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Silentbloc upgrade

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TWightman
Posts: 1
Joined: Tue Mar 01, 2016 12:57 pm

Silentbloc upgrade

Post by TWightman »

Does anyone have experience of the phosphor bronze replacements for the silentbloc bushes in the Dart steering tierod? Do they significantly reduce turning effort? I'm tempted by a rack and pinion conversion but my steering isn't really too bad and if this does offer an improvement it would seem a sensible idea...although pricey in itself. I've been told that self-centering suffers as there's obviously no 'wind up'. Any thoughts on this? Thanks, Tim

Ian Slade
Wise Man
Wise Man
Posts: 791
Joined: Sat Feb 13, 2016 9:54 am
Location: Sevilla Spain

Re: Silentbloc upgrade

Post by Ian Slade »

Self centring has nothing to do with the silent block bushes, that is to do with steering geometry, might be wrong but Ackerman angle rings a bell. One of the SP's I had was extremely light on the steering, though I never found out why, it always looked OK but due to its history I suspect that there was some change in the geometry, probably the spacers on the inner end of the lower wish bones made them unequal lengths, there being no other adjustments. Perhaps Daimler Steve over in Kiwiland may have a suggestion as he plays with this sort of thing and has the equipment to measure differences in suspension settings.
Owner since the 70's, Genghis is slightly to my left.

TonyZim
Posts: 24
Joined: Sat Feb 13, 2016 6:31 pm
Location: Zimbabwe

Re: Silentbloc upgrade

Post by TonyZim »

Castor angle affects self centering.

Had the experience on my SWB Land Cruiser after my son bought it off me and raised it with different spring mounts.

It is curable with a small wedge fitted between the axle and the spring to restore the castor angle.

The fundi who explained it all to me reminded me of the front wheels of a supermarket trolley. They are not designed to stick out to savage other shoppers' ankles : it is because that without castor they would flap about in an uncontrolled manner.
Tony

1958 104 Lady's Model

daimlersteve
Helpful Person
Helpful Person
Posts: 496
Joined: Wed Mar 09, 2016 11:20 am

Re: Silentbloc upgrade

Post by daimlersteve »

The 2# of caster offers little self centering in the sp . If the silent block bushes are bonded to the pins and and tightened up when in the straight ahead position there will be some degree of self centering as the bushes try to resume the unloaded position of straight ahead.
A rack conversion actually diminishes the Ackerman effect ( toe angle difference on turns ) unless tr 4a-6 steering arms are used which because of the extra length from the rack c/l ( steering rack arms angle forward) this angle creates some toe change. The best solution using bolt on parts is to use the late tr4 3# trunnion and matching top arms and b/j in conjunction with the SP vert. link. This gives 5 plus # of caster and restores self centering when used in conjunction with a rack conversion.- best of both worlds -- light steering with good turn in and self centering .

steve.

Ps. may just have my new heads back this coming week.


Interim flow bench testing shows 141cfm of a possible 146 cfm from that sized port ( 28.5 mm dia. ) so we are currently at 97.5 % of the maximum @ 350 fps. Good for 280 hp at 6500. Will order the JE custom pistons for the 2.8 as soon as we have the heads back. A silicon mould of the port is most impressive in its progressive shape change up to the valve. The Inlet seat cutters have seven angles to them.

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