Hi i am looking at ways to increase castor on my 120y i thought of castor camber tops but with such a large diameter spring theres not much room to gain much caster.

Going through the tech wiki i came across this from a datsun competition suspension manual were the machiene down 15mm of the castor rods to the same diameter as the threads.

So when you tighten it will pull the bottom of the strut giving positive castor.

Does this sound safe? As i have heard people rethreading rods and it later fails due to the stresses if you run to much castor?

Cant seem to upload the picture but its like half way down the page on how its done

http://datsun1200.com/modules/mediawiki/index.php?title=Castor

I would recommend buying adjustable caster rods from a reputable Datsun parts shop. I used re-threaded LJ Torana caster rods in my 1600, and whilst they never broke, re-threading by 'cutting' a thread rather than 'rolling' a thread is an engineering crime against nature. Cutting threads creates stress risers at the thread root, whereas 'rolling' a thread 'peens' the material it is forming. Virtually all proprietary bolts/threaded items have 'rolled' threads as they are strong, easy and quick to produce.

Extra caster via the radius rod will also distort you bottom LCA bush too, so be aware of accelerated wear and extra tension. Wheel base will also change slightly too as the wheel moves forward.

Note that some of the spherical rod end caster rod kits will alter the pivot point slightly, though this probably isn't really too significant in the scheme of things.

For bushed rods I personally like the re-shaped Falcon arms as these are beefy and only the bolt on part is re-forged to suit.

Lowering the car can also put a lot of strain and wear on the caster rod bushes so bump steer spacers between the strut and steering arm help out a lot getting things back in the original plane.

Datsun Competition didn't use cut threads, instead they reduced the rod diameter 15mm so the bushing slipped on further

You can gain more castor without modifying the rods: replace the soft long bushings with shorter, stiffer bushings. This will gain you about 20mm and makes a noticeable different with better road tracking. The stock LCA bushes are soft enough to flex and work at a sharper angle with no obvious issues. See bushing modification. It's not "technically" the best way to do it, but it's better than stock

Do you think the method datsun competion used would be dangerous? As i have access to a lathe to turn it down.

If theres chances with breakage i will just go with cutting the bushes.

I'd avoid cutting threads at all costs.

Another consideration could be remounting the caster rod boxes (IIRC these are bolt on in 120Y) by drilling another set of mounting holes if they allow.

I had a look at the Datsun Competition method and I'm not a fan. The square shoulder produced by machining them down is another engineering no no as there is virtually no radius to avoid stress raisers. It would probably be stronger if you undercut it with a radius believe it or not. I would recommend looking at modifying the box location or modifying Falcon rods. Les Collins might have the Falcon type rods on the shelf(?).

Havnt heard of the ford falcon castor rods being used.

Whats required in terms of modifications?

Are they just from a xf falcon?

Firstly what are you trying to achieve here? Is this for a race car or has someone just told you that increasing the caster will make the car handle better?
Secondly and most importantly DO NOT UNDER ANY CIRCUMSTANCES machine or cut threads into those radius ( caster ) rods - they will break.
The whole idea of trying to increase caster without modifying the bottom arm bush ( preferably with a spherical bearing or rod end ) is flawed as all you are doing is loading up ( binding ) that bush.
Have a look at the Pit Road site and their radius rods to see how it should be done.
Cheers
Dave

+1 what Dave said; beyond the possibility of the radius rod breaking the immediate concern is binding the control arm bushing. Fitting a spherical bearing to control arm isn't a huge task but for a road car it will be really harsh.

The first camber tops we had on my car worked as follows; there was top hat on the strut was actually mounted above the strut tower. There was a set of three spacers, around 25mm I think (it's been 25yrs since we used them), the spacers had studs on each end, one end bolted to the strut tower and the other end bolted to an aluminum ring. The strut hat bolted to the same aluminum ring (6 holes total). The ring was oval shaped so that the top hat could be moved in and out for camber adjustments. It wouldn't be hard to add caster to this.

Realistically I don't think the benefits of more caster are worth the bother on a street car. Ifmthismisma car you plan to use at some track days or the like than you need the parts to do it properly.