156 replies to this topic

[miniBrain]

analogue_radio & tony, thanks for looking and taking the time to comment, greatly appreciated

[F1L8EY]

brilliant thread, good skills. safe clean work and very informative.

please keep it up

Filbey

[miniBrain]

Thanks mate, will try!!

[miniBrain]

Hi folks,

I mentioned earlier that my engine had poor oil pressure and was producing a lot of blue smoke just after startup. I was sure the smoke was due to oil being drawn in through the valve guides/seals so I took the head off and took it down to an engine builder (Blackburn Bros. in Preston) for checking/repair.

The state of the head was fairly typical, lots of carbon etc,:



Blackburn Bros cleaned and stripped the head and checked the guides. They said that the guides were fine and were pretty sure the oil burning was due to worn piston rings. They also said that Mini heads rarely caused oil burning issues but the A-series had a problem with oil bypassing the rings, which is why BMC made a number of changes to the pistons in its early life.

So they just gave the head a de-coke, fitted new seals and lapped the valves:



I was thinking of buying a recon head from Minisport for £200+ but this cost me £30 and achieved the same result!

So, no option now but to strip the engine. Here's some of the worn parts that I found. Firstly the oil pump was in a right state – it had the texture of a pumis stone!





Not surprising really when you consider the Mini engine shares the engine oil with the gearbox. It shows you how important the oil filter is for protecting the rest of the engine!

The bearings were all pretty smooth other than one of the middle mains which was starting to break up:



There was about 30 thou end float on the primary gear when there should be about 3 thou. This was due to the “c” washer that holds the gear on the crankshaft:



With a new “c” washer, the end float was about 12 thou but should be less than 6. The thrust washer was 0.112”, so I needed a new one at 0.118. I opted for a .118" to .120" primary gear thrust washer, to give 4-6 thou float.

There was some pitting on the cam followers, so these were replaced also:



The crank thrust washers were worn on one side only:



The pair on the left were still at the original thickness of 90 thou. Whereas the pair on the right were at 86 thou, i.e. 4 thou undersize. I measured crankshaft end float at 5 thou, so a new std size thrust washer set would do.

The crankshaft and camshaft were in good condition – no scoring or pitting – so I opted to reuse these as standard. I don't have the equipment to measure wear in the bores, but there was no sign of significant damage so I opted to stick with the standard bore and pistons. Might be a bit risky to avoid a rebore but when you consider the cost of pistons etc, its just too pricey for me at the moment.





Here's the rebuild parts list:

FW Thornton:

Piston rings and bearings from the various mainstream suppliers – Minisport Minispares, etc – vary greatly in price, rings from about £50 to £150, so I wasn't sure what I would get. Instead, I went to FW Thornton, as I thought they may know a bit more about engines than the “ordinary” parts suppliers. Thorntons supplied:

Goetze rings (3 compression rings + 1 oil control)
Glyco main and b/e bearings
Plus crankshaft thrust washers

Minispares:

Oil Pump Spider 2 Bolt (GLP141)
Flywheel Keyway - Pre Verto (88G508)
Primary Gear C Ring On Crank Genuine (22A319)
By Pass Hose Kevlar "S" 1275cc Only (AEG484)
By Pass Hose Clip (3H2963)
Performance Cam Follower (2A13EVO)
Camshaft Gear Locktab (2A759)
Head Gasket Set With Std Copper Head Gasket 1275cc (AJM1140MS)
Primary Gear Thrust Washer 1275cc .118" To .120" (DAM6488)
Crank Pulley Lock Tab (12A398)
Timing Cover Oil Seal All Pre 1992 (88G561)
Clutch Oil Seal Upto 1992 (13H2934)
Block Gasket Set All 1300 Except S (AJM206MS)
Duplex Timing Gear Kit (C-AJJ3323)
Flywheel Bolt Locktab Pre Verto (22A1155)

Plus a set of ARP big end bolts from ebay at £75!

The rebuild was pretty much drama free, just followed the Haynes manual plus the excellent engine build thread on the engine projects page. Used Redline assembly lube on all bearing surfaces plus cam lobes.

I have a cheap torque wrench and I found it pretty useless for lower torque settings – far too inconsistent. So I use one of these from Machine Mart instead:



Seems to work well – I can use a large breaker bar for high torque and a normal-size ratchet for small bolts at lower torque settings, making it a lot easier to set the torque accurately and less likely to stretch a bolt or strip threads.

Although its not a performance build, I opted for the duplex timing gear as it is so cheap (about £28). I've not fitted the tensioner:



Note that you have to fit countersunk screws underneath the crank sprocket where there were bolts previously. I used thread lock on these and also “staked” the head (whack it with a centre punch near the edge to dent it and prevent it turning).

Pistons refitted and big ends torqued-up:



Nice new copper head gasket fitted. (Not sure about these yet – some good stories on the forums about these - and some bad.



Before re-fitting the engine to the car I set the timing statically as you can turn the engine on the flywheel or crank pulley bolt.

I used cheapo oil (£9.99 – Wilkos) for running-in. I've done about 60 miles and so far the motor seems to be running strong and smooth. Oil pressure comes on instantly, it runs cool, the plugs are about the right colour and there's no smoke from the exhaust.

Thanks for looking!

Edited by miniBrain, 17 August 2013 - 09:25 AM.

[grahama]

Hi MB,

looks like my engine rebuild a while back, you have done a nice job there. I had a right job finding new piston rings for mine, how did you go on with yours?? It sounds like you have the engine in and running, did you test it before fitting?? Also how do you set the timing statically, I take it that is for sorting the dizzy position??

Graham

[miniBrain]

Hi Graham,

On the rings, Thornton seemed to know exactly what was needed for this particular engine/piston so I went with them. They fitted the pistons exactly with no noticeable gap. I set the timing by firstly setting the crank at the required advance - e.g. 10 degrees BTDC. Then with a battery/bulb connected to the dizzy points (or some other method of indicating if the points are open or closed), turn the dizzy body until the points just open. Then tighten the dizzy bolt a little and crank the engine round until it approaches the required advance. Slowly turn the engine until the bulb goes out - i.e. points open - and check the advance. If its within 2-3 degrees of the specified static advance, that's probably fine for first start. You can also check to make sure the dizzy drive is correctly fitted. At near TDC the rotor should point roughly at 2 o'clock (no. 1 cylinder). Mine was initially pointing at 8 o'clock meaning I had the dizzy drive 180 degrees out!

That's about all the testing I did before fitting. So long as there's fuel, a spark at the right time and a charged battery, what could go wrong?

Bob

PS
What condition was your oil pump in after you stripped yours? Just curious to know if the sort of wear on an oil pump like mine is typical or not?

Edited by miniBrain, 15 January 2013 - 02:45 PM.

[grahama]

Hi,

thanks for the timing info will cut and paste so I don't forget where the info is !!

Didn't take a pic of my oil pump but checked it and tollerences were bang on so reused it. Surfaces were smoothe and shiny, no pitting at all, looked brand new and the surfaces were polised like the cam journals. Looks like yours has had a very hard life and there seems to have been some metal spinning in there along with the oil. Better finding it though and replacing it.

Graham

Edited by grahama, 29 December 2012 - 11:16 AM.

[miniBrain]

Hi Graham, thanks for the oil pump info. I think my diff suffered a catastrophic failure in the past as there was a pinion gear tooth lodged in the selector mechanism when I stripped it earlier in the year. So its probable that this oil pump was damaged by the remnants of the diff failure rather than through general wear & tear.
Bob

[munkey26]

Hi Folks,

Not much of an update but just a couple of photos showing some recent mods:

Upgraded performance with 1275GT stripes :




Bought a new pressed ali number plate - so much nicer than the black on yellow (but not sure if its legal for a '77 car? )




The engine is getting worse in terms of burning oil through the valve guides. So much so that one of the plugs regularly oils up and won't spark, so I need to take it out and clean it to get the engine running properly. Next big step is therefore to get the engine out over xmas and get the head sorted as well as replace the oil pump, bearing shells, piston rings, etc.

That's it for now, thanks for looking!

Looks great - well done on the car as they are getting rare now.

Noticed that the old plates are a different reg number to your new ones is it 334R or 324R???

[miniBrain]

Thanks Munkey26 - plates have been "photoshopped" to protect the innocent! I always hide or disguise the proper number - don't really know why, its just a habit now.

[Andymini]

What a great build I have just read this from start to finish. Brilliant top work there. What's your trade? Currently in the process of buying a GT myself. To hopefully get to the same standard.

[miniBrain]

Hi AndyMini, thanks for the comments, much appreciated. I'm not from the motor trade, just an enthusiastic amateur, with more enthusiasm than skill! Hope to see a project thread soon for your GT.

[miniBrain]

Hi Folks, I've not posted in a while mainly because the restoration is essentially finished and I'm just enjoying driving the Mini. Man, what a great driver's car the Mini is - just love it!

 

 

Shortly after I'd rebuilt the engine I decided to tune the car a bit better now that I had a good base to start from. Minisport supplied an AAV carb needle with the stage 1 kit which was hopelessly weak at any revs above 2000 and just wasn't usable at all. After some internet research (http://www.mintylamb.co.uk/) I decided to switch to an AAM. What a difference this made - the car just ran so much better - I could floor the throttle and it pulled like a train with no hesitation.

 

However, this needle proved too rich and the exhaust was quite sooty and was only getting around 25mpg (with "spirited" driving). Of course the best way to set the needle correctly is on a rolling road. But since I have future mods in mind (bigger single carb or twin) I didn't want to keep forking out £100+ a go for an RR session. So I fitted an O2 (lambda) sensor so that I could see whats going on.

 

 

4824

 

This is a universal 4-wire sensor that you can buy for about £20 plus £3 for the adapter. Its wired up as follows - basically the white wires are the heater circuit and the black and gray are the sensor output.

 

 

I understand the heater circuit should be switched which I think is just to increase the longevity of the sensor. Instead of switching the current I added a current limiting resistor (5.6ohm). The sensor is then simply connected to a voltmeter.

 

 

The above picture shows a voltage of 0.94 volts with the engine on fast idle – well on the rich side. As you are probably aware, around 0.45V indicates an air/fuel ratio of 14:1 – i.e. bob-on. Over 0.45 and its too rich, under and its too lean.

 

I've now fitted an AAU needle which sits between AAV and AAM. The engine runs fine with this except for a slight hesitation on light throttle/low revs – the O2 sensor readings indicate its too weak low down. To be honest displaying the lamda voltage on its own isn't enough – I need to record the lambda voltage along with RPM and manifold vacuum so that I can see what the air/fuel ratio is under accel/decel and cruise and at various revs. So I might be adding a data logger in future.

 

Thanks for looking!

Edited by miniBrain, 17 August 2013 - 05:37 PM.

[malcs_miniturbo]

Love this gt I was reading looking through your thread the other day

[miniBrain]

Thanks m8, really appreciate the comments