Author Topic: setback measurement question  (Read 3706 times)

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LittleLiner

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setback measurement question
« on: July 13, 2011, 03:44:10 PM »
How is engine setback measured when an engine is mounted transversely?  Specifically, where is the “front-most sparkplug hole?” measured in these configurations?

Offline NathanStewart

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Re: setback measurement question
« Reply #1 on: July 13, 2011, 05:13:12 PM »
You think too much.
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LittleLiner

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Re: setback measurement question
« Reply #2 on: July 13, 2011, 06:18:51 PM »
You think too much.

True . . and it drives my wife nuts.

Although in this case I really am trying to position a transverse engine in a Modified Category coupe.  Where should I measure from?  The electrode?  The Opening in the Cam cover where the plug gets inserted?  Somewhere in between?

Offline dw230

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Re: setback measurement question
« Reply #3 on: July 13, 2011, 07:39:04 PM »
Most cars that are using a transverse mounted engine are front wheel drive. Moving the engine/trsns pacake can add more work than the shift in balance. Are you shre you want to do this? What class are you aiming for? Are you converting to rear wheel drive/

DW
White Goose Bar - Where LSR is a lifestyle
Alcohol - because no good story starts with a salad.

Don't be Karen, be Beth

LittleLiner

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Re: setback measurement question
« Reply #4 on: July 13, 2011, 08:28:48 PM »
Most cars that are using a transverse mounted engine are front wheel drive. Moving the engine/trsns pacake can add more work than the shift in balance. Are you shre you want to do this? What class are you aiming for? Are you converting to rear wheel drive/

DW
Dan
I am still trying to figure a way to get my bike engined Metro back into Gas Coupe.  The revision in the Gas Coupe radiator position/size rule made my previous design all but impossible.  I sold the Honda engine and bought a Suzuki because it doesn't lean as far forward as the Honda CBR600RR did.  That might give me enough room to fit the right size and located radiator to be legit.  I am also trying to see if mounting the engine behind the drive-axle would work .  . Although that involves a rats nest of chains and jackshafts to work with front wheel drive.  Plus I then get into the engine setback problem.   Since Gas coupe has a setback limit of 2% that only gives less than 2 inches of setback for the little Geo.  Thus I am asking how to measure setback . . . .  And I would have the same question if we go Altered and run chain drive to the rear axle . . . .  I know, I know . . I should build a roadster!!!

Offline Stan Back

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Re: setback measurement question
« Reply #5 on: July 13, 2011, 09:48:45 PM »
I'd be willing to bet that the front-most spark plug is located real near the same distance as the rear-most spark plug.  I'd guess the center of the spark plug hole -- Dan?
Past (Only) Member of the San Berdoo Roadsters -- "California's Most-Exclusive Roadster Club" -- 19 Years of Bonneville and/or El Mirage Street Roadster Records

Offline dw230

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Re: setback measurement question
« Reply #6 on: July 14, 2011, 12:54:31 AM »
I think that if OEM engine location would need to be determined. The set back can be measured from there using the crank center line.

Too much work for me at my age.

DW
White Goose Bar - Where LSR is a lifestyle
Alcohol - because no good story starts with a salad.

Don't be Karen, be Beth

LittleLiner

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Re: setback measurement question
« Reply #7 on: July 14, 2011, 08:36:24 AM »
I'd be willing to bet that the front-most spark plug is located real near the same distance as the rear-most spark plug.  I'd guess the center of the spark plug hole -- Dan?
I would tend to agree.  And admittedly this is a non-issue for 99.9% of existing LSR cars. 
Would it be reasonable to define the fore/aft location of the front most sparkplug for transverse in-line or V configuration engines as being near a vertical line that cuts through the center of the head to block mounting surface? 
That is sort of a long-winded way of saying "somewhere close to the spot shown in the circle on the photo of the CBR600RR engine in this photo."

I am just trying to avoid a debate in impound (if I ever get there) some date in the future, where someone says, "hey your engine location exceeds the setback rule."
Dan's comment about crank location of the OEM engine. . . .That seems like a reasonable idea.   
In any case, I guess I need to come to terms with building the car as an Altered . . . .
« Last Edit: July 14, 2011, 09:05:16 AM by LittleLiner »