23 replies to this topic

[norris2002]

Some of you may have seen some posts from me before on here, and they all tend to have the same theme: Start enthusiastically and then trail off. I am determined for this to be different, however as I cannot log into mini forum when at work, and my time at home is very limited, it may be some time between posts... so please be patient and continue to contribute whilst I appear to be ignoring this. I am most likely reading it at work but unable to comment myself...

 

I have bought myself a new engine for my Clubby Estate with the following spec:

 

- 11 stud engine from an Allegro 1300GT. There is no engine number unfortunately, but I understand these to be very similar to the 11 stud cooper S blocks except the crank will be EN16, not EN40 and some other changes.

- 2 x 12G940 11 stud heads. One of them is marked 12G1805 above the thermostat also. All parts in tact for both heads, although a couple of the valves in one were binding in the valve guides when i took them out, so I guess these were slightly bent (and pobably damaged the guides also).

- I have been told the block has a 649 cam. I have not delved this deep into the engine yet to confirm, and also do not know if it was an original BL Tuning 649, or an aftermarket one.

- also told the timing chain has been replaced for a minispares belt kit. not sure on the benefit this will give other than I assume being quieter.

- Engine also has a later metro distributor without vac advance, and a small pulley on the water pump.

 

The engine arrived with no head attached, and feeling the bores i think they may need a re-bore. the pistons are already marked +40, so i guess the next step is +60 which would make this a 1340 after the bore? The tops of 2 of the pistons that are currently in there have some pitting on one side so i think these may need replacing anyway, and might as well pay the extra to clean up the bores.

 

THE PLAN:

 

- Skim head and get unleaded exhaust seats fitted. I have been quoted £220 for this. is that about right? (I am in SE London/North Kent near Brands Hatch if that helps).

- Re-bore block to +60 and fit new pistons. I have been recommended 21253 pistons for this, but do not really know the difference between different types?

- general health check all around and re build engine to go in the clubby. 

 

I have the occasional assistance of some friends who have done this thing in the past, one of which used to race minis and seems to know the lingo, but generally i am heading into this a little blind (although quick and keen to learn)

 

I would like to know what people think, any advice or really obvious things to look out for, etc. The intention is to have a car that is happy on a motorway and not a big handful around town. I dont want to set any land speed records in this thing, or have to get the engine to 1 million RPM before it will respond :)

 

Also, can someone explain to me what compression ratio means in an unleaded engine? I understand roughly what it is, and how to calculate it, but have not read anything definitive on what is a 'good' or 'optimal' compression ratio for an engine running unleaded petrol.

 

many thanks

Neil.

 

I will look at getting some pictures up for everyone soon too.

[carbon]

The +60 rebore will give you an engine just under 1330, the 21253 pistons sound like a good choice.

 

If you are not planning on big mileage and the exhaust valve seats on the 12G1805 head are in decent condition I would keep as a 'leaded' head and use Castrol Valvemaster. Only skim if necessary, as you will already be close to 10:1 CR.

 

If it has a 649 cam then sell this and get a 'fast road' cam instead. The 649 is a race cam, very little power under 3000 rpm.

[minilee94]

That's very expensive I think just for skim and seats I know it's a travel mate but take it to bill Richards in Ashford he is a top bloke

Also you need to be careful on fitting unleaded seats depending on valve size mine are 36mm and 29mm and there to big to have unleaded seats fitted as you run the risk of them falling out as you need to overlap the seats

We're was you going to get the work done as I'm from Bromley

And the main thing about piston types it down to really what the car will be used for and how deep your pockets are

[Vipernoir]

From painful experience, not all blocks will accept a standard 21253 if it has been skimmed or decked at all.  I had to have a large lump taken off the top of the pistons to make them useable (and it was still a better option than using 21251s).

 

No such thing as an Allegro 1300GT - you are probably thinking of the Austin 1300GT which was an ADO16.

 

£220 sounds in the right ballpark for a good machine shop to do seats ( which done properly involves new guides and recutting valves & seats) and a skim - yes, it can be done cheaper, but how good will the end result be ?
I pay probably above average for my machining, but Hamlins are utterly superb.

[Cooperman]

If you want the car to be capable of being driven around town you most definitely do not want a 649 cam. That is a full-on race cam giving best performance from about 5000 to 7500 rpm and unlikely to run cleanly at below about 3000 rpm.

 

Best cam is the MG Metro cam which is probably the best cam ever for a road-going Mini.

 

Ideal compression ratio is around 10:1 or slightly higher.

 

The non-S 1275 block is very different from a Cooper 'S' block as the 'S' block has removable cam chest covers on the back and smaller big-end journals.

 

A +0.060" over-bore will give 1330 cc.

[norris2002]

Thank you for the replies guys. I have attached a couple of pictures f what I have so far.

I am planning to do fairly high miles in this. I will be using it daily to drive around 29 miles, and plan is to take it down to Italy later this year for a few weeks, so I don't want the seats eating themselves away. I am particularly concerned as this seems to be what. Has happened with the 1100 currently in the clubman estate, killing the compression and meaning that engine is currently running on 3 cylinders.

If I was to keep the head as it is, and use some sort of lead replacement additive, what do people recommend and how frequently? I have also heard good things about the 'lead balls in a cage' you can put in your petrol tank. Does anyone have any experience here?

What should I expect to pay for a replacement cam? And is the 649 desirable for the racers?

[norris2002]

[Cooperman]

That head will need work around the valve seats, so best option is to go for unleaded seats. At the same time you can get the head gas-flowed and finally, after a 'trial build' strip it and get it skimmed to give a C.R. of about 10:1.

Best pistons for your use will be the 21253.

Make sure you have the crank re-ground, or at the very least micro-polished if the journals are not at all scored. Set the crankshaft end float to a maximum of 0.004" by fitting the appropriate crank thrust bearings.

[minilee94]

What size valves have you got

And as you have 11 stud already you might find it's been polished and ported

So have a clean up and look and see if it's smooth

Edited by minilee94, 01 January 2014 - 05:20 PM.

[Cooperman]

They look like 35.6/29.5 from the photo.

[carbon]

You mention problems with the valve seats in your 1100 clubby estate - if this is not already running unleaded conversion then what are you using as additive?

 

I have been using Castrol Valvemaster since LRP was phased out in UK, never had any issues but I am not doing more than 5,000 miles per year.

 

Lead balls in petrol tank are exactly that in my opinion - a load of balls. There is absolutely no evidence that these provide any protection to the valve seats whatsoever. If anyone tells you otherwise ask for evidence from properly controlled tests.

[minilee94]

I have the same type of head but has 12g938 stamped on it so from a midget etc but that has 36mm 29mm valves and has leaded seats but got advised to use castrol valve master +

[carbon]

Information about effective petrol additives for 'leaded' heads can be found here : http://www.fbhvc.co....el-information/

 

Several years back the Federation of British Historic Vehicle Clubs commissioned engine tests to assess the level of protection against Valve Seat Recesssion (VSR) provided by fuel additives for use in historic vehicles with unsuitable metallurgy.

 

The following additives were tested and shown to provide the required level of VSR protection, and were afforded FBHVC endorsement :

- Miller VSP Plus

- Red Line Lead Substitute

- Castrol Valvemaster

- Castrol Valvemaster Plus

- Tetraboost

[samsfern]

I can highly recommend dartford rebore for machining work, having used them a few times myself, everything's always been spot on, done quick and for a fair price.

[norris2002]

Thanks for the info on additives. It is not something that I had used much before, and blame the 1100 valve damage on this. I think they are too far gone now that they probably need to be re-cut.

 

I will try to give Bill Richards a call tomorrow, or next week (as a lot of places are taking the long break over christmas/new year). Dartford Rebore is actually one of the places that I have been to, and their cost was a little more than 220. I will give them a call again though next week to double check the price, and what work it involves. I have been recommended them before, and have lived in and around Dartford for years.

 

I have not measured the valves, but Cooperman, I think you are right, they are 35.6 and 29.5. Also thank you for the advice on crank float and journals. What do people recommend using to clean the head (chemical or non abrasive before I go at the cylinders with a wire brush or dremel to clean them up). I want to check out the ports. from memory they are all quite smooth on this head. As mentioned earlier I have 2 x 12G940 heads, and this one seems to have slightly larger ports/less step from the inlet/exhaust face from memory.