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kevs 1961 mk1 wrote: ↑Sat Jun 12, 2021 12:39 pm id get ac dodd to tune it he will find the problem for sure

I spoke to him before I sent the carb back to KAD. Thoroughly decent chap, and although it will be costly for me to get him up here, it may well be the way I end up going.

Catmint wrote: ↑Sat Jun 12, 2021 2:42 pm a quick google - some info on HIF Choke arrangement here

https://www.mgexp.com/forum/mgb-and-gt- ... m.2373310/

https://sucarb.co.uk/technical-carburet ... ttings-hif

Kieth Calvers comments on the HIF https://www.calverst.com/technical-info ... -hif-type/

(I was wrong about the bimetal strip for the choke, it is a variable hole for the choke and the bimetal strip is for fuel metering when running)

to grasp at some straws

If it works OK on a dyno setup, is there something else going on when the engine is in the car ???? - connections, fuel, venting, air leak ? Is there a good heat sheild between the carb and exhuast? - might be just one of them random things that you don't take into account when you put it all together

What is the inlet and exhuast manifold you are using ? I seem to recall that the single HIF manfolds are a different thickness to the exhuast and I had to make up stepped washers so it all bolted together nicely - grab hold of the carb and see if it moves independant of the engine

What is the carb's history, what has been replaced in it - the needles are renouned for wearing as they are spring biased. What air filter are you using compared to the dyno set up?

is the fuel pressure still too high?

Photos of the installantion may help. ATF oil is a good compromise for the dash pot.

the final option would be to get it on a rolling road dyno with someone who knows su's. The final setup can be a real pain when you think everything is right, been there

Thanks for the links, I’ll go through them.

I’m 99% certain it is not an air leak, otherwise it would be running lean rather than rich. I have however had a very sore head from spraying copious amounts of Ether around with no change (once I’ve got the b’stard idling). Mini spares inlet and Maniflow LCB. Carb history is unknown but it is a KAD refurb that was supplied with the engine, so cannot be a worn needle.

Fuel pressure was set by a localish Mini specialist so I’d be surprised if that is out, but certainly worth a second look.

I agree re rolling road with an SU specialist. I think Mini Sport would be the closest, but I’ve no idea how they compare to others.

bwaminispeed wrote: ↑Sat Jun 12, 2021 7:09 pm Tight throttle and air leaks, won't cause the over rich situation he has......

It starts cold with no choke, then gets very rich, so, not a gasket/air leak/spindle leak problem.....

You’ve got it in one

Fanfaniracing wrote: ↑Sun Jun 13, 2021 7:24 am Even a Engine set up on a engine dyno needs to be set up on a rolling dyno once fitted in the car.

It's always different once the engine runs on the own fuel pump, radiator, alternator ect...

This money should always be calculated when building-/buying a new engine...

Believe me, the few £ that a rolling road session will cost will be insignificant to the money spent on the engine & car so far. I’m more interested in finding out what is causing the issue.

Did you ever check to see if it has the right size needle for the jet......needles and jets come in .090 and, .100......

If you have a .090 needle in a .100 jet (quite possible to do), it will be super rich on low throttle settings......

Easy enough to check, by pulling the dashpot.....remove the needle from the piston, and, drop it into the main jet if it is the correct size for the jet, it will have very little side to side movement when all the way in the jet........If it is the smaller .090 needle in the .100 jet, it will move around quite a bit.......

Again, just grasping at straws here.....

When KAD ran the engine on their Dyno, were they actually using this carb ? Might be worth asking,

You need it on a good rolling road operated by someone that understands SU,s

251 ENG wrote: ↑Wed Jun 16, 2021 6:43 am You need it on a good rolling road operated by someone that understands SU,s

Problem is they're getting more and more difficult to find

imack wrote: ↑Wed Jun 16, 2021 10:21 am

251 ENG wrote: ↑Wed Jun 16, 2021 6:43 am You need it on a good rolling road operated by someone that understands SU,s

Problem is they're getting more and more difficult to find

Have you tried Neil Slark now near Bristol (unfortunately) .. I found him excellent, he won’t give up!

On the HIF44 the fuel inlet port and the float chamber overflow are beside one another. If the fuel line has mistakenly been connected to the overflow, it would be massively rich as the fuel will just come straight up the jet. I suspect it may prove almost impossible to start the car in this condition, but would be worth checking. Perhaps a photo of the installation would help here?

bwaminispeed wrote: ↑Tue Jun 15, 2021 11:17 pm Did you ever check to see if it has the right size needle for the jet......needles and jets come in .090 and, .100......

If you have a .090 needle in a .100 jet (quite possible to do), it will be super rich on low throttle settings......

Easy enough to check, by pulling the dashpot.....remove the needle from the piston, and, drop it into the main jet if it is the correct size for the jet, it will have very little side to side movement when all the way in the jet........If it is the smaller .090 needle in the .100 jet, it will move around quite a bit.......

Again, just grasping at straws here.....

Am I right in thinking the correct needle for the .100 jet will be the B prefixed series as in Bxx and not Axx. Easy to check as you say.
The .090 needle will run in a .100 jet but obviously super rich and especially sensitive to the discrepancy at idle.
You would think this would be too obvious a mistake for KAD to make however.

Symptoms would appear to point to a problem with the O ring on the fuel enrichment device which can perish or chafe, allowing too much fuel via this secondary jet into the inlet port. No tell tale from the overflow.

But if it has been re-furbed these should be OK.

So it needs opening up and checking. Or substitute a known good carb to eliminate choke (fuel enrichment) issue.

OK this thread is few months old , Craig is a good friend of mine and was sick to the teeth of this £10,000 engine that KAD built ,it has never run properly from day one , i told him to post on this forum hoping he could get a result , Craig mentioned in is first post that it was a bastard to start and ticking over problems and had contacted KAD , they told him to send the carb back which he did , when the carb arrived again it was no diferent , he took the car to well known mini specialist in Bradford , £400 later it was still no better , OK he contacted AC Dodd and made arrangements for him to have a look at it , AC Dodd came along and started working on the engine , checked everything over and said the carb is way out , on stripping the carb he found a BIG FILE mark on the needle at the thickest point , YES this is KAD's work , AC Dodd fitted a new needle same has and then did some adjustments including putting the needle in a little chuck ( Lathe ) and removed a bit from the needle , refitted it checked again and everything was then spot , Craig say's it's a completely different engine and is superb , all credit to AC Dodd he knows what he is doing and it did not cost Craig a fortune , Take a look at the photo of the needle , it looks like it's been filed with a 9inch grinder , one happy chappie Craig is now

Get a hold of Peter Baldwin at John Degan's in Cambridge 01223 324050, Im sure he will get to the bottom of it.

That's terrible from a respected place like KAD, what did they do? let the apprentice/work experience kid loose on it? Great to hear AC sorted it.

How do you know if that’s KAD’s handiwork or the ‘Bradford’ specialist’s?

GraemeC the engine was sick from day one , as i said before Craig sent the carb back to KAD on there instruction and when it came back still the same , then went to a Bradford specialist and was no better when he drove back home !!! , so i would definatly say it came from KAD from day one .

Whilst I can’t see what KAD hoped to achieve by having the carb back, it would be a strange thing for them to do. I suppose they may have though it just needed to be richer.

The Bradford specialist though, if they had the car, I’d assume would at least have put a sniffer up the tailpipe and attempted to adjust the fuelling from that.

GraemeC wrote: ↑Wed Sep 15, 2021 9:14 pm How do you know if that’s KAD’s handiwork or the ‘Bradford’ specialist’s?

My car / engine. I now have it in writing that it was done by KAD to give the “correct” progressive Air Fuel Ratio.

I’ll button it at that because I am still completely steaming….

GraemeC wrote: ↑Thu Sep 16, 2021 6:49 pm Whilst I can’t see what KAD hoped to achieve by having the carb back, it would be a strange thing for them to do. I suppose they may have though it just needed to be richer.

The Bradford specialist though, if they had the car, I’d assume would at least have put a sniffer up the tailpipe and attempted to adjust the fuelling from that.

KAD asked for it back because I was insistent that something was clearly not right with it (was I right, or was I right?).

The car had been to the Bradford specialist before I sent it back to them, not unreasonably they fitted a “filter king” regulator and “set it up” on a CO meter but it did not improve the overall running. That was just before the first lockdown, and I have had no intention of using public transport since. I still think that they should have found it though IMHO.

Looks to me like that needle has been pulled out with some pliers and damaged then put back in……

Whoever put needle back in should know better….it is shocking

Really, I think both companies are at fault, “The Bradford specialist” should of picked it up, even if KAD did it…..

EDIT Just an after thought, are you sure the needle was mangled by KAD, and not by the Bradford specialist ?