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Heavy Duty frame rails and connectors

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tunnel patched

     patching trans tunnel

weldind right floor

     welding right side floor in
Got back from a trip to Japan.   More patching in the transmission tunnel.   Some were rust related and others were from the previous transmission
mounting holes.   Welding the right side floor panel in was easier than the left side as it had less corrosion.


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   interior reinforcement plate



reinforcement plate

    mock up firewall shape guide


  bottle jack used to trial fit connector


   rear connector test fit


   front connector holding jig

rear connector jig

   rear connector holding jig

exterior reinforcement plate

   exterior reinforcement plate


I was delayed for couple of weeks as my air compressor broke down.   As usual. all the necessary parts had to be ordered from the Mainland.  Finally got the parts in and compressor fixed.   Sure was difficult to work without a air compressor.   Hope to get back on track now.






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My Z Project has been delayed by a deal that I could not pass up on.   One of my customers had a C-Aire 7 1/2 HP two
stage compressor with 80 gallon tank.  It wasn't running because of a broken inlet valve.  The price was $500 so I said "Sure"
and load into my truck.   Had to wait for couple weeks to get the compressor head rebuilt kit.  I spent the time cleaning and
checking the parts.   The parts came in last week and I reassembled the compressor.  Everything is ready to go except the
wiring and control devices.  Should be only a weeks more before I can get back to my 240Z project!!!


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 right side interior floor reinforcement
Waiting for magnetic starter switch for my air compressor so I decided to finish the floor reinforcement plates.  These 16 gauge
steel plates are located inside the vehicle at the bottom end the firewall and front section of each side floor panel.   They will
reinforce the floor and firewall directly above the frame rails.  The plates are about 4 inches wide about a foot long.  This should
spread the frame load over a wider area of the floor sheet metal.


  left side interior floor reinforcement



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IMG 0959

  Welded the frame rails to floor pan and rear crossmembers.


  In the front, rails welded to reinforcement plates attached to floor pan.

rightr frame backend

  Rear section was welded to existing rear crossmember.  Rails were also spot welded in the middle sections.


  In preparation for engine compartment rail construction, the engine compartment was boxed to prevent body shifting while cutting off the front rails.


  The photo shows using the bubble level on the top of the engine
to sidewards level.   The car must be set level before any cutting can be done.







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IMG 0979

  L/S frame rail cutoff using plasma cutter

IMG 0988

  crossmember box removed from frame rail

IMG 0987

  new frame-2 1/2 X 1/8" square steel tubing being setup

IMG 1007

   notice gap-about 1" between square tubing and wheelwell.  A filler piece fill
this gap.

IMG 1017

  the filler piece consists of 6" strip of 16 gauge sheet metal connecting tubing with existing wheel well housing

IMG 1022

  the firewall end of the square tubing was capped with 1/8" metal plate.  Notice  the 
plate was made with about 3 /16" edge around it.  This was to allow easier welding the tubing to the firewall.

IMG 1026

  mockup of the connecting piece between the square tube frame and underfloor
frame connectors
One of the most difficult potion of the front frame construction will be connecting the crossmember to the square frame rail.
The connector will need to be smaller than the width of the square tubing.








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IMG 1042

  right side frame rail mocked up on jack stands.  Shimmed to be level lengthwise
and  sideways.

IMG 1067

  frame rail contoured to match firewall to provide easier welding

IMG 1072

  top view of rail and firewall

IMG 1086

  outside view of rail and firewall

IMG 1116

   top inside view of right frame rail






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sideways (2)

  The  front frame rail checked with bubble level.

sideways (2)

   Level check was done sidewards for both  front and rear section of the frames rails.

right side

   Rignt side frame was checked for levelness.

left side

    Left side rail checked levelness too.  Both rails were also checked for squareness.  This is done both measuring diagonally the opposide cotners of the frame rails.  

New front frame2

    A new 2 1/2" tubing was cut to join the two frame rails together at the front.







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I researched all methods of mounting the engine crossmember to frame rails(both untilized  or steel tubing construction.  Everyone notched

the frame rail to mount the crossmember.   This method requires a lot of time and effort so I decided on a simpler method.  I relocated the two

mounting bolt holes about 3/4" inward.  See photo.   This method does require two holes drilled on the top of the frame rail to install frame bolts.

I drilled two 1" holes directly over the crossmember bolts(inside the frame tube).   Caps will cover the assess holes to prevent water from entering



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Labor Day Weekend gave me extra day to work on the Z.   Unfortunately  the holiday also meant most of my neighbors headed

the beach and were not around to me carry the heavier stuff.  The first picture of the new subframe  on the ground.   Had to drag it under the

car and lift on the jack stands.   Second and third pictures show aligning the subframe to existing body using datum line(center line and plume

line(vertical line).  



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 The first picture show a better view of the plumb line. The second photo show the left suspension mockup.  The third picture is of

the right side suspension mockup.   The fourth photo is a closeup of the left side crossmember.   Note the two 1" assess holes in the top of the 

frame rail.  The holes will capped off later to prevent water and debris from entering.





Edited by toolman

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First photo is the left side frame rail with the frame connector welded to the firewall.

Second picture is the passenger side frame and frame connector welded to the firewall.

I was glad that put a 16 gauge reinforcement plate under the frame rail.   Otherwise, welding 1/8" frame to 23 gauge  firewall

would be extremely difficult.



Edited by toolman

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First photo is the "before picture" of the left side of frame rail. Notice 1" gap.

Second pic is 3/4" X 2" right angle 20 gauge sheetmetal  welded to subframe and existing sheetmetal

Third picture is outside view of right angle connecting pice welded to subframe and wheel housing.

Fourth pic is an additional 20 gauge 3" wide and about 48" long welded to the subframe and existing sheetmetal.   This will provide additional strength and looks better.

Fifth  photo is right side frame rail with connecting right angle support plate.

Sixth pic shows welding the right side  "cover plate'" to sheetmetal and subframe.

Seventh photo is engine compartment view of the subframe and connecting piece.  All the mig welds will covered with urethane seam sealer after

media blasting.   Next step is construct tension rod support brackets for both sides.








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First photo is the left side stabilizer bar mounting holes( a plate with corresponding nuts welded to it will be installed in the frame rail later)

Second pic is the right side stabilizer mounting holes.

Third picture shoes mocking up in preparation for welding of the tension rod bracket.

Fourth pic is the completed left side bracket.  It is constructed of 3" x 1"x 1/8" steel tubing (same as frame connectors)  The angle section is set at 20 degrees.

Fifth photo is the inside view of the bracket.

Sixth photo is the outer view of the right side tension rod bracket.

Seventh pic is the inside view of the tension rod bracket.   Both left and right tension rod brackets will have 20 gauge plates welded to

inside and outside of them.  This will replicate the factory appearance.













Edited by toolman

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Nice work, I had to do a similar thing as well as my front sub-frame was damaged.  I decided to make my own TC mounts however - i'll see if I have a picture or two.  This combined with full length sub-frame connectors has really made my car stiff.  You will like it when done.





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Wheeler,  Your frame rails look great.  Are you going to race the car?    I started to do detail work on the engine compartment and decided to work on the radiator support instead.

While measuring the areas in front of the radiator-area where the bumper and hood hinge attach to)  needed straightening.   First picture shows the old radiator support.  Second pic is of 

both areas stripped of paint and cleaned. The third photo has the right side with the reinforcement rib removed to fix under it.  Fourth pic had the rib replaced and ready to rewelded

on.   The fifth photo is the left side with the rib removed and damaged area repaired.  Sixth pic show the rib replaced awaiting to be welded back.   The vehicle was in an accident before

I bought it and the area( crush area) was not repaired as that would require rib removal.   Next to be done will the construction of the replacement radiator support.








Edited by toolman

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Tool man - I have only done some autocrossing with the car.  That and weekend use is really what I use it for.  It is fun and handles great and is loud and a little smelly...but it is fast.  I followed a similar path to the one you are on.  Once I redid the front subframe, I went on the the core support.  Mine was a little bent (probably from an accident) and I thought I could improve it a bit.  Here is one picture that I found. Lesson learned - you need to make sure the hood hinges work with your core support in the open and closed position.  Mine contacted the sheet metal on either side of the core support and needed to be cut a little to allow the hinge to clear.  Keep up with the great progress that you are making.  


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Hmm... isn't it traditional to make a tube frame first, and THEN construct a body for it?  Looks like you did it the other way around! :P   Much more difficult that way - like going through the tail pipe to do a valve job.

I thought I had it bad when the "repaired" frame rail beneath my battery turned out to have been fixed with chewing gum and aluminum foil.  You've got a much bigger job, and although I don't envy your task, I do admire your work.

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Thanks for the support.   Sometimes these projects become bigger than anyone can predict.  While the ribs were off,  I double checked the front area in front the both struts and found the left side was 1" higher than the right.   I called my friend who has a 70 240Z to take measurements off his car.   I confirmed that the right side was correct and left side was high by 1".    Since I didn't have a frame machine handy, I decided to section the left side and raise it 1".   See photo 1  welded a 2" sheetmetal strip to reinforce the joined area on the inside,   This area will be covered by the new radiator support.   Pic 2  show the rib rewelded in and new section above the rib to provide a smooth transition between altered section and old area.   Pic 3 show additional sheetmetal strip  welded in to reinforce the outer section.  This was necessary as this panel has handle the hood hinge and bumper brackets.




Edited by toolman

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First pic is the "before" of left radiator support.   Second is the paper template for replacement section.  Third one shows the replacement mocked in.  Fourth is of the"before" pics of the

right radiator support.  Fifth shows the replacement section mocked in.  The last photo is the overall view of the radiator support awaiting welding.







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