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MG Midget and Sprite Technical - Hif44 problems

I've just finished putting my refurbished hif44 on and got it idling ok. However I went for a short spin and for the first 150 yards it went like a rocket but then something bad happened. Hard as I try it won't go over 40 mph. The engine feels like its stumbling, could this be a miss fire? It ran Ok with the old twin carbs on (although I had been fiddling with these and had them running very rich prior to the change). Where should I start looking?

From a review of the archive

Do I have a big air leak, my manifold is a filed down metro job and although I took great care in getting this level I may not have been good enough.

I am using the needle that came in the carb its a normal metro one. Would this give such dramatic effects. BDL needle in box waiting to be fitted.

At idle I get a spark at each plug but could there be an ignition problem. Where do I start checking. Coil, HT leads,distributor. The plugs were quite fouled when I checked could this give these symtoms.

Thanks in advance
tm wainwright

My guess would be weak mixture. I would change to the BDL or richen up with the existing one. Starting point for the mixture setting is two clockwise turns of the screw after it has been levelled with the bridge. Clockwise richens it, anticlockwise weakens it. Is your engine a standard 1275? What happens if you pull the choke out (assuming you have it connected).

Steve
Steve Church

Its almost standard except for the K&N filter RC40 single rear box and tubular steel exhaust manifold.

I'll try the choke idea and get back to you.

The loss of power is very dramatic can this realy be caused by the wrong profile needle.
tm wainwright

Do you have a fuel pressure regulator fitted? When I had my twin SUs my regulator was set to low and I had similar syptoms to yours. I turned the pressure up and things got better. Lack of fuel. With a K&N you will get more air flow so will need more fuel to compensate to achieve the same fuel air ratio. Of course it may be something completely different!!
Steve Church

Few more pointers from me, as I ended up with a blown engine following my rather disastrous initial HIF44 setup.

Firstly, check for an air leak, as soon as you can, just to remove those fears. Spray WD40 around the inlet manifold gasket with the car running. Watch to see if it is blown out the way by a 'draft'. I cannot emphasise enough how much you should check this as this problem (a badly filed manifold, no less) blew my engine big time.

I don't know what engine you've got, but if you're standard spec, with a metro needle you'll likely be getting problems, as I believe the metro profile is inappropriate for lower spec midget setups(?) (correct me if I'm wrong). You CAN get some problems from needle issues, although from what you describe, I'd say something else may be up as the needle would have to be very inappropriate to cause those issues. Fitting the BDL is a good idea as they are known to be a reasonable profile and would eliminate one factor.

My HIF44 behaves really nicely now, although it hasn't been RR'ed fully yet and I do find even with a fairly close to spec needle, the motor has flat spots and an imbalance of air/fuel higher up. The HIF44, like all carbs, is one of those things which benefits so much from the 'last 5%' of work on it.

I hope this is of some help.
Rich Amos (1330cc Blaze Red '72)

Rich,
I've just installed my HIF44. What mixture setting have you arrived at (how many turns)? I can't remember your setup but I have a 1330 with MG Metro head at 10:1. Also K&N. Would also be interested in you rfuel comsumption figure.

tm,
did this happen just the once and ran badly the next time or does have similar symptoms every time you start it from cold.
Steve Church

Steve,
I'm a 1330 with 10:5:1 with standard (but ported and unleaded) head. The HIF also had everything possible done to it to improve the flow, vizard style. It in real terms only gives a marginal increase (1-2hp more) but I wanted as much as I could without going towards Webers.

Unfortunately, I don't know my mixture setting because it ended up being set by the tuners who rebuilt the blown engine. What I do know is that it has a needle profiled approximately for what my engine specs are, and with this needle it tends to run a little rich (or lean, I forget) at around 2-2.5k, but has a reasonably good curve considering it was a guesstimate. I'm itching to rolling road it so may take it over to the garage and do this soon as it could do with tightening up a bit.

I haven't calculated fuel consumption, and I'm never sure how accurate it would be because I drive the car quite hard. Generally, it seems really quite good (I reckon it must be getting 30-35mpg) and with things like motorway driving it goes a long way on one tank. However, I do find that if I am on slightly more fun roads, and go full throttle a lot, it absolutely pisses fuel.... though that sort of goes without saying. It's a nice carb for 'power on tap when needed, economy also available if you want to be a bit gentler please'

How is yours?
Rich Amos (1330cc Blaze Red '72)

Mine is also Vizardized. Smoothed out body, throttle spindle halved etc. My head has had a little work done on it mainly grinding out the shoulder around the exhaust guide. I had the carb set to 2 3/4 turns and reconned I was getting about 25 mpg. I changed the oil in the dashpot from cycle oil to 20/50 and the engine picks up better now. I have since backed the mixture off by 1/2 turn. I shall probably put the Colortune on it to check but I find they are not as easy to use with unleaded. I have to sort out a better exhaust system (currently a MGOC stainless LCB twin box system) before I get to a RR. Not that common around here. May take a trip to Peter Burgess.

Sorry to hijack your thread tm, any further news?
Steve Church

Hi Steve

Cheeky I know ,but I have been looking at the MGOC stainless system. What do you think is wrong with it.
My car is standard so maybe it would be ok?

Cheers Carl
C Bintcliffe

"What do you think is wrong with it."

Dare I say: It's not a maniflow :-).
Rich Amos (1330cc Blaze Red '72)

Carl,
It's the same bore as the standard system, which I think restricts things a bit. Plus its a twin box system which also saps power. I haven't seen a Maniflow + RC40 (seems to be the preferred performance system) to compare against. As a replacement for the standard system it was ok especially at the price I paid for it. Now I'm looking at getting the best from the mods done to the engine and carb and the exhaust is probably restricting things. I'm not sure how the prices compare though but I'm assuming the Maniflow is mild steel not stainless.

Steve
Steve Church

Ok thanks for that Steve, It would seem that the Maniflow is the prefered choice.

Carl
C Bintcliffe

Steve,
The Maniflows are mild steel manifold to backbox, aside from the small length of exit pipe which is in stainless.

The setup is absolutely fantastic and has an incredible note, although when they start to rust after a few years, they REALLY rust! ...as I am experiencing right now. HOWEVER, they are great and worth every penny, especially now they've even FURTHER improved the manifold flow.

Oh and did I mention? I quite like them...
Rich Amos (1330cc Blaze Red '72)

I fitted the HIF on my car with the original needle that came with it, and it was awful - though not exactly the symptoms you describe. Mine was rich at idle and starved at 4000. The needle was a BER - hardly any taper at all - and fitting a BDL made a BIG difference.
Nick

You'l never guess what the problem was.

Unscrewed the dash post lid to check oil level and the damper rod was no longer attached to the lid. Therefore not damping what so ever.

The lid has a small crack and nolonger holds the ball joint end of the road tightly enough. The first call on monday will be to Burlen to see if they can supply the screw top.

BTW Pushing the rod tight into the lid did allow me to risk a trip round the block. Significant increase in power and thats with the old metro needle. Can only think my original twins where no pulling their weight.

Well worth the effort.

One query on the set up. I have real trouble in getting the final tune correct as the small change in revs is very hard to pick out with your head under the bonnet

Thanks for the help
tm wainwright

Tm,
I found that just holding my hand to a part of the engine (that isn't too hot...) makes it easier to pick up the correct tune slightly more accurately. You'll 'feel' it when it feels 'right', I find, although there are MUCH more scientific ways than this!!!!!
Rich Amos (1330cc Blaze Red '72)

Rich,
On the Maniflow front do you know the dimensions of the exit pipes on the branches (pipe diameters). I'd like to compare against my LCB manifold.

Steve
Steve Church

Steve,
Sorry but I don't know the exact size and can't measure it as my manifold was damaged when it hit a plank of wood on the motorway(!) so was re-welded.

Maniflow I'm sure can tell you though if you phone them:
http://www.maniflow.co.uk/

Rich
Rich Amos (1330cc Blaze Red '72)

This thread was discussed between 12/04/2008 and 14/04/2008

MG Midget and Sprite Technical index

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