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MG MGA - 1500 or 1800?
|My MGA 1500 has not been out for 24 years. Bob West will start work this January and I am committed to fitting a Peter Gamble 5-speed gearbox as well as other work. My 1500 engine is original but now I am considering changing to an 1800 unit. Would love to get opinions from owners who have changed to an 1800, and, if a 5-bearing engine is the way to go. How hard to find an 1800 engine? Thanks, Doug Wallace|
|Hi Doug, personally, I wouldn't change my 1500 engine for anything, I also love the original gearbox, and to me, the ratios seem just right. I guess it depends what you want from your MGA. Obviously the 1800 engine and 5 speed gearbox are better if you want to drive a lot of miles in excess of 70 mph on motorways, but if you want an MGA that sounds like an MGA and not an MGB (although MGBs do sound nice) and the fun of wringing as much as you can out of that dear little 1500 unit, leave it as it is. |
As another long term 1500 owner I replaced my 1500 unit with a 3 bearing 1800 last winter. It transformed the car. It isn't only the 30% power increase but more importantly the 50% increase in torque which does a great job of eliminating the performance gap between 3rd and 4th on the standard gearbox. in recent years when I first got the A out it was feeling distinctly slow but not this year.
I went 3 bearing as it is so easy with only incompatibility being the water pump, see my input on the MGA Guru site. It is far more difficult to get your hands on a 3 bearing rather than 5 bearing engine. I got mine as a non runner from Andy Jenning (http://www.mg-cars.org.uk/andyjennings/other.htm) and then paid for a full rebuild. I believe 5 bearing units are stronger and easy to find.
I have stuck with drum brakes but discuss this with Bob West.
|Go for the power, transforms the car and makes it more compatible with modern traffic, although in your neighbourhood, there are not any hills to speak of where you would really notice the performance improvement|
|!800 engine (3 or 5 main) with the 5 speed and 3.9 diff is the way to go if you intend to drive your car for significant mileage. We just completed a drive from Vancouver to Ottawa and back, 6,500 miles in all, and we were able to cruise consistently at 60 - 65 mph for days on end.|
Peter Gamble does bell housings to fit either engine.
|I have the 1800 5-bearing with the t5 gearbox. Externally the engine is the identical size to the 1500 so no problem swapping over other than putting on an mga front plate and modifying an mga backplate to take an mgb rear oil crankshaft seal which Bob will know all about. This mod will also need an mgb electronic Smiths tachometer as there is no tachometer off-rake for the mga version Other than that it's a great modification.|
I have owned a MkI with a 1588cc engine, a 1600Mk II with a 1622cc engine and I now run an MGB engined Mk I with a 1900cc engine.
The 1900 is obviously has much more pulling power than the 1500 which makes it great for climbing hills and it can maintain a comfortable 80 mph cruising speed quite easily.
The problem is that the standard MGA handles so well that when it comes to the really twisty roads that really suit the car, a 1500 is pretty much on par with all the other cars.
I was recently following Richard Days 1500 through some wonderful twisty roads in the Pyrenees and I had to work really hard just to keep up with him, particularly on the level and downhill sections, in spite of my car having almost 30% more power than his.
It says a lot about the competency of both, the cars design, and also Richards driving ability.
Richards car is the OEW California import which caused such a stir when he brought it to the MGA Register Weekend in Wales a couple of years ago, it is as original as they come, with (some) of the original paint still on it.
The other thing I have found is that the most comfortable cruising speed for the MGA with the top down is around 65 to 70 mph. Above that speed the buffeting from the slipstream gets to be a little tedious after a time. This could be because I sit pretty high in the car being over 6 ft tall. I often find that I start out at 80 mph but then after driving for a time I then notice that I have slowed down to 70mph without realising it.
So the choice of engine is down to what you want from the car and how you want to drive it.
Dont worry about the 5 speed gearbox changing the way the car drives, it wont. The first four gears are almost the same ratios as in the standard four speed box, maybe with slightly better ratios for 1st and 3rd. Probably the most noticeable difference is having synchromesh on 1st gear.
5th gear is the bonus as it makes a real difference on motorways, it makes for much relaxed cruising. But if you want to to drive like it as it was designed by MG, just use 1st to 4th gears.
If you do go the MGB engine route, the 5 bearing MGB engine is much more plentiful than the 3 bearing, you will probably not be able to find a 3 bearing one today.
Some will say that the 3 bearing engine has a weaker crankshaft than the 5 bearing although when MG raced these engines they apparently preferred the 3 bearing as it had less friction losses.
But the chances are that you will only be able to find a 5 bearing engine and so the choice is easy!
|I tried to add that my car has the standard 4.3 diff which seems perfect for my 1900cc engine/ 5-speed set up, but I missed the editing time.|
I get the better motorway cruising but keep the low down pulling power that I enjoy so much on the twistier roads.
|Firstly Steve, thanks for inviting me to join this forum after your several previous emails with advice; it has taken me a while! |
Thanks to Lindsay, Paul[I am from Dundee near you!], Dominic, Peter and Colyn, all great advice to consider.
2015 will be my 40th year of owning "The White Lady" and it's something of a big deal for me, plus, first time on the road in 24 years.
Bob West fitted me a Peter Gamble 5-speed gearbox in my TD this year and I love the result. It was not difficult to decide, I had to do something as the original 'box was "kaput". Paul, I take it that you kept the standard 4-speed gearbox?
My heart tells me to keep the original 1500 engine but my head says listen to all that good advice of the benefits of an 1800 with 5 mains. Anyone have ideas of approx. costs of an 1800?
if you do swap for the MGB engine and 5-speed, just make sure that you store the original 1500 and box somewhere safe with lots of oil and grease all over them to preserve them.
That way you will you will have the best of all worlds, Firstly, a great car to drive that you will love. Secondly, the next owner then has option of switching it back to original with a little spanner work and elbow grease if they really want to. Keeping the original parts will mostly likely preserve the cars value too.
|If you can find a 3 main MGB engine that is the best swap.|
PS - they aren't weak. I've raced with them for many years.
|Hi Doug again. Welcome on board. As you already have experience of the T9 in the TD you probably do not need reminding of the benefit of getting Bob to fit the right angle drive for the speedo. Saves routing the speedo cable across the driver's floor and allows you to use the original cable.|
By the way, although you should let the DVLA and insurance know if you change to an 1800 the DVLA are not interested in the engine number, receipt nor engineering inspection certificate. I have correspondence to prove it.
|There is no right or wrong to this query but if you want a bit more omph then the bigger motor is what you want. My preference is the 1950cc 5 brg with the T9 gbox and 3.9 diff. |
|Thanks Colyn, for sure, good advice to keep the 1500 well preserved, as I am leaning in that direction. Great to get different points of view as a lot of it is indeed personal preference as Steve mentioned a while ago.|
Hi Bill, just wondering why you recommend the 3 main bearing instead of the 5? Doug
|clutchentioned before I thought 3 bearing engine were impossible, as many others do, but I got mine last year as a non runner from Andy Jennings for|
|Paul, checked Cameron Gilmour online, what did he do to your 1800 engine and how was the cost? I don't live in Dundee but my brother is still at home there, he has an MG TF for many years, I don't think he knows Cameron so it sounds like a great contact.I live mostly in Indonesia, will be in Dundee in January..|
Thanks everybody for such an amazing response to my dilemma whether to stick with the same engine that has been in the "White Lady" for 56 years, or try something new with more oomph... after driving the TD with the T9 'box this summer, I am definitely going that same way for the MGA and I am feeling that the 1800 engine is also the way to go. Cheers, Doug
PS trying to upload a photo but does not seem to work...
I don't really want to put cosings on the list but if you email at: -
I will get back to you with details.
|Doug, the 3 main just drops into the MGA (use the rear engine plate off the MGA engine). Everything matches up and it has the mechanical tach drive like the MGA.|
We always liked those engines for racing - they ran a bit more freely and seemed to get an extra bit of power over the 5 main which had additional friction losses.
|Thanks Bill, from all that I am told and from reading up on the different options, seems the 3 mains is much more difficult to find than the 5. I will not be doing any racing but will be looking for reliability combined with a decent road performance. What is your take on the T9 gearbox which appears to be so popular now? Thanks, Doug|
Something to bear in mind is the 3-bearing has the MGA-type rear oil scroll, whereas the 5-Bearing has a proper seal. So less oil on the driveway/garage floor.
I also have the 3.9 diff with my 5-bearing and Type 9. Great for cruising in modern traffic, especially on trunk roads and motorways. If you are on windy hilly roads then the MGA diff is probably preferable. I love the Type 9 box. No way could I ever revert to the old 4-speed.
Might be worth asking Bob West about a drain plug in the gearbox. The T9 does not have one - sealed for life. My oil has been in for 14 years!
|Steve, thanks for these pointers, I telephoned Bob West last night to discuss, Bob repeated exactly what you mentioned about the rear oil seal. After listening to all the sides of the argument and reading up online, I finally made the decision to change over to the 1800 unit with 5 mains, and have asked Bob to look for an engine for me. Then we can move ahead on a full rebuild. Bob said that his engine-builder is in Kidderminster and he has used him for 30 plus years.|
By the way, about the diff, is the 3.9 original on the MGB? Would this mean less torque? Cheers, Doug
|Thanks Paul, I sent you an email, cheers, Doug|
Either a late night or very early morning for those two posts!
I am not the guy to write anything authoritative about torque and performance. My limit is that 'seat of the pants' feel.
The 3.9 diff is standard in the MGB. The early 18G and 18GA Bs used the same differential unit as the A. These are interchangeable although the differential wheel splines differ in number, so it's a case of transferring your existing differential wheels across. Later MGBs used a semi-floating (Salisbury) back axle; the diff in these is not transferable.
Obviously the 3.9 diff gives a higher speed for any specific RPM in any gear. I really only truly notice it starting off from stationary, requiring a little more clutch slip and rpm to get her moving. After that I find I can use each gear longer (faster in each gear) and this gives oodles performance at medium to high rpms. Like most things in life, it is different/strange/awkward when you change to something new, but you soon adapt and alter your driving style to suit. Since moving down South to the busier, hillier, winding roads around Hampshire and Surrey the only change I would consider to my transmission train would be to revert to the MGA diff ratio.
These are the figures I worked out a while back with my set up.
1800, Type 9 and 3.9 diff in 5th gear (not that I have tried it at 1000 RPM!):
1000 rpm = 23.5 mph
1275 rpm = 30 mph
1700 rpm = 40 mph
2000 rpm = 47 mph
2125 rpm = 50 mph
2550 rpm = 60 mph
3000 rpm = 70.5 mph
3400 rpm = 80 mph
3800 rpm = 90 mph
4000 rpm = 94 mph
4250 rpm = 100 mph
|23.5 mph per 1000 RPM must give you really comfortable high speed cruising Steve.|
Just for comparison, my 1800 (actually 1850 I believe)/ T9 5-speed has the standard 4.3 diff which appears to give 20 mph per 1000 rpm in 5th gear.
2500 @ 50 mph
3000 @ 60 mph
3500 @ 70 mph
4000 @ 80 mph
5000 @ 100 mph
I guess it does. Got used to it now and take it for granted. With the sports screen as a bonus the old girl has eased through 100 without a screaming engine. Not saying where or when!!!!!
|Steve, sorry not so early morning or late night, 11:30am as I am writing from Bali, Indonesia. Bali 1 hour ahead of Jakarta, 8 hours ahead of London!|
Interesting comparing yours and Colyn's rpm to mph figures, what actually is the lowest speed you did in your 5th gear? I am now completely confused whether to keep the 4.3 diff or change to your 3.9 set up...
Spoke with Bob West by phone and now on the hunt for an 1800 with 5 mains. Hopefully can start work on a rebuild before I move the MGA to Bob mid-January.
Colyn, I have read ALL your Pyrenees blog and magnified EVERY photo. Great report! I worked in Lourdes in the Pyrenees as a waiter in the Hotel Bethanie in 1969, saw a bit of the region, Gavarnie etc. Your trip covered a superb part of France! I am guessing you will be on the Lands End to John o'Groats?
|One comment on the diff ratio is I remember reading a 1961 roadtest on the 1600Mk2 when it came out that said they felt the edge was taken off the expected performance increase by the fitting of the higher ratio diff. I guess this confirms what I think Steve is saying that you don't need both the higher 5th gear and the higher diff ratio but I have no personal experience as I am std gearbox and diff.|
I am away for next few days but when back I may try and find the roadtest.
I did those figures about 6 to 8 years ago so I cannot really remember the precise details. I am guessing I did it at 30 and every 10 mph upwards, then back plotted. I do not use 5th often below 40. Most modern manual cars have 5 or 6 gears and I use the gears much the same as anyone else these days.
|Remember that the MGB has 14" wheels, the MGA has 15".|
From memory, the MGB is geared 17.9 miles per 1000 rpm in direct top with its 3.9:1 diff ratio, and the MGA Mk II, such as mine, with its 4.1 differential is 18.1 per 1000 rpm, so already marginally "taller" than an MGB.
An MGA with its 15" wheels and 3.9 diff may be a tad "over geared" unless you do mostly highway miles, and little stop/start motoring, exactly as Steve is now finding.
I certainly don't feel a need to go to a 3.9 from my 4.1 in my car, even at highway speeds. (I also have a T9 conversion with a 0.82:1 top gear in my Mk II).
Could anyone give me the link to Colyn's Prenees blog. I'd love to see the photos.
thanks for those kind words about the blog, glad you liked it. It was a fantastic trip and I decided to put as many of the best pictures and video clips in so that everyone (including me) could sit back and remember just how amazing the experience was.
The trouble is that you see so much amazing scenery every single day that you just cant remember it all and the blog helps to bring it all back.
Everyone has probably seen it by now but if not, just search for mgachallenge.wordpress.com
And yes, I am booked for the Lands End John o Groats trip and I am thinking of starting a new blog for that too.
I personally wouldnt fit the 3.9 diff with the 5 speed, I would stay with my 4.3 ratio.
I found that on the twisty, narrow and steep mountain roads we experienced in both the Alps in 2012 and the Pyrenees this year, we spent most of the time driving up the hills constantly changing up and down between 2nd and 3rd gears. If I had a 3.9 diff Im pretty sure that I would scarcely ever been able to pull 3rd gear.
To be honest, even with the 1850 MGB engine, it would have been better on the Tour de France type roads we were driving on, to have had an even lower 4.55 diff so that I could have used 3rd gear much more. But that would have made the 800 mile motorway run down a bit tedious.
On the other hand, if you spend most of your time on wider A roads with more gentle inclines then you would probably prefer the 3.9 diff, or maybe a good compromise would be a 4.1 diff, if you can find one!
It really depends how you intend to use your car.
My car doing 4000 rpm at 80 mph in 5th gear compared to Steves pulling 3400 rpm, does seem a big difference but it is still much better than the 4600 rpm it used to rev at in the old 4 speed gearbox at that speed.
I would try out the 4.3 with the T9 gearbox for a time, then you could always swap to the 3.9 later if you prefer.
|T, I have attempted to add the link to my blog, not sure if I have managed to do it but if not, just enter it into Google and it should come up for you.|
|Tried to edit my last entry but ran out of time, If you do look at the blog you can find the earliest entries by looking into the blogs archives which you can find at the bottom right hand side of the page as you scroll down. March this year is the start point and is mostly about me getting the car ready for the trip.|
If you click on the archives for july you will find the start proper of the trip where our neighbours give us a send off.
Then there is a day by day report of the whole trip.
Dont forget that in a blog you have to scroll down the page to get the earliest entries.
Or you can use the search box on the top RT side of the page.
|I too would counsel against the 3.9 diff in the MGA with a five speed, it's just not geared right to be exciting. The standard diff and the five speed make high speed cruising much more comfortable, but having tried the 3.9, I switched back to the original diff because the off-the-line performance was otherwise lackluster.|
I have a bored out 1622, lightened flywheel, fast road cam, SC-optimized cylinder head and Judson SC, so when I was not enamoured of the 3.9 diff with the extra power in the rest of the drive train, I expect you would also be disappointed with even an 1800 engine.
The extra torque of the later engines is a big improvement over the 1500 and 1600 versions.
|Being always somewhat irritated by the low first gear on my MGB and MGA, I optioned my T9 gearbox with the alternative higher (numerically lower) first gear that Peter Gamble offers. While this would have suited my MGB very well, and likely my MGA if I had the 4.3 differential, (or an 1800 engine), with the 1622 engine and 4.1 differential, in hindsight I think the better initial acceleration with the standard first gear ratio would have suited the car better.|
Colyn, thanks so much for the link to your blog. Wonderful photos and clearly a fantastic experience. My wife and I look forward to the freedom to doing such adventures ourselves within a couple of years, after our youngest (of four children) finishes high school at the end of next year.
Incidentally 35C temperatures (and more) are commonplace here in Australia. (I saw 47C on my BMW outside temperature gauge last Sunday!!!) Thankfully I was able to completely sort my MGA's engine temperature issues with a number of measures, so much so that I've no need for an electric fan, no matter what the ambient conditions and gradients. (You may possibly have seen a summary of what I did in a few places, including Safety Fast, MGA Guru and the NAMGAR site which have all run what I wrote about my experimentations and deductions). Minor fuel vaporisation after switching back on after a hot run aside, (erratic running for 5 to 10 seconds till it "clears its throat"), I now never have a problem. Even this hasn't been severe enough so far to warrant the "bilge blower fan" solution.
|Thanks for this advice Dominic, I have decided to stay with the standard diff certainly for the time being.|
Really appreciate the input and great advice from all you guys out there, I feel quite at ease now to move ahead with the 1800 engine and T9 box.
|Having difficulty uploading a photo, always receive the message "Request Timeout" any ideas? Doug|
Possibly too big a picture. I keep all mine down to about 100kb.
Glad you have made your mind up. Will you be sourcing the Smiths electronic tachometer or leave that to Bob? It depends whether you are positive or negative earth as to which version you need.
Bob does brilliant restorations. The one I monitored progress on when I was doing mine went on to be a concours winner.
|I fitted a 3 bearing B engine and 3.9 Diff in my Twin Cam in 1964 as I was often driving from Sussex to Sweden in those days. The conversion has been trouble free all that time and I would recommend it and the original gearbox.|
However I now need to replace the exhaust system from the standard MGB manifold and mild steel twin branch down pipe, to a one piece SS 3 branch manifold, but here
Spoke with Bob, he will be able to find the Smiths tach.
I have decided this is too good an opportunity NOT to upgrade the old girl, so for sure the 1800 engine, 5 main bearings and definitely the T9 gearbox, after all this will soon be 2015, not the 1950's any more!
Ok will try to add a pic. this was 1977 down in Devon or Cornwall, forget exactly.
John, Sussex to Sweden sounds a good run. I did London to Germany quite a number of times, in the MGA and also in the old TC. Any photos of your Twin Cam to share?
Just use MGA Parts all the way through the exhaust. The MGA manifold will fit. B block no problem.
I have read that the standard cast iron MGA exhaust manifold is a pretty effective design, comparable in performance with most aftermarket 3 branch manifolds.
|Many thanks for all the advice chaps|
This thread was discussed between 19/11/2014 and 04/12/2014
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