Chev C20 RHD

[Thomo5150]

Spent the weekend grinding the frame, its now at the Blazer wheelbase. I've split the frame from all of the crossmembers to weld the front and rear rails together. Plan for this week, finish welding and cleaning the rails then re square the frame fit it to the chassis table then fit the Cab. Good news there is no clearance issues with the gearbox and frame crossmembers.......

[Thomo5150]

More progress....

I turned the frame on its side an bolted the front and rear sections of frame together. By cutting the frame at the centre of the rear cab crossmember it is very easy to reassemble.

Frame joined, you can see the 3 crossmember hole in the right side of the frame



Bolting in the crossmember



First hole drilled on the rear of the frame



Because 25 inches was cut from the frame it does tapper in on the rear section, by jacking and using a straight edge the rear was squared again there is a 3mm tapper in the rear frame section added....

Passengers side



Drivers side



The frame wont be welded till its back on the chassis jig and squared and set at ride height with is 6 inches to the lowest part of the frame under the cab....

[Thomo5150]

This is where I am, need to go back to work for a week. I'm still working out the ride height, problem is my Cab is stored else where so I can't place it on and check things. The drivetrain is in, it needs to be lifted at least 2 inches but you should get the idea of how this will work. The firewall will need to be recessed I have the motor set back where a normal LS engine would sit in one of these trucks....

Ground clearance for the sump is only 4 inches atm...



Frames lowest point is set at 6 inches, this may change....( Please feel free to comment on the height, I have never owned one of these trucks its all a learning curve for me



Started adding threaded rod between the frame rails to help square and hold the frame before final welding...

[Thomo5150]

Mockup of chassis height ( Note engine and torque tube to be raised 2 inches) Motor will just clear the firwall, no mods to the back of the cab only floor.



Level is the back of the cab



Torque tube to be raise 2 inches ends up level with the top of the crossmember



Cab reference photo room for the shifter rod




ride height with tire mockup, not centred just a ruff idea...






Probably best to explain suspension and crossmembers. I've kept the factory cradle on the rear for a few reasons. First its very simple to remove the trans for service or to replace a clutch (A few miss this point with custom frames and tubes every where they sometimes forget how am I gunna pull this out) Remember with the Corvette ZO6 C6 it has 325 tires and a 12 inch wide rim so fitting these under the wider C20 rear quarters is not a drama.

Front suspension is different, I've gone a narrower track than the C5 Vette, reason being I want a dish rim with a wide tire under the front hopefully a 285/25/22. Because the frame of the C20 trappers in at the top mounts, my crossmember will be designed as a 1 piece bolt on with the top and bottom A arms fitted to it. The engine is set back behind the front axle centerline so I don't have to buy $1000 custom drop steering knuckles, my steering rack stays at the C5's original position. Heres some mock up pic's of C5 suspension.







Using a 22.25" pivot point the C5 mounts are in the way so custom mounts will be fabricated



Front axle center line will be changed to even the look of the 22" rims under the front fenders




Truck weight will be around 1600kg..........

[coolwelder62]

Very interesting project.

[Thomo5150]

Working out measurements for the front crossmember using Corvette C5 clip to help...





Using fixed lower arms I now have to work out how far to bring the top contol arms in to allow for camber adjustment.







Corvettes 26 inch pivot point. New crossmember brings this into 22.25 inches.



Can any one recommend a sway bar set up?? The frame is 28 inches wide at the front rails...

cheers
Tim

[Thomo5150]

Spent today doing final tweaks before I start on the crossmembers.... Ride height is done, everything starts to line up perfect.......

Motor and drivetrain at height and centred.




Exhaust clearance both sides....







This is the start of the center or gearbox crossmember... 2 inches will be sectioned from the center to give the torque tube clearance, then sectioned at the bottom for the cats to clear. If my planning is rite the cats will sit just above the bottom of the frame....



with the exhaust bolted up the cats will tuck into the center crossmember giving it a clean look under the chassis.....

[Thomo5150]

This is a warts and all build, happy to share mistakes and boy did I make one today.................

Started marking and cutting out the center crossmember
( Note Old Skool build basic tools )


Got the shape of the crossmember done then drilled holes and punched them out to be dimple died. In this pic the holes been punched no drama's. I then thought to myself I shouldn't dimple the hole till I have added the top and bottom plates and gussets to strengthen the crossmember......

Got a phone call, went back to the shed, for some reason I picked up the dimple die and punched the crossmember with it. Instant fail the pressure distorted the metal and just wrecked 2 hours of work....



At least with the exhaust bolted up the cats are tucked up near level with the bottom of the frame.....

[Thomo5150]

More crossmember design...........



Trail fit of crossmember.



Checking the balancer clearance.



Crossmember cut out and the 2 halfs clamped together.



Trail fit.



Lower control arm fitted ( not in postion cause of the engine mounts stopping the arms from moving further back)



Hitting the engine mount, trail fit so wasn't going to unbolt the mounts



With the lower control arm in the rite position there will be enough clearance with the crossmember.



Quick mock up to showing how the top arms will look when the side plates are added to the crossmember.









Results from the days work!!! Start again. The crossmember will change from 4 inch to 5 inches in length, it has to be narrowered down from 900mm to 850mm. Also the weight, I can afford to step up from a 3mm to 5/6mm thickness, the weight will still be half of the factory crossmember. Instead of L angle steel the next crossmember will be shaped out of 150mm x 150 mm (6" x 6") box steel. This will be easier to shape....

So did I waste time doing all of this? NO!!! This is a one off design, things will need to be reworked and changed. As I said this is a real world build, I'm over seeing project with A pic B pic and everything fits and the builder pretends its all straight forward. I'm happy to show problems / rework, to help others looking or thinking I can build something like that.....

After all I'm just a simple Truck driver with a gimp hand, if I can do this anyone can or should try......

[Rick D]

Looking good!!