Lead Additives & Fuel Stabilizers

[Chuck B.]

Looking for lead additive product recommendations for my 1963 327 CI 340 HP Solid lifters original engine. What stabilizer product should be used with the lead additive?

[Jim D.]

Re: Lead Additives & Fuel Stabilizers

Don't waste your money, but if it would make you feel better, you can send me your money and you're car will still run the same with or without the "snake oil".

[Joe C.]

Re: Lead Additives & Fuel Stabilizers

Looking for lead additive product recommendations for my 1963 327 CI 340 HP Solid lifters original engine. What stabilizer product should be used with the lead additive?

There are a few products out there which contain real TEL. Some are mixed in a diesel/kerosine-like base and one contains toluene, which in itself is a mild octane booster. Any of these products contain fairly low concentrations of TEL and will realistically not boost octane of pump high-test (93PON) motor gasoline higher than about 97-98 PON. There is a point of "diminishing returns" with these products, and any boost higher than about 97-98 PON requires proportionately more additive.

I have tried one of these products containing TEL, and can attest to the fact that it prevented/forestalled detonation (ie:raise octane rating). It is an expensive "band aid", and if your engine detonates, I recommend backing off of the ignition timing until it stops and/or richening the fuel mixture.

If you are under the misconception that you need leaded fuel for your exhaust valves, then you are mistaken.

There is no need for any "stabilizer" or other such additive. I have stored cars/boat motors and small engines for years and with no problems, without adding any fuel "stabilizers". There is no need for them, whatsoever, AFAIAC.

[Dan H.]

Re: Lead Additives & Fuel Stabilizers

Chuck, I run plain 91 Octane unleaded with NO problems, plugs stay clean, ring arn't all gummed up etc. Running high compression pistons, about 10 degrees timing, don't create problems or waste your money on additives, however, a splash of Marvel Mystery Oil will help your rubber parts stay soft etc. if you feel you must put something in the gas.
Dan

[Claus S.]

Re: Lead Additives & Fuel Stabilizers

I have always used led additive when i fill up
So there is no point of doing this?

[Joe C.]

Re: Lead Additives & Fuel Stabilizers

I have always used led additive when i fill up
So there is no point of doing this?

No need to protect the exhaust valve seats.

If your engine doesn't detonate without it, then no need for it. If it detonates without it, then there are other ways to address this condition rather than resorting to expensive additives, most of which are nonsense. The only lead additives which will give you an honest increase in octane number are the ones using REAL TEL. There are three products that I know of which are sold in the USA, although others here may know of more. I don't know which, if any, are sold in Europe.

[William F.]

Re: Lead Additives & Fuel Stabilizers

I've mentioned this in other posts on this same subject, but have never gotten any discussion. In a 50's or 60's "Corvette News", put out by GM, article on tuning, authors warned about setting timing "by ear" since they said there is a form of detonation that is detectable ONLY by special monitoring equipment and this non audible detonation causes significant ring wear.This advice is contrary to the "if you don't hear ping, don't worry about it" advice often given in these posts.Therefore, it seems some form of raising octane in the 11:1 compression engines is advisable, whether this takes the form of mixing 100 LL Av gas, or racing fuel, or one of thee additives. I trust the former 2 over the additives.Also, concerning adding MM oil to keep rubber parts soft, are you adding it to gas or oil or both? How much?
'67 L79

[Paul H.]

Re: Lead Additives & Fuel Stabilizers

You do not need an octane booster, lead additive or stabilizer for your 340 horse motor. I've been running all my cars, big and small blocks, for many years on unleaded 93 octane (no additives or stabilizers) with no issues whatsoever.

[Duke W.]

Re: Lead Additives & Fuel Stabilizers

Depending on chassis/body acoustical characteristics, light detonation may not be heard, but this is more likely to occur in high load situations such as a truck pulling a long grade, but our Corvette engines, on average, are very lightly loaded even when pulling a long grade on the highway.

All of my cars are set up with very aggressive spark advance maps because they allow the engine to operate at peak efficiency down to very low revs, which means I can "short shift" due to plenty of low end torque, and this also maximizes fuel economy. Low revs/high load on the ragged edge of detonation is the most efficient operating point for most engines.

Depending on coolant and ambient temperatures my engines may get into transient detonation while accelerating from low RPM after shifting, but I can "drive around" this by increasing shift points with less throttle to achieve the same acceleration performance.

Most fifties vintage spark advance maps are lazy, so "tuning by ear" often results in over advance in the mid to upper RPM range, and sustained detonation can cause cumulative damage, though I have never heard of failed piston rings due to sustained inaudible detonation. Has anyone else? But I do view "tuning by ear" with a jaundiced eye, and with dial back timing lights being available for about $50 there is absolutely no reason to use such an imprecise, stone age procedure.

Detonation (that doesn't cause failure) can often be seen in piston crowns at overhaul time. The crown may look like someone took an ice pick to it. Detonation increases heat transfer to the combustion chamber boundaries by about an order of magnitude, so local overheating on the piston crown can melt tiny amounts of aluminum resulting in the pitted appearance.

Detonation is most likely to occur at low revs/high load, such as when you pick up the power in a higher gear after shifting. If this only occurs at high coolant and/or high ambient temperatures, you can "drive around" it as I do. If it is persistent then the spark advance map needs attention.

Most vintage Corvettes with the OE compression ratio will operate without significant detonation on today's premium unleaded fuels. If detonation is a persistent problem, look at the spark advance map. If detonation persists even after the spark advance map is made more conservative (and most OE maps were conservative to begin with) then one will have to find a blend of higher octane fuel (such as 100LL avgas or "race gas") to quell the detonation, but these cases are rare and in most the CR is probably higher than when the engine left Flint or Tonawanda.

And keep in mind that the actual as-built CR of vintage Corvettes engine is actually about a half-a-point lower than advertised, so if you take all the measurements to compute the true CR of your "11:1 compression ratio engine" you will very likely find that it's actually a lot closer to 10.5:1. Also, over the years many vintage high compression ratio engines have been rebuilt with "low compression" - so low that many will probably run detonation-free on unleaded regular.

Duke

[Stuart F.]

Re: Lead Additives & Fuel Stabilizers

I use Max Lead 2000, and have for many years in my 63 L-76. It allows me to run an aggressive spark map for maximum efficiency, and allows the engine to run cool in traffic. My usual driving time is to and from cruisins or back road blasts on weekends. At the shows, I commonly have to wait in long lines where before Max Lead I used to sweat the temp gauge. That is no longer the case. On my week end blasts, even though I try to limit my revs to 5500, I occasionally like to see if it will pull redline ok. I recently switched to non-ethanol 90 octane and have noticed much improvement, but Istill use the Max Lead as I got a couple cases - probably enough for this old geezer's lifetime.

Stu Fox