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MG MGB Technical - cold start unit

I've leapt over from the V8 page as there are so few viewers over there!
I've been trying to obtain info and specs from Burlen regarding the HIF 6 cold start unit. Failed! I have two pairs of HIF6's which I am re-building from "Bits".. I have three cold start units engraved "10","12" the other "13". This seems to relate to the size of the "bleed" hole in the outer section of the units which are 1.0 mm, 1.2mm and 1.3 mm respectively. But Burlen hit the buffers on Factory V8's when it comes to such detail. They kept getting 10-2!!??
If there is anyone currently re-building a pair of HIF's, of any size, it would be interesting to know which unit is fitted to theirs, if not 6's, at least i might be able to sort this by a process of elimination.
Allan Reeling


Allan Reeling

Allan
There seems to be a bit of info here----with adjustments etc---

sucarb.co.uk/technical-chokes-thermos-auxiliary-enrichment
William Revit

Different animal Willy. Mine are just the usual HIF's with a rotary enrichment, cold start. Burlen SU just didn't have the spec for any of these units. Hence I don't know, and can only guess which drilling suites the 3.5 V8. Just hoped someone had a pair of 1 1/2" or indeed 13/4" on their bench in bits.
Allan Reeling

Hi Allan,
if you don’t have AED that could be that is your car either HIF 44E (electronic choke ) or maybe KIF 44. HIF 44E was often used on Rover SD so maybe some fitted to your engine?
I have few details of both (but not very in detail) so I can send you if you are interested.
toni
Toni Kavcic

Thanks Toni, but mine are definitely HIF 6 as originally fitted to factory V8's. I have since found out that SD1's and P6's were fitted with HIF 6's with a 1.2mm (number 12) cold start unit so I am left with a 1.0 and a 1.3 unit., my guess is a 1.0, but only a guess!!
Allan Reeling

Allan can you post picture of that - would love to see it.
Toni Kavcic

Toni,
These are the cold start units removed from the carbs, minus "O" rings and fitted.
It seems it will only upload one pic at a time, so see next post.


Allan Reeling

Cold start units.


Allan Reeling

Allan I am pretty shore that you have HIF 44 carb because of shape of manifold and inlet flange. That what is shown on your picture is metric carb (HIF 38 or 44). HIFs in imperial sizes 4 and 6 have same flange pattern as HS carbs.
I checked Burlen spares catalogue and it looks that is only one type of starter spindle for both HIF 38 and 44 carb (item CUD2791) but there are different sizes of starter body in which is sitting spindle. Do you have tag number – usually is stamped on metal strip.

I have one complete starter spindle, it is marked as 11, but it comes from HIF 44.



Toni Kavcic

AUD 613. According to Burlen, MG and the rest definitely HIF 6. era 1973, I have two pairs of them, both definitely from Factory V8's and the verniers confirm 1.75". Similar HIF 6's were fitted to the Morgan +8 and Rover P6 and SD1. 44's superseded them, as far as i can tell from the SU catalogue, in the mid 80's. The flanges were identical. In my SU bible HS flanges were entirely different. All HIF's shared common flanges right up to KIF's
The size of the drilling, in your case seemingly 1.1mm is specific to the vehicle application. Is the spring anchor fixed to the starter unit? And is the number 11 also engraved on the outer barrel, behind the anchor?
44mm is 1.73 inches, i.e., slightly smaller than the HIF 6 1.75 inches. It was maybe the drive to go metric, can't see it making much difference in performance terms.
Allan Reeling

I have a couple of HIF6 on the shelf, one is supposed to be for a BV8 the other for something else - a Princess possibly. Of course I have 2 originals on my V8.

Are those markings always and only on the valve clamping plate as in Toni's picture ? Seems odd when that could possibly fit to any spindle. There obviously were different spindles for different cars, and the matching valve bodies ( "outer barrel" ) were different as well. But I've never seen any listed details of drilling sizes.

If the numbers are that obvious I can try to look at all mine in a day or two, but if any markings are on the actual spindle then it would mean some dismantling, as would actual measurement.

Sorry if that's not a lot of help.

J N Gibson

The numbers are on the outer brass barrel, visible when the unit is fitted. The spindles look identical, the different drilling of the outer particular to the application. The units are common to HIF 4's and 6's. It would seem that the later 38's and 44's had the spring anchor and outer barrel as one unit.
My guess is 1.0 mm for GTV8. But would be good to have it confirmed though, thanks.
Al
Allan Reeling

You are right, I see you have HIF6 carb – I never come accros that (AUD 613LH and AUD 613 RH). My starter spindle is form turbo HIF 44 (FZX 300). As I told earlier two holes on spindle are same for any application but hole in spindle body is in my case bigger that 1 mm but smaller s 1,3 mm (marked 11)- I measured with drills and I don’t have them in 1 mm steps so that is max accuracy. I noticed marking only on retain clip nowhere else but that one is anyway pressed on so not easy way to mismatch.


Toni Kavcic

anohter one


Toni Kavcic

OK, I've had time to dig into my shelves ...

On the AUD 613L carburettor ( old stock, never been on a car ), the number stamped on the valve body is 10. SO seems to agree that 1mm is correct for the B V8.

The other carburettor ( old stock, never been on a car ) has no identification tag but I have a vague memory it was for an Austin Princess. It has the same body but diferent bore for the piston damper ), the number stamped on the valve body is 13.

The ones on the V8, I can move the cam return springs aside but see no stamped number, it may be in a different position around the body so not visible from above. I'm afraid I'm not going to take those carburettors off to look further, unless it becomes really necessary !!

I didn't disassemble the carburettors further as I have no means to measure the drilling. ( perhaps a selection of small drill bits ? or known wire sizes ? ).

You have probably done more research than I could to find out any size specification, so the following is likely to repeat what you know.

The BL Parts Catalogue and Workshop Manuals give nothing.
The SU Reference Catalogue ( my May 1993 Edition anyway ) doesn't even list part numbers for the starter valve, the SU website just says "ASK".


The original SU AUD 613 Schedule Sheets for ADO 75 ( ie MGB V8 ) just give the part numbers that the BL Parts Catalogue give, no detailed specification.

An additional sheet, Schedule AUD 613T "ALT'VS WITH TAMP'PROOF BODIES" says "Use Use LZX 1426 VALVE BODY & PLATE ASSEMBLY LH Carb, RH INTERCONNECTION Use LZX 1427 VALVE BODY & PLATE ASSEMBLY RH Carb, LH INTERCONNECTION" but I bet nobody knows any details about them either. They might be the combined units you mention ?

Actually I'm tempted to think that it probably doesn't matter too much, how much time does the car spend with those valves open anyway, just a few minutes so a little inaccuracy won't be a problem.
J N Gibson

Thanks for "digging". Yes I resisted removing my V8 carbs too, and similarly couldn't see the stamping. I'm now 99.9% sure the units are number 10, i.e., 1mm drilling. I take your point about the relative importance of the hole size. After all, I'm sure many V8 conversions are running quite happily on SD1 or P6B pairs with 1.2mm drillings. But I like to know...........it's a weakness!!!
Thanks again,
Allan
Allan Reeling

You are talking about manual choke on your carbs. You just curious about if 10 or 11 or? Maybe some slight change occurred over production of the car, with larger coming after complaints full choke not enough, or too much, and some change happened in response? Either way those HIF's get real iffy when one or more O-Rings become iffy.
R Owen

"with larger coming after complaints full choke not enough"

That's almost an issue with the HIF carbs on my 75 V8. It needs full choke to start and for several seconds after, and only gradually reduced from there as it warms while driving.

By contrast my 73 roadster (HS) gets full choke to start (although may not need it) but immediately has to be pushed back to half or it is obviously massively rich and can stall and flood.

Whilst one can reduce excessive enrichment, one can't really increase insufficient enrichment.
paulh4

It seems that the MGB 1800 HIF 4's used a 1.3mm drilling, and P6B's and SD1's 1.2mm. One assumes when developing the MGBV8 that they used modified the Rover twins. Who knows why they reduced the bleed hole size for the same capacity engine. Maybe something to do with how the Rover's were angled over.
Allan Reeling

Allan, This is a very interesting thread, I only wish I was reading it a month or two ago. I just finished rebuilding the factory MGBGTv8 carburettors I picked up in the UK last year. I used parts from SU Burlen. I know getting the chokes right is very important because I had choke problems (o rings)years ago when I rebuilt the setup that is currently on my V8.
When reconditioning the recently acquired set of carburettors I damaged the actual spindle on one of the choke assemblies and sought a second hand one from the local MG parts supplier. I did not know there were different drilling sizes! Interesting, did I fit the same size as before?
I am currently in the US otherwise I would rush out into my garage and dismantle the chokes again.
Another issue with the chokes is how many O rings to use between the brass spindle and the outer. There are grooves for two and some diagrams show two and some show one.
I asked SU Burlen and they said one O ring and the paper washer is used on an MGB V8.
Does anyone have knowledge of this?
cheers
Ian Buckley

Ian,
First, the variation in drillings is only on the outer part of the unit, the inner shaft seems universal on all HIF's.
Second, all the ones I have re-built have all "come apart" as one "O" ring and gone back as one, mainly on the grounds that there is only one in the rebuild kit. But there doesn't seem to be a logical reason why 2 couldn't be used. I have to say too that the supplied "O" rings do seem a bit "mean" in their dimensions.
Allan Reeling

Allan, thanks for confirmation about the 0 rings. I guess with one 0 ring it can go on either groove?
There is a problem putting in two 0 rings in that it makes the assembly too tight and the choke return springs have difficult rotating the spindle to the off position. I lubricated them with 0 ring lube but the return was very slow. The size of the 0 rings supplied by SU Burlen does not seem correct to me. They are too big and difficult to fit. This is the reason I damaged one spindle fitting it and had to source the secondhand replacement I mentioned earlier.I had a machinist slightly deepen the grooves to allow use of the 0 rings supplied.
Ian Buckley

It's now close to 4 years later and I have very recently fitted my previously acquired factory V8 inlet manifold and carburettors I reconditioned myself.It's not that I haven't been active with my MGs but my TC has been keeping me busy lately and now corona virus has grounded me a little and I have been doing jobs on my mgb roadster conversion. I thought I would reactivate this thread because I have been searching the archives because the car won't start. The ignition is fine because it was running perfectly before and will fire on Aerostart.
Because the carburettor setup has been on the shelf for some years I removed the float bowl covers again and made sure the needle and seats are free and leveled the jets with the carburettor bridges as recommended and lowered the jet (clockwise) 2 full turns of the adjusting screw.The car still will not start.
With my previous set of HIF carburettors it was always impossible to cold start the engine without full choke. This makes me suspect the chokes are the problem and perhaps I have an issue with the enrichment devices as is discussed in contributions to this thread from 2016. I am hoping someone has some advice on my issues. Best wishes
Ian Buckley

I have HSs on my roadster and HIFs on my factory V8 of course. The V8 always needs full choke to start and for the first few seconds, and only gradually eased in after that. The HSs get full choke but can be pushed back to about half immediately.

I can imagine that is deliberate on the HIFs to reduce the emissions by only allowing the minimum enrichment that should be necessary. However, in South Australia I shouldn't think it's particularly cold at the moment, unless the environment has chosen to throw ice at you after the fire and the floods.

I can't see anything stopping you getting full choke on the V8 HIFs, unlike HSs and HIFs on the 4-cylinder, as the cable trunnion acts directly on the choke cams (on the factory installation anyway) and not via a lever which can be maladjusted.

If the cams are moving fully then any lack of enrichment can only be down to the valves themselves, which are more complicated and easier to assemble incorrectly than the HS enrichment mechanism.

If, after cranking a while on full choke, the plugs are wet or at least smelling strongly of fuel, then fuel would appear to be getting through so it's something else. But if they are dry with no fuel smell, then no fuel. You could also try starter fluid, and if it starts and continues to run then it's lack of enrichment. But if it fires then dies (without continually spraying fluid) then fuel isn't getting through.
paulh4

Ian,
We are still here! The factory V8 thread seems to have died!
Interesting that you should bring up the cold start issue.
I went to crank mine a couple of weeks ago and it wouldn't fire.....it was cold but in the garage.
The first thing I checked was the cable itself and it turned out, after removing the air box, I had clamped the cable with more free play than I normally do.
I usually lock the choke knob no more than 3mm out and the tighten the clamp screws with the choke levers just about to move.
This time it was more like 5mm.
Re-adjusted and vroom vroom!!
It seems to be that sensitive!
I have a pair of 1.2 chokes which, when lock down boredom sets in again, I will install as an experiment.
As Paul pointed out, why it was deduced that an 1800 needed more enrichment I can't guess.
So check the free play!
Allan Reeling

My guess is that since the airflow in the V8 is higher at cranking speed than the 1800's (bigger cylinders and supplying 4 instead of 2) more fuel gets sucked though and therefore needs a smaller drilling to get the mixture right.

Going back to the O ring issue - the O ring does NOT go in the grooves on the spindle - it goes on the end of the unit ...



Chris at Octarine Services

Co-incidentally, I had the cold start on my single HIF6 apart this week, to replace the o-ring.

I noticed that it had '13' stamped on the body.

According to a PDF (attached) from the State of California Air Resources Board, that I found online, the tag on my carb relates to an Austin Marina automatic.

The PDF also has a little MGB information.



View PDF:
Dave O'Neill 2

I was thinking that the HIF gives less than the HS by design, not that the 1800 needed more than the V8. It would be interesting to hear what 4-cylinders with HIF need by way of choke.
paulh4

Paul, my standard 76 roadster always needs full choke to start from a cold engine. As soon as it fires up, I then have to immediately decrease the choke to half way. After around a minute, it needs to be decreased again to only a fast idle of around 1100 rpm. This sequence is the same in both warm and cold weather. Once started the car really doesn't like a lot of choke at all.

Andy
Andy Robinson

HIF4 have 13 choke.
Chris at Octarine Services

Paul,
My experience is the same as Andy's on my standard 1980 roadster.
Cheers, Charles
Charles9

Thanks Charles and Andy, much the same as my HSs then.
paulh4

I reckon Chris is onto it Ian--too many O rings
Probably blocking off something that needs to be open
If the 4 cylinder carbs are being sucked by 900cc each and the V8 carbs are getting sucked on by 1750cc each then the orifice in the V8 unit will need to be the smaller to stop overfueling I would think

willy
William Revit

No Willy - if he has put the O rings on the spindle and not the casing then the fuel will leak round the end of the casing - either causing too much fuel to flow or maybe breaking the suction that pulls the fuel - not sure which is the case.

The spindle is sealed by the external seal, not O rings.
Chris at Octarine Services

Got it--Sorry Chris I misunderstood that, you obviously know what's needed with them
I haven't had a lot to do with Hif's apart from a couple where the floats wanted to sit on the bottom
Sometimes I wonder how many of them are running around with partially sunken floats and drinking fuel until they get bad enough to flood up
William Revit

1800 cylinders are 449cc and V8 are 437cc, and only one at a time is being fuelled in each case. Yes the V8 carbs are pulsing fuel twice as often, but each pulse is pretty much the same.
paulh4

William Revit

Thanks Chris, Paul, Allan, Willy, Dave and others. I remember my difficulties 18 odd years ago trying to sort this same sort of issue with HIFs so I was quick to seek your wisdom. When I put the current set of HIFs back together (over 3 years ago) I now remember that I put 2 O rings in each side because I read it somewhere (SU publication) and as I recall my spindles had provision for 2. Again thinking back I subsequently removed one of the O rings on local carburettor guru advice mainly because it was too stiff and would not return properly.
A friend visited in the afternoon after I resurrected this thread and while observing our local distancing rules I asked him to sit in the car. With the air filters removed and the induction airbox in place I asked him to crank the engine while I put my hands over the intake. I had checked that the chokes were fully 'up' and after 3 or 4 revolutions the engine started. Because the engine had shown no signs of life previously I was amazed when it started.
Making sure we released the choke very slowly, otherwise the engine would have stalled we brought the engine up to normal operating temperature. An hour or so later the car started easily and I went for a 5 mile drive past the airport using airport transfers sevenoaks where there is a 50 mph road and the car performed flawlessly. A definite improvement over my previous home made factory V8 replica using a plenum chamber from Clive and a rover manifold milled down. I even have a steam pipe now and I will be interested to see what difference that makes.
Thanks again for your input and its good for the archives to have Chris's photo of the enrichment device with an O ring correctly fitted. I am very happy that I did not have to remove the enrichment devices again because as some of you know it's a very fiddly job.
Ian Buckley

Ian
Being an inquisitive little git, can I ask what car this is on, do you have a V8 in your old roadster or is this another car
willy
William Revit

A bit of a faff if you have to do that every time, you should get a steam engine :o)

It'll be interesting to hear what happens at the next cold start, as you don't seem to have changed anything/found a cause.
paulh4

Paul, earlier this morning I was thinking that I left something out of my previous post about actually getting the engine to start. In the lead up to getting the engine started I removed the carburettors and plenum a couple of times because I was concerned that I was not getting fuel through somehow. I could not see fuel down in the jets with the pistons removed and when I put a tooth pick down in there there didn't seem to be any fuel. I had checked the supply and the pump was delivering to the engine bay and was ticking away as normal. The usual parts, floats, needles and seats and metering needles were all new and I had checked for blockages and found none.

I am guessing that I had some sort of airlock which was not allowing the fuel supply to get through and by blocking the air intakes with my hands the engine got fuel and started. And yes, the next morning it started perfectly and I went for a 30 mile drive and the car performed well.

Am I kidding myself about the airlock theory?

Willy, this car is my 1964 MGB I have owned for 52 years and converted to V8 almost 20 years ago using motor ancillaries, gearbox, diff and brakes from a factory V8 car, except the short engine which is an early range Rover motor, was 8.25/1 and is now 10/1 compression. I was fortunate to get an engine which had only done 40,000 kms. When I found this original intake and carburettor setup from a factory V8 it really completed the project. I do have tubular block huggers now from Clive and a gear reduction starter motor. (much easier to work with!)
cheers
Ian Buckley

This is my intake system complete with the custom made air box. I do now have an original air box. While searching for a photo of this I did find a photo of the enrichment device. I am now 100% positive that I had removed the second 0 ring.


Ian Buckley

Cheers Ian
Your manifold and plenum look fantastic and the fabricated airbox as well
Your car was dark green if my memrory is going ok
Are you using the V8 wheels on it as well
Love to see a pic of the car

willy
William Revit

Wouldn't be an air-lock unless the jets were blocked, which of course would stop fuel getting to the cylinders anyway. Could have been both float valves stuck closed, if one carb had been working I'd have expected some indication of it trying to run.

Normally after being switched off a while you should get several clicks from an SU fuel pump, many if it has not been powered up for weeks or more. If the float chambers are not being recharged you will only get one or two. If you inverted the carbs when they were off you should have fuel pouring out if the float chambers had been full.

A test for fuel in the float chambers as well as checking the plugs after cranking for a while is to blow gently in the overflow port with the ignition on, and if they are full i.e. float valve closed then fuel should bubble up from the jet.
paulh4

Willy, here's a photo of me in my car.

Guess what happened this morning! After refitting the inlet manifold carefully I had the carburettors on the bench and I thought I might have another look inside the float chambers and it looked OK until I saw....!

In the photo I have removed the jet. Can you see a problem?





Ian Buckley

The choke cams are offset, but I wouldn't have thought that was enough to cause failure to cold start.

Did fuel come out of both carbs when you inverted them to remove the covers?
paulh4

Paul, fuel did come out of both float bowls this time as I removed the covers and plenty of it. I actually put 2 long bolts vertically in a wide vice and 'mount' the plenum and carburettors horizontally when making some adjustments off the car and removed the bowl covers from underneath allowing me to see how much fuel (and dirt) comes out. Once they had drained I turned the assembly over and was just checking the needles and seats when I saw the nut was very loose that holds the jet bearing in place. In fact the other one was finger tight too. You can see the 2 hex nuts in the photo and one is clearly slack (right side).ie the carb with the jet removed.

I must have left them loose when I assembled the carburettors 4years ago.I wonder what effect that has been having?
Ian Buckley

Fantastic photo, thanks, the car looks just as I imagined it would, Hard to beat a good chrome bumper B, the driver looks like he's still going ok as well--
With the jet tube nuts being loose, I guess, depending on how much clearance there would be around there, it 'could' suck air round the outside and effect the mixture at cranking but you'd think that the vac in the carby would suck the tube up into position while it's running, so maybe it could effect starting,but not when it's going,, Although the choke system is seperate it would be sucking fuel from the main jet tube as well when cranking

They're the cleanest pair of floats I think I've ever seen

Cheers
willy
William Revit

I wait with bated breath to hear the results of the next cold start.
paulh4

The floats look too low, but that might be a camera angle issue.
Here's my V8 and me!!


Allan Reeling

You look happy in there as well Allan-another nice car
I've got my money on the float levels would be adjusted spot on by Ian---possibly several times
I too thought they looked too low in that pic (too high right way up)but as you say I think it's just the angle of the dangle--The glare off their ultra white surface is playing with my eyes-------
William Revit

and mine makes three - BRG metallic V8 roadster - waiting for the Dover - Dunkerque ferry back in 2016.


Chris at Octarine Services

All lovely looking cars, I like racing green too, but Allan you lose points for not having overriders, but get them back if it helps with cooling at all (and you lose more points for an extra l in your name that I'm not used to).

Chris's front spoiler is a bit showy but I'm sure it's also practical too.

:)
Nigel Atkins

No overriders on Chris' car either!! I have an on-off relationship with them Nigel!!
Allan Reeling

Chris's photo is too small for my eyes, I didn't notice.

I must admit I'm not sure about overriders or not too (unless you mean you keep knocking them off) and I alternate with if I prefer the ones with rubber facing too. If either were fitted and were in reasonable condition I'd leave them as they are but if not I'd not worry about replacing them.

I'll have to borrow your car to make a firm decision. :)

(with a full tank obviously, and perhaps a can in the boot, just in case)
Nigel Atkins

Lol - here's a bigger one for you Nigel.

What you cannot see is that the side strips are also not there and all the seams have been filled - no "T" strips any more.

Certainly not original in so many respects and completely unique in its exhaust sound to.

The spoiler is certainly needed on German autobahns at 130 mph...


Chris at Octarine Services

Ahh V8 conversions---nothing better
Lost count of how many I've done over the years
First one in the mid 70s created a bit of a thing with the purists in the club here, the old you've stuffed up a good car got thrown at me a bit but then they were the first that wanted to go for a drive which amused me a tiddle
Green seems popular, I was going to have a little stir but the car I'm working on at the moment will be green so I best zip it
Chris
You mentioned a unique exhaust sound, what have you got going there,, On one car I did I made up a set of up and over 180 degree headers, fantastic sound, real headerey, sounds a bit like a flat plane crank engine not like a V8 at all,

willy
William Revit

Cheers Chris.

Certainly a big spoiler.

I've only been on an autobahn once, we were in my wife's Daihatsu Copen, 657cc, turbo, triple (no doubt whatever my car was at the time it was unavailable or unreliable as usual). We were with club friends in an "air cooled" Porsche (we'll associate with anyone) and our friends in their Toyota Supra and I told them to go on ahead as I'd stick to 80mph as we'd already previously proven the Copen's claimed top speed of 106mph was possible. Well never mind 80 60 would have been good, it was nose to tail in drizzle type rain and even came to a couple of stops, such much for the unlimited autobahns.
Nigel Atkins

Willy,

Block hugger manifolds into a 2" diameter stainless pipe with a single straight through big box at the back and a 2" tailpipe.

It doesn't have the V8 "burble", sounds more like a deep throated 1800 at tickover and a lion clearing it's throat under hard acceleration but very quiet at cruising speed.

The engine is bored out to 3600cc and has high compression "Vitesse" pistons giving 9.5:1 cr and a flywheel bhp just over 200.
Chris at Octarine Services

Cheers Chris, I can almost hear it from here. magic

bit of thread drift I guess, but it's Allan's fault ,he started it-------lol
William Revit

I haven't looked on here for a couple of days and it's good to see the thread is still going. Nice photos too. Paul, I too am waiting with baited breath for the next cold start. I have fitted the inlet manifold now I believe (hope) I have found the source of the leak which was the temperature sending unit reducer into the manifold. It was difficult to confirm with the manifold still in place because there is just no way to get a mirror in there with the sending unit and the 3 hoses at the front.
I haven't started the engine because I decided to replace the 2 smaller hoses at the front of the engine with silicone ones from Clive Wheatley. I do have his silicone hoses all around but I slightly damaged one at the front removing it so when the parts arrive I will be right back into it.
Willy, Allan, Paul, Chris, Nigel, because I assembled the carburettors a few years ago with new parts I have forgotten what I did to confirm the float levels. Recent viewing to me shows they are both set at the same level.
While I am waiting for the parts from Clive (he is staying home at the moment and Michelle is doing parts and sending (has sent) my order promptly) I think I should take your advice and check the levels. What is the best way to do this?
Ian Buckley


Here you go Ian-

Turn the carb. upside down (yep, off they come again)
Remove the float bowl
Let the float just sit on the needle valve under it's own weight (don't compress the spring in the needle valve, just let it sit as is)and measure like this with a straightedge at the lowest part of the curve in the float----

https://www.mgexp.com/phile/1/320053/su-hif4-float.jpg

To adjust ,just bend the little tag that sits on the needle -(carefully) to get the required height
I believe the original spec was 1/32"-1/16"max so 1mm would be perfect

Stay safe
willy
William Revit

Willy, thanks very much. I have not bolted the plenum and carbs back in place so now really is the time to re check the float level. I followed what you said and they are OK. It is nice for me to know that for the future. cheers
Ian Buckley

It started perfectly this afternoon after I finished fitting the carburettors/plenum. The fuel pump ticked for quite a bit longer this time and I do wonder if there was some air lock but I cannot substantiate that. Apart from that maybe it was the loose jet bearing nuts.
The parts from Clive Wheatley (2 small front silicone hoses and breather hoses arrived via DHL in 7 days, amazing.
Ian Buckley

The car is now starting and running well and finally I have fixed the coolant leaks. I was cleaning up today when I found the left over parts from when I rebuilt the carburettors 4 years ago including the cold start spindle that I replaced because it was slightly bent. This photo shows the provision for 2 x O rings that I referred to earlier.


Ian Buckley

Great result then young man-

Freight from the UK has been magic lately ,wifey bought a hammer on fleebay and because of the virus situation I thought it'd be ages coming but same as you 6 days, can't complain about that.
Looking at your bent shaft I can see how it'd be easy to think it needed 2 O rings, must remember that--

willy
William Revit

Ian, Are the breather hoses also silicone?
I find they "sweat" oil.
By the way Clive used to get his hoses from China............you might want to disinfect them!!
Allan Reeling

Those grooves are NOT for O rings - the shaft seal is on the end of the shaft.

Not sure why the grooves are there but my guess is to stop the shaft galling in the housing / reduce friction.
Chris at Octarine Services

Cheers Chris, I had noted you said that earlier on-

willy
William Revit

Chris, doesn't this show O ring(s) on the valve spindle. It does show plural in the text?

The boxed drawing in the first photo shows the complete starter unit assembly.

I wish I had asked these questions of you chaps 4 years ago! cheers





Ian Buckley

This the reference book I am using 5th edition 1994.


Ian Buckley

The inset (22) shows the O ring that sits on the outer body and the seal that fits on the end of the inner part after it is inserted in the body and under the metal dust cap.

Chris at Octarine Services

The inset (22) shows the O ring that sits on the outer body and the seal that fits on the end of the inner part after it is inserted in the body and under the metal dust cap.

I have added the page from the parts manual - it shows that later carbs had an additional "outer" O ring but not HIF4 or HIF6 carbs.




Chris at Octarine Services

Looking at the reference catalogue, I believe that the carbs with a second outer O ring had it fitted on the body next to the paper gasket, so still not on the shaft itself.
Chris at Octarine Services

Chris

This is from :-
http://sucarb.co.uk/technical-hif-type-carburetter-dismantling


Dave O'Neill 2

Going by the sizes as drawn it looks like either the O-ring ends up pushed right to the end of the spindle to butt up against the end of the valve body rather than fitting inside the body, or it goes over the outside of the valve body to seal to the carb body, with the small seal fitting over the tip under the dust cap. But never having taken one out I don't know, and none of the 'official' sources I have read describe fitting it, or show it partly assembled. However the attached from MGE may help.


paulh4

This thread is going to be an excellent resource next time I remove my valve spindles. Thanks everyone.

Allan, the breather hoses from Clive are certainly not silicone and they do sweat oil. I don't think the quality is very good. I was supplied with 2 left hand upper breather hoses and when I queried this I was advised they have run out of right hand hoses and left one can be tweaked (twisted) sufficiently to fit the right side.
The hoses are a slightly loose fit on the flame traps, carburettor and rocker cover connections. Unfortunately I think I will have to fit clamps as they can come off too easily when they become coated with oil.

It would be good if this thread could be re-titled 'HIF Cold Start or Choke' which would make this information more readily found in future. Allan, it started as your thread you could ask the moderators. What do you think?

I drove about 60 miles yesterday in our perfect sunshine in the hilly countryside and the car ran beautifully.
Ian Buckley

I've enjoyed reading this on a rainy morning - many thanks to all the contributors.
Gordo

I put clamps on my breather hoses as it was getting oily round there. Non-silicone, and since then things have stayed clean so it must have been coming from the fitting and not sweating in my case.

I think crankcase pressurisation is quite common on hard acceleration, I've fitted a long hose to the crankcase breather filter as before with just the short U-shaped one I was getting oil fumes in the cabin on acceleration. Roger Parker pointed out on one set of removed gaskets there were signs of blowby on the inner edges, and recommended the extra bolts on the other side of the head were barely more than nipped up. This leaves four equally spaced round each cylinder at normal torque, and some later engines may have had them omitted altogether.
paulh4

I am glad others are getting some oil around the breather pipes. My engine is not high mileage and on standard bore so I am (was) a little concerned about my blow by.

It now comes back to me about not tensioning the extra bolts.
Ian Buckley

'Non suffix B' engines specify 11 to 14 - outer row as 44 ft lb, the remainder at 66 ft lb.

'Suffix B' engines specify stage 1 as 15 ft lb, stage 2 a further 90 degrees, then stage 3 a further 90 degrees.

The factory supplement for the MGB GT V8 makes no distinction, at 68 lb ft.
paulh4

This thread is growing, maybe we ought to start another, concerning head bolts/studs and torque.
Based on the fact that the later LR V8's, interim onwards, don't have the outer row of bolts, I torque them to 10ft/lbs only. It's said that full torque "tips" the head.

Back to enrichment. I had my air box off a few weeks ago and when I put everything back together it was pig to get started.
Doing the logic, i.e., what's the last thing you disturbed? I checked the choke cable. Normally before clamping it off, I pull and lock the knob 2 - 3mm from the dash then pull the cable up till it's just beginning to pull the linkage, then do up the screws. My knob "free play" turned out to be 5 or 6mm. RE-set and I was good to go!
It's very sensitive!
Allan Reeling

This thread was discussed between 07/08/2016 and 29/04/2020

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