ron hausmann

How to manage HIGH COMPRESSION ?

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All -

    I have a freshly overhauled 6 cylinder engine in my 1918 Kissel. It’s a six volt system. Head and block were milled and new pistons and modern rings installed. It ran very well then on an engine stand at my overhauler. 

    Now the engine is in the car, the engine struggles to crank, even with a brand new 700-cranking amp 6v battery, and even with two Six volt batteries in series. The batteries test fine and the starter tests fine. Very, very tight. 

     When we hook the starter directly to a 12 volt marine battery, she cranks well and starts. My mechan8c friends say that the engine is “tight” because it’s brand new and not “broken in”, and because we increased the compression by milling the head. Once started the engine runs just beautifully and smoothly at various revs.

     How can this problem be fixed? Will running the engine for hours help break in. Should we carry around or jury rig a 12 volt battery starting system on it until the engine wears in. 

     Any advice will be appreciated.

     Ronald n Hausmann P.E.

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Posted (edited)

I think your friends are somewhat correct about tolerances being a little tighter than they will be after break-in, but I don't know that it would affect starting significantly. Possibly, but that would have to be a VERY tight engine. I doubt you raised the compression enough to be a factor, either--whatever it is, there were cars with more compression in the '40s and '50s that started just fine on six volts. Matt's advice is always my first bit of advice, too. Big (00 gauge) cables and clean grounds, plus an extra ground from the starter to the battery's ground point on the frame often reduces or cures hard starting on 6V cars. I used two 6V Optima batteries with new cables and good grounds and The Car Which Shall Not Be Named fired up instantly, hot or cold, and that was 414 cubic inches of V12.

 

You probably have a combination of all these issues. If your engine is freshly detailed, make sure there's no paint interfering with the grounds. Same with the frame. I think you're experienced enough as a hobbyist to know about the big cables, but if not, get big cables from one of the vintage wire suppliers (Rhode Island Wiring will make you any battery cable size and type you want). I wouldn't try to use the 12V battery as any kind of solution. It'll spin the starter pretty vigorously but it's not a solution.

 

Finally, some 6V cars just crank slowly. Every single 356 cubic inch Packard straight-8 I've ever had would crank so slow that you'd think it would never start, but they always did. My 1941 Cadillac 60S would crank until you thought it wouldn't start, and then it would fire. Every single time. You just have to get used to what is "normal" for each car, because they won't be the same, even if they're identical cars. It's just the nature of the beast.

 

Hope this helps and please keep us posted on what you find--solving hard start issues is one of the most common topics on this forum and your solution could help someone else.

 

 

Edited by Matt Harwood (see edit history)
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From my old shade tree mechanic days "tight" engines were normal, to the point I've seen some that had to be towed  to get them started...but those weren't Classic Car Type engines but well worn beaters/drivers being (hopefull0 temporarily rehabilitated...

I'd be inclined to raise an eyebrow at a professional shop dealing with rare/expensive engines that turned them out so tight they had serious starting problems; I'd expect the shop to

run them in" a bit themselves if it couldn't be avoided...

You might ask the shop what king of voltage they used when the engine started normally in the shop...

It's perfectly true that the engine will "wear in" with driving; it's why new cars in my day came with "break-in" instructions for the first 500 miles or so, but, again, those were mass production engines, not engines turned out individually from a skilled professional rebuilder...

An excessively tight engine could experience damage before comfortably "wearing in"...

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Ron,

Do you have 00 or 000 , or welding cable?

or has someone used ordinary 12-Volt style battery cables which will NOT carry sufficient current for a 6-Volt system?

Also, I hope yoour two (2) 6-Volt batterys are wired in PARALLEL which will give more cranking Amps at 6-Volts, NOT SERIES  which would give 12-Volts

 

My early cars (at least some of them) have a pair of Optima 6-Volt batterys side-by-side in the battery box, wired in Parallel, 

and have either Double Aught, or Triple Aught (00 or 000) battery cables,

AND Battery cable ends are Soldered, not Crimped to assure proper Voltage/Amperage

 

Best of luck with your project

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Ron.  You should be able to use a compression tester on each cylinder to see what psi you are achieving.   That should give forum input on compression worries and either address them or focus on getting full power to the starter as others have suggested above.   

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Hi Ron !

Let me take a kick at this can, and add to all the above good advice. Regarding the possibility of compression ratio/pressure being a major factor here : YES, it most certainly MAY be THE major factor. But we on the forum don't have enough data yet to arrive at a definitive conclusion. Therefore I will make a best case assumption, propose an experiment, and offer what I hope is a helpful suggestion.

 

Assumption : Without knowing what your target increase in compression ratio is, let me just assume that you did superb engineering and execution in order to raise your compression. If you were able to bring a 4.X 1 compression ratio ancient flathead engine up to 6.X : 1 (a remarkable and desirable feat), you would indeed notice the increased demands on the starter. But we don't know how much the compression PRESSURE has been raised through head and block milling, new piston design, and any + or - change by way of cam profile modification, if any. 

 

Experiment : Open 5 primer cups and the throttle, and pull the plug on the remaining cylinder. Measure the compression  and compare to one of your similar unmodified engines tested in the same way. Hopefully there will be quite a difference in pressure. NOTE : As I am winding up my long winded epilog regarding octane vs. compression ratio relationship, Bob McAnlis has anticipated this.

 

Suggestion : Use the current state of the art break in oil. Unless there has been a breakthrough in petroleum engineering since I last checked, that would be the specifically designed Amsoil product. Please look it up, and you will find an interesting and convincing read.

 

Disclaimer : I have absolutely no connection with Amsoil in any way whatsoever. 

 

 

I have written from time to time about the relationship between octane and compression necessities. In order to fully extract all the BTUs from modern 87 octane fuel, you would need a compression ratio up in the 8.X : 1 range. But I don't know any way to achieve this in 90-100 year old flatheads. You can only do the best you can with what you have. In the late 'teens, gasoline was right around 40 octane. Rather sophisticated engineering, and testing facilities with dynamometers, high pressure range manometers, etc., produced 4.X : 1 engines capable of developing maximum BMEP (call it torque if you like), from the 40 octane fuel back then. In order to achieve this level of efficiency, the power stroke must be just shy of preignition,(detonation), during its entire travel ! Yes, detonation can occur at any point in the power stroke depending on a number of factors. Now, running a 4.X : 1 compression ratio engine on comparatively high detonation resistant 87 octane fuel, will preclude this level of maximum efficiency. You quite simply can not develop the BMEP and  HP and efficiency on 87 octane fuel with an engine designed to do so on 40 octane fuel. The only way to approach the original capabilities, is to significantly raise compression. You will not be able to EXCEED the original 40 octane BMEP specs by simply doing this, and you will not want to be running maximum BMEP at all times. But it is good to have it on demand if needed. In any case, fuel, economy will increase, and your exhaust valves will thank you.

 

You remember tinkering around with timing for maximum performance : "advance her till she pings, and back off a few degrees ".

 

I hope this helps you, Ron. Of all the contributors here who I immediately turn to when I see their handle, you are at the very top. Truly fantastic work from a formally trained well organized mind, with a massive amount of hands on experience. If my humble prattlings serve any purpose whatsoever, it will have been a privilege to have done so. Thank you for sharing so much with us.  -   Carl 

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Posted (edited)

Try the larger cables. What is probably happening is that your starter needs more torque (amps) to turn the tight engine over, which in turn is dropping your battery voltage down. Lower the battery voltage, slower the turn speed of the starter.

 

PS; starter motor speed is directly related to the voltage applied, not the current/amps.

Edited by maok (see edit history)
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Did you rebuild your starter.  When I worked in a GM dealership in the '60's we had a terrible convincing customers that if your engine need to be rebuilt your starter did as well.  

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Post reminds me of the movie “ The Gods Must Be Crazy”. Overhauled a Land Rover and it was so tight the fellow didn’t dare shut it off. No parking brake. All gates at top of hills. Hilarious.

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If you have a copper cap tube to a heat gauge or copper line to a dash mount oil gauge just hold your hand on it while you crank the engine. If one gets hot you might find you have an alternate ground.

 

It is an easy test.

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Can you put a torque wrench on the crankshaft and find out how much torque it takes to turn it, with the plugs out? This is a measure of friction. I remember from an article years ago, about rebuilding an engine, that if it was done right it took 17 foot pounds of torque to turn the engine. Too low or too high, something was too loose or too tight, or out of line someplace. This was on a sixties Detroit V8. If you give the torque reading maybe some more experienced mechanics can tell if it is too tight.

 

C Carl looking forward to the article on compression vs fuel octane. No doubt you know, that you can lower octane by mixing some kerosene with the gas. Most low compression engines from the teens and twenties respond well to this, develop more power, run smoother and cooler etc.

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Higher compression/octane usually needs more advance. If the crank suddenly hesitates then there is probably not enough spark advance. Other comments are great just had not seen this one.

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11 hours ago, Rusty_OToole said:

Can you put a torque wrench on the crankshaft and find out how much torque it takes to turn it, with the plugs out? This is a measure of friction. I remember from an article years ago, about rebuilding an engine, that if it was done right it took 17 foot pounds of torque to turn the engine. Too low or too high, something was too loose or too tight, or out of line someplace. This was on a sixties Detroit V8. If you give the torque reading maybe some more experienced mechanics can tell if it is too tight.

 

C Carl looking forward to the article on compression vs fuel octane. No doubt you know, that you can lower octane by mixing some kerosene with the gas. Most low compression engines from the teens and twenties respond well to this, develop more power, run smoother and cooler etc.

 

Rusty,

this car has primer cups so with them open, I have cranked it and now I will put a torque wrench on it.

ron

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All,

    Thank you for your very sage advice !!

    I will first add/change all the cables to 00 or 000 size. I have a cutoff switch in the car which might have smaller cables which would contribute to the problem .

    Then I will check all the grounding connections. It’s a positive ground car. My grounding is to the engine which was freshly painted and I’m wondering if the contacts were on partly painted surfaces. 

    We will see if these two actions help cure the problem.

    Thanks, Ron 

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Paint can act as insulation. You may need to scrape off the paint under the lug for best connection.

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I see you resorted to the "plumbing fixture" solution to the wiring tube and carb crossover problem. We did the same on the Kissel we restored but replaced  them after we bought a tubing bender for a different project.

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Not that it will help your situation, other than possibly a good laugh:

 

I have an early John Deere that is hand cranked. This one is early enough, Deere hadn't figured out compression release petcocks were a good idea. When I was much younger, I could crank it. Now it is parked facing downhill on a good grade! ;)

 

Jon.

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Posted (edited)
On 8/28/2019 at 8:11 AM, ron hausmann said:

I have a freshly overhauled 6 cylinder engine in my 1918 Kissel. It’s a six volt system. Head and block were milled and new pistons and modern rings installed. It ran very well then on an engine stand at my overhauler. 

    Now the engine is in the car, the engine struggles to crank,

 

I know nothing about these engines so pardon me if I show my ignorance.  From reading what was quoted above, is it possible that something that was added after the engine was installed in the car is causing it to be hard to turn. Like a generator, water pump or fan? Or maybe something about the clutch or transmission?

Edited by Ronnie (see edit history)

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My little story can from a guy who asked why his dashboard glowed red above the oil gauge when he started the car. It turned out that excess tubing was coiled near the gauge and clamped to the back side of the gauge. Due to other issues it was the only path for an electrical ground. It may have been the temperature cap tube, but the message is the same. Expect the unexpected.

 

Back in the early 1980's I taught Adult Ed nights in a High School trades shop. While explaining HVAC electrical circuits I put my meter on a white neutral wire explaining it would read zero. There was 110V. Unwinding an overhead extension cord reel we found a splice about 20' from the plug. Under the tape; two wires, black to white and white to black. "Trust, but verify"

 

 

 

 

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1 hour ago, 60FlatTop said:

My little story can from a guy who asked why his dashboard glowed red above the oil gauge when he started the car. It turned out that excess tubing was coiled near the gauge and clamped to the back side of the gauge. Due to other issues it was the only path for an electrical ground. It may have been the temperature cap tube, but the message is the same. Expect the unexpected.

I had a similar problem in the seventies on an Olds powered Willys hot rod. One day the choke cable got red hot and melted off while driving along.

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Posted (edited)
On 8/28/2019 at 9:53 PM, padgett said:

Higher compression/octane usually needs more advance. If the crank suddenly hesitates then there is probably not enough spark advance. Other comments are great just had not seen this one.

I always thought high compression required less advance? I would try timing the ignition to TDC or 1 or 2 degrees after, for easy starting. You can always adjust it again later when the engine is broken in. Later timing will  be easier on the engine while breaking in .

Edited by Rusty_OToole (see edit history)
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On 8/28/2019 at 8:11 AM, ron hausmann said:

The batteries test fine and the starter tests fine. Very, very tight. 

I'm curious what you mean by this, especially the very very tight part?

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On 8/28/2019 at 7:46 PM, 60FlatTop said:

If you have a copper cap tube to a heat gauge or copper line to a dash mount oil gauge just hold your hand on it while you crank the engine. If one gets hot you might find you have an alternate ground.

 

It is an easy test.

A 1918 car would have the engine bolted solid to the frame, no rubber motor mounts. They weren't invented for another 14 years.

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