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Author Topic: ENGINE SIZE.... How close is too close?  (Read 11840 times)

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Offline gearheadeh

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ENGINE SIZE.... How close is too close?
« on: December 12, 2009, 07:19:42 PM »
Not wanting to have a situation where the engine fails tech if Iam ever lucky enough to set a record. Iam putting this question out to you guys because while according to the math the bore size Iam considering is legal, it is a little close for comfort. Like .0356 CI or .000584cc under the max size listed.
On page 15 Section 2a It states that an Engines maximum displacement goes to a _ _ _.99CID. Then it states that CID will be converted to Cubic  Centimeters using the formula(CID/61.024liters)
So I did the math to the 5th or 6th decimal point and Iam technically safe by .000584cc.
How will this work when they use a pump on the engine and with the piston rings bigger than the actual piston it would be a little bit bigger bore, Will they measure the actual bore, the piston or just go by what the air pump says?
Thanks for your help with this, If this bore size will not work then Iam looking at other possibilities I guess.
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Offline donpearsall

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Re: ENGINE SIZE.... How close is too close?
« Reply #1 on: December 12, 2009, 07:25:01 PM »
You did not say whether your vehicle is a car or motorcycle. I have had them measure my bike engine several times and they always measure the bore and stroke and calculate the displacement. I've never seen them use anything else.
Don
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Offline gearheadeh

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Re: ENGINE SIZE.... How close is too close?
« Reply #2 on: December 12, 2009, 07:29:18 PM »
Car Engine.....The only time I was able to see what was going on in tech after a record was set was in 1988. They used a funnel and pored in tranny fluid into the engine after taking out the spark plug. What is the procedure in tech nowadays?
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Offline Stainless1

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Re: ENGINE SIZE.... How close is too close?
« Reply #3 on: December 12, 2009, 07:34:47 PM »
bore X bore X .7854 X stroke X number of cylinders.   If you are close to the limit, you will have to physically be measured, not by air or fluid.  Had that issue with a 750 cc motor in the lakester.... those are really close to 46ci.  
If you are in a car, then you better measure under the next class.  
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Offline desotoman

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Re: ENGINE SIZE.... How close is too close?
« Reply #4 on: December 12, 2009, 07:39:24 PM »
When we set a record at El Mirage, Tom Evans actually measured the cylinder bore and stroke.

Tom G.
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Offline gearheadeh

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Re: ENGINE SIZE.... How close is too close?
« Reply #5 on: December 12, 2009, 07:41:53 PM »
Quote from: desotoman on December 12, 2009, 07:39:24 PM
When we set a record at El Mirage, Tom Evans actually measured the cylinder bore and stroke.

Tom G.

Okay, With a dial bore gauge on the piston top for stroke and a vernier in the bore of the block?
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Offline desotoman

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Re: ENGINE SIZE.... How close is too close?
« Reply #6 on: December 12, 2009, 07:52:45 PM »
Oops, ours was for a bike, sorry.  But yes he did use a dial caliper and was very precise when he did it. In fact as I remember he did it twice to be sure.

Tom G.
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Offline gearheadeh

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Re: ENGINE SIZE.... How close is too close?
« Reply #7 on: December 12, 2009, 08:26:45 PM »
Quote from: desotoman on December 12, 2009, 07:52:45 PM
Oops, ours was for a bike, sorry.  But yes he did use a dial caliper and was very precise when he did it. In fact as I remember he did it twice to be sure.

Tom G.

Yes indeed, I bet if I pull off this stunt he would be VERY carefull. I will have to blueprint the engines bore and stroke on all the cylinder's to check that 1 throw isn't slightly longer in the stroke and that the bores are EXACTLY what they are supposed to be!
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Offline Nortonist 592

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Re: ENGINE SIZE.... How close is too close?
« Reply #8 on: December 12, 2009, 08:27:12 PM »
I was fortunate enough to set a record (at El Mirage) in June, July, and Sept. of this year.  Each time my engine was measured with a dial calipers.  June measured at 499.5 cc.  July measured at 497 cc and Sept. measured at 498 cc.  Same cylinder, piston, rod and crank.  I would suggest you leave a bit of "wiggle" room if you can.  Atomic clocks are accurate too God knows how many decimal points.  Dial guages aren't quite so.
« Last Edit: December 12, 2009, 08:28:55 PM by Nortonist 592 »
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Offline willieworld

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Re: ENGINE SIZE.... How close is too close?
« Reply #9 on: December 12, 2009, 08:48:23 PM »
bill   sounds to me that your bore isnt round----LLLLLOOOOOOLLLLL      willie buchta
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Offline Nortonist 592

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Re: ENGINE SIZE.... How close is too close?
« Reply #10 on: December 12, 2009, 09:36:29 PM »
Could be, Willie.  I put it down to flexible calipers.
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Offline willieworld

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Re: ENGINE SIZE.... How close is too close?
« Reply #11 on: December 12, 2009, 09:46:43 PM »
know what you mean---i have a pair of those myself---bill if you think you might outrun your tires this next year i may have a couple of tires and rims for you                         willie buchta
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Offline RichFox

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Re: ENGINE SIZE.... How close is too close?
« Reply #12 on: December 13, 2009, 10:05:13 AM »
But they will measure the bore. Not the piston. So if you are that close using piston dia. You may be in trouble
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McRat

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Re: ENGINE SIZE.... How close is too close?
« Reply #13 on: December 13, 2009, 11:56:53 AM »
Pumping seems to be the most common method, but will not work with all engines.

While not practical for everyone due to logistics, having your engine certified and sealed when it's built saves potential grief at the track, and saves time in impound.  For some engine configs, like two strokes, it will have to be measured with the head off regardless.  IIRC, if the engine displacement is close to the limit, it's supposed to be measured with the head off anyhow, pumping is not allowed.  I could be wrong.

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Offline Nortonist 592

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Re: ENGINE SIZE.... How close is too close?
« Reply #14 on: December 13, 2009, 12:25:00 PM »
Quote from: willieworld on December 12, 2009, 09:46:43 PM
know what you mean---i have a pair of those myself---bill if you think you might outrun your tires this next year i may have a couple of tires and rims for you                         willie buchta

I'd love to outrun my tires but I think Sheri has put a curse on her record!  I don't think I'll go fast at all next season.
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