Coupe into Speedster Conversion

[Phil Planck]

As my wife occasionally asks: : When can we take it for a ride?

[John Pierce]

Justin,

It's turning out nicely. Do you have to fabricate the parcel shelf too? Quite a project.


John

[JTR70]

Thanks a lot Don, very much appreciated!

Phil, my neighbor teases me all the time with "is it ready yet?" or "so we going for a ride this afternoon?"

Thanks John! Its been far more work back here than I ever could have imagined on the day it showed up.

The "new" parcel shelf is from the same donor car and was part of the deal when I bought the new cross-member and seat pan. It too is a cherry piece of metal however it was removed hastily and will need a new rear flange and some messaging but there is no serious rust to deal with.

Its a T2 version with the large square embossment which I'll be able to convert to T1 with that additional donor section pictured above with it. So there are a few things to do before it goes in for good. Its never straight forward is it? Thanks again you guys! Justin

[JTR70]

6/11/14
Donor parcel shelf prep

Large square T2 style embossment removed and new donor section which continues the ribs T1 style is ready for a few tack welds.

Section tacked and in for a test fit. Removal of those remaining pair of anchors for the T2 carpet strip was next.

An interesting detail I just noticed about this shelf panel is how light of a gauge sheet its made from. Its a touch thinner than the 20 gauge I'll be using to repair it. As I tacking this piece in the weld wanted to blow out very quickly and I had to take extra caution. Also cutting with my shears is a breeze and has the consistency of a cutting an old tuna can. Really not too many demands placed on it to do its job so lighter sheet metal was used here.

Prepping it for the new rear mount flange next. Thanks for looking! Justin

[roy mawbey]

Very nice Justin. Its those little differences between T1 and T2 only a small percentage of people really know about and that you need to know, almost 60 years on.

Roy

[JTR70]

Thanks again Roy! Its just little things that become familiar the more time that is spent with these cars.

6/13/14
Parcel shelf repair and prep continues
New rear flange is welded up and am now down to adding slivers of metal along the sides for proper gaps.

New flange in process of being stitched on here.

Came up shy on the upper left requiring a filler strip

One more for the lower right vertical section. Just about ready to install this in for good. I'll be very happy to be done with this.
Thanks for looking! Justin

[JTR70]

6/15/14
Rear seat pan and closing area repairs finally complete.

A very labor intensive rebuild-detour but at long last the repairs to the back of this frame are all but finished!

Repairs to this shelf including the rear mount flange and lower sides were finished this afternoon. In for one last trial fitment before the underside was sealed in primer and paint.

One more detail I wanted to add was this "pleat-line" which runs the length of the lower leading edge.

Now mounted for the final time. Installing my screws for the final adjusted fitment before I put down the first of the welds along the rear flange.

Thought it best to draw and weld the rear flange tight against the cross-member first then work my way forward along the sides to the leading edge. Flange contours tight against the embossments as originally done.

Onto the front leading edge now, sides and the rear all welded up at this point. This piece of course fought me the entire way due to the heat from the repairs and being man-handled during its hasty removal from the original donor car. Even though this is thin-gauge steel this last side was quite resistant to fitting tightly against the seat pan. Screws had to be installed to draw it in tight.

Front set and a couple of welds laid down. I was pleasantly surprised to find the old original spot welds nearly lining up. Took a quick break from it and completed welding and trimming the new lower kick-panel to the front of the new seat pan.

That was another "to do" chore that was nice to get out of the way. Well there it is, solid steel once again with no more cancer lurking deep in the bowls of this old frame.

A quick recap on how far this area has come.

The day it arrived.

The day I touched bottom and began working back upward.

Still have some weld dressing and detail to do but I can at least consider it built back here. Rear floor pan will be installed next then the tunnel and internal tubular conduits will be repaired after that. After that... the phase of actually converting this frame into a speedster can begin. I think... Thanks for looking! Justin

[John Pierce]

Fantastic work Justin! You must feel really good to get that part of the project behind you.

[MMW]

Wow, looking awesome! Great job Justin!

[Don C]

Like the others said...great work Justin! What an accomplishment!

[roy mawbey]

Justin,

Great job, painted it will look like factory new. Well done and thanks for that part of the story.

Roy

[tperazzo]

Congrats on another big milestone. Curious to know how flexy that chassis is throughout your repairs and what components firm it up ?

I'm sure you're taking factory chassis measurements from time to time too.
Thanks,
Tom

[JTR70]

John, Mic, Don, Roy and Tom, Thank you so much you guys! It was more work than I could have imagined but I did learn a lot delving so deep into this wreck.


Fortunately Tom there has been no detectable chassis flex since the day I finished welding in that tubular holding jig. As you know the weak link in any car frame is at the door opening thresholds. Once the sub-frame was installed to both bridge and triangulate the cockpit the ends of the frame had no leverage to twist or flex. Because this frame was so rusty and weak I took the extra precaution of not mounting it on the hoist until the longitudinal were both built. As you know it is these finished "tubes" that ultimately give this design most of its integrity through the middle.

I only felt safe cutting the rear of this jig out (to install the new seat pan) after both longitudinal "tubes" were complete and capped. Much to my relief when I cut through the length runners from the rear torsion mount to remove it only a slight bit of unloading occurred but there was still no twisting or movement. The jig itself was also meant to be a sight of reference so I made sure it sat square and level in relation to both front and rear torsion housings. A quick check after cutting the rear free confirmed that both the jig and rear torsion housing remained square and even with one another.

Going from the rear torsion housing back to this main cross-member posed no danger either. Again there was no leverage or force going through the outer runner stub ends. All I had to do was sight it level and square with the jig and rear torsion housing and it was good to go.

Here is one realization I did pick up from doing all this: This cross member is technically the "end" of a 356 chassis. Meaning there is no more load bearing or torsional force past this cross-member. All of your shock mounts, bump stops and of course the motor mounts do not go past this point. You could cut a 356 frame short like the photo above and the car would run up and down the road just fine. When you stop and think about it the "frame" past this point is only asked to support the engine compartment sheet metal, a tail skin and a bumper.

The construction says it all. Like the longitudinals which form a "tube" so does the inner rear seat pan closing panel. As you can see the "tube" ends at this cross-member. Past this point are "naked" sheet metal runners with a thin sheet metal cross-member. With this new realization I now look at 356 with a 911 engine conversion much more critically. Most conversions I've seen keep this configuration intact with only diagonal corner members added to carry the 911 motor mount. There is no real tubular or triangulated strength past that original motor mount cross-member just 19 gauge corrugated sheet metal forming a box which is really only at its strongest with straight vertical force. So now can you imagine hanging 400+ pounds of 911 drivetrain off of a structure that was never meant to hold any real weight let alone force from an operating engine. I have new eyes for those conversions...
Thanks again you guys! Justin

[Phil Planck]

Justin
Great tutorial on the 356 frame. Thanks. Phil

[JTR70]

Thank you Phil

6/19/14
Beginning tunnel repairs


About as knarly and rusted as it can get before requiring an entire replacement.

As well as being a speedster conversion this is also a T1 conversion so off comes the T2 waffle spacer plate.

Prepping the sides for the new mount flanges next.

Decided the best place for the weld joint was along the center of the inner reinforcement plate flange.

Two reasons for placing it here; the weld joint will be reinforced and there is not chance of a welding burr chaffing against the eventual wiring harness that will run through the right hand side conduit that this inner plate creates in the upper corners. Thanks for looking! Justin