A series budget engine rebuild

[garellikatia]

Picked up the crank today £150 all in for 10thou of the big ends and main bearings. 

 

 

 

Happy with that. On the down side. My 12g295 head looked to be in worse nick than I first thought. The valves were Really sunk into the head. I will need to go up a valve size for it to get an effective seat. 

I therefore decided to take the mildly ported 12g202 1098 head to the machine shop. They're going to take off 40thou and recut the seats. 

I've left them with the bigger 12g295 valves to fit them to the head. 

 

So far the cost has been:

Engine: £60

Pistons £100 ish

Rebore £120

Crank £150

Next on the shopping list is:

Crank bearings

Camshaft

Assembly lube

Piston ring compressor. 

The whole build will be estimated to come to around £700. I'll use my original gearbox that will just need new baulk rings.

[MiniMinorMk3]

With the dished pistons you would have needed a big skim of the 295 head to get any sort of decent compression ration. And with a big skim you risk going into the water ways.

They are still in demand on so you will have no trouble passing it on either on Ebay or one of the Mini forums.

What sort of cam are you thinking of using?

[garellikatia]

 Absolutely! It would have needed at least an 80 thou skim to get it to something like. 

The 12g202 head had 26.1cc chambers so a 40thou skim I hope will reduce them to just over 23cc ish

Taking into consideration I should get 8.8:1 with an estimated 20thou   piston deck height (before i stripped it) . But I haven't got the new pistons in the block yet to fully work out piston depth in the block. I might be able to get 10 thou skimmed off the block too to get the compression up a bit more which would get it to 9.07:1

Which still isn't as high as I'd like. 

Thanks that's reassuring,  I've put it on FB see what happens. Although I may just keep It and rebuild a 998 bored out with flat tops and bigger valves sometime in the future. 

Im thinking the minispares evolution 001 cam. I was contemplating the swiftune sw5 or Kent 266 or even MG metro. But I'm trying to keep to a budget build so probably I'll go with the minispares one. 

 

[Stinkwheel]

2 hours ago, garellikatia said:

Picked up the crank today £150 all in for 10thou of the big ends and main bearings. 

 

 

 

Happy with that. On the down side. My 12g295 head looked to be in worse nick than I first thought. The valves were Really sunk into the head. I will need to go up a valve size for it to get an effective seat. 

I therefore decided to take the mildly ported 12g202 1098 head to the machine shop. They're going to take off 40thou and recut the seats. 

I've left them with the bigger 12g295 valves to fit them to the head. 

 

So far the cost has been:

Engine: £60

Pistons £100 ish

Rebore £120

Crank £150

Next on the shopping list is:

Crank bearings

Camshaft

Assembly lube

Piston ring compressor. 

The whole build will be estimated to come to around £700. I'll use my original gearbox that will just need new baulk rings.

Pretty good value really, I mean I know your own time has gone in but it’s worth having a really fresh, better performing because of upgrades, engine at the end of it and the smug/ satisfaction levels are brilliant as well 

[Tommyboy12]

I do love a good A-series build. Not sure how I missed this thread. Looks like a good build so far. Im glad you got the crank ground as that didnt look healthy despite being in tolerance.

The risk of skimming the head depends on how much has already been taken off. Taking 80 thou off a unskimmed head isnt as much of a risk vs. an already skimmed one. You can take a fair amount off the small bore A-series head though

[garellikatia]

On 04/12/2024 at 19:48, Stinkwheel said:

Pretty good value really, I mean I know your own time has gone in but it’s worth having a really fresh, better performing because of upgrades, engine at the end of it and the smug/ satisfaction levels are brilliant as well 

Absolutely,  even the potential £100 loss on the 12g295 head taught me  a valuable lesson in valve seating etc... 

I can't wait to get it properly together that first start is going to be so satisfying.... I hope 😂 

[garellikatia]

3 hours ago, Tommyboy12 said:

I do love a good A-series build. Not sure how I missed this thread. Looks like a good build so far. Im glad you got the crank ground as that didnt look healthy despite being in tolerance.

The risk of skimming the head depends on how much has already been taken off. Taking 80 thou off a unskimmed head isnt as much of a risk vs. an already skimmed one. You can take a fair amount off the small bore A-series head though

Thanks mate  to be honest it was your thread that got me back into minis. 

Aye I did measure down the rocker oil feed on the head which was 2.59" deep if my memory serves me. That would suggest that with the head been 2.75" I'd have around 160thou from the head face to the oil hole. With a safety margin of 50 thou I'd essentially have 110 thou to take off.

Hopefully the 12g202 isnt too bad despite lower compression than wanted. If it is I cam just whip it off for another skim. 

 

[garellikatia]

Nothing too exciting tonight but before I fit my pistons to the conrods I measured the ring gap.

I'd like to have 0.0003" of a gap per Inch of  bore size. But I went for 0.0004" as a safety margin . 

This would suggest that with a bore of 2.582 inches I should have 7.756 thou of ring gap. 

Its suggested by many of the mini gurus that the maximum ring gap should be 0.009 " per inch of bore size. So effectively 23thou. 

All of the rings so far are measure 11 thou gaps so happy with that. So that should equal the same blow by on each cylinder.

 

 

 

 

[garellikatia]

Little update, 

I fitted the crank and tested the end float with feeler gauges. Reading 6 thou of movement, backed up by my DTI According to the forums it can be acceptable but there's also varying trains of thought.  

I therfore followed the sensible suggestion of ordering thicker thrust washers. I will add these to one side of the crank which runs next to the centre cap. 

This will reduce the end float to 3 thou of movement. 

 

[garellikatia]

On the way from minispares is a new cam and adjustable vernier duplex timing set, followers etc...  

I've also bought some proper assembly oil as the gear oil I'm using isn't tacky enough to prevent a dry start. 

Once I take the crank apart again I will coat everything liberally in it. 

Note: the bearing shells themselves actually go in dry. Only the frictional surface that makes contact with the crank journals gets lubricated. I've seen a couple of engine assembly videos where they lube the rear of the shell but this can apparently risk a spun bearing. 

[tooSavvy]

10 hours ago, garellikatia said:

I've seen a couple of engine assembly videos where they lube the rear of the shell....

I have seen Utoobs where *Toyota motors are re-assembled with coke tin shimming behind the shells 😮.

I have built a few Imps = cannot think why anyone would oil behind a shell.

Keep @IT

🚙💨

[garellikatia]

20 minutes ago, tooSavvy said:

I have seen Utoobs where *Toyota motors are re-assembled with coke tin shimming behind the shells 😮.

I have built a few Imps = cannot think why anyone would oil behind a shell.

Keep @IT

🚙💨

Absolutely. It goes against all logic doesn't it. But It was only the comment section of utoob which made it apparent to me. I guess just because these guys are pros they can still make mistakes or bad habits.  

[Tommyboy12]

Properly assembly oil is well worth it. Priming these engines can be a bit of a pain so it's important for the first run to have something there. Personally my tolerances are based on build type. A more highly strung hotter engine needs bigger gaps as things get hotter and expand more, especially piston rings. Closer to standard can definitely nip up the tolerances

[garellikatia]

On 17/12/2024 at 13:33, Tommyboy12 said:

Properly assembly oil is well worth it. Priming these engines can be a bit of a pain so it's important for the first run to have something there. Personally my tolerances are based on build type. A more highly strung hotter engine needs bigger gaps as things get hotter and expand more, especially piston rings. Closer to standard can definitely nip up the tolerances

Absolutely.  Some arrived yesterday and I can already tell the difference in viscosity. So much better.  Just annoying now having to wait for parts to arrive

 

[garellikatia]

So I noticed an ever so slight spec of grinding dust in the engine block. As small as a bit of kids glitter.

Despite having already cleaned it a bunch of times. I'm now flapping about the cleanliness of the block.

This evening I will be stripping it back bare and cleaning everything again.

I couldn't bare to think of wrecking a new engine because of some rouge swarf 

[comfortablynumb]

Just to add to this, following on from @warninglights comment on oil pumps, and @Merryck, and everyone else who might be doing this.

We've got to the stage of rebuilding the van engine, new oil pump, and guess what, oil pump is thinner than the original, and the bolts are bottoming!

We wouldn't have noticed it without the input, so thanks very much for that, it's saved us much grief further down the line 👍

[warninglight]

Glad my hard won experience from 2009 has helped someone!

[Tommyboy12]

Its crazy that they still havent fixed the shallow pumps. I also suffered it when building my 998 'Cooper' spec engine. I actually didnt realise I had a shallow pump as I didnt feel movement in the pump and ended up changing it in situ without removing the engine ater about 2000 miles. I wont be doing that again and its coming out next time!

[garellikatia]

1 hour ago, Tommyboy12 said:

Its crazy that they still havent fixed the shallow pumps. I also suffered it when building my 998 'Cooper' spec engine. I actually didnt realise I had a shallow pump as I didnt feel movement in the pump and ended up changing it in situ without removing the engine ater about 2000 miles. I wont be doing that again and its coming out next time!

I think at one point BMC/ rover were just using up what fit and in the "parts bin".

I might be wrong but I'm sure my brake servo pipe had an imperial union on one end and a metric on the other.

On something so safety critical it seems barbaric. 

 

 

[garellikatia]

I've been thinking about cylinder heads again today. I'm really tempted to get the 12g295 skimmed and use it until I can afford to get bigger valves and unleaded seats sorted on it.

Its a weekend car but would hopefully get it on the road while I can save the cash to buy all the proper bits and send the head away to a pro.

This is the worst of the valve recession although putting liquid in it. It keeps a seal. 

 

[garellikatia]

I'm glad I stripped the engine again. I found another few bits of swarf.

I'm unsure as to whether something so small could cause major damage. But I reckon I'd be surprised. 

 

[garellikatia]

I also double checked the depth of my oil way plugs. They're 12mm deep. I also checked whether this would impeed the oil way that runs to one of the main bearings. Which it doesn't. 

I can now seal them in. 

Again noddy stuff but I'm scared that any little thing over looked will wreck the whole thing. 

 

[garellikatia]

I've bought the duplex vernier type adjustable timing gear from minispares. And if you don't use countersunk screws the chain can catch on the bolt heads.

Couple of quick easy jobs tonight, countersinking those holes on the timing plate.

I then fit some waterway Welch / core plugs. Excuse the lathering of sealant. I will clean that up when dry.  All you do is slot them in place and then hit the convex part with a punch to force the plug into position, and flatten it out a little.

 

 

[garellikatia]

Not a great deal of progress. Painted a few things but was waiting for my thrust washer to arrive since 13th Dec

Stripped the dizzy and realised it has 11 degree weights, suggesting it has 22 degrees of advance plus what ever its set at. The springs are quite springy.

I will spin it up In a drill with a tacho to measure what RPM I get full advance. Then I'll be able to trial and error some different springs , and curve it to my engine. 

 I managed to bag a new old stock engine crane for £60 which I had to pick up an hours drive from me. 

On the down side I got flashed by two consequtive gantry speed cameras on the way back from collecting it. Stupidly It was a variable speed area and I was doing 70 as there were no signs visible to suggest otherwise (not that I could see, but accept full responsibility and accept this is my fault).

On a plus side my engines nice and snug in the dining room, hope the family have enough room for Christmas Dinner. My wife is an absolute gem. Must be hard to live with car bits everywhere haha

 

[garellikatia]

finally got the Cam timed in properly. 

Funnily (Although not at the time) I spent until 3am one night timing the cam in very accurately.

Woke up about 7am to spend the day with the kids. Then whilst looking over admiring the block I noticed the pushrod was in the wrong hole.

I'd timed the cam in on the exhaust pushrod and not the second one along (inlet) pushrod. Hahaha

I also realised that I had been checking my tolerances with a metric DTI gauge. Not imperial. So went about checking all my tolerances again. 

Timed the cam in properly

But at least these things happened now and not when the engines in the car. 

I've dropped my spare (uncracked) 12g202 1100cc head off at the machine shop for the valves to be recut.

They're charging £40 which I'm happy with. Albeit using grinding stones. Not cutters. 

If it comes back without any cracks I'll probably get it skimmed by 80thou to get the compression up. Which will be about  another £100. 

All in all a steady yet productive period

 

 

[garellikatia]

Also started taking the engine out of the mini. I was tempted to overhall  the gearbox as the baulk ring has gone meaning I double de clutch on second. This has never been an issue for me. So I'm more inclined to get the engine back in and sort the gears at a later point.

The big hassle is getting the car in and out of the carcoon to work on it,  but I'm extremely lucky having that and a garage sl first world problems on my eyes. 

 

[Tommyboy12]

I would do the gearbox now. More power will only accelerate wear on an already worn out gearbox

[garellikatia]

On 11/01/2025 at 19:50, Tommyboy12 said:

I would do the gearbox now. More power will only accelerate wear on an already worn out gearbox

Thanks mate  I decided to strip it and with exception of the idler gear it looks pretty good.  So hopefully just the baulk rings that need seeing to

[garellikatia]

So I got the engine out and the engine bay is in surprisingly good condition. As is the gear box. 

The only exception is the idler gear that has a huge chunk out of one of the teeth.