22 replies to this topic

[Jimmyarm]

Hi All,

My first post have been snooping around as a guest for a while and seems like there are lots of knowledgeable people around !

Anyway to the issue in hand, at the weekend my and my mate were driving his mini up to our local tescos and just when he pulled into the carpark the engine started misfiring like a *&^*&^ and shaking like you wouldnt believe.

After about half an hour of us poking around we decided that the gasket had blown, or one of the valves had dropped. A quick call to the AA man (who turned up in less than 5 mins as he happened to be on his break in that very carpark!) confirmed our suspicions, no compression at all in No 2 cylinder and No. 3 was no firing. The mini was towed back to my mates house.

Following a lot of swearing and general greasiness the head came off on Sunday and guess what, the worse of the two problems was revealed. The head gasket was fine but No 2 cylinders intake valve is sitting a good 2mm below its seat and there is visible bendiness inside. We are obtaining a spring compressor to take it out to assess the full extent of the damage.

My queries are;

- Is it possible to fit a new valve seat at home ? I cant seem to find much info on this around, and what I have read would indicate that this needs to be done in an engineers/specialists shop.

- If the valve seat is (hopefully) undamaged, is it ok to obtain a replacement valve and using the appropriate paste etc, install this ?

- It has been considered that fitting a stage 2 or 3 head may be an option but my little Clive Trickey book makes porting and polishing look fairly simple to a minor extent (ie matching up the ports with the manifolds and general smoothing, nothing too major like grinding out the combustion chambers), has anyone attempted this and what tools did you use for the grinding, I have one of those little multitool jobs and with the right bit, I reckon it will do the job perfect ?

Anyway, all advice appreciated, Happy Miniing!


Jimmy

:tongue:

[vasi]

Welcome to the forum...

You probably don't have the tools needed to replace the valve seat, better take it to a machine shop.

If it's undamaged, then yes, even with a hand grinding tool, some paste and a little patience you should be just fine.

A dremel (or similar clone) will realisically not be powerful enough to do porting / chamber work. Better to invest in a die grinder and some carbide bits. You can buy electric die grinders if you don't have a compressor.

[Jimmyarm]

Hi Vasi,

Thanks for the response

Will have a go with the little Dremmel thing to see how it goes, we want to keep the cost of the operation down to a minimum so if it is C**p I will see if we can hire a die grinder from somewhere.

Hopefully should get the valve out later, I'll try and get a pic up for y'all to see

Jimmy

[Guess-Works.com]

I did mine with a dremel, took f'ing weeks ! but does give a little more presicion than a die grinder...

[Jimmyarm]

Lol, I better get started then ! We were hoping to get her back on the road over the weekend !

I got the tool for doing some mods to a HS4 we got off ebay, the metal on that is quite soft though

If you guys are interested I can put pics up as I go through the carb modding Not doing too much too it, just flaring the intake end, knife edging the choke plate and making it super shiny !


Jimmy

[Hagar]

I've been playing with a 12G202 head and a ' toy' rotary tool. I got the head for nothing and the tool was AU$30 on special at Supercheap (think:Halfords). I have no experience porting and polishing, all info used was found on-line. I'm not trying to turn the Mog into a rocketship, just trying to get a bit more from him.

Starting with the head full of mud wasp nests (it had been on an engine in a shed with the plugs and manifold studs removed, so the face is good, but chambers rough), I found the rotary tool to be more than adequate at removing cast iron quite quickly. In fact it was almost TOO fast. The trick seemed to be to use virtually no pressure and not quite maximum speed. The supercheap grinding stones were ok, but the moment you put too much pressure on them they wore down to the shaft.

These pice are from partway through the exercise.



Fully expecting the whole experiment to be a dismal failure, I was pleasantly surprised at how smooth I was able to get the chambers and ports on just the first pass. I'm not finished yet, need to do a light polish and have the head skimmed (apparantly 60thou) to maintain compression ratio. I'll be interested to see if it makes a difference, but if it doesn't I'll be out about $100 for the whole exercise.

[Jimmyarm]

Hey Hagar,

Looks good I had a quick go this evening on a bit of the head and it seemed to work ok, need to get some decent bits though...

Will try and remember to take the camera up to his tomorrow so I can take a pic of the head and the busted valve, we didnt get hold of a spring compressor yet so its still in there !

Been Polishing up the HS4 with the rotary tool, makes light work of that Will get some pics of my super shiny Dash pot too

Jimmy

[Guess-Works.com]

Don't polish too much, as this will prevent the eddies from forming in the air flow which helps the air/fuel mix..

[Jimmyarm]

Hey Guessworks,

Only the outside of the carb is getting the super shiny treatment The main tube bit is just getting a light clean and enlargement at the intake end.

Am pretty impressed with this carb, cost me about £20 including postage off ebay and apart from some slight cosmetic damage on the outer surfaces it is in perfect working order

Jimmy

[BMV]

Fitting new seats is not a job that can be done at home. the old seats need cutting out and new seats pressing in then the valve and seat need cutting.

moding the carb on its own is not going to see any performance increase, taking it too big will reduce power, and porting heads is a long slow process requiring something a bit better than a dremmel. Its not about just opening the bit of the port were it joins the manifold, there is a lot more to it than that. Try looking in vizards big yellow book for info.

[lepeemp]

I found a cheapo dremel clone in woolies with flexi shaft for £20 and with Aluminium oxide bits(proper dremel ones) it took about three days to vizardise a head,for that price and £20 for the head its well worth having a go.

[Jimmyarm]

Funny how some peeps say that it cant be done with a dremmel or similar (who appear to have not attempted it), and then there are peeps that have 'actually' done it with one ! I have made my own mind up here and KNOW that it can be done as I started having a go the other day, just need slightly better bits and it will be fine.

I dont particularly want to spend £100 on a Die cutter that I will only use once or twice when I have something that may be slower but still works adequately for my needs.

BMV, any modification you make to the intake/exhaust path to improve the flow is going to be a good thing, as long as you keep the balance. I have read quite a bit about this and I have my own ideas about what is going to help and what isnt for the time and money we want to spend. We arent going for massive performance gains here, just slight mods whilst the head is off.

I didnt say I was making the carb any bigger mearly enlarge/flare the intake end into a slight trumpet shape and knife edge the choke flap to create a slightly better flow, again we are not seeking to create massive performance gains, just slight improvements on the original design.

Half the fun of doing things like this is working it out for yourself. Its great to read books by people like Vizard and Trickey but I dont read them to follow what they are telling you to do to the letter but to gain an understanding of why they are doing certain things and then adapt their ideas to my situation.

How do you think they worked out what to do !

Jimmy

[Jimmyarm]

Ok no laughing !

We managed to get our mitts on a valve spring compressor yesterday, extracted the offending valve and guess what was stopping it from closing properly........

Lets see who gets it right ! Winner gets to slap me and my mate around the face with a wet salmon !

Jimmy

[Jammy]

A wine gum?

[kada1980]

a wooden spoon?