24 replies to this topic

[James_1]

Posted a question RE shot peening in the general section.

http://www.theminifo...3-shot-peening/

The big order arrived from Mini Spares this morning and all is looking good. I'm going to have a good cleanup in the garage and get the 'new' gearbox stripped, cleaned and checked. There was some metal floating about in the oil so I want to get it all cleaned out before putting new bearings anywhere near it. I also need to find which final drive it has fitted. At the moment the car has a 3.44 which is okay but tiresome on the motorway with 13s and fairly low profile Yoko A008s so I am considering changing the ratio as they don't seem to expensive. Apparently the 2.9 is best?

[coopdog]

Posted a question RE shot peening in the general section.

http://www.theminifo...3-shot-peening/

The big order arrived from Mini Spares this morning and all is looking good. I'm going to have a good cleanup in the garage and get the 'new' gearbox stripped, cleaned and checked. There was some metal floating about in the oil so I want to get it all cleaned out before putting new bearings anywhere near it. I also need to find which final drive it has fitted. At the moment the car has a 3.44 which is okay but tiresome on the motorway with 13s and fairly low profile Yoko A008s so I am considering changing the ratio as they don't seem to expensive. Apparently the 2.9 is best?

i have a 2.9 and i find the accelaration good in my car and the top end,
found no reason to change,
also i can hold on to the gears and go up pretty much anything in 4th :)

[James_1]

The gearbox is almost finished now. I've decided to stick with the 3.4 that's in it at the moment for now so I don't have to worry about messing around with finding a good replacement diff, rebuilding it and getting the speedo reading correctly. It's on the list of things to look out for and I may change to a 2.9 when the engine next comes out.

My digital scales have arrived too and seem pretty good but only go to 500g - I should have checked the weight of the con-rods before I bought them but they were only a fiver.

The big end weight on the polished rod is down to 456.4g compared to 463.3g on the standard rod and the little ends are 125.5g and 134.8g respectively so there has been a fair bit of metal removed.

Photos to follow.

[James_1]

Finished the gearbox rebuild and I've stripped down the reconned 12G940 head and port matched it. I was really shocked by how bad the exhaust ports are. I was able to grind out another 10% before they matched the gasket! The inlets were better but needed some work further down the port to smooth things out. With that done I gave the valves a wizz in the drill to clean them up and gave the head a coat of MOWOG green paint.

I'm interested to know how much power a simple port match will gain, there was a lot of metal removed!

EDIT:

I asked at CCK Historic about shot peaning and was advised that their engines run with just lightenened and balanced rods, not peened so I'm going to leave them for now unless I can find somewhere.


Ported head


Good crank


Shiney new gearbox

Edited by James_1, 26 June 2012 - 08:00 PM.

[James_1]

The engine is out - I'd forgotten how much I hate roll pins and CV joints! I've taken the head off and the pistons are a little coked up (the head was fine tho) and the bores are in perfect condition.

I know it's going to be frowned upon but I'm hoping to take the pistons out, clean them and refit without removing the rings so they end up back in their original bores and can carry on as before. Unless someone can give a good reason for coughing up another £60-odd for new rings and then whatever the honing comes to I can't think of any good reason why not to do this.

Sadly the pistons are, as I suspected from the engine number, flat top. Interestingly, being a bottom of the range 'doesn't even have a radio' City X, the car should have been fitted with a low compression eco engine from the factory. Good old BL.

I just need to figure out something exhaust wise. The exhaust I've got is only 2 years old and in very condition but it's restrictive. It's not quite as bad as a Mini peashooter as it's got a slighter larger bore and the cast LCB but it isn't great. With Metro sports exhausts not to easy to find I'm wondering if making one may be a solution.

James

Edited by James_1, 28 June 2012 - 04:35 PM.

[MiniElliott]

Are you sure the engine is original for you car ? Also I wouldnt take the pistons out and not fit new rings. I decided to simply not take the pistons out and take the risk.

Edited by MiniElliott, 27 June 2012 - 11:46 PM.

[James_1]

The engine is now partially stripped and in remarkable condition. It has covered 40k since 1984 but doesn't show it. The cam bearings are unmarked, as are the mains and big ends and the crank is as new. The tappets had very minor pitting and have been binned. The simplex timing chain was still tight with no slack and the tensioner is as new.

Surprisingly, given the state of the rest of the engine the oil pump was in a terrible state, one of the worst I've every seen with deep scoring on every surface. This must be the source of the low oil pressure when warm.

The plan as it stands is to strip the engine fully and remove the core and gallery plugs to fully clean the block, then tap the block and fit set screws in the oil galleries. I also plan on modifying the main bearing oil feed to match the bearing. The backplate and chain cover will both need minor alteration to allow fitment of a duplex timing setup.

Given how well the engine has lasted I now plan on using the existing rods rather than the polished set and just balancing them. As for piston removal I'm going to ask in the tech section and see what peoples opinions/experience is.

James

EDIT: Asked about rings/pistons etc http://www.theminifo...conrod-removal/

Edited by James_1, 28 June 2012 - 11:37 PM.

[coopdog]

youll also need to knock a bit flat on the timing chain cover for it to fit

[James_1]

Thanks coopdog, I've gone one already modified from an old build :)

[James_1]

Well, it's built, in and running at last!

I found now real wear to any of the bearings and all were well within factory tolerances when checked with plastigauge so I reused them. I removed the pistons and noted down the orientations of the rings for reuse. The pistons were then balanced. All the parts were cleaned and the block completely stripped. The oil gallery bungs were removed and taped to 1/4BSP. The block was then cleaned with gunk, then a pressure washer before being dried out and coated in WD40.

The engine was rebuilt with an the MG Metro cam which was 3' out when checked so an offset woodruff key was needed. I timed the cam to 110' after asking on here as there are various numbers floating around for this cam. A new timing chain on duplex gears was used using the original tensioner which was unmarked.

I used the original rings so have a set of STD rings that I need to send back/sell on.

Top end wise the head was stripped and gasket matched then cleaned and reassembled. The bypass pipe was taped and blocked. The valves are recessed to enlarge the chambers to around 22.5-23cc giving a CR of approx 11:1.

I cut the inlet off the cast manifold and ground down the top to give clearance. I am currently using an MG Metro Turbo alloy inlet manifold that also needed a lot ground from underneath to clear the exhaust. This meant breaking into the water jacket which is a shame but I wasn't planning on running a heated manifold anyway. The flanged also needed a lot of filing to match the cast flanges. Finally it was gasket matched, as was the exhaust manifold.

The engine is currently using the original HIF38 to get it going but I'm planning on testing a series of carbs to get the best for the engine. Ignition is a standard Lucas with Accuspark. I suspect that the advance will need tweaking.

After an initial run in for 10 minutes at ~2000rpm to bed in the cam and re-torquing the head I spotted the clutch release bearing sitting on the workbench so that was a wasted hour. More than worth it when I finally got it running though, it really pulls well and shouldn't need much in the way of running. Just needs a very good tuneup and check over tomorrow.

I bought the 'Cooper S' type relief spring and a ball bearing instead of the standard plunger which is now giving me an oil pressure when cold close to 100psi which seems rather high to me so I'll be investigating that further tomorrow. It doesn't go below 60 when hot which is good though.

James

Edited by James_1, 11 July 2012 - 09:29 PM.