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MG MGB Technical - 2000cc - 2100cc Engine
|I've finally come along far enough in restoration of my 65 and have been thinking about engines - 1924,1950,2000 or 2100cc. I was looking for information on the 2000cc and 2100cc engines - bore sizes and stroke lengths. DOes anyone have any thoughts? Thanks, Geoff|
|The 2l engine is achieved by re-grinding the crank to give a longer stroke, combined with a max overbore. If I was doing this again I would stick at 1860cc, the 1950cc does give you good torque without hurting fuel consumption but there is not much metal left in the block.|
I have a 2.1Litre engine in my '67 Roadster which was built for me by Crankshaft Rebuilders, Melbourne, about 8 years ago.
I have since covered about 15000 miles of mainly longer distance driving.
My previous car (MGA) had a 1950cc engine and I am able to offer a direct comparison between the two large bore and the standard motor - there is none!
The 2.1L engine has been completely trouble free with virtually no oil usage between services (every 3000miles) and can return in excess of 30mpg in overdrive top at 60-70mph.
In our summers I often see water temperatures in the 90-100degrees range when climbing hills or in traffic but it then settles back to 82-85degrees under normal conditions.
There is abundant torque from very low revs right thru the range and it will safely rev all day at 5000+rpm.
It is the next best thing to a small V8 ( I am nearing completion of my '77 GTV8 conversion) so will be in a position to compare the two in the not too distant future.
If you like I can dig out the work sheet for the engine build and fax/email it to you.
|Peter M (member)|
|Hi Peter M.|
I am also interested in doing a rebuild in the not too distant future and am interested in your worksheet. Would mind sending me a copy via e-mail.
|Peter, if you can find it and it's not a problem please send it to email@example.com Thank You, Geoff|
if you are planing for road use, try to drive one with this capacity first and ask for details about carb, cam, comp ratio and ignition.
Then try a very good .060 over with fast road cam, HC pistons, larger carbs...
Although the extreme capacity will give an increased torque, the engine does not feel as 'sporty' as a good .060 overbored one in rally/race tune. If yo want to use it's theoretical performance benefits, you will end up with a racer that won't pull anything below 3500 rpm.
A well built 1868 will give you more than 120 rwhp and is capable for 6700 rpm. Larger capacity engines develop more torque at lower rpm but do not reach these rpm. They simply 'feel' a little more lazy. For street use they do not 'bite' as the smaller high compression versions.
It simply depends upon your style of driving and a possible risk of waekening the crankgear by stroking the lift and risking exteme piston velocity.
|Geoff and Dave|
I'll dig out the docs and email you both.
You are right when you talk of driving styles and circumstances. I live in the Victorian Alps and, as a consequence, do a lot of mountain driving where the torque is really appreciated. My engine too will rev freely to over 6000 - I haven't tried anything higher as there is no necessity. It has bags of grunt for street use.
I have 1 1/2" SUs (probably should have 1 3/4") with Performance pointless ignition, large core aluminium radiator, Wade 240 (Stage 2) cam, 9:1 CR, Holden 308 valves, thermo fan etc.
I do enjoy, absorb and appreciate your regular input - we just differ slightly in the area of engine sizes.
i did not think about mountains as i live close to the boarder to the Neatherlands and at a sea level of + 54 Metres i can go hundrets of Km without even seeing a hill. For this reason i can understand it quite well when some drivers go for torque although comparing my V8 to the roadster the 1868 engine is amazing (an incorporates a lot of detail work too).
Would you be so kind as to include me on your list of recipients of your engine build work sheet?
I don't want to hijack the thread, but I have a few related questions which I hope Geoff Lund will find relavent. FWIW, I have heard that when boring out to 2 L, there are a lot of individual differences in blocks; that an 18V block is best for this, and one should be prepared for the possibility of going through the water jacket on two or three blocks before succeeding. But can one sleeve such a block and still bore to 2 L?
Also, is there a table out there on the net somewhere that shows how many ccs we get with various overbores - from .010 all the way out to .060 and beyond? How much overbore equates to 1868, to 1950, etc.
My '73 GT was bored .030 of necessity and currently has 9:1 pistons. I'm guessing the overbore brings it out to about 1830 ccs. I'm running 1-1/2" HIFs, stock manifolds, stock cam, K&Ns and MSD ignition. I am awaiting a well-ported head with three-angle valve job.
as long as the original stroke of 88.9 mm stays unchanged the capacity changes this way:
Std. 80,26 -> 1799, +20 80.77 -> 1822, +30 81.02 -> 1833, +40 81.27 -> 1845, +60 81.78 -> 1868, +80 82.29 -> 1891, Lotus 1600TC Std. 82.55 -> 1903, Lotus 1600TC +40 -> 1950.
Larger capacities are reached by stroking the crankshaft. Many professional engine builders do not risk overbores in excess of +60 without fitting sleeves to the block first.
Hope this helps
|Ralph + Allen|
Also 84mm--std stroke--1971cc No sleeves .offset bores . reliable.
thank you for this interesting information. Where are these pistons taken from and how much offset is used without compromising the function of the head gasket?
Pistons are Mitsubishi Astron 2000
ACL part No. 2691 They have a compression height of 39.8 mm compared to a B piston of 41.6 With a std. 43cc head the result is approx 9.5:1 comp. ratio
Bore centres are moved .5mm 1-3 forward 2-4 backwards
With 84mm bore this leaves 4mm between the bores (6.8 std.) and the big bore headgasket is 4mm wide at this point. It all fits up very nicely. The only catch which involves a bit of work on the conrods is the fitting of the 22mm press fit gudgeon pins. Cheers Willy.
thank you very much for this interesting and usefull information!
This thread was discussed between 18/09/2008 and 25/09/2008
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