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Front frame / Front crossmember blueprints - feedback needed (not for a T)

the project can be found here:

frame material will be 2.5 x 2.5 by ??? wall (forget what it is i have outside, think its 1/8")

car will be getting a full cage with engine bay / trunk bars

car will be converted from strut to dual a arm, which includes new spindles and fabbed upper and lower control arms

the side view picture has a blow up of the gusset, the pink lines are double the diameter of the hole size to show spacing which i believe is correct

any questions / suggestions / insights / problems that you see ?


Why the 'spaceframe-like' front cross member? To save weight? If you are considering road racing and autocross don't you want a little sprung weight on the front to help the car plant in the corners?
the engine going in this thing weighs more then a small block chevy, so the car is already moving away from being 50/50 weight distibution, plus its going to have a chevy overdrive trans in it, which also adds weight over the stock tranny

and since im making new lower control arms, i just decided to put the forward most crossmember in a position that would also be suitable for the motor mounts and a bracket to hold the turbo, instead of trying to reuse the factory strut rod setup

not sure what tube ill use for the engine cradle yet, might buy something, might see what i can get at work
It's going to be a good looking front end. Too bad it will be hidden by body work. Front steer or rear steer?
All though this is not my strong suit, let me through a couple of ideas in here.

I take it you want to build a front sub-frame. The problem with that is the weak points aren't in the sub-frame but with the body attachment. My thought would be to build a complete frame, cross brace the body and cut the floor completely out. Build outriggers to the rockers at the firewall and behind the doors. And then weld the body to the frame at those points and at the rear of the frame. With the Chevy in there, you're going to run into the same problem we did with a sub-framed Vega. A month on the road and the passenger door would open automatically during a left turn.

By designing your suspension first, you are going to have to make compromises in your body. Set this up like a T bucket project. Set your body at it's ride height, mock up your rims and tires and then design your frame. At least this way you can reference off the mock up instead of guessing.

You talked about new spindles. A more checkbook friendly way would be to use existing spindles and brakes. The beauty of building a suspension like this is that you can adjust it to suit your needs. In your mock up, set the spindles where they need to be and they will tell you what you need to do for a frame and control arms. You might not need that much kick in the frame. The lower you can keep your frame rails, the easier it is to set the engine in and out. You also keep the center of gravity lower which will help with steering.

What you're looking at would be a awesome project and an expensive one. Make no mistake, I'm not trying to talk you out of it, just the opposite. By keeping it simple, you stand a much better chance of a successful build. Read the signature under my name. As they say...just my 2 cents.

a number of good points for sure, lets see if i can cover a bunch of them

ill actualy, in the end, be building a full new frame for this vehical, as the original has a number of rust holes thru the bottom of the frame rails due to standing water / brake fluid leaking from the master.

the reason the frame is z'ed as much as it is is because thats where the stocker runs, and eventually i would like to offer frame kits to the 240sx community. the leaky master cylinder is a result of booster failure and is common in these cars, finding one with a good drivers front frame even in the nicer climate ares of the country can be a problem

the easiest way to sell kits, obviously, is if they can be installed with minimal work on the buyers part. lower would probably be better for my application, but as a kit it creates alot of headaches for people that would be installing one into a car they intend to build in the typical fashion for 240's, that means the frame has to meet the factory firewall, factory strut towers, and factory radiator support

i will be cutting away the original frame channels except for a few spots here and there to use as "alignment tabs" for this frame, and then it will be stitch welded to the floor all the way down, probably using a 1" on 4" stitch weld spacing, which should be more then enough

i have to run outriggers to the rocker panels anyways, as the car will be getting a full cage setup including engine bay bars, and gussets to the unibody all the way around the door openings

for spindles i was going to get some Chro-mo tubing (drops from someone that does cages in it) and build my own. ill just need to get some chromo plate to go with it for the wheel bearing flange, and have some tie rod / control arm mounts machined. the new spindles will mostly be copies of the factory mounts, except ill add some upper control arm mounts to mine instead of strut mounts. again theres plenty of 240 guys that would be interested in light weight spindles to make this a good plan on my car

and most of my materials come free from work, after the 4th of 5th time i asked for a pile of scrap material the boss looked at me for a moment and asked "what are you doing, building a RACE CAR?" .... actually yea ... i am

i think hes given up on asking what exactly im going to build out of this or that, after i asked for some steel sheet out of the rack, and i wound up explaining to him why i have to build a custom firewall for my car to move the engine back 4 inches so that my taurus engine fits in my nissan and my dry sump oiling system clears the crossmember while also having room for my diesel turbo in front of the motor BEHIND the air extractor for the radiator thats going to vent out the middle of the hood :)
Sound like a plan. Good luck with it.


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