Question: frame measuring

[35classic74vette48]

i have a c3 frame and want to measure the frame to see if it is straight. the service manual shows the centerline and datum plain, can any one please explain how to get the measurments for the datum plain, as it says nothing about how high the car should be to get these measurments it just shows the datum measurments and how do i take these measurments from the level floor or what, i have a tram gauge and centerline guages. any one out there that could help me with this would be great.

 

[TimAT]

Assume it's a level floor- height would be a fact, but not a high priority. You do have the frame dimensions from a frame machine manual or the factory? Set the frame up at whatever the datum calls for- lay out the centerline and start measuring. Keep in mind the datum plane(s) and centerline are setting on a frame machine- a KNOWN level and true surface.

 

[35classic74vette48]

Assume it's a level floor- height would be a fact, but not a high priority. You do have the frame dimensions from a frame machine manual or the factory? Set the frame up at whatever the datum calls for- lay out the centerline and start measuring. Keep in mind the datum plane(s) and centerline are setting on a frame machine- a KNOWN level and true surface.

yes the floor is level,i have the car up on jack stands,i have the centerline guages under the frame and they have sight levels showing the car/frame is level,i was just needing to know,how do you get the measurments that the service manual frame demitions show from i guess the floor as some of the measurments are over 14 to 20 inches in height,that means the car would have to be at a certain height or am ilooking at this the wrong way and thanks much for the input. richard;help

 

[TimAT]

Just a guess- IF the service manual dimensions are ride height- IIRC that's 4.5 inches to the front lower control arm bushing center. So you'd need to do the math on that one.

There's a body shop guy here someplace-- that would really be the one that could give you a 100% answer= All I can do is tell how I'd go about it and see if I liked the answers I get- if not, I'd try something else. I've seen too many frame shop guys go about straightening a frame like a bull in a china shop-= it can't be that exacting.