Very (?) mild upgrade.

[palacebear]

My Moggie is a 1956 Series 2. It's done at least 85000 miles. As far as I know all the running gear is original 803cc except the engine which is a 948cc gold seal (9G-R-J prefix). I believe the engine has done around 56000 miles and has been in the car since 1961. Mileages MAY be higher. MOT certificates suggest several years where the car has only done 6 miles (to and from testing station) each year ... used with speedo disconnected at other times (?). The car was subject of a good quality body/structural restoration in 1990. It retains nearly all original features, and I'm determined to keep it visually original as far as possible.
The 803 gearbox is making lots of noise (sounds like worn bearings). Clutch needs renewing. 948 engine is smoking a little on over-run and needs a new timing chain / tensioners.
I want to try and keep the car on the road if possible until transplant time so my plan is to source another 948 engine. Rebuild it so I know it should be good. Source a 948 box and axle. I want to keep the long gear-lever. I understand that converting a 948 box in this way is easier than a 1098 hence I'm keeping to a '948 plan' I also want to keep a gold faced speedo (later type), and not have to bother too much about a brake upgrade.
Questions are:
1. Will it all fit straight in?
2. Will I need different mainfolds and carb (I think my current engine still has the original carb specified for the 803 engine) along with what may be an Austin air filter ... black cylindrical fitted horizontally on top of the carb with gauze-filled intake to one side (looks a bit like an air-raid siren perched on top of the carb!).
3. Is there anything I need to be aware of, aside from ensuring second hand units ar actually viable?
4. Am I doing the right thing or should I seek counselling???

[philthehill]

1. It will fit straight in and as you intend to modify the 948cc gearbox no cutting of the floor required.

2. I would use the respective manifold, carb and air cleaner for the replacement 948cc engine.

3. There should be nothing untoward to worry about. A simple conversion which has been undertaken many times.

4. You are doing the right thing and you do not need counselling.

5. If you stuck with a 803cc engine I would suggest that you would need counselling.
Though purists may disagree.

[myoldjalopy]

I went down this same route several years ago.
I installed a 948cc engine and gearbox - and kept the long gearstick by 'marrying' the 803 box rear casing with the 948 bellhousing. If you want to retain the 803 reverse gear selection (i.e. lifting the gearstick to engage reverse) you will also have to use the 803 reverse selector rod in the 948 box.
As Phil advises, I used the manifold, air cleaner and carb assembly from a 948. However, I didn't change the diff but have had no problems as a result of this.

[liammonty]

As above. The only additional point is that if you want to retain the speedo you have, as opposed to using a similar Minor 1000 version, you'll need to change the speedo drive gear inside the gearbox (on the third motion shaft IIRC) as well as the gear that it drives which screws into the gearbox - I.e. you need to retain the SII ones. Otherwise, your speedo will over-read by around 50%. I would also change the diff - the one you have is so low geared it will drive you crazy with a good engine. It will put the speedo out a little but in my experience they over read so much that a higher geared diff actually makes them more accurate.

Yours is a good plan - I did the same with my early SII and the result was super.

[ampwhu]

I have 948 internals in my 803 box along with a 948 engine. I have fitted a 4.2 diff. all runs like a swiss watch

[myoldjalopy]

[quote="liammonty" I would also change the diff - the one you have is so low geared it will drive you crazy with a good engine. [/quote]
Well, you would think so but, to be honest, I don't notice that (maybe I'm crazy already! ). Its quite perky and cruises quite happily at 60mph. Much improved on the old 803cc, which was pretty tired anyway.
Thinking about all this, I'm wondering if someone had previously put in a 4.2 diff, for some obscure reason, and that made the 803 seem tired?? Can you tell which diff it is when its on the car? If so, I'll take a look.

[liammonty]

Well, you would think so but, to be honest, I don't notice that (maybe I'm crazy already! ). Its quite perky and cruises quite happily at 60mph. Much improved on the old 803cc, which was pretty tired anyway.
Thinking about all this, I'm wondering if someone had previously put in a 4.2 diff, for some obscure reason, and that made the 803 seem tired?? Can you tell which diff it is when its on the car? If so, I'll take a look.

If you can cruise at 60, then I'd put money on the fact tht the diff has been changed already - with the 5.375:1 diff in the 803, anything over 50 mph is genuinely traumatic, and 60 is approaching the red line. If the diff has been changed to a 4.22:1 from a 1098 Minor, it should be easy enough to spot, as it will have the oil filler in the back of the axle casing, rather than in the front of the diff unit itslef (or more accurately, the diff itself won't have a filler plug in it). However, it could be a 948 (4.55:1) diff, in which case it's harder to distinguish as the filler plug set up was the same as the later 803-engined cars with the Austin back axle. I think if you look carefully enough you should be able to find the crownwheel/pinion ratio on the outer flange of the diff - this will give the definitive answer, but could be a bit tricky to find with the diff on the car!

[IslipMinor]

A sure-fire way of determining the rear axle ratio:

Put a short horizontal line with a light-coloured marker pen on the end of the propshaft nearest the rear axle, put blocks ahead and behind one of the wheels on the opposite side of the car, release the handbrake, gearbox in neutral and make sure that the car does not roll backwards or forwards!

THEN jack up the car on the same side as the mark, until the rear wheel is clear of the ground, make sure that it is stable, check that the mark is still visible and note where the valve is on the jacked up wheel. Turn the jacked up wheel 2 full turns EXACTLY and whilst doing it, count the turns that the propshaft makes:-

5.375 = a rear axle ratio of 5.375:1
4.555 = a rear axle ratio of 4.555:1
4.222 = a rear axle ratio of 4.222:1

You do not need to super-accurate with counting the propshaft turns, just is it ~4 1/4, ~4 1/2 or almost 5 1/2? Run the process twice to make sure.

From what you have said, my guess it is likely to be the standard 4.555 from a 948 engine car.

[oliver90owner]

 quite perky and cruises quite happily at 60mph. 

myoldjalopy,

How do you check it is a real 60mph? Even my modern car needs to read almost 65 for an actual 60mph. Speedos are notoriously inaccurate.

A good sat nav (not a cheap dash cam - mine indicates 2mph low at 30mph!) or a check over a multiple of the 100m countdown markers on a motorway seems to be the better ways of determining the true speed at any particular speedo reading. The odometer will also be wrong if the diff/wheels/tyres, etc have been changed from original (if it was actually correct from new!).

RAB

[myoldjalopy]

Well, it is not a 4.22 then, as the filler plug is on the front. It has an old style metal breather too. Maybe it is 4.55? I will try the IslipMinor method some time when I next adjust the brakes, perhaps. Thanks, Richard.
How do I know I'm going at 60mph? I just know, from experience, roughly how fast a car is going...........

[IslipMinor]

The filler plug location is not a reliable indication of the ratio. The 4.22 was available in both configurations, with the filler in the diff nose and later in the axle casing. The 5.375 was never available with the axle case filler, and the 4.55 only as a Special Tuning 'Competition' version, so a diff casing without a filler is likely to be a 4.22, 3.9 or 3.7 ratio.

With a filler, it could be any of the ratios!

[Rabbitt]

I went down this same route several years ago.
I installed a 948cc engine and gearbox - and kept the long gearstick by 'marrying' the 803 box rear casing with the 948 bellhousing. If you want to retain the 803 reverse gear selection (i.e. lifting the gearstick to engage reverse) you will also have to use the 803 reverse selector rod in the 948 box.
As Phil advises, I used the manifold, air cleaner and carb assembly from a 948. However, I didn't change the diff but have had no problems as a result of this.

Hi all .... I want to do exactly this tried and true by all accounts. Engine swap an 803 with a 948.
Our 1956 split-screen 4 door 803 is fine at the moment , but on reading all posts opinion is that if something goes radically wrong with the 803 , it's more advisable to source a 948 rather than go down the recond path. So ... 2 scenarios:
1.If I can find a 948cc with gbox = simple swap and just reconnect the rear casing from the 803 to keep the "wand" stick.
2.If I do engine only - simple swap with nothing else required - right ?
(except in gbox case often better to change the diff 0 but not essential.)
MOJ .. sorry if I didn't get it .. but could you further explain the retaining the 803 reverse selector comment for me ?
All said , I just want to have a spare motor/box on hand - and hopefully disaster never happens . (Murphy L)
Lastly, 803 to 1098 = not an option I understand?

[palacebear]

As mentioned earlier in this thread, engine upgrade only is not a great idea.

Slight improvement in acceleration but not much as the gearing is so low. No increase in top speed. Shortened gearbox life.

948 engine, 948 box (with gear lever conversion if required) and either 4.55 or 4.22 diff is best. You may also need to get a second hand speedo out of a 948 car to get correct readings. Supposedly the smoothest power train ever fitted to a Minor!

(If your budget will stretch to it, get the 803 box reconditioned and sell it).

1098 engine and box will go in but gear lever conversion is not possible and (I think) complete rear axle casing would need changing. Also upgraded front brakes. 8 inch drums for 1098 power!

What ever you do, remember that the Series 2 standard 5.3 diff will hold the car back.

There is a 50mph road near my home with a long downhill stretch. My Moggie (948 engine, 803 box 5.3 diff) needs to be driven at half throttle going down the hill to maintain 45mph

[liammonty]

I agree in general with the above, but having done the engine, box and diff swap from 803 to 948 myself, I'd note the following.

1. It's often said that the 803 box is weaker than the 948 box - having had both in bits to convert a 948 box to take the 803 gear lever, I couldn't see any difference in terms of the strength of the innards. the main difference is the ratios of 1st, 2nd and 3rd gear (which are terribly low and close on the 803 box) - 4th remains the same (at 1:1) so doesn't impact on revs in top gear. The 1098 box is definitely stronger, with baulk ring sychros and ribbing to give the case additional strength.

2. I agree that it is, however, best to change the box to a 948 one, as the ratios are far better suited to the engine, with nicer spacing between the gears. As mentioned before though, it is wise to change to a 4.55:1 (948) diff to get a vast improvement in 'cruisability'. Personally, I wouldn't go for a 4:22:1 diff from a 1098 with a 948 engine,as it isn't torquey enough - ampwhu has said he's got a 4.22:1 in his car with a 948 engine, but I think that might be an A30, which is quite a bit lighter (sorry if I've got that wrong, ampwhu).

3. Regarding the question about the reverse selector - in the 803 box, you have to lift the lever to engage reverse, but in the 948 box, there is a spring to prevent inadvertent selection of reverse in the remote tailshaft - once you replace this with the 803 tailshaft, there is nothing to prevent the gear lever from moving across into the reverse gate. Hence it's best to remove the reverse selector form the 803 box and replace the reverse selector in the 948 box with it - this way, you preserve the requirement to lift the lever to engage reverse gear.

4. The 1098 box can be adapted to take the 803 tailpiece and gear lever, but it requires machining work. A few people on here have done it, but it is quite involved. Have a search for it - I think it might have been 'win' who did it but I could be wrong.

5. It's a good point regarding brakes - as 7" front drums were also standard on 948 cars, you shouldn't have any trouble with insurance if you change all the running gear to 948, as the brakes of a Series II are the same.

6. I did mention it before, but in case it's been forgotten - if you do change the box, you will need to remove the speedo drive from the 3rd motion shaft of the 903 box and fit it to the 948 box. That way, you can screw in the correct speedo drive to the new box (i.e. the external piece to which the cable attaches) and your speedo will read correctly. If you don't do this, it will read around 50% too fast . To be honest, that is the only part of the process that is a bit of a faff.

EDIT: Palacebear - just going through the previous posts, as I guess you've already sussed out, the easier route for you regarding the speedo would be to use one from an early Minor 1000 - that way, you don't have to mess around stripping the gearbox to replace the speedo drive and you can still have a gold-faced speedo which will read correctly. Fitting a 948 diff will in all likelihood make the speedo more accurate, as they mostly over-read wildly as standard. When I did this, it made it fairly accurate when checked against satnav (as was also the case when I fitted a 3.9:1 to my 1098 car!). Finally, I don't think anyone answered the question regarding the carb - the 948 has an 1 1/4", whereas the 803 carb is 1 1/8". You'd be well advised to swap it, but I am certain you'll be able to fit the SII air filter which will keep it looking original.

[philthehill]

The carb question was answered above in my point 2. where I recommended that the respective manifold, carb and air cleaner for the 948cc engine should be used.
There are qty 8 SU carbs listed on the Burlen web site in respect of 948cc Minor engines so it is important to get the right combination.
I do not have a 803cc or 948cc SU carb to hand but if I remember rightly the 803cc carb to air cleaner tract which bolts onto the 803carb carb has different bolt centres to the 948cc SU carb.
http://sucarb.co.uk/cf/vehicle/list/?ma ... icle=Minor

[liammonty]

My apologies Phil - I am duly humbled.

[philthehill]

[palacebear]

In answer to the last posts by liammonty and pth...
I had indeed sussed the speedo issue, and my current 948 engine is breathing (very richly) through an 803 carb and manifold.
In my case its getting a bit academic. Mrs. PB doesn't like Max and wants seatbelts, Newton seats etc etc. As Max is a nice original-looking car, it seems he may soon have to go, as I can't bring myself to spoil that carefully restored originality.

[jagnut66]

In my case its getting a bit academic. Mrs. PB doesn't like Max and wants seatbelts, Newton seats etc etc. As Max is a nice original-looking car, it seems he may soon have to go, as I can't bring myself to spoil that carefully restored originality.

You could always trade in Mrs. PB instead and keep Max......................

[firedrake1942]

I did that with the ex Mrs FD. Best decision ever made!