seam welding, what is the basic theory behind it?, are the benefits really obvious?, is it worth the cash?, and roughly how much does it cost? thanks

As far as I know seam welding the chassis just tightens the whole car up. Less flexing and movement. This would give the car a more solid feel.

I would also like to know the cost involved as I know welding thin metal is a pain without a good quality welder.

I don't think Andrew's CA18DET powered coupe was seam welded. Seam-welding is popular with the rally guys, and has to be done properly. It can actually harden some structural areas and create faultlines.

If Andrew's is not seam welded then I don't think most owners need it, unless rallying to the extreme. Andrew has circuit-raced, hillclimbed and dragged his car, and I don't recall him having alignment or door-fit problems.

Remember race cars aren't supposed to last forever, they eventually crack up from the pounding. So if you don't mind chasing cracks like a brickhome owner in California..then seam welding might be the go.

Chris.

Seam welding is a a job which can take days. To do the thing properly all the underseal and sound deadening must be removed. I am lucky and have a rotating spit to mount cars onto and can spin them around to do things more easily. I would'nt recommend doing it unless you are really committed to going really hard in your Datto. I would reweld around your leaf spring mounts and down the strut towers and run a brace from the end of the sill to the underside of the strut tower.You can strengthen around the front tension rod mounts as well.A strut brace which bolts on( I've seen drongoes weld them in!!)helps to stiffen the engine bay box. Fit a well engineered rollcage that connects all the suspension pick up points and tightens up the shell. If your really keen you can convert your rear leafs to a slipper type arrangement, that is the rear spring eye is cut off and the spring leaf is retained between some bronze or alloy rollers. This helps stop the springs winding up and steering the rear of the car. Most of the sucessful coupes have had their rear shocks turreted (mounted straight up & down) as this is the most efficient way for a shock to work and you can fit longer travel ones as well. You can then tie the top shock mounts into the flash new cage you will be building.

thanks for the tips, i wasnt planning to do seam welding myself but a joint near me (1600 workshop) does it and has a rotating thingamy i just wanted peoples opion on it. id love to turret the rear but it just aint legal in the world of rally

seam welding not a good idea for many old car the body has been streesed and weakend from those arsewholes who thrash the old dattos and when you seam weld it the body tends to crack next to the welds

what you mean like the arseholes that rally them

I am not on the idea of Seam welding, but I like Strut braces and 6 point roll cages to the suspension mounting points as well is exellent
idea. Then you can have racing seat belts too...
Oh damn an age old topic hehehe

The 1600 workshop near you does an excellent job of seam welding....
The main benefits are if you are fitting high horsepower engines... As engines tend to twist and distort engine bays (transmitted through the engine mounts) the "factory" spot welds can break. Seam welding primarily strengthens these "factory" welds. If you dont like seam welding (with a mig) then you can run more spot welds (prob costs heaps more though). Overall it does stiffen up the car, which is why you only weld for about an inch and then leave a 2-3 inch gap.. to still allow for flex, and to stop cracks.

seam welding is commonplace for all rally cars and circuit race cars. It is done to increase the rigidity of the body to provide a stronger, more stable platform for the suspension in circuit cars, and to withstand the buffetting dished out by rallying. Cornering forces on the track (and jumps and bumps in rallies) will deliver higher torsional forces through the body than any motor you can squish into your Datto.

My coupe (not seam welded or caged) for instance has stress marks around the strut towers, A pillars and C pillars. Floorpan also separated from the chassis on the drivers side. This is defeinitelty due to cornering forces rather than engine torque!