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240Z - Snailed style

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I did one smaller patch today and then dressed all the welds on that side and metal finished them. It's pretty smooth but it would need more work if I was trying to make a show car. I might straighten it out a little bit after I media blast the whole car later. I threw on a coat of primer so it doesn't rust while I finish the rest of it. It's easy to wipe it off with thinner if I need to weld something, like the seam between the rail and the inner fender.


I'm thinking of using a progressive rate BMW steering rack...I'm doing lots of research on the suspension now.



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I have been working on taking the manifolds and wiring off the engine and cleaning up parts of it as I go. I also got some aluminum 300zx or skyline calipers. The rears bolt on to the q45 spindles with a little trimming of the dust shield and the fronts may be fit to the Wilwood spindles or I may look at something a little smaller to help get the brake bias to the rear a tiny bit since I am guessing I'll have a 55%+ rear weight. I'm starting to think I won't make my weight goal...looking at lighter seats and maybe not making the tunnel quite as strong as planned.


Today I started fitting the engine and removed the tunnel. I'm raising the engine and moving it back a little, mostly so I can duct the radiator and intercooler exhaust through the top of the hood. This put the #1 spark plug slightly behind the front axle line. It looks like with the engine and pinion both at 0 degrees, I can get about 2 degrees total on the driveshaft split equally front and rear. I need to play with it a little more ans then start making front engine mount brackets. I'm thinking about using poly bushings for the engine mounts.








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The engine and transmission mounts are up next. The factory engine mount brackets are a pretty excellent design but I don't want to mount the engine to the suspension subframe. I'm going to use 1.75" DOM tube and bushings attached to tabs on the frame rails. I believe mounting the bushings close to the frame rails should give me the least idle vibration with the most resistance to engine movement from Tq and shock from shifting for a given durometer.


I made the the plates that bolt to the block out of 1/4" mild steel with a 1.75 ID hole in the center. I tried to make them as light as I think I can get away with. There will be gussets to try and get the bending forces off the mounting plate somewhat.


I decided to start with rubber bushings because I think they will still be nice and stiff while absorbing a little more vibration than most poly bushings. I spent some time looking for OEM bushings that will press into standard DOM tubing sizes and I found the leaf spring bushings for a '91 Isuzu Rodeo fit a 1.75" x .120"  wall nicely. They are about $4 a pair for the higher grade Raybestos rubber ones and poly bushings are available if I change my mind later. The outer sleeves are just a piece of scrap DOM that I cut to length and cleaned up on the lathe. I figured out a cheap and easy way to make the inner sleeve too. 3/8" sch 40 pipe is the perfect OD to fit the bushing and the ID is good for a 12mm bolt. I bought a 12" galvanized pipe (needed 9") from the hardware store for $5.


I have engine position almost perfect but I want to refine it a little more before finishing the mounts so I made a couple holders for a $5 laser pointer. I bought 2 of the pointers but one of them was so out of alignment I couldn't use it. One holder just threads into the output shaft of the transmission and the pinion one is a magnet for the base. The pointers are carefully pressed in and then bent into alignment until the red dot does not move when the shaft is rotated. I saw this on some forum (here maybe?) and always wanted to try it.








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I got the engine mount brackets welded up. The big tube is the same as the bushing sleeve, 1.75" x .120" DOM. The gussets are 14g. The pair ended up saving 2lbs over the stock aluminum bracket and rubber mount. No huge lightness "gain", but at least I'm not adding more than it had. The bushings feel pretty soft, but I don't think I can rock the engine even a 32nd of an inch at the valve cover. Can't wait to see how they work when it's together.


The tabs on the rails are made from 1/8" hot rolled steel. I think I will add some doubling plates around them and up onto the top out of 14g just to make sure they don't fatigue the 2.5" square tube. I think the steering shaft will just clear the tab on the drivers side, but I don't know the exact rack location (or even what rack) yet so that might get interesting.


I'm getting started on the framework for the tunnel too. Somehow the stock shift lever is just about perfect even though the engine is back a bit. I can reach 1-3-5 without pulling my shoulder off the seat, and 2-4-R don't jam my arm into the bolster. The knob will be close to the steering wheel too, which just makes it easier to drive.


The idea on the tunnel is to make it pretty strong in torsion without making it much heavier than the stock one. I already added a bunch of weight in the four lengths of 1x3 that run in the rockers and down the floor. In hindsight, I might have done that a bit differently so I could make the tunnel out of bigger chromoly tubing. As it is I'm just going to use 3/4" and 1/2" square tube and simplify it a bit. I will roughly follow a truss design and there will be four main tubes or chords and the middle will be filled with diagonal webs. It will be skinned with 22g steel. Beyond strength, design concerns include; room for plumbing/wiring up top, transmission cross member, heater box mounting, heat shielding for exhaust and room for seats. I'm open to suggestions on this project if you think I'm overlooking something or could improve my plans.





Edited by Snailed

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Here is the start of the tunnel. I mocked up the top panel out of 1/2" square tube with a .065" wall (6" wide by ~55" with no diagonals) and just that part had quite a bit more torsional rigidity than the entire stock tunnel I took out. The comparison was done using the step-on-it-and-twist-it testing protocol. It difference between the two was noticeable. I'll be welding up the whole thing on the bench so I hope to rig up a lbs/degree test to compare the two parts while divorced from the car.


You can also see roughly how the exhaust will be run. The bottom of the exhaust in the tunnel will be flush with the bottom of the car, which is the height of the rockers and the 1x3 that runs under the seats. It will be very easy to have it tucked up all the way back with the slightly raised drivetrain.



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The problem with comparing rigidity of your new framed trans tunnel and the stock trans tunnel when both are removed from the chassis, is that the original was really part of a much larger structure, including teh floor pans, firewall and rear support to tie everything together and re-enforce other areas. 


Looks good.

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Hey! I'm not dead.


The tunnel frame is welded in and I have fitted an Acura wipermotor in preparation for reworking the rain tray and upper firewall. I have also gone a different direction on the front spindles...That's about as far as it went. I've been focused on building for other people but I might dig into the Z a bit more.

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