Brass Era Valve Timing

[DavidMc]

I would be interested to know whether the valve timing on the early brass era cars can be improved by changing the timing of the valve opening and closing.

I guess it comes down to a question of whether the "state of the art" available to the manufacturers at the time was optimum for the particular engines or whether later knowledge would allow us to modify the timing to advantage.

For example, the timing of the inlet valve opening directly affects volumetric efficiency (getting as much fuel into the cylinders as possible). Modern engines have the inlet valves opening much earlier than the old ones. This is no doubt due to many factors such as combustion chamber design, number of valves, fuel injection, increased engine operating RPM, and possibly improved fuel.

I have no interest in modifying for increased speed but I would like a little more low speed torque so that I am less of a nuisance to modern traffic on the hills.

I hope others with experience in this area will comment and if it is feasible, how to go about determining the improved valve timing. Trial and error?

[Mark Shaw]

You might try posting this on the BrassBuicks Yahoo site for more responses...

[Rusty_OToole]

The power characteristics of any engine can be altered by retiming the camshaft. Advancing the cam improves low speed cylinder filling and therefore low speed power, retarding the cam does the opposite.

By retiming the cam it is possible to "rock" the torque curve about its midpoint.

Here is one method that requires only a compression gauge and a means of adjusting the timing. For modern engines there are offset keys available for those that use a key, and offset bushings for those that use a pin to locate the cam.

You will need to find a method to advance and retard your cam a degree or 2 at a time. Then, do a compression test. The adjustment that gives the highest compression reading will give the best low speed torque.

Incidentally this is the first time I heard of a brass era car lacking in low speed torque. Most of them will idle down in high gear to a walking pace or slower, and pick up speed without complaint.

You might try adding 25% kerosene to the gas for more oomph.

[DavidMc]

Rusty,

I like the idea of using a compression gauge to measure the best cam setting to determine maximum filling of the cylinder. Its a static test, the results may not apply entirely to the dynamic conditions when the engine is running but its a lot better than just trial and error.

The cams on my car are pinned to the shaft so it is possible to remove the pin and tap a thread for a grub screw to allow the cam positions on the shaft to be temporarily changed.

It would also be possible to test a promising setting with the engine running by temporarily locking the cam to the shaft with the screw plus high strength Loctite. This could be released with heat.

All of this is about whether the original factory valve timing is best for the car - and it may well be. I am seeking improved performance under the normal low speed use of the car. Its not about increased high speed use.

The car has been mechanically rebuilt has strong compression, good spark and I have tried it with both a modern carburetor and the original. I have experimented with changed ignition timing and found the original setting of about 25-30 deg BTDC works best when running . Retarding this at low revs when climbing makes little difference.

In response to your comments about brass era cars in general, this car already runs well at low revs but it has very poor hill climbing ability compared to other cars of the same era.

Thanks for the comments, I will report any findings.

[DavidMc]

Rusty,

I forgot to comment on the use of 25% kerosene. I have used this in 1920's cars to to overcome vapor lock problems. I am intrigued, why would it give improved low speed torque in a brass era car? Is it because it is more like the fuel these cars were designed for? If this is so then that implies that modern fuel does not suit these old low compression cars. I am not aware of any problems with modern fuel in the old low compression cars, part from vapor lock problems. I would be interested in the reasons behind this suggestion.

[Rusty_OToole]

Rusty,

I forgot to comment on the use of 25% kerosene. I have used this in 1920's cars to to overcome vapor lock problems. I am intrigued, why would it give improved low speed torque in a brass era car? Is it because it is more like the fuel these cars were designed for? If this is so then that implies that modern fuel does not suit these old low compression cars. I am not aware of any problems with modern fuel in the old low compression cars, part from vapor lock problems. I would be interested in the reasons behind this suggestion.

Modern fuel is made for high compression engines and is too high octane for old, low compression engines.

It may seem strange to talk about octane being too high. But if you have a low compression engine built to run on low octane fuel, it will run better, cooler, smoother and produce more power.

The general rule is the octane should look like the compression ratio. So if you have a new car with 9.2:1 compression you need 92 octane hi test. If you have a minivan with 8.7:1 you need 87 octane regular.

Your car probably has about 4 or 4.5:1 compression and needs octane of 45 or 50.

Naturally this is not an exact ratio, just a general guide. But if you look up the fuel available in the past, and the compression ratio of the cars of the day, you will find it is pretty close.

By the way if it was my car I would not think of trying to improve it. I would put it together as the factory intended. I know you have good intentions but chances are the factory got it right in the first place and your efforts will do more harm than good.

[Rusty_OToole]

It was explained to me that a low compression,long stroke, slow turning engine needs heavy fuel, like kerosene or diesel fuel, to develop full power. High octane gas burns too fast and too hot. The heavier ends burn slower and give more oomph. You need a combination of light and heavy fuel to burn properly.

The only function of high octane gas, is to suppress knocking or pinging due to preignition. If the fuel does not knock or preignite, the heavier lower octane will produce more power.

[Rusty_OToole]

Indeed, your car was designed for unleaded heavy fuel.

This is one of those sidelights of history that intrigue me but I suspect, bore everyone else. Nevertheless here goes.

When the first gas engines were designed one of the advantages was to use a cheap fuel that was otherwise being thrown away. In the late 19th century the oil companies sold mainly coal oil or kerosene. There was no market for gasoline except as a cleaning fluid or for a small number of gas stoves and gas lanterns.

There was so much surplus gasoline the refiners often were forced to throw it away. They put as much of the low grade gas into the kerosene. Accounts from the late 19th century describe kerosene as having a piercing odor, and kerosene lamps being prone to explode especially if not kept filled up.

Gas in those days was a light, high octane, unleaded. I saw one account of an early motorist in 1899 or 1900 who filled the tank on his car which only held about a gallon, but he forgot to put the cap on and when he came back a few days later, the tank was empty. All the fuel had evaporated.

This sounds like what we call naptha gas or Coleman fuel today.

By the time your 1910 car was built the tables were turned. Gasoline was selling, kerosene was going out of fashion due to electric lights and gas lights. So the refiners made purer kerosene and put the light ends into the gas. By 1908 the gas was getting heavier and oilier, some makers were forced to lower the compression of their engines. After 1913 it was a real problem, this is when the long stroke motor became popular and you saw more and more gadgets for vaporizing fuel such as hot spots in the intake manifold. All to try and make the engines run on the new heavy oily fuel.

This kept on until the cracking process was invented to allow making gasoline out of heavier oilier fuels. Also the introduction of leaded gas in the late twenties permitted compression ratios to slowly rise year by year.

Your car was built when gas quality was at an all time low. It contained no lead but it did contain a lot of kerosene and heavy or oily material.

It just occurred to me, the diesel engine did not become popular until the thirties at the earliest and did not take over in trucks until the sixties. So I bet a lot of what we would now call diesel or heavy fuel, ended up in the lower grades of gas.

[Guest cben09]

Hi David,,Does your engine have 1cam or 2

T head or side valve??Ben

[jdome]

Just to throw in some information, The 1903 -08 single cylinder Cadillac used variable valve timing. The throttle control actually varried the time & duration of the intake valve and the engine sucked in the appropiate amount of fuel/air mixture depending on the open valve duration. It did not have a conventional carb. Cadillac called it a "Mixer" and the intake valve and lifter was part of the mixer.

[DavidMc]

Thanks to those responses, replying to each.

Rusty your explanation of the early fuels far from boring me is a subject that has always been of interest. My main interest was because of the vapor lock problems but also to understand any other effects on early engine design. Some time ago on a Forum I referred to the followingweb site and it is relevant to this topic <!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:PunctuationKerning/> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:Compatibility> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <w:DontGrowAutofit/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument> </xml><![endif]--><!--[if gte mso 9]><xml> <w:LatentStyles DefLockedState="false" LatentStyleCount="156"> </w:LatentStyles> </xml><![endif]--><!--[if gte mso 10]> <style> /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} </style> <![endif]--> http://www.bp.com/liveassets/bp_internet/australia/corporate_australia/STAGING/local_assets/downloads_pdfs/f/Fuel_news_modern_petro_vintage_engines.pdf

If that does not work google "BP MODERN PETROL IN VINTAGE ENGINES"

If I change the valve timing it will be with new cams, The original camshaft will always be available to refit especially if the changes don't work which is likely. It will also be the first time I have attempted to modernise an old car, all previous projects have been to restored "warts and all" This is my first venture into a brass era car and it is a nuisance to drive with modern traffic. If the valve timing could be improved to allow it to climb modest hills in top gear instead of low gear at about 5 mph then it would be better. Besides the topic is interesting, I have learned something already!

CBen,the car has 2 cam lobes pinned to the shaft so the shaft can be withdrawn, its an "L" head side vale twin horizontally opposed engine.

jdome, so the early Cadillacs had variable valve timing which is how all modern cars work except that the Cadillac used instead of a throttle valve in the carb, very interesting. These Brass cars are certainly interesting in understanding the development of automotive engineering.