Buying a Series MM

for those with Series MM sidevalve cars produced between September 1948 and February 1953

Moderator: Moderators

Online
palacebear
Minor Legend
Posts: 2186
Joined: Mon May 16, 2016 4:39 pm
Location: Kidderminster, Worcestershire.

Buying a Series MM

Postby palacebear » Wed Jun 28, 2017 10:23 pm

I'm going to have a look at a '53 Series MM 4-door this weekend. It's being sold by a dealer of sorts. I'm not very familiar with the side-valve powertrain.
What advice would you give me when inspecting the car? What potential issues does the MM powertrain have, which I would need to be aware of? In addition, would I be correct in assuming that the under-body is the same as a Series II 4-door? (In view of the asking price, I'm hoping that body/structural problems won't be an issue!!)
Max the Moggie

jagnut66
Minor Legend
Posts: 1780
Joined: Fri Apr 11, 2008 7:28 pm
Location: Mansfield, Nottinghamshire.

Re: Buying a Series MM

Postby jagnut66 » Wed Jun 28, 2017 11:01 pm

Good luck with your purchase.
Dimensions for an MM (from Wikipedia):

Wheelbase 86 in (2,184 mm)
Length 148 in (3,759 mm)
Width 60 in (1,524 mm)
Height 60 in (1,524 mm)
Curb weight 1,708 lb (775 kg) (four-door saloon)

Whilst the site lists the details of the later models it shows no difference in dimensions, so inferring they are the same.
As to the side valve engine, the words 'slow' and 'underpowered' spring to mind, an ALTA head conversion would be a nice talking point, though I believe they are like hens teeth to find these days.
Link below. I hope this helps, if you buy lets see some pics.
Best wishes,
Mike.


https://www.google.co.uk/url?sa=t&rct=j ... gTjEnUuzwQ
Olwyn Image

BLOWNMM
Minor Fan
Posts: 292
Joined: Tue Dec 09, 2014 6:14 am
Location: Australia

Re: Buying a Series MM

Postby BLOWNMM » Thu Jun 29, 2017 2:52 am

viewtopic.php?f=4&t=63865
The standard MM motor is a very understressed and breathing restricted motor. The crankshaft and conrods are very robust.and with minor mods will allow the motor to be tuned for performance in various stages up to the modified motor in my MM.
Just as a matter of interest I have had my modified side valve Minor with 4.22:1 rear axle and 185 60 R14 tyres up to 7500 RPM in 3rd gear which is just on 80 MPH.
Bob
Image

jagnut66
Minor Legend
Posts: 1780
Joined: Fri Apr 11, 2008 7:28 pm
Location: Mansfield, Nottinghamshire.

Re: Buying a Series MM

Postby jagnut66 » Fri Jun 30, 2017 9:12 pm

Very interesting and 80 mph from a side valve, wow!
I'm aware that the A series is highly tuneable but I'm surprised you could modify a side valve unit to that extent.
Did you do an article on the rebuild, as you were doing it, detailing all the MODs to the engine as they were added / installed?
I'm sure there are those on here that would be interested in a step by step guide to what you did.
Best wishes,
Mike.
Olwyn Image

BLOWNMM
Minor Fan
Posts: 292
Joined: Tue Dec 09, 2014 6:14 am
Location: Australia

Re: Buying a Series MM

Postby BLOWNMM » Sat Jul 01, 2017 1:12 am

Mike - just a reminder that 80 MPH was in 3rd gear. Have attached a description of the mods to the bottom end. Will make another post re the top end for general info a bit later.
Bob
TUNING A SIDE VALVE MINOR – BOTTOM END - June 2014
The first thing is the crank. If you are going to have the pins and journals ground undersize it is important to maintain the fillet radius on either end of the pin or journal. This must not be less than 2.0 mm. radius. I understand cranks from the first Series E in 1939 to the last MM were interchangeable. In earlier days the Morris motor developed a bad reputation for breaking cranks. This was later found to be due to cranks having been ground U/S with a smaller fillet radius resulting catastrophic failure. The next thing to look at is the rod bolts. Of all the Morris 8 and MM motors I have worked on none had what you would consider properly fitted bolts. They were all a bit loose in both the rod and cap. I prefer to use ARP Datsun A14 rod bolt kit their part no. 102-6002. These are 8.1 mm. shank dia. as against 8.0. The holes in the rods and caps are reamed out to give a light push in fit in the rod and a light tap on fit for the caps. The rods then need to be closed and resized. These bolts are made from Hi Performance 8740 alloy steel and are substantially stronger than OEM Nissan and I suspect a lot better than Morris bolts.
I have built a Morris 8 motor using JP pistons at 0.080 inch oversize. This motor revved regularly to 6000. The weight of one of these JP0201 pistons with pin is 260 grams to which you have to add the weight of the piston rings. The weight of a standard 57 mm. piston with pin and rings is 200 grams. Considering that when the piston and rod nears TDC it is still wanting to keep going up but the crank then has to stop this upward movement and accelerate it back down again. When this happens the total load to stop the assembly continuing to go up then accelerate the rod and piston back down is taken by the big end bolts. At 6000 RPM this force is enormous and occurs 6000 times a minute at TDC and another 6000/min at BDC hence the need for good rod bolts especially when you have increased the weight by 60 or more grams. The stress at BDC is taken by the big end bearing not the bolts. If you wanted to bore say to 60 mm. (3 mm. oversize) using JP pistons the weight would be even more because they only have one cast for their 0201 pistons.
When deciding on what bore size if you intend going over +.060 ( + 1.5 mm. ) the bores should be sonic tested. This is because sometimes a core can shift during the casting process and leave the metal thin on one side. The results of the test will show this. Before the test is done the block needs to be cleaned of all rust by molasses bath, electrolytic or Redi Striping. It might be worth considering citric acid rust removal. This is because the sonic waves or what ever they are cannot distinguish between the parent cast iron and the iron oxide rust scale. Whatever size you choose +3.0 mm. is a reasonably safe limit depending on the piston you use without having gasket problems, and when deciding consider the weight of JP pistons if you are using them. Also there should not be less than 0.080 inches ( 2.0 mm. ) wall thickness left after boring especially if supercharging as the walls may flex allowing combustion gases to bypass destroying the rings.
It is always sound practice to strap the centre main bearing cap. I do this using a piece of 25 X 20 mm. steel bar against a flat ground on the cap. Spacers are then used that are 0.0005 thou shorter than the gap between the cap and strap which gives a slight pre load to support the cap and prevent the crank being punched through the bottom of the sump. The other main things for a strong bottom end is a full balance including the flywheel, clutch pressure plate and crank pulley, good quality bearings preferably Vandervell or Glacier and an oil pump with all the right clearances to ensure maximum oil flow. My crankshaft was a NOS one so I did not consider crack testing. If using an older crank and rods it would be a good idea to have them crack tested.
As a matter of interest if my motor was normally aspirated with a suitable cam and valve springs and twin 1 ¼ S U’s, I would have no hesitation to rev it to 8000 or more RPM. This is because my rods are I beam and were made by Argo, CNC machined and shot peened from 4340 high tensile alloy steel. They also have fully floating gudgeon pins 17 mm. dia. as against 15 standard and are fitted with ARP 2000 series rod bolts. This adds up to an immensely strong rod. The all up weight of one of these rods with cap and bolts is 479 grams against 486 grams for a standard rod, cap and bolts and nuts. This is 7 grams lighter and puts a lot less stress on the bolts. The pistons are also forged from 2618 HT aluminium alloy and at 60 mm. dia. ( 3 mm. O/S ) their all up weight with 17 mm. pin and circlips and rings is 211 grams just 11 grams heavier than standard and 49 grams less than JP’s at 0.080 inch O/S to which you need to add the weight of the rings. All this adds up to a normally aspirated motor that will rev very high or in the case of mine a strong bottom end to take the 15 PSI boost it gets and still hold together and not melt pistons. Another reason for such detail and expense is that if you blow a motor you do not just bolt on your new beaut ported head with big valves etc. Being a side valve you blow all the port and valve work along with the block.
It will be most likely that the 8 mm. threaded holes in the sump and timing cover will be stripped or in poor condition. I always fit ‘Recoil’ stainless steel thread inserts to all 8 mm. threads in alloy parts, and where necessary any other 8 mm. threads ie. water rail, water inlet port at bottom of block, water pump cover at front of block and manifold retaining stud holes. Use an insert 1.5 D long. It is wise to retain the 8 mm. X 1 mm. pitch metric fine for uniformity throughout the motor. It may be found necessary to fit inserts to the head for the alloy thermostat housing bolts whilst you are at it.
The top end and cam are another story for later.
http://www.classiccargurus.com.au/Argo_Engineering
http://www.specialpistonservices.com/company
Last edited by BLOWNMM on Sun Jul 02, 2017 4:21 am, edited 2 times in total.
Image

BLOWNMM
Minor Fan
Posts: 292
Joined: Tue Dec 09, 2014 6:14 am
Location: Australia

Re: Buying a Series MM

Postby BLOWNMM » Sat Jul 01, 2017 2:06 am

Here is the second part re the top end:
TUNING A SIDE VALVE MINOR – TOP END – June 2014
On my motors I have opened up the ports to a maximum and fitted Nissan EXA turbo exhaust valves to both inlets and exhausts. They have a head dia. of 30.5 mm. as against 28.0 for a standard valve which is an increase of 19% area. The stems of the valve need to be cut to length and collet grooves machined. To prepare the block for porting I machine out the exhaust ports to a dia. of 28 mm. and the inlets to 31 mm. square using a 10 mm. dia. cutter to give a 5.0 mm. radiused corner. These increased port sizes relate to an increase of area over standard of 78% for the exhaust and 37% for the inlets. All of these ports are only machined out about 4 to 5 mm. deep. Then the valve seats need to be enlarged to suit the Nissan valve but only roughed out. The reason for these steps is to give the porting guy something to aim for both at both the port face on the block and the valve seat. The port size directly below the valve seat will end up being about 25.5 mm. dia. Don’t hesitate to take metal from the guide to give a good smooth flow to the gases. This is not of to great a concern because there is no side thrust on the valve stem but only upward thrust from the follower. The reason for roughing out the valve seats is if the porting guy slips and marks the enlarged seats then they can be finish cut after the porting. For springs use a Crow spring their part no. 0607. They fit straight in with no mods and are good for at least 7500 RPM with the heavier valves and the cam I am using. The Nuffield manual quotes the standard spring pressure when the valve is closed is 19 lbs. and open 37 lbs. I have measured these lengths at closed at 1.509 inches and open at 1.214 inches. Measurements of a Crow spring increases the pressures to 44 lbs. closed and 72 lbs. open for the same lengths when using a standard cam. The open pressure will vary according to the lift of the cam you use.
The choice of cam is a matter of preference. For head gasket try to get NOS copper ones. They will have been around for donkeys so soak them in water for 24 hours to soften the stuff between the copper so that it will compress OK. If necessary machine the top face of the block and head and when installing I prefer to give the gasket 2 to 3 coats of VHT copper gasket cement allowing drying time between coats. Use assembly lube on studs and torque to 45 lbs/ft. When disassembling the VHT can easily be removed with acetone.
Carburation is best taken care of with twin 11/8” HS1 SU’s. either by a home made manifold or a Monaro Motors manifold if you can source one. To get the best performance from the mods made it is really essential to use a 4 into 2 into 1 extractor type exhaust with a tailpipe diameter of 13/4” all the way. If not using forced induction the compression ratio can be raised by machining the head. The amount removed will depend on the bore size you have chosen. Because my motor is blown at 15 PSI (a little over 1 bar) I have kept the unblown compression to a measured value of 7.03:1 with a 60.0 mm. bore. This raises to over 10:1 with full boost. I have attached a pic of my exhaust headers. Would dearly love to find somewhere to wind it out in top but no roads available around here without the risk of falling foul of the plod.
Bob

Image
Last edited by BLOWNMM on Sun Jul 02, 2017 4:20 am, edited 2 times in total.
Image

RobThomas
Minor Legend
Posts: 2259
Joined: Thu May 11, 2006 10:34 am
Location: Cardiff

Re: Buying a Series MM

Postby RobThomas » Sat Jul 01, 2017 9:16 am

Nice Bananas!

Did you cut much out of the flywheel, Bob? For export markets BMC sold individual ring gears but for the UK they only originally sold replacement flywheels complete. Our 1952 will eventually need a new ring gear and that would be a good time to lighten it.

BLOWNMM
Minor Fan
Posts: 292
Joined: Tue Dec 09, 2014 6:14 am
Location: Australia

Re: Buying a Series MM

Postby BLOWNMM » Sat Jul 01, 2017 10:02 am

Have attached drawing of flywheel mods. Fortunately I have recorded about every dimension on a MM block including valve centres, head stud locations, bore locations and just about every threaded hole - they are all referenced to a common point that being the centre of the No. 1 head stud threaded hole.
Bob
Image
Last edited by BLOWNMM on Sat Jul 01, 2017 12:07 pm, edited 1 time in total.
Image

BLOWNMM
Minor Fan
Posts: 292
Joined: Tue Dec 09, 2014 6:14 am
Location: Australia

Re: Buying a Series MM

Postby BLOWNMM » Sat Jul 01, 2017 10:22 am

Rob - If you cannot source a ring gear there are places here in Oz where they are available.
Bob
Image

Online
palacebear
Minor Legend
Posts: 2186
Joined: Mon May 16, 2016 4:39 pm
Location: Kidderminster, Worcestershire.

Re: Buying a Series MM

Postby palacebear » Sat Jul 01, 2017 12:22 pm

jagnut66 wrote:Good luck with your purchase


Perhaps fortunately there has been no purchase. The black paintwork was heavily microblistered under the superficial shine. The clutch was either badly out of adjustment or just plain s*****d out and the oil pressure gauge only managed 40psi with a cold engine (and about 25psi accelerating up hill in 3rd). As Max suffers from slightly sub-standard paintwork and a worn clutch, I decided the MM would be no improvement. It had a VERY nice interior complete with a working clock, which almost won me over. Common sense prevailed eventually and the search goes on!
Max the Moggie

RobThomas
Minor Legend
Posts: 2259
Joined: Thu May 11, 2006 10:34 am
Location: Cardiff

Re: Buying a Series MM

Postby RobThomas » Sat Jul 01, 2017 1:43 pm

and about 25psi accelerating up hill in 3rd


Wow, that's good! :D

Clutch change isn't hard since you can separate the engine and box even more easily than the later cars. Same basic clutch as the 948 so not expensive. Engine might just be down to tired oil. Biggest worries are rotten floors and rattling engines. Any chance of a link to it, PB, assuming you aren't going back???

PS. Thanks, Bob.

Online
palacebear
Minor Legend
Posts: 2186
Joined: Mon May 16, 2016 4:39 pm
Location: Kidderminster, Worcestershire.

Re: Buying a Series MM

Postby palacebear » Sat Jul 01, 2017 8:26 pm

RobThomas wrote:
Any chance of a link to it, PB, assuming you aren't going back???

PS. Thanks, Bob.


There is no link to the car. Its currently a 'word-of-mouth' thing. The car's owner died very suddenly a couple of months ago. His widow is selling the car, with her daughter-in-law dealing with viewings. They don't feel capable of dealing with classified advertising at the moment. The car is located near the Herefordshire/Shropshire border. I can ask the seller if she is willing to let me give you her contact details.
Max the Moggie

RobThomas
Minor Legend
Posts: 2259
Joined: Thu May 11, 2006 10:34 am
Location: Cardiff

Re: Buying a Series MM

Postby RobThomas » Sat Jul 01, 2017 8:55 pm

Thanks for the offer but it might be best for me not to intrude. Did you get any photos?

Online
palacebear
Minor Legend
Posts: 2186
Joined: Mon May 16, 2016 4:39 pm
Location: Kidderminster, Worcestershire.

Re: Buying a Series MM

Postby palacebear » Sat Jul 01, 2017 9:37 pm

No photos taken. I felt a bit like an intruder today to be honest. A friend of mine is 'in the trade' and a friend of the sellers' family. He came with me today. I suspect he'll end up dealing with the sale on their behalf. If he does, I'll suggest he advertises the car on the forum.
Max the Moggie

sparesman
Minor Addict
Posts: 533
Joined: Tue Dec 25, 2012 7:40 pm
Location: norfolk

Re: Buying a Series MM

Postby sparesman » Mon Jul 24, 2017 7:40 pm

RobThomas wrote:Nice Bananas!

Did you cut much out of the flywheel, Bob? For export markets BMC sold individual ring gears but for the UK they only originally sold replacement flywheels complete. Our 1952 will eventually need a new ring gear and that would be a good time to lighten it.


Rob
We have 3 nos MM ring gears in the club stocks.
Bryan

RobThomas
Minor Legend
Posts: 2259
Joined: Thu May 11, 2006 10:34 am
Location: Cardiff

Re: Buying a Series MM

Postby RobThomas » Tue Jul 25, 2017 7:35 am

Thanks for that, Bryan.

I'll e-mail for more info. I'm sure there are a few other bits I'd like to get hold of.

Cheers

Rob

irmscher
Minor Legend
Posts: 4405
Joined: Wed Jul 14, 2010 10:53 am
Location: South Manchester

Re: Buying a Series MM

Postby irmscher » Thu Jul 27, 2017 12:54 am

Why spend all that money :lol:

RobThomas
Minor Legend
Posts: 2259
Joined: Thu May 11, 2006 10:34 am
Location: Cardiff

Re: Buying a Series MM

Postby RobThomas » Sat Jul 29, 2017 12:40 pm

Well, I was thinking of buying a late Convertible but the bloke selling it never seems to switch his phone on. :D


Return to “Series MM Register”

Who is online

Users browsing this forum: No registered users and 2 guests