Jump to content

Heavy Duty frame rails and connectors

Recommended Posts


  After cutting open the front rail where there was a small rust spot, this is what I found-more corrosion.   So I guess I have also to replace the two front frame rails.


  close up of corrosion


  picture of a Datum Line which is used a  reference point for frame work.




  overall view of Datum Line


  As of now, I planned to install a Chevrolet LS3 crate motor with T56 6speed manual
transmission.  This motor is rated at 430HP  but they now have a updated version of this motor rated at 500HP.  I waiting to complete the major bodywork before I order the motor.  Chevrolet might have a better choice in the future!


  Description of LS3 motor






Link to comment
Share on other sites

  Those slotted holes in the front cross member are for an eccentric bolt that provides about one degree of camber adjustment.  At the time,

I had access to automotive wheel alignment machine so I slotted the hole while checking the camber.  Now days, everybody is going to slotted camber plates on the top of the struts.   This was done in the mid 70's when only aluminum eccentric camber bushings were available.  Good catch!

Link to comment
Share on other sites


  right side floor pan template


    redneck sheet metal brake-1


    redneck sheet metal brake-2


   floor pan sheet metal  shape template


   test fit for floor pan
  I constructed a redneck sheet metal brake for making the floor pan.   Using c-claps, vise grips, steel
tubing and steel plates.  It did the job.  I made a sheet metal shape template to aid in creating the slope in the floor plan.  A narrow about 1" wide was hand bend to match the shape of the existing pan.  The
floor pan was then test fitted.  The floor pan will be trimmed and attached with cleco clips.






Link to comment
Share on other sites

  • 3 weeks later...

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.


Link to comment
Share on other sites

  • 3 weeks later...


   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.






Link to comment
Share on other sites

  • 4 weeks later...


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!!!


Link to comment
Share on other sites


 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



Link to comment
Share on other sites

  • 2 weeks later...

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.







Link to comment
Share on other sites

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.








Link to comment
Share on other sites

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






Link to comment
Share on other sites

  • 2 weeks later...

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.







Link to comment
Share on other sites

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



Link to comment
Share on other sites

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).  



Link to comment
Share on other sites

 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
Link to comment
Share on other sites

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
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...