another SU conversion

[djc]

At very long last... I got the carb and manilfold about 3 months ago but just got round to doing the swap.

My own humble advice to anyone yet to do this would be: don't underestimate the volume of faffy work involved. I'll admit messing with spanners in the cold doesn't get close to fun for me, so bear that in mind if I sound a tads jaded.
It looks like this, just needs choke connecting at carb end (lost the screw thing, ordered another), and coolant top-up, route the fuel overflow pipe, fix choke firmly into dash...

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Here's a bit of what I found out along the way. I've never done this before so had to work a few things out. I did get to see Chan's conversion which helped a lot.
If I was doing this again, I would very definitely do loads of the prep work before even starting - making up a longer throttle cable (about 10" longer); fabricating (or getting) a suitable air inlet to fit the SU; any fabricating for the air inlet side:

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[I know this isn't muckproof, it'll do for me].
There's a list of bits you need to hand I think, and it's worth having everything ready: 6mm (and maybe 8mm) hose, clips various sizes, air hose, throttle cable bits, inline fuel filter, breather filter, air filter, coolant, gasket material, and more I've probably forgotten.
Basically I'd say the more you can do before taking the old carb off the better, and a lot of the ancilliary stuff can be done in advance I think.

On the SUs, I have two. That's because I bought an OK one off an SJ but found it was missing choke lever and was generally a bit worn. So rather than a rebuild kit, I got a second good one. You either pay top money for a genuine rebuilt, or assume it will need some work. Burlen are good but it takes a bloody age for the bits to arrive I found. Like ~Chan I took the vac advance off the existing 6mm pipe coming out of the SU rather than drill for a new line. Chan was happy his was advancing nicely and as it's a pressure not flow connection it should be OK. Soon see I hope. I understood use an inline fuel filter to step from the 6mm incoming to 8mm out to carb. On mine I didn't need it, my SU fuel in is 6mm - but I have a fuel filter there anyway.
I've put a BDL needle in but also have a BCZ (recommended alternative according to Ray Rhino). On the charts the BCZ may be a fraction leaner at higher revs, but probably won't notice the difference. If I have a problem with emmissions it may be handy, not sure really!!
I got a manifold from Richard Rockwatt. I know Chan made a really nice one but I think it cost him over a hundred, plus all the work. Richard's are about 160 plus the donor manifold and shipping - 200 really once you're done.
Yet to fire it up of course - it had better work...

I hope this may be useful to someone out there considering. And to the experts, if you spot anything dodgy in the pics above, do let me know !

[Anton]

Just wondering how you got on?

[RickUK]

That does look like a nice little carb conversion,not complicated like most setup's,lucky that mine has a injection setup which has never gone wrong but if it ever did i guess it would be a bloody nightmare to try and sort out.

Keep us updated on how the conversion works out.

[twiss]

Its not that hard... I think the only problem I had with fitting was that my inlet was from a 1300 and the fuel pump is slightly bigger on the 1600, so I had so dremel the cut out so it was a bit larger...

[djc]

Got it running sweet today. Had a few minor set-backs on the way. Call me dumb but I overfilled the oil in damper, I'd been reading a manual for a different SU I think. All a mess, oil into mani etc. Sorted that and got it firing nice... on 3 !! No 1 not firing - Fat spark etc, puzzled, then spotted a missing plug in new mani (between tstat and no1) - no idea what that's for but it was blanked on the old mani so blanked it again - all very nice and happy running. [btw, I'm calling the cyl nearest cambelt No1...?]
So far on road test runs v well indeed, smooth tickover and nice pick-up and I think the vac advance seems to be working, I'll check with strobe later. Can't see any tech reason not to take vac feed off that fat pipe (next to fuel overflow). I'll check it anyway.
My own conclusion - a really worthwhile conversion. I'm sure it runs nicer and will see how power/fuel is over time. It's a simple rig so maintenance and tuning easy. I didn't say it was hard Twiss. My advice to anyone about to do the switch to an SU is do all possible prep first (as I said above). I get the impression Twiss knows the engine and carbs inside out, but I did not and was frustrated pratting about with throttle cables, choke linkage, all the air-in side etc.
I also reckon get an SU well in advance and check it over well - getting inside is easy and it helps a lot I reckon to actually see how it all works (like the mixture screw etc). Many SUs around are missing choke lever, cable pinch bolts etc. Minor but a sod unless sorted in advance.
Anyway, well happy indeed - and I made a right big meal of it. So if you are a bit more experienced it should be quite easy, and fairly quick if you have all the bits ready.
Looks nicer under there now too, I think i'll tidy the rocker cover maybe.

Thanks for the mountain of info here (the main SU thread) and Chan for a few tips along the way.

p.s. red spring, BDL. I checked the spring a lazy way. It needs to compress to about 38/40mm with 140g on it. Got a packet of ingredient from the kitchen that weighs about 140 g, put it on spring - confirmed. Worth noting the other springs have quite different values so even though this seems rough it's close enough to be sure what you have, and it's quick

[Anton]

Glad it's running well! SU carbs really are the nuts.

[twiss]

Haha I wouldn't say I'm an expert but I've fitted a fair few now!
When I first fitted the SU onto my 88 sammy 1600 8v I didn't really know what I was doing haha
Just what I had read on the interwebs!

[djc]

Been doing a bit of 'on-the-run' tuning, carry a screwdriver around with me. I think I have the mixture about right but prob need to get it tested. I'm not sure the best approach as generally here the guide is close the mixture screw right in (max rich) and then back about 2.5 turns. On the SUCarbs site (Burlen) they say start from the other direction - get jet flush with bridge (max lean) at top then 2 turns down/clockwise (>rich). On my SU the range from each end seems to be about 7 turns so these 2 don't get me to the same place. I've settled with the right in and 2.5 out, then tweaked to 2.75 out... seems nice and tickover good/regular. Choke doing it's thing lovely, unlike the old Aisin. I do like having choke control a lot!!
Best just get it tested and see what's coming out the back.

[Anton]

I have a colortune kit if you want to try that?


Click Here for Youtube Video

[djc]

thanks Anton, may come back to you on that - was going to hand it over for an MOT to my local place and ask hime to measure it all for me, needs a mot soon anyway and there must surely be a list so soon may be smart