I understand setback, but where do you measure from?

[gowjobs]

I can dig that gassers were allowed to setback the engine in the chassis a distance equal to ten percent of the wheelbase, and A F/X cars were allowed twenty-five percent. What I wanna know is:

From what point on the engine is this setback measured? Is it measured from the flywheel? The waterpump? The front-to-back center of the crankshaft? The driveshaft yoke?

The reason this seems important is that if you swap from an inline-six or eight to a V-8, it already will be a shorter engine, shifting weight toward the rear if it's bolted to the same bellhousing. In other words, if I drop a 383/Torq-flite combo in my '63 Rambler American, how much further back can I put it and stay within the original guidelines set forth for Gas-class cars?

Can anybody here answer this one?

[Unkl Ian]

I always thought it was from the front axle centerline to the #1 sparkplug hole.

[C9]

Unkl Ian has hit the nail on the head.

Like he does most times....

[Deuce Roadster]

[ QUOTE ]
I always thought it was from the front axle centerline to the #1 sparkplug hole.

[/ QUOTE ]


True........the Hemi guys in Pro Stock ran dual plug heads (for awhile) because they could use the front most hole and get MORE setback.


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[porknbeaner]

[ QUOTE ]
I always thought it was from the front axle centerline to the #1 sparkplug hole.

[/ QUOTE ]
the unkle got it (as usual) http://www.jalopyjournal.com/ubbthreads/images/graemlins/wink.gif

[Unkl Ian]

[ QUOTE ]
........the Hemi guys in Pro Stock ran dual plug heads (for awhile) because they could use the front most hole and get MORE setback.



[/ QUOTE ]
They were only allowed one plug per cylinder,and the motor made more power using the rear plugs instead of the front plugs,but #1 cyl they ran the plug in the front to be able to move the engine back a couple inches more.

[Deuce Roadster]

[ QUOTE ]

They were only allowed one plug per cylinder,and the motor made more power using the rear plugs instead of the front plugs,but #1 cyl they ran the plug in the front to be able to move the engine back a couple inches more.

[/ QUOTE ]


I was at Sox and Martins shop " back in the day " and saw the dual plug heads on their car. A friend of mine hung around and sorta worked there. He was a 1932 Ford guy too.

Good times back then......


http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif

[AnimalAin]

By the way, A/FX cars were allowed hardly any setback at all. (Altereds were the class that was allowed 25% setback.) That was one of the things that led to the Plymouth and Dodge cars with altered wheelbases in 1965. NHRA said, "not so fast..." and they competed in AHRA and as match racers. They were certainly funny looking.... i.e., "funny cars." The match race bragging rights were a big deal, and as a result, the cycle of one-upsmanship was pretty well out of control...... which gave us the plastic flopper in 1966.