. The regular pump gas of 85 or 87 octane today is way more than was available when new and you can advance your ignition timing way beyond factory specification and it will run much better than new.

It may actually run poorer with even higher octane than 85/87. Higher octane actually slows the combustion process. With the low compression of these engines you will pass the point of diminishing returns with advancing the timing and you will start to lose some power if the octane is too high...

So, with the higher octane in the modern gas, are we still wasting money on lead additives or do we need to put the lead into the gas??

No lead additive is needed. It's just fouling your plugs and emptying your wallet. It was not common in the fuels when these cars were new and is not required now. The valve seats do not need to be hardened either.

Just buy regular unleaded from a quality retailer and set your timing a little more advanced the next time you tune up. Keep the gas fresh by buying small quantities.

Regular gas in 1935 did not have lead and was around 65 octane. Preimum gas in 1935 was called Eythl and contained lead. It was intended for a few high compression engines back then and the Chevrolet owners did not use it becase it was not necessary and cost 2 cents a gallon more.

I took my 35 (207 engine) out a couple weeks ago. Ran 93 octane and found that advancing the timing beyond 0 made it run better. However, as Canadian Tim noted, there is a point of diminishing returns... if you advance too much, it runs worse. Love how easy it is to advance/retard the timing!
--John