ANOTHER Datsun Z/LS3/T56 Swap Thread

[mr.mike]

nice work, keep the updates coming! 

[Ironhead]

Finished the fabrication to mount the fuel cell:

 

 

 

 

 

 

My original plan was to weld the actual cell "cage" into the framework, but while test fitting it I realized that it was very bulky and blocked access to many areas under the car.  In particular, seam sealing and painting several areas under the car would have been very difficult with the cage in place.  So I decided bolting it in was a better long term plan, as far as future flexibility and serviceability of the car.  This will also allow me the get the entire cell cage powder coated rather than having to paint it.  Painting it would have been a difficult proposition as it is nothing but nooks and crannys.

 

It is bolted in with eight 3/8" ARP bolts, that screw into weld nuts on the underside of the framework.  Perhaps not quite as strong as welding it in, but more that strong enough for any plausible eventuality.

 

 

 

Cell then drops into the framework and bolts in as shown.

 

 

 

The attachments on the bottom of the cell cage are stainless steel stock that I made into jacking/jackstand points.  They are stainless as I intend to leave them unpainted, since jackstands always seem to remove paint anyway....and at least they won't rust.  A bit over-engineered...I know.  They are off to the sides because I am about 80% sure I am going to run my exhaust right down the middle below the fuel cell (with heat shields).

 

 

 

 

Thanks for looking!

[LLave]

I think you will be just fine with bolt in. How do you plan on routing the fuel lines? Through the cabin? 

[Ironhead]

2 minutes ago, LLave said:

I think you will be just fine with bolt in. How do you plan on routing the fuel lines? Through the cabin? 

 

No...SCCA rules allow fuel lines to go through the cabin as long as they are braided steel or metal hard lines, but the idea doesn't really sit well with me.

 

I have an aluminum cover made that goes over the fuel cell, again as required by the rules.  I am going to simply run the fuel lines out the cover and under the floor with bulkhead fittings....so perhaps 6" of fuel line is all that will be inside the car.  Then I am going to run the fuel lines in the trans tunnel, pretty much like stock. 

 

Plumbing is made pretty simple by this particular cell, as the fuel pump is inside of it, so I don't need to conjure a place to mount the pump and such.

[Ironhead]

Finished fabricating the mount for my Woodward steering rack.  The new rack is significantly quicker than stock, with a 2.36 ratio, and also simply serves as a replacement as my stock rack was pretty tired and loose.  I was unable to find most of the parts to rebuild it, so I figured this was another area where going aftermarket was a good long term strategy.

 

The crossmember is the one from Apex Engineered, and all I did was cut off the stock rack mounts it comes with and make my own for the Woodward rack.  The crossmember has some useful features, like multiple control arm pivot point locations and bracing attachments to the rear control arm mounts.  It was also much easier to modify for the Woodward rack than the stock crossmember would have been. 

 

As shown, the rack is mounted in the stock location relative to the crossmember mounting surface, but it can easily be moved up or down as need be down the road, simply by removing the two bolts and changing the spacers.

 

I am banking a lot that the electric power steering will work as I hope, because with this quicker rack and the 275 tires I plan to use in front....I doubt I would even be able to turn the wheel at parking lot speeds.

 

 

 

 

 

 

Edited June 30, 2018 by Ironhead

[HuD 91gt]

Very impressive work.   Quality is A+++

[Ironhead]

Added engine mount bases to the cross-member.  I am using the Hoke mounts that actually bolt to the block, these bases will interface with them.

 

I figure a reasonably competent fabricator could have banged these out in four or five hours.  Took me about a week of faffing about and stepping on my dick to finish them.

 

I realized as of this week I have been working on this project for a full year.  When I started it I guessed I would have gotten farther in a year than I have.  

 

 

 

 

 

[Ironhead]

On 2/19/2018 at 4:02 AM, rossman said:

Awesome build!  I'd recommend something different than the T3 front differential mount.  That type of mount is known to move around under load.

 

Well, in the process of mocking up the diff installation (short nose R200), the truth of what Rossman said was really brought home (thanks again Rossman for the heads up).

 

The T3 front diff mount is very flimsy and minimalist, and started bending significantly during the process of getting it bolted in.  It also didn't really fit worth a crap, at least not in my car.  It doesn't take much figuring to realize the diff mounts are going to have to absorb tremendous loads, and hopefully transfer them to the car chassis without doing any damage.

 

I figured a few months ago (since I couldn't find a beefier mount on the market) that I would have to make my own.

 

Here is the result, with the T3 mount next to it for comparison.  It is made of 1/4" plate, braced and gusseted in the areas I figured would need it.  The long plate that bolts to the top of the mount, bolts in turn to the top of the driveshaft tunnel, again to spread the loads to as many places as possible.  It will also serve as a reinforcement for a hydraulic handbrake I plan to mount there.

 

 

 

 

 

Edited July 12, 2018 by Ironhead

[Ironhead]

Installed:

 

 

 

 

 

[JoeK]

As usual with this build, looks great.  What will you do for the control arm mounts in the front? The original piece also held the front of the long nose diff, but also seemed to tie the left and right together. Now you've also got a brace across on that front mount.  I haven't done the diff alignment yet on mine, but it currently looks like the pinion flange will hit the original cross brace.

[Ironhead]

I am planning to use the original cross brace/front control arm pivot.  The two "U" shaped cutouts on the sides of the mount I constructed provide clearance for the cross brace.  The pinion flange sits approximately 3" behind the cross brace and perhaps 1" higher up, so the driveshaft should clear well above the cross brace.

 

At least I hope I haven't miscalculated.  I am running into multiple interference problems that need to be sorted.  I am planning on running a diff cooler, but there is almost no room between the diff fill plug and the rear control arm pivot mounts to install a threaded fitting....so not sure what to do.

 

Does that answer your question or am I not understanding...?

Edited July 15, 2018 by Ironhead

[rossman]

On 7/12/2018 at 12:12 PM, Ironhead said:

Well, in the process of mocking up the diff installation (short nose R200), the truth of what Rossman said was really brought home (thanks again Rossman for the heads up).

 

The T3 front diff mount is very flimsy and minimalist, and started bending significantly during the process of getting it bolted in.  It also didn't really fit worth a crap, at least not in my car.  It doesn't take much figuring to realize the diff mounts are going to have to absorb tremendous loads, and hopefully transfer them to the car chassis without doing any damage.

 

I figured a few months ago (since I couldn't find a beefier mount on the market) that I would have to make my own.

 

Here is the result, with the T3 mount next to it for comparison.  It is made of 1/4" plate, braced and gusseted in the areas I figured would need it.  The long plate that bolts to the top of the mount, bolts in turn to the top of the driveshaft tunnel, again to spread the loads to as many places as possible.  It will also serve as a reinforcement for a hydraulic handbrake I plan to mount there.

Your bracket looks like it will hold the load much better than that flimsy T3 bracket.  To drive the point home all you have to do is run some simple numbers.  Lets assume your engine will be putting out 400 lbs-ft of torque at the crank with a 2.66:1 first gear ratio, 3.7:1 differential, and the mount is 6" from the center of the output flange.  With that setup your engine will be applying (400 x 2.66 x 3.7) / .5  = 7,873.6 lbs at that interface!  And that's just constant load, not considering the dynamic effect when you dump the clutch from a stand still.  That case would be at least 2 times higher.  To make things worse, the t3 bracket is cantilevered so you're applying that load in bending on chassis mounts that were designed to take the straight pulling load from a stock,  ~150 lbs-ft engine.

Edited July 15, 2018 by rossman

[Ironhead]

Clearly most of the twisting torque from the engine would be absorbed by the rear diff mount, which I am sure is why it is about three feet long, to give it a degree of "leverage" to counter any tendency to twist in place.  But the rear mount would have almost no ability to stop the front of the diff from flipping up and down with acceleration/deceleration, so I designed the front mount (hopefully) to address that.

 

The T3 mount is so flimsy, I am surprised they haven't received sufficient negative feedback to change the design.

[rossman]

8 hours ago, Ironhead said:

The T3 mount is so flimsy, I am surprised they haven't received sufficient negative feedback to change the design.

Yah, me too. I've seen at one other person on HZ notice the issue.  Maybe others just don't realize it's moving around. 

 

I also found it ridiculous that T3 put the cut-out for their logo right in the load path, further reducing the stiffness of the mount. 

Edited July 15, 2018 by rossman

[Ironhead]

 

10 minutes ago, rossman said:

Yah, me too. I've seen at one other person on HZ notice the issue.  Maybe others just don't realize it's moving around. 

 

I also found it ridiculous that T3 put the cut-out for their logo right in the load path, further reducing the stiffness of the mount. 

 

I was pondering my "design" today, and even though it seems sufficiently rigid on its own, I am concerned about the ability of the four OEM thread locations to absorb the torque from the mount itself wanting to twist.  Particularly the rearmost pair, as the captive nuts are secured in very flimsy looking sheet metal brackets.

 

So, I think I am going to weld the mount onto the OEM crossmember/control arm bushing mount.  This will tie the whole thing in with four more bolt locations, and should add vastly more strength and rigidity with no additional weight.  I didn't really want to do this, because it will probably require removing the whole mount whenever the driveshaft is removed or attached.  But, not a big deal really, and how often does one need to remove the driveshaft anyway?

 

I want to get this right the first time, even if it involves some over-engineering, rather than having to dick with a flawed design down the road after the car is finished and painted.

[NewZed]

Build a similar plate to the one you already have but put it directly over the mounting points.  Run some pipe up the plate, or build a structure from more plate.  You could even use threaded pipe portions for pinion angle adjustment.  Or tie it in to the tunnel.  Removes the leverage problem and clears up a lot of space.  Looks like you have the fabrication skills.

 

 

 

[Ironhead]

14 hours ago, NewZed said:

Build a similar plate to the one you already have but put it directly over the mounting points.  Run some pipe up the plate, or build a structure from more plate.  You could even use threaded pipe portions for pinion angle adjustment.  Or tie it in to the tunnel.  Removes the leverage problem and clears up a lot of space.  Looks like you have the fabrication skills.

 

 

 

 

I pondered doing something similar to what you describe, because there definitely would be a significant advantage to having bracing directly over the diff mounting tabs.  What dissuaded me was that I didn't think it would install from the front when the diff was already bolted into the rear mustache bar mount.  In other words, it would have to be bolted to the diff then the entire assembly raised and installed....hard to explain....it just seemed like it would greatly complicate installation/removal of the relevant parts.

 

I have already partially welded the cross member to my mount, and I am convinced this setup will give immense rigidity.

Edited July 16, 2018 by Ironhead

[calZ]

If you made it a separate piece from your current mount, you could just leave it installed on the car when you raise or lower the diff.

[Ironhead]

3 hours ago, calZ said:

If you made it a separate piece from your current mount, you could just leave it installed on the car when you raise or lower the diff.

 

Yeah, I was looking over things today and I think I am going to do something like that.  The area NewZed is referring to is more or less dead space, and installing a vertical brace up there should provide good insurance against having to re-do all this crap down the road.  I would rather do a little extra work now that the car is stripped and not risk having to worry about it later....

 

Anyway, here is Diff Front Mount V2.0.  It should be pretty dang rigid now....as all the forces are now spread out and secured by eight M10 bolts and 4 M6 bolts. 

 

Still....better over-engineered than under engineered, so I think V3.0 will be coming soon......😐

 

 

 

 

 

 

Edited July 16, 2018 by Ironhead

[softopz]

First thing off epic build thats some crazy stitch welds never seen that many. I was once told by an old timer that too much could be overkill and be counter intuitive if god forbid accident since these are areas that need to be crumple.

 

With that said torque usually raises the diff up and most of your mount/bracing is targeting to the bottom. Hence I see why you want to do a 3.0 maybe just a simple brace from where you already have the mount like attached in the pic in yellow? you can go straight or do a little bend with a slight gusset.