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MG MGB Technical - 1950 cc Block with Sleeves
Would someone have a photo of the top of a block after it has been sleeved to take 1950 or there abouts cc pistons.
I'm interested to see how much material remains between the cylinders for the larger gasket to seal on.
Many Thanks in advance
|Mark, I don't have any photos but check out Doug Jackson's site at www.mgbmga.com. He comments on boring and sleeving the block to 1950. It looks like the success is on a block by block basis.|
Been down this route. Block cast at Longbridge with AF codes near the dip stick appear to be better than those cast at West Yorkshire Foundaries with WF codes.
Do you have the exact link on the mgbmga web site, as I was unable to search for any info on that site?
anyone else got a photo of the top of the block after sleeves have been fitted?
|Go here to see a complete set of pics on building a 1950cc engine - http://www.octarine-services.co.uk/alex1950.htm|
There is more than enough metal to seal the gasket and there is no need to use the larger gasket - the standard one intrudes very little - a matter of thou over a short distance and works just as well.
|Chris at Octarine Services|
|Mark, see if this link works to Doug Jackson site. http://www.mgbmga.com/tech/mgb12.htm|
Thanks for that link but that block does not appear to be seleeved?
I'm interested to see how far the sleeves intrude between the closest cylinders.
Does anyone have a photo of a 1950/1924cc sleeved block?
|It's hard to tell if it's sleeved with the head gasket in place, but the pistons do look rather large. RAY|
|All my 1950 blocks are sleeved but you can't see the "join" once the deck has been skimmed.|
There is precious little material left - around 20 thou.
Here is a picture of an old block which had raised rims to the liners to aid sealing - it didn't work and the other thin land is burnt through!
|Chris at Octarine Services|
Do you mean 20 thou of liner left that seems thin?
I just measured a before and after fitting and finishing liners. Gap left before fitting liners 65 thou, gap left after liners fitted,bored then honed 155 thou, therefor liner after all machining is 45 thou thick. This is on a 1950 engine.
Many Thanks for that photo. Just what I was after.
I still don't get why you would not offset the bores to increase the gap here.
After all standard MGB's blow gaskets between the cylinders easily enough and we are talking about reducing this surface by less than half.
Why not build your engines smaller if you are worried about failure? We can only say what we do and the reliability we achieve.I do not 'do' 1950 engines for road use I prefer 1867, last years longer.
With 1950 cc it isn't necessary as the metal between the bores is still as wide or wider than the BB headgasket
The secret is to make sure your machine shop doesn't cut a leed on the top of the bore as this greatly reduces the area for the gasket to sit. All that is needed is the sharp edge cleaned up by hand with a good sharp scraper and to be super carefull fitting the pistons (rings) into their bores.
On 84mm bore (1970cc) blocks I move the bore centres .5mm each. 1-3 frd 2-4 bck to retain a good sealing surface. and with 85mm you need to measure very carefully to match up with the gasket- the std blocks do vary a tiddle. The last 85mm one had to have the front two moved .8mm no.3 1mm and the rear .5
|Consider this from an old pal of Peter's ~|
"Now I know from experience that there is much that can be extracted from the B series engine, but bear this simple fact in the back of your thoughts. Torque is what provides acceleration and for a road car this is what is most important. Many of the mods that are regularly used do not do any favours for low to mid range torque, but provide sometimes significant higher rev BHP increases. This will alter the character of the engine and often seems faster, but is often no better as you have a 'rob Peter to pay Paul' syndrome. This is where low end torque is sacrificed to achieve high end bhp. The effect makes the car seem alot faster, but be aware that 'seat of the pants' evaluations can often be misleading.
"Bear in mind also that any power changes that is less than 10% of the existing power delivered will have little actual effect on the 'on road' performance. The feel and response of the engine will be changed, but performance lags well behind.
"Plus 060" gives 1868cc but with the correct piston crown height and shape to induce good squish. Mix this with a head done to the same specs as Pete Burgess does his and you will have an engine that pulls as well as almost all 1948cc engines, but then runs away from them at plus 3000 rpm.
"What many also don't realise is that it is not just a matter of how much power and torque that an engine delivers, but the manner in which that power and torque arrives. I have driven many engines of various specs and always find that the engine that is eager and responsive is so much more pleasurable to use. The smaller capacity (plus 060") is an 'eager whippet' when compared to the 1948cc which is a 'powerful bloodhound' The latter pulls like a train but always seems to make an effort of doing it, whilst the former is always chomping at the bit for more.
"This may be a little colourful but is quite simply a fair comparison of the different characters. Compare bare power figures and they may not be that much difference, but there is in other ways.
"Ring Pete Burgess up on 01773 520021 and tell him I suggested you disturb him. Guaranteed to get his ear. Pete calls a spade a spade and tells things how he sees them. If after talking to him about what you want he points you to a particular spec take note. This may mean he does himself out of work, but he would rather that than sell you something he knows isn't exactly what you want as that spoils his good name and gives him more problems for the future.
Rog" (Roger Parker)
Maybe you really don't need 1950cc???
No - I mean only 20 odd thou of original block left between the liners - the liners in this engine are thicker than my normal ones (which start at 80 thou and end up at 40 thou after boring).
As Mark says - the block width between the cylinders is still wider than the gasket so no problems in getting it to seal.
I couldn't agree more - which is why I always ask "how do you drive the car" when a customer wants an engine. There is absolutely no point in having a fast road engine if you always change up before 3500 rpm! In fact the econotune engine will perform better than the fast road up to this rpm level.
Despite what some people say about "cubes" (cubic inches) being everything - I have an 1840cc full race engine being used in a TVR which is beating practically everything else on the circuit! It's a crossflow (head by Peter) and runs a Piper 320.
Moreover - it has done 2 full seasons without a strip down.
|Chris at Octarine Services|
|Is that an MSX head Chris? I have one of these on my 1950 and alltho i love the drive and sound from the twin webers its not as buzzy as the 1860 with HRG head that was (and still is) on my other engine. The HRG weaped a little onto the dizzy so this was the only reason I swapped engines. I may have to dig it out and get it repaired.|
|Yes it is an MSX head.|
HRGs are so old now it is not unusual for them to leak - Peter did on for a customer of mine that had to have lots of welded repairs made to it before it was water tight - many used heads have had repairs but still command a high price.
|Chris at Octarine Services|
I'm not approaching this from your usual angle. See attached.
If an MGB has considerable weight above the gudgeon pin, then think of what we have to contend with building a 1900+ twin cam engine.
Many have considered 7" con rods to reduce the weight above the gudgeon pin but I intend to use the standard length rods.
Thus sleeving offers more than one advantage.
One being the wear properties.
Peter we are certainly not looking to push to the maximum. Since mga twin cams are 1600cc, the 83.0mm pistons we have chosen will give us approx 1924cc which is obviously a healthy increase.
To answer Chris's question, this engine will get raced but at 10.0:1 it's far from a full race engine.
I'd be interested to see what an MSX headed engine will produce against a twin cam head with the same compression and cc. I guess time will tell.
Chris & Peter, from your experience. When you've stripped down sleeved engines that have done considerable mileage is there less wear from piston rocking, etc?
Wear rate is down due to the superior liner material. Why not shorten the stroke while you are at it to reduce the wear rate. Short stroke crank with bigger bore, nice smooth package.
|Thanks Chris for the info. |
Peter, expect a call in the next week.
As you a guru at head work.
Would you have the flow rates for an MGA Twin Cam head?
I would be interested to see the comparisons between the best a 5 port head can offer vs MSX cross flow head vs Twin Cam head
Sorry I don't have figures for TC head. From the work I have done on TC heads I reckon a 1.69"-1.74" inlet valve would be the way to go.
Yes we are going for 42mm inlets but they are currently out of stock.
If we were to get you a standard twin cam head do you have the facilities to map all the flow rates?
Yes but what is the point of having figures if you don't develop the heads? As you are having a batch of heads why not pay for a batch of special shaped valves from G&S?
Firstly collecting data for the twin cam group, as it's a good starting point.
There is also a CNC program that can be run down the ports, but I've not seen the flow rates for pre and post this procedure yet.
Obviously each head is slightly different as they were mass produced ( well all 2500 ish of them)
Once we get the larger valves fitted then we can flow test it again.
I'll see if I can get hold of a head for you, as both mine are in Oz.
Yes if you could email me the details for G&S I'll try and get a quote from them.
G&S valves website http://www.gsvalves.co.uk/Company.htm
I thought you were using new heads?
It would be best if you could send a before and after head or a head that has been done in one port and maybe untouched in another. Then when my friend David Gollan next visits we can flow test the two different ports. That way I wouldn't charge you for testing standard and what you have developed as modified.
|Here is a 1950 block. Enough to seal but nothing extra between. Any bigger than 83.5 mm must (IMHO) be offset bored.
This thread was discussed between 20/01/2010 and 08/02/2010
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