Which engine?

[robedney]

Mildred -- whom I've only had for about a month now -- is nearing the point that I'll be driving her daily. She's a 1967 MM1000 2 door with I'm assuming the 948 engine (engine number 9M-U-H 397126). The engine seems to be in fine shape with excellent compression. There seems to be a bit of timing chain noise, and I can detect some play when rotating back and forth while watching the distributor rotor. That's an easy fix. I got her onto the freeway a few days ago and she's got a bit of a miss at speed, which doesn't surprise me as I've not given her a real tune-up yet. Nonetheless I wasn't able to really test her out -- along with the front wheels clearly needing balancing!

So, here's my question: I'll be driving her a lot. Will the 948 cruise comfortably at 65 miles per hour? I'm not terribly worried about acceleration, but cruising at the legal limit of the freeway would be nice. Will the engine hold up reasonably will doing that (we're talking about maybe 40 minutes a day and then the occasional trip). Is there a relatively simple way to increase the power output of this engine if I need to?

If not, would it make sense to upgrade to a 1098? Is that a straight engine swap (same gear box, mounts, etc.)?

Or, how much more work is it to convert to a 1275 Midget engine?

I've been tracking EBay here in the US and both of these engines seem to be relatively available, either used or rebuilt.

Lastly -- and this is becoming important -- how do these three engines stack up when it comes to fuel economy?

Thanks!

[deano69]

A '67 should have the 1098 engine i believe.Dont know whats required for the 1275 swop but im told its straight forward swop, not difficult if you got experience.Someone more knowledgable will be along to tell you more.
Don't think the 948 or the 1098 will cruise at 65mph, cruising speed's about 55, but might do it for the short periods mentioned but will probably generate a lot of noise from the diff.Suspect your best bet for fuel economy will be the 1098 but not at 65mph...

[mike.perry]

Unless someone has dropped the wrong engine in, you should have a 1098. The 948 is cast 950 on the block behind the carb manifold and the 1098 has a plate with 1100 on it in the same place.
The 1275 Midget engine is almost a straight swap, only problem is they are getting rare.
The 1275 Marina/Ital is another option but requires a bit more work

[JOWETTJAVELIN]

Fuel economy important in the U.S? Thought you had it dead cheap over there... Anyway you shouldn't get any less than 35 miles per Imperial gallon.

[Alex'n'Ane]

Don't think the 948 or the 1098 will cruise at 65mph, cruising speed's about 55, but might do it for the short periods mentioned but will probably generate a lot of noise from the diff.Suspect your best bet for fuel economy will be the 1098 but not at 65mph...

A 1098 will easily cruise at 60-65, and return good high 30's low 40's mpg in my experience. Especially if you add on some slight tuning bits to warm it up, as this would be easier than trying to source a 1275.

[chrisd87]

The 1098 will cruise without issue at 65mph, but is starting to get quite busy by that point with the standard 4.22 diff. 60mph is OK, however, although it will of course be doing more revs at this speed than most modern cars. If the current engine needs work and 1275 engines are readily available, then this is probably the best route if you want easy cruising at high speed. The greater power will allow you to run a higher ratio differential (easily available from a late Midget axle) which will lower the engine revs at any given speed.

Fuel economy is unlikely to differ dramatically between these engines. Most tend to find the standard 1098 does about 40mpg (~33mpg US), so not likely to break the bank with fuel at ~55p/l (cf. 133p/l here).

[dellerie]

i run an A30 with a 948 engine and a 3.9 diff. it happily sits on the motorway at 65-70mph.

[Alex'n'Ane]

The a30 is considerably lighter, and more aerodynamic than the minor. But i have heard of people even pulling a 3.7 from a 948 in the a35's, but that must be close!

[robedney]

Just confirmed that it is a 948, which perhaps explains why the rocker cover says MG on it. Someone must have blown the original engine. This engine, however, has excellent compression - it's all a mystery.

At any rate it sounds like the thing to do is watch for a 1275 engine. I'm not likely to find one here locally, but they do seem to exist here in the US on Ebay -- in whole or in pieces. I can gather up all the bits over time, get the machine work done and build an engine, then slip it in this spring or summer. Given the shipping, it might be cheaper to find a good block and head separately:) I have to do all of this on a boat -- a big boat however with a decent shop space. The boat is on the end-tie, meaning that the distance from my shop to the car is about 300 feet -- a real treat when I forget one small part or tool in one place or the other.

I don't mind noodling about with the 948 for a bit. My biggest issue is that I live in an odd spot where the only way in and out is on the freeway. To leave, I have to use an on-ramp that dumps me into the fast lane along with all the traffic coming over the Richmond/San Rafael bridge from Marin County -- which includes BMW's, Mercedes, SUV's and hybrids all coming along at at and often well above speed. Fortunately I don't have to merge right away -- the on-ramp creates a new lane -- but I do need to eventually get over. I'm adding some obnoxious LED sequential blinking turn signals in the rear window just to make sure. I want to be noticed, and noticed as "SLOW".

As for the price of petrol, you all definitely pay more that we do -- but then I pay close to $600 US monthly for health insurance just because I'm 61 years old -- not because there's anything really wrong with me. You all have national health care, which I greatly envy!

[mike.perry]

Check out which gearbox you have, 948 smooth casing, 1098 rib casing

[bmcecosse]

The ultimate best economy will be with the 948 engine -and the number you quote is for a 948. As mentioned above - look for 950 cast in the side of the block. But your fuel is so cheap - i'm amazed this matters to you! Best cruising will be with the 1275, and so the compromise is the 1098 engine. It will cruise at 65 - even 70 if you need it to, without any problem.
But the 948 is the 'smoothest' engine of the bunch (because it has short stroke) - and with some simple modifications it too will cruise at 65/70.

[robedney]

What sort of modifications to the 948? I did confirm the casting number on the side of the block. I'll have a look at the gear box tomorrow. Thanks for all the input -- keep it coming!

[bmcecosse]

Well the simplest mod is to fit the cylinder head from a 1275 engine - and since you are looking for that anyway......, and a slightly larger carb -you want a 1.5" SU either an HS4 or an HIF38. Ideally the camshaft needs changing too, but that's a bit more invasive. That head and a larger carb will give you 80 mph top speed and cruising at 65 no problem at all. The head number is 12G 940 - was fitted to Austin America if that helps the search.

[Alex'n'Ane]

Isn't that slight overkill on a 948? Thought most just fitted the 12g202 (1098) cylinder-head, and an hs2?

[bmcecosse]

Well -you could - but the power increase from a 202 would be hard to detect, and the HS2 is no better carb - it does need a larger carb to get more power - on a non-heated manifold of course! And the 202 head would need 60 thou skimming.... the 940 is a straight bolt on with the 948 - since the exhaust valve lift on that engine is pathetic....... And - the OP wants to collect 1275 bits anyway!

[Alex'n'Ane]

You learn something new from bmc every day

[robedney]

Yes, BMC is a resource! If he were a bit closer I'd ask him over for tea. I envy you all over there, where moggie parts are plentiful and quick to get. I did confirm that the gear box is the ribbed type, so all is good there. I finally got enough done that I had her out on the freeway today for a bit -- used my cell phone as a speedometer (yes, there's an app for that) as the one in the car has a broken cable. She seems to have a sweet spot at about 58 MPH, which is fine for now. No real need to go any faster than that commuting. I can't wait for the new rubber bits to arrive for the windows -- she rattles up a storm on the rough part of the road -- and it's all the windows. So, I'll start haunting EBay for a suitable head and carb -- that sounds like a good place to start. A head, manifold and carb swap is a perfectly doable one day project after all the bits are lined up and ready.