Tips for first 1380 engine build?!
Discussion
After a 400 mile trip in my high mileage mini mayfair, my engine gave up, and with an mot in a couple of weeks i thaught that now is the time for a revamp, so im planning on a 1380 half engine kit, refurbished big valve head, might have a go at some porting, a new gearbox as the one i have is very close ratio, 2" big bore exhaust not to sure about what cam i should have.. hif44 carb uprated oil pump new ally rad bucket seats and semi slicks.. i have baisic mechanical knowledge and this is my first engine build so i feel quite clueless, any advice? id like to get it above 80bhp. cheers
Best advice is to go for a 1330 cc over-bore which is +0.060"
The reason for this is to avoid getting to a point, which happens with 1380, where the block could be scrap at the next re-bore or require very expensive sleeving and boring. There will never be any more 1275 A-series block cast new.
The gain from 1330 to 1380 is negligible, but at 1380 offset boring is needed to give sufficient space between cylinders 2 & 3 and there is still a chance the bores will come very close to the water jacket. 1330 is a straight re-bore on existing cylinder centres.
What is important is to match the required use to the engine build specification.
If it's to be a road car a good option is a 266 or 276 cam (or equivalent), a bore to 1330 cc, 21253 pistons, a 10.3:1 C.R., a gas-flowed head with 35.6 mm inlet and 29.5 mm exhaust valves.
Personally I can never see the desire to go to 1380 with all that is involved when a 1330 can give the same power with an accurate engine build. Maybe it's because the two 'comics' make a big thing about 1380 engines.
The reason for this is to avoid getting to a point, which happens with 1380, where the block could be scrap at the next re-bore or require very expensive sleeving and boring. There will never be any more 1275 A-series block cast new.
The gain from 1330 to 1380 is negligible, but at 1380 offset boring is needed to give sufficient space between cylinders 2 & 3 and there is still a chance the bores will come very close to the water jacket. 1330 is a straight re-bore on existing cylinder centres.
What is important is to match the required use to the engine build specification.
If it's to be a road car a good option is a 266 or 276 cam (or equivalent), a bore to 1330 cc, 21253 pistons, a 10.3:1 C.R., a gas-flowed head with 35.6 mm inlet and 29.5 mm exhaust valves.
Personally I can never see the desire to go to 1380 with all that is involved when a 1330 can give the same power with an accurate engine build. Maybe it's because the two 'comics' make a big thing about 1380 engines.
Only go to the next oversize. If the block is on standards +20 will take you to 1293cc. I'd reinforce what Cooperman Advocates here - 1380cc gives you only an extra 50cc capacity - but at huge expense (Pistons) and exposes you to risk on the offset boring block work unearthing shortcomings in the original block manufacturing process.
Keep the cam timing sensible (MG Metro/Kent 266/Piper 255) - torque is king.
Keep the cam timing sensible (MG Metro/Kent 266/Piper 255) - torque is king.
Is the block newly re-bored to that size. if it isn't and the bores are slightly worn you may be looking at another block as to get a 1380 needing a re-bore back to 1380 is not easy. You have to have special sleeves made, then the block bored even further, which can often mean boring through the water jacket and the sleeves bored to correct size.
Be very careful with this. if you don't have the pistons, consider sourcing a block which has not been re-bored more than once, i.e. to 1293, and go to 1310 cc which is +0.040".
A better block may cost a few quid, but it'll be loads cheaper than subsequently trying to re-bore a 1380, sleeving it and re-building from there.
I blame the two 'comics' for all this 1380 nonsense!
Be very careful with this. if you don't have the pistons, consider sourcing a block which has not been re-bored more than once, i.e. to 1293, and go to 1310 cc which is +0.040".
A better block may cost a few quid, but it'll be loads cheaper than subsequently trying to re-bore a 1380, sleeving it and re-building from there.
I blame the two 'comics' for all this 1380 nonsense!
jamesburke998 said:
Im afraid i have already baught the 1380 block, it was part of an engine kit, im abit worried about cam timing, will i wreck the engine if i dont get it bang on?
So what was in the kit ? Presumeably the block has a fresh rebore and honed finish ?I'm surprised at people recommending the tame cams....the 1300 or larger bore engines are proportionally less affected by installing longer duration/larger overlap cams than the 1000cc range of engines.
Go for at least a 544/643 (in old parlance) / 286 cam and time it in 2 degs early.
My first 1380 pushed out 83 bhp at the wheels on Aldons RR with a 643 cam, Janspeed stg II head and exhaust with a 45 DCOE....and was a riot to drive on the road with a 1275GT box and 3.9 CWP....96 mph @ 6000 rpm though so not really any good for distance on motorways.
Edited by Chuggaboom on Tuesday 14th April 16:54
Cooperman said:
I blame the two 'comics' for all this 1380 nonsense!
ive always been a massive fan of a 1071 - ive had loads of them and love them.my gtm is a 73.5 bore one (reused a old 1380 block with a iffy face - so nice bit of recycling there)
my mk1 cooper s thing is a 1430 and that's a beast - compared to the gtm, the low revs and huge amount of torque is amazing - I just stick it in 4th and leave it there
The kit is 1380 ofset bored block new core plugs bearings washers big ends ect stroked crank power max pistons and some decent con rods, since I've got a turbo oil pump, lightend duplex timing gear new dual core ally rad the cam I have got is a minisport ca2 fast road.. I have been told I need a new dizzy drive clutch and flywheel..
jamesburke998 said:
stroked crank
...with a 1380....interesting ???jamesburke998 said:
the cam I have got is a minisport ca2 fast road
Would have to look that up to see the spec to understand how mild or wild it wasjamesburke998 said:
I have been told I need a new dizzy drive clutch and flywheel
You will defo need a different or modded dizzy to give your engine an advance curve that suits a modded engine from std.Can you provide a link to the kit you bought as I wouldn't expect to see a stroked crank in a 1380cc engine.
You don't need to offset the bores for a 1380cc rebore but the offsetting would provide increased wall thickness which would reduce bore flexing/ring bypass and allow the engine to run a higher static compression ratio.
With the cam supplied, suggest that you fit it and see what it is like, it has been supplied in the kit otherwise it is just wasted money. Minis are expensive enough to tune without buying bits you don't use.
With regard to clutch/flywheel, you will need to buy an uprated clutch due to the anticipated increase in power/torque. As for flywheel/back plate, you will need one from a 1275 engine that is in good condition but that is all, whether you to decide to have lightened one or not is down to driveability. Light weight ones don't smooth the idle like a heavy one does so the engine will feel lumpy and vibrate more but with less mass to spin up should pick up revs slightly quicker.
You don't need to offset the bores for a 1380cc rebore but the offsetting would provide increased wall thickness which would reduce bore flexing/ring bypass and allow the engine to run a higher static compression ratio.
With the cam supplied, suggest that you fit it and see what it is like, it has been supplied in the kit otherwise it is just wasted money. Minis are expensive enough to tune without buying bits you don't use.
With regard to clutch/flywheel, you will need to buy an uprated clutch due to the anticipated increase in power/torque. As for flywheel/back plate, you will need one from a 1275 engine that is in good condition but that is all, whether you to decide to have lightened one or not is down to driveability. Light weight ones don't smooth the idle like a heavy one does so the engine will feel lumpy and vibrate more but with less mass to spin up should pick up revs slightly quicker.
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