The 2 inch HS8's. We had fun together, but sometimes it's just time to move on...
As some of you may know, I have recently converted my 2000 TC to run on the twin SU HIF6 carburettor setup of the later 2200 TC models. I'm very pleased with the new setup, and am currently enjoying the increased torque and economy as anticipated.
For anybody considering the conversion, I thought it might be worthwhile to put all of the salient points of the conversion into one post, as I had to glean a lot of information from various places before starting, and even then had to experiment somewhat to get the setup how I wanted it.
I don't wish to detract from Demetris' excellent post last year - which in all honesty was the inspiration for my own conversion - I just want to highlight the things I had to find out along the way.
My car is a RHD UK spec Series II 2000 TC, and originally had the stock twin SU HS8 carburettors as fitted 1970-73 (engraved flat-topped float chambers, and crankcase emission pipes).
-SU HIF6 carbs from 2200 TC. Complete assembly including all mounting brackets, tie plates and balance bars. No need for manifold or exhaust heat-shield.
-Throttle linkage rod-to-cable 'see-saw' adapter.
-Length of rubber fuel hose.
-2200 TC throttle cable.
-SC or universal choke cable, and grub screw cable grip fitting from HS8 choke lever.
-Air filter solution.
The original manifold can be retained, and need not be detached from the car during the conversion. A longer non-return brake servo valve with separate banjo fitting to operate the HIF6's air filter box internal valves can be obtained if desired.
The usual rules apply to servicing the carbs, so I won't go into it. However, as the float chambers are inverted and inaccessible when the carbs are in position, it is essential to check the condition (or replace) the O-ring seal on the float chamber lid, and in the brass choke 'tap' to prevent leaks.
To set the float level, remove the cover, invert the carb and place a ruler across the top, passing through the centre. The middle of the float's curved side (half way along its length), should sit 1mm below (+/- 0.5mm) the ruler's edge. Bend the brass tab against the valve to adjust. Check the bi-metallic jet adjusting bracket correctly engages the jet and lowers it when the screw is turned.
The needles should be biased (tip of needle) towards the throttle discs (as opposed to the air filter). The stock 2200 needles (BBX) perform reasonably well, but I'm sure careful experimentation could yield better results.
Along with the manifold, the exhaust heat shield, and flexible-mounting adapter plate for the rear carburettor only can all be retained from the HS8 setup. You will need a second adapter plate for the front caburettor, as the cast-in throttle shaft bracket on the HS8 setup fouls the HIF6 carb body.
The flexibly-mounted tie-bar and spring, the cable mounting point, and the carburettor link plate must all be changed for the 2200TC setup.
FITTING THE CARBS
I found the easiest way to fit the carbs was:
-Remove the adapter plates from the manifold by extracting the two 1/2 AF bolts (top and bottom) and levering them free. Check the condition of the rubber O-rings and smear them with some silicon grease and ease them back into the grooves in the manifold.
-Fit the flexibly-mounted tie-bar and spring.
-Bolt each carb to its adapter plate (making sure the brackets for the exhaust heat shield are on the right sides). Place the throttle and choke balance bars loosely in place between the two carbs and offer them both up to the manifold as one unit.
-Push them squarely home and then refit the 1/2 bolts. If they don't go cleanly in, the bolts can be used to pull them in. A good waggle should get them in - be persistent, the rubber O-rings have to be squeezed round the adapter plates' shoulders.
-Fit the link-plate across the front of the carbs.
-Tension the spring with the adjusting nut until the gap between the manifold and adapter plates are equal on all sides.
-Bolt the heat shield on underneath with the 7/16 AF bolts.
The standard 2000 TC fuel pipe (from the pump to the carbs) is too short to reach the HIF6 setup. It could be extended (ideally with an in-line filter), but needs a 90 degree bend at the end which causes the hard plastic to kink. So either mate some rubber onto it, or for the easy life just get a pipe off a 2200 SC or TC (they both have the bend in the end, and are long enough to reach).
You will also need a 7" length of rubber fuel pipe (int diam 6mm) to supply fuel to the rear carb from the front, and some jubilees to fit.
Can be retained without compromise as far as the double-ended ball-joint rod at the steering idler bracket.
The rod-to-cable 'see-saw' throttle adapter from the 2200 TC setup is bolted onto the steering idler bracket in place of the throttle shaft retaining bracket of the 2000 TC setup with 9/16 AF bolts. Elliptical slotted holes allow a limited amount of adjustment - mounting the adapter at the top of this travel will give the greatest range of adjustment elsewhere.
If the ball-joint is missing on the see-saw adapter, one can be obtained separately as part no 14 on page 22N, 24N & 26N of the Rover 2000 workshop manual. It just bolts in place.
The throttle cable is a special part with adjustment threads at either end and bespoke fittings. It is not possible to make one up from a universal cable. Wadhams sell remanufactured items for under £30 after VAT and delivery.
SETTING PEDAL HEIGHT
The advantage of the throttle cable is that it allows all of the 'slack' to be taken out of the linkage for a much more responsive pedal action. However, this sets the pedal very high and at an uncomfortable angle. The solution is to the screw-in the throttle pedal stop bolt in the footwell until the pedal is at a comfortable position. Then adjust the cable securing nuts at either end of the cable until it has been extended sufficiently to allow the throttles to close. If this is not possible (ie, the cable is too short), move the cable securing nuts to the inner ends of their threads, tighten them, and then unscrew the pedal stop bolt until the throttles are just closing (idler screws touching the carb bodies), and then unscrew a further 1/4 turn. Over the first 100 miles or so, the cable will stretch significantly, and this slack can be taken back up at the pedal if desired.
Unlike the HS8 setup, HIF6s have a choke balance bar, so only one cable is needed to operate both carbs (a great improvement!). A universal choke cable fits easily, but if you want to keep the original choke knob/indicator light arrangement you need to get an SC choke cable. One of the grub screw fittings that holds the cable to the choke mech on the HS8 setup is needed to secure the new cable to the balance bar. A 9/16 AF open jaw spanner releases the choke knob from behind the speaker grille. A mirror helps!
Fire up, set, balance, and tune!
Despite my belligerent intentions, it is definitely NOT possible to fit the original 2000 TC air filter box to the later setup. The original box requires the round cast aluminium adapter plates to fit, and as the air intake holes on these plates are bigger than those on the front of the HIF6 carburettors, unnecessary air turbulence would be generated. That, and the plates would need to be extensively modified to fit.
The only options are to fit the correct 2200 TC air box (which has an automatic warm-air valve, requiring the banjo fitting on the brake-servo non-return valve), or chrome pancake filters. I've made up some pancake type ones for the time being (as I can't get hold of the proper filter box), but can confirm that the induction roar is not intrusive, and only audible at full-throttle at low road speeds.
Original HS8 carbs before conversion.
Old and New. HIF6 on the left is a considerably more compact carb.
Manifold and heatshield need not be removed. Front carburettor adaptor plate must be changed for one without the throttle bar. New (shorter) tie-bar and spring was fitted at this point.
Rod-to-cable 'see-saw' adapter bolted to the steering idler bracket. Cable length adjustment thread visible at top.
Complete HIF6 setup in place. Temporary air filters are homemade from aluminium sheet, steel wire, glue and stock filters. Beady-eyed ones will notice that the crankcase ventilation inlets on the carbs have been connected together with a balance pipe. I chose to remove the crankcase ventilation pipes and route them away beneath the car.
Hopefully that covers just about everything.