ron hausmann

How to manage HIGH COMPRESSION ?

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To check all your electrical connections, use a VOA meter and perform a voltage drop test at each connection including your grounding system back to the battery. If you have a voltage drop higher than .2 volts when cranking, the wire or connection is most likely  the problem.

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1 hour ago, C Carl said:

 

 

Compression testing is done with all holes open.

 

160 psi ? Not on any flathead. Read and heed our great friend Rusty'. These 'teen machines were designed to run on gasoline of about 40 octane. Way I learned it, cranking compression pressure  is LOWER with LONG duration "bumps", all other things being equal. Long duration camshafts have more overlap. They are particularly suited to higher revs, where fluid dynamics rule for increased volumetric efficiency.

 

Did we ever learn the results of the Kissel's compression test ?   -   Carl 

 

i just used 160 as a reference.

 

compression is reduced the more advertised duration a cam has because the intake valve closes at a later point. the overlap and lift can also affect it but that's a very lengthy subject. the dynamic compression is a more accurate reference for when detonation etc will occur.

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Yes. Also exhaust can stay open a bit longer for more effective scavenging. With properly tuned intake and exhaust, volumetric efficiency can exceed 100% across a given rpm range. And dynamic compression is dependent on manifold pressure and the operating torque, or perhaps more accurately, Brake Mean Effective Pressure, (BMEP). Detonation  can occur  at any point of the power stroke. As you say, this is a complicated subject, and it can be difficult for a non-engineer like myself to wrap my head around it.    -    Carl 

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     Well With the new 00 cables thruout, and grounding the system directly to the steel block instead of the aluminum clutch housing, the engine cranks very well and continuously until the battery starts to give way.
     So my problem, which is now cured, was either a) too small cables for a new 6v, b) connections not properly tight,  or c) grounding to aluminum instead of steel. Not sure Whitch of these factors was the guilty culprit, but the malady now has been cured. 

     Thanks to all of you for guidance and ideas. 

     Ron Hausmann P.E. 

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Good to know you figured it out. Probably inadequate cables,  less likely bad connections unless they were loose. After all this was a 'new' engine.  Grounding to the  clutch housing should not be a factor, if the clutch housing is bolted to the engine.

 

Is it starting like a new car now?

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It's starting. I just need to tune the carburetor, which is way out of whack.

RON

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Want the theoretical compression reading ? Just multiply the expected CR by 14.7. 5:1 compression would give 74psi. 160 psi is about 11:1.

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Just an FYI Ron but aluminum is a VASTLY superior conductor than steel.

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As I mentioned the problem with aluminum is not is conductivity but the issue of keeping the connections tight. Only way I know to explain it is that under pressure Aluminum is liable to flow and must periodically tighten the connections or they become loose/resistive and that generates heat. To a lesser extent, lead (battery posts) does the same thing.

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I would do two tests. First pull the spark plugs to see how it cranks over with zero compression. Next get it fired up and purposely lug it in high gear; if no pinging then compression and advance are okay.

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On 10/29/2019 at 2:29 PM, ron hausmann said:

     Well With the new 00 cables thruout, and grounding the system directly to the steel block instead of the aluminum clutch housing, the engine cranks very well and continuously until the battery starts to give way.
     So my problem, which is now cured, was either a) too small cables for a new 6v, b) connections not properly tight,  or c) grounding to aluminum instead of steel. Not sure Whitch of these factors was the guilty culprit, but the malady now has been cured. 

     Thanks to all of you for guidance and ideas. 

     Ron Hausmann P.E. 

 

If the connections were clean and only lightly tightened, they would easily have a good enough connection, in which case the culprit would have been that one or both of the cables were too small or an original cable with a weak connection on the end fitting was used.

Edited by barnett468 (see edit history)

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