stupid question

how do you measure the capacity of an engine without pulling the head. I'm thinking race marshalls and how they check to see if you qualify for F750 class.
my memory tells me they fill one cylinder chamber with stuff and measure how many mls fits then multiply it by the number of cyliners

what do they fill the pots with?

Thats a good question.

For International events, for many decades anyway not sure if it still applies, the engine was stripped (head off)
and they physically measure the bore and stroke.

If it was measured with liquid, the capacity of the cylinder head combustion chamber comes into it,
and the precise displacement would be somewhat difficult to measure with any accuracy or certainty..

There are famous stories in the past, where the secrets of the performance would be on display with the cylinder head exposed -
and some riders were instructed to take the head into their custody, and sit on it !!

haha

I thought they dropped a plug and filled the bores with something. maybe castor oil or the like?

How would they know what was bore and stroke, and what was combustion chamber volume ?
Turning over the engine would spit out the volume of the oil displaced by the piston movement,
but that would only be a rough measurement.

Normal engine oil would be a better candidate for a quick-n-dirty measurement, since castor oil can react with mineral oils,
depending on varieties.

Any ring or valve leakage could make it a very imprecise business...

Hi Dkt26.
Piston displacement volume is (area of bore) x stroke.
Engine displacement volume is above x no. of cylinders.
Knowing the combustion chamber volume allows compression ratio calculation i.e. piston displacement volume:combustion chamber volume.
Ta.

The way I've been told was that they lockwired and sealed the engine and had it stripped after the meeting so they could measure it properly ( bore/stroke).

If the fuel is specified, you can assume what the comp. ratio will be and back calculate the capacity.

here is a way it has been done on larger engine's with out a teardown , it is called a p+g gauge.

http://www.precisionmeasure.com/test1.htm

bill said:

here is a way it has been done on larger engine's with out a teardown , it is called a p+g gauge.

http://www.precisionmeasure.com/test1.htm

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Unfortunately, that doesn't work on a Norton, because you can't remove the pushrods without removing the head. I've been through the process several times with Norton engines at Bonneville, where a displacement verification is required before approving a record run. We Norton folks have to pull the head so they can measure bore and stroke. A lot of the modern OHC engine guys get by with just pulling the cam cover and removing the cam(s), and using something like the gauge you mention. They refer to it as "pumping" the motor.

If you've set a record, and want to do more runs, they will seal the engine and let you wait until the last run to go through the process.

This is the tech guy checking my bike for displacement in 2006.



Ken

as you stated it wont work on SOME engines and on a norton it will be either remove the head to actually measure it or remove the cam drive or rocker's so you can pump it. but I also was showing that it is possible to measure MOST engines with out a tear down.

lcrken said:

Unfortunately, that doesn't work on a Norton, because you can't remove the pushrods without removing the head. I've been through the process several times with Norton engines at Bonneville, where a displacement verification is required before approving a record run. We Norton folks have to pull the head so they can measure bore and stroke.

Ken

Click to expand...

I was a member of a crew for dirt oval track car racing. We raced cars in 2 of the 4 classes and helped out our 2 pit neighbors on their cars. I can't remember all the details, but any racer could pay to have the race officials, tear your car down to the block for measurement after a race. It cost the racer requesting your "tear down" money, presumably to pay you for the time you would need to spend to reassemble your engine after the race officials inspected it. The fee, kept the accusers from asking for tear downs just to try to screw with other racers who had their engines dial in...

Along with displacement limits for certain classes, there was also certain modifications that weren't allowed in certain classes, like roller rockers,... etc. Plenty of racers were caught with illegal modifications and plenty with extra displacement. Also there were racers who would rather be DQ'ed from a race they won rather than submit to a tear down. I recall once my crew chief ranting about a guy one race night who accepted the DQ after he won his race rather than let race officials look at his engine. My crew chief used the word "cheater" 5 times in just one sentence.

Hey Ken, Same guy same year, lol lol After checking bore and stroke he said "I have good news and I have bad news" at which point the engine builder looked at him and said WHAT????? The good news is you have a record, The bad is you gotta get this outta here NOW! At that point we all laughed and high fived each other, but for that split second I think my brother and the builder were stunned. Cool guy!!!

Yeah, he's quite a character. We encountered him several times for teardowns over a few years, and he was great to deal with, although he did get a bit stressed sometimes. As long as you had a good attitude, he had a good attitude. But not a guy you wanted to get pushy with.

Ken

From my experience at Bonneville I believe his name is Drew. He pre-race teched my bike and gear.

Yep, Drew he is. I was trying to recall his name, but it was lost inside my head somewhere.

Ken