Engine swap - measuring the change

[welshrat]

The old girl walked her MOT today so decided to bite the bullet and do the jobs I have been threatening for several years. Fitting a rebuilt midget 1275 (currently has a 1275 but on its last legs and drinking oil like it was the sixties) with a 3 into 1 manifold & 1 and 1/2 inch bore exhaust (currently has the original pea shooter job) and a Hif 44 (has the original 1 and 1/4 twin midget set up at moment). Any suggestions on a before and after type test so I can establish/share the improvement or possible disaster of the changes to be made, all I can think of is getting on the M4 and recording the top speed and working out how many miles it currently does on a gallon of petrol.

[beero]

MPG possibly won't improve but your smiles per gallon will.
What about 0-60 time? That would be a good indicator of any improvement.

[bmcecosse]

Top speed is not wise on the public highway. You need a decent long hill to compare pulling power. But frankly -the new engine will be obviously better.

[charlie_morris_minor]

have you thought of going to Llandow?

http://www.llandow.com/

you could probably get a whole host of figures running around the circuit

[welshrat]

Turned out to be a disaster, old motor out, new clutch fitted for good measure, new motor in (decided to fit original carb and exhaust until I new it was running OK), good oil pressure on turnover without HT leads. Major water leak from between head and block at the front end, this is even before its fired up so no pressure. Guess I am looking at head off to see whats occuring. Any Ideas, pretty sure I followed the head tightening precedure to the letter, how I wish I had bench tested the motor, two days lost.

[bmcecosse]

Hmmm - head fouling on the water pump casing? Bypass hose? Who rebuilt the 'new' engine?

[welshrat]

That will be me BMC so there are a number of things that could be wrong. Water pump was fitted after the head, will have a look tomorrow with fresh eyes but the water seemed to be comming from between the head and block where the engine number plate sits. When I say rebuild it had a clean up, new shells, oil pump, gasgets etc. I am thinking the worst distorted head or crack somwhere, I do hope I'm wrong.

[bmcecosse]

Oh dear hope it's something simple...........

[welshrat]

Turned out to be the top hose, water running around and under the termastat housing and showing as if it was comming from between the block and head. Slight leak from one of the core plugs, thankfully one i can get at. Next task is to get it started and await the next potential disaster.

[bmcecosse]

Good news !

[welshrat]

Very good news I'd say. Managed to do a bit of fetling this evening, checked timing that was 180 degrees out (pretty sure that I put the dizzy drive in right so the old engine may have been wrong), any how after ensuring that the firing order was correct turned it over and started first kick. Need to sort that leaking core plug (posted this on parts wanted if anyone has a single one for sale) and then add hiff 44 with mg metro manifold and larger bore exhaust with 3 into 1 manifold. Keeping me fingers crossed.

[welshrat]

A bit of progress this evening, manifolds and carb on, hiff holding fuel which I am delighted about. Not so happy about having to change the choke cable (not long enough), would welcome any ideas as currently running with the original switches and knobs. Now need to fit exhaust which is not gonna be easy, 3 into 1 is 38 mm, exhaust is 45mm so a bit of fetling required. Added a few pics.[frame][/frame][frame][/frame][frame][/frame]

[win]

I extended my choke cable, by using a cycle, rear outer cable, and a copper earth cable, from flat twin and earth, for the inner cable, soldered in to the choke knob stem.
Mine is a twist to lock choke, and the inner cable was just soldered in.

Regards Win

[bmcecosse]

That lcb exhaust is only suitable if you have a wide timing cam in the engine....... And yes - I too extended the 'choke'.... I wouldn't do that with an acc cable - but the 'choke' isn't that important...

[welshrat]

That lcb exhaust is only suitable if you have a wide timing cam in the engine....... And yes - I too extended the 'choke'.... I wouldn't do that with an acc cable - but the 'choke' isn't that important...

What's a wide timing cam then BMC?

[bmcecosse]

544 - maybe a 731 in BMC speak.... That would be 286 or maybe 276 in modern speak...

[welshrat]

544 - maybe a 731 in BMC speak.... That would be 286 or maybe 276 in modern speak...

Well only have the standard midget cam what ever that is, its only a inch and a half lcb mind, fitted a two inch one to a 998 cooper a while back that seemed to be fine. What problems are you anticipating, surely its has to be better than the previous manifold that had a one inch exhaust hanging off it.

[bmcecosse]

Yes - but it is designed for a long timing cam. The engine would be better with a 3 in to 1 manifold when using a standard cam......

[welshrat]

More worries, motor starts and runs well, no knocks, odd noises or leaks, however oil pressue is shocking when hot. Drops to about 35 on tick over, and up to about 55 with revs. Any thoughts would again be very welcome.

[bmcecosse]

That's not 'shocking' - but it's not great either. Is that the pressure after a good hard run ?? And with 20W50 oil? What did the rebuilding consist of - crankshaft regrind and new oil pump??