Twin Su VS hif44 (Running issues)

[harrymini]

I am currently running a pair of 1.5 Su carbs on my 'fast road' 1300 mini and not having much success, went to an engine builder first to have the cam changed to something more mild and a basic set up just to get it running. Then went to a local rolling road with great reviews to get the final tune.

The car is pretty tricky to drive, stalls really easily, soots plugs up like nothing else and pretty difficult to get started.

I bought a set of 'reconditioned' twin su carbs from a triumph and am thinking if i want to make it more drive-able on the road if it is worth just buying a hif44 carb kit from the likes of MED:

https://www.med-engineering.co.uk/hiff44

In the new year i am going to take out an use some tank sealer on it to try and eliminate some issues.

Not being an engine / carb savy person it is pretty difficult on what to do. I am more than happy playing with metal / bodywork and paint but struggling with this and considering going down the bike engined route.

This is the car:

viewtopic.php?f=6&t=29194

[Polarsilver]

Harry, none of us of know everything .. clear that your bodywork skills are second to none .. so while they are a bit of travel time south from you i would book your car into SMMC at Southam & let Colin sort out your Engine Set up issues of that i am sure .

[Dearg1275]

My trip to Colin at Southam is from the north of Scotland. I have to say the journey has always been worthwhile. Colin seems never ever to be phased by carburettor issues and takes the time to get one problem sorted before moving on to the next. That to me is what you want.

D

[harrymini]

Perfect, i dont want to get rid of twin carbs as i think the look alone is great. I will get booked in with them in the new year.

[InnoCooperExport]

You mention the carbs came of a Triumph, do 1.5s (and Triumphs for that fact) need the same angled float chamber adapters as a Mini? That could maybe cause irregular fueling which could make it run oddly? But I would expect a Mini-savvy rolling road tech to notice the floats chambers being at the wrong angle as well... Just a brainfart as they say.

[LarryLebel]

The HIF 44 will probably be cheaper and start and run better. Use a BDK needle.

[Dr S]

Wonder if twin 1.25’s would be more appropriate?
Carbs need airflow to work well.
Big carbs at low flow rates will likely need to run rich to keep ticking along as they won’t be atomising the fuel well.

[111Robin]

Definitely do not go the "bike engine" route. There are 1000's of Minis running on twin 1-1/2's with no issues. I had them on a 998 (over carburetted but I wanted to use them) with a 266 cam and it ran sweet as a nut with basic carb' setup tuning, no rolling road etc. There must be something specific with your carb's or inlet causing the issues, maybe air leaks somewhere who knows. The point about the float chamber angle is a good one. You might be wasting time and money travelling to a rolling road if there's an inherent issue with the carb's so a better option would be to replace them with a pair of 1-1/4's first and see if it runs properly. You might even be able to borrow a pair if someone has a set lying around, just to prove the point.

[Peter Laidler]

I agree with Robin and the good Doc plus a bit more. Like most things mechanical, it's best to trouble shoot starting from scratch or '....the known good' as we called it. Move forwards from that and errors become apparent as they occur and so are easily identified. Much as Robin suggests with reverting to 1 1/4' and start from a known good........

Wish I lived closer..... a couple of colortunes, my trusty stethescope, depression gauge and carb mixture and linkage spanners (tied around your neck with string !!!) and we'd be away Harry

[Allen Brzeczek]

I run a pair of 1-1/2" which perform extremely well on my 1380 - not sure of their origins. However, the relevant literature on my cam choice described the tick over as "lumpy", together with the engine having been lightened I have opted to increase the tick over speed to approx 1500 rpm.