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Posted by: amfab Feb 12 2017, 09:52 PM

After some minor welding, I wanted to check the car’s level and dimensions again. I hung the doors, made a couple of jack stand adjustments, and everything looks pretty good.
I measured key dimensions and I am wondering how precise I need to be.

I measured:

• -Between roll bar and windshield flange (f) and both sides are on the factory dimensions within less than 1/32nd of an inch.
• -Diagonal distance across roof opening (x) measured between outer corner of roll bar and inner edge of roof on opposite side—both are right on the factory dimensions within less than 32nd of an inch.
• -Diagonal distance across passenger compartment (y) measured between outer corner of roll bar and outer edge of lower hole for hinge—again, right on the factory dimensions within less than a 32nd of an inch.

These measurements are essentially dead on. I think the inaccuracy is probably because of my measuring ability.

I also measured between the hinge and door lock pillars (h). These are a little big. They are about 3/64 of an inch more than the factory dimensions, but they are the same on each side.

With all the other dimensions being so accurate and the doors looking pretty good, I am wondering if I am being too worried about the precision of this.

Or am I?

Are these numbers pretty good for a car made in the 70s?

Thanks,

-Andrew

Posted by: tygaboy Feb 13 2017, 10:19 AM

I'd say if you're that close, you're well within the tolerances.
That said, when you're measuring, be sure the car is supported in the same way that the suspension will load the chassis. I've noticed that depending where I've supported my chassis, and if the drive train is in it or not, I can see measurable flex at the "f" locations.
But my car is currently missing the lower firewall, jack plates and rear half of the floor so YMMV.
If they don't chime in, you may want to PM Rick-918-S, ScottyB or Jeff Hail. They have tons of experience. I'd defer to them for the straight poop on chassis stuff.

Chris

Posted by: amfab Feb 13 2017, 11:03 AM

Thanks Chris. I am a bit paranoid because I did not go through removing the suspension and making a jig.

I am supporting the car with stands at the front of the torsion bar tubes and the bars that stick out at the rear suspension console. I think that is pretty close to how the suspension puts pressure on the chassis.

However,

I also have screw-type adjustable stands with a bar across the back of the floor pan and one on the rear of the transmission. These add support as I work to remove rusty metal or weld in new metal. I jacked the car up and lowered it on the main stands, and screwed the other stands upward to support. Even though I screwed them tight, I think the main stands are carrying the majority of the weight.

This is how I plan to keep it supported for the long repairs and the front of the Brad Mayeur kit install. I will have to switch the rear jack stand position to install the rear parts of the Mayeur kit as they bolt to the console. I was thinking of using the engine mount bar as I do that. Then I will switch back to the console bar to do the lower firewall and floor pan.

Thanks

-Andrew

Posted by: rick 918-S Feb 16 2017, 04:25 AM

Andrew, 3mm is the standard. 914's are particularly sensitive to welding stresses due to the design. Do yourself a favor and be sure you brace the chassis before continuing to weld. Rely on the lower set of measurements and less on the upper windshield measurements as you can simply push the frame and change the measurements by hand.

Posted by: amfab Feb 16 2017, 10:36 PM

Thanks Rick, Im definitely under 3mm. I probably wouldn't have spent so much time tweaking my stands and braces if I had I known that ahead of time. Really good to know I am within spec.

I welded the lower end of my door braces inside in front of the door opening rather than using the hinge mount so I can take the doors on and off while I work—and I built a little stand that mounts on my floor jack to make getting them on and off easier so I can keep checking as I weld.

Ill just keep measuring a lot

thanks again.

-Andrew

Posted by: timothy_nd28 Feb 16 2017, 11:01 PM

Hey Andrew,

It seems that you are having great luck to where to place the measuring tape when making measurements. I'm trying to decipher the location points for "D". I have looked at the pictures and drawing a blank like a idiot.

I bought a 914 shell and recently just started to fit panels to it. I think the front face panel has pushed in, as I only read 40".

Posted by: cary Feb 17 2017, 08:14 AM

I don't think you can get THAT measurement from a tape. You'd need a body measurement tram with drop down plump bob dealies. The Porsche measurement looks to be a flat/horizontal plane. From the picture, the measurement points look to be the inside of the seal channel. Using a tape, point to point would be at an angle.

After the sun comes up I'll go and measure the parts car here at home for a comparison.

Posted by: amfab Feb 17 2017, 10:13 AM

I'm not working up there so I haven't made something for that, but I find measuring anything with a tape to be a problem. What I do is use dowels that I cut to the dimension to measure between easy stuff like in the door jamb. for the harder dimensions I use dowels with screws perpendicular through the end that stick out a bit. To get "D" you will probably need to make a custom trammel gauge out of a metal ruler with a plumb bob on one end like cary said.

Posted by: cary Feb 17 2017, 12:00 PM

From tape end against the back rail of the front channel. To looking down on the front rail of the back6 channel. 41 7/16s.
At +/- 3mm we need a couple more comparisons, then average them out.

Posted by: timothy_nd28 Feb 17 2017, 12:44 PM

Thanks guys, really appreciate it!