Midget engine rebore

[olderisbetter]

On saturday i purchased a 1959 2 door minor, it has a midget engine fitted by the previous owner which had a conrod problem and has left the bore scored, it is already bored to 1293, can i do anything with it? the block engine code starts RKM1108E
which shows up as a silver seal rebuilt midget engine, just looking for options to save the block.

[bmcecosse]

Yes - it can be bored out further - depends how deep the score, but worst case it can be sleeved - maybe just that one bore if the others are good?

[olderisbetter]

Good to know i have option to save the black, I have not had the head off yet, the guy i got it from was very honest and said it had a problem, it is very lumpy on tickover but has twin carbs which i am going to swap for the single hif44 from my 1989 cooper engine as soon as i get a manifold, it also has a hotter cam fitted so i need to go through it a bit at a time, when i remove the head i'll snap some pictures and post.

[IslipMinor]

First of all check to see if it has already been linered - look up from underneath after removing the sump.

The biggest 'standard' overbore is +0.060", which gives a capacity of 1330cc, after that it is 73.5mm and 1380, but this needs offset boring and I don't know if it is possible if the engine has already been linered? 1380 also has known reliability problems with head gaskets (some first hand experience of this over the last 18 years and 50,000+ miles!).

Ours has a 276 cam and HIF6/44 and did have a lumpy tickover with the Aldon 'Yellow' distributor. Not the fault of the distributor, and very recently fitted a 'NODIZ' 3D mappable system and playing with the low speed advance settings it now idles very nicely, but of course with any load the timing is instantly retarded to avoid detonation.

[olderisbetter]

Thanks Richard, i will have a look when i take the engine out, the car came with paper work so maybe i will spt something in that, and 1380 seems to create problems i do not need, i just want a nice useable engine, I will look up the NODIZ and see what that does.

[olderisbetter]

Well the damaged bore might explain some problems but i have just spotted the dizzy is not bolted tight and has a tie wrap around it back to the bulk head, looks like a road side fix but if the dizzy is shaking it might be part of the problem.

[bmcecosse]

[philthehill]

I very much doubt that the engine has been sleeved as it is only a Silver Seal re-conditioned engine.
A Silver Seal reconditioned engine had only the bare minimum done to it to get it back into a serviceable condition.
It may have had a re-bore and possible crankshaft re-grind but not much more.
Only when you have stripped the engine and examine the bores will you be able to determine the next move.
A 1275cc engine can be re-bored to 73.5mm on the original bore centres but to maximise the use of the block it is better to offset the bores as it enable one more re-bore to 74mm. Because of the ability to extract one more re-bore I always offset.
If the bores are sleeved based on the original bore centres they cannot be offset bored as the sleeve will be too thin on two sides/aspects as the offset boring is offset in two directions.
You cannot offset bore and then fit sleeves - there is not enough metal in the block to enable that to happen.
Even when bored to 73.5mm on the original bore centres there is a good chance that the oil transfer passage behind No: 4 bore will be broken into and a sleeve having to be inserted into the oil passage to repair.
Good quality 73.4mm pistons are not cheap and good quality 74mm pistons are even more expensive.
So far I have not had any problems with head gaskets fitted to both my 1380cc 'A' Plus block or my 1400cc MG midget block but I do always fit competition head gaskets; and there is not much metal between No: 2 and No: 3 bores with the 1400cc block.
Phil

[bmcecosse]

Many a 1275 block was sleeved from new ! They ran through a 'porous'period.

[philthehill]

bmc
The 1275cc Midget engine seemed to have escaped the 'porous period'.
I have yet to come across one that was sleeved from new.
Here is a gold seal 1275cc Midget block that has been sleeved but it appears to be a Gold Seal unit which when re-conditioned were nearly always put back to 'as new' specification.
http://www.ebay.co.uk/itm/MG-Midget-127 ... Sw3mpXMxEJ
May be worth a punt at the current price.
Phil

[IslipMinor]

Phil,

What head gasket do you use?

I normally use the Payen BK450, but when the current engine was built 2 years ago, I used a 'competition' copper gasket that went across 3 & 4 after ~6/7,000 miles. No damage to either head or block so has now been rebuilt with the Payen BK450.

[philthehill]

Richard
I will have to get back to you on that as the old and new gaskets are in a box at the back of the workshop.
Phil

[olderisbetter]

Well this is good that i can re-use this block, if i can get away without a full strip down to use the car for now that will be great, so this week i am going to do a compression test and take the head off, the carb and manifold of my 1275 mini should fit ok to replace the twin carbs, should be a fun week.

[olderisbetter]

Thanks phil, if i decide to go for a rebuild i will try and find someone who knows the A series well, i am sure there must be a specialist in the midlands.

[bmcecosse]

Any decent copper gasket should do the trick - I never had any 'fancy' /expensive gaskets on any of my competition engines - and never had a head gasket failure. Indeed - I used to 'salvage' the gaskets that came off my mates' rally Mini (being a poor student) and reused them on my own engines. Cleanliness - wipe of grease, and good even torquing down is what is required. On 'extra big bore' engines - some lay a strip of copper wire between the bores under the gasket, to be squashed down as the head is tightened. Never done it myself -but I do know it is sometimes done. Never really understood the 'extra big bore' philosophy - not a really significant gain in swept volume (over a normal 1293) - heavier pistons, much expense - and the air flow is limited by the cylinder head anyway!

[philthehill]

Whilst it is expensive to go above 1293cc you cannot beat cylinder volume.
If you want volume you can go with over boring & stroking the crank to 1600cc but that it taking it a bit too far as regards reliability.
The pistons these days are so light I doubt they are any heavier than a 1293cc piston but they do cost - eye watering expensive.
Whilst a lightly modified head is a restricting factor a 940 head can be made to give good flow but again expensive. My modified 940 five port head modified to 7 ports cost a small fortune but gives excellent flow as the valves and ports are about as large as you can go but the drawback is that the best flow is at high revs - though picking the right cam does help with lower revs.
The size of the tuned 'A' Series engine is usually dictated by competition class size i.e. 850cc, 1000cc, 1100cc, 1300cc and 1400cc which are then supported by spares suppliers.
Sealing rings for the top of the block are now made commercially but it does require the block to be machined to accept the ring - again expensive.
http://www.bing.com/images/search?q=cyl ... ajaxhist=0
As regards liners:-
http://www.minispares.com/product/Class ... .aspx|Back to search

Regarding getting work done and parts supply Peter May Engineering is a good bet:-
http://www.petermayengineering.com/
Phil

[ManyMinors]

Thanks phil, if i decide to go for a rebuild i will try and find someone who knows the A series well, i am sure there must be a specialist in the midlands.

Southam Mini & Metro Centre (SMMC) would be a good start. Very helpful, very experienced and very well respected "A" series specialists.

[olderisbetter]

Thanks phil peter may is not that far from me, and price wise the liners look a good option so i can keep the block, all i am looking for is a nice engine that keeps up with modern traffic and that goes up hills nicely, i think anything above 75 bhp would be a bonus, but it really is nice seeing those deep pockets type engines , and i will check out the Southam place as i get round that way once in a while, the engine has a tubular manifold and a moded cam so i live in hope. Here are some of the pictures from the previous owner in various stages if you want a look http://imgur.com/a/xaZww/all

[IslipMinor]

Looks like an interesting combination of parts on the engine?

MG 1275 with unknown cam (?Kent something maybe, as there is the Kent timing disc lurking in one of the photos), LCB, standard HS2 twin SU's with pancake filters and then 1.5:1 ratio roller tipped rockers!

Without knowing the cam, but if it's a Kent or Swiftune of any kind, their default is 0.016" with standard ratio rockers, so 1.5/1.3 = 15% more gap which means setting the tappets to at least 0.018" inlet and 0.020" exhaust.

AC Dodd use 0.014" and Piper 0.012" as standard, with the same 15% more for the 1.5 rockers.

I would definitely want to know what cam is fitted, but swapping to your HIF44 is a good short-term move.

The distributor would also be a high priority as, unless the 25D fitted has been sorted out with a different advance profile, it is unlikely to be suitable for a modified engine. Options are a straight swap for something like an Accuspark distributor with an electronic trigger module, but I don't know what curve(s) they do?

Or go to an 'ECU' approach, starting with the Accuspark 'Stealth Black Box' which maps advance and dwell, but not 'load' i.e. manifold vacuum, or a full '3D' mapping ECU, e.g. NODIZ which is not cheap, a real fiddle to fit, but once done does give total control over the ignition map. If you do consider going this route, please contact me as it is very far from a fit and forget kit!

My son has the Stealth on his modified MGB, and it is definitely better than the standard 45D distributor, but with no load mapping capability feels a bit limited, which is why I went the very frustrating NODIZ route. Their support is very patchy, but once engaged is very knowledgeable. Also their offering is more complete now than it was when I bought late last year.

The 'hotter' the cam is the less that a simple distributor can provide a good solution for the complete range of driving needs - setting it up for maximum high speed performance, will likely compromise the lower speeds. I am amazed at the difference at idle, running from cold and low revs there is now that the ignition can be profiled precisely for all speeds and loads. I have yet to get it on a rolling road, so there is very likely more to come!

[olderisbetter]

The invoice i have that came with the car has one from swiftune with part no.s SW5-07-DP1275 and SW-CHRR-15 which seems to be the cam and rockers it has, and the hif44 is more about me not being able to set up the twin carbs, this week is a big tidy up for me and the good bit is in the box of bits i have an accu spark 45d dizzy and triple spark plugs and there sporty coil, i think it may be a positive earth one but i am sure i can play about and if i keep looking i might find other bits i put away and forgot about, i am sure we all do that right?