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MG MGA - 3 bearing 1800 build for A

Hello,

I am interested in building a 3 bearing 1800 B engine for my A. mildly grinding the 8 in the 1800 in the side of the block to become a 5 and you would never know what's deep inside.

My spec is going to be fast road, but nothing too wild as to leave the traditional B series looks externally.

I have a 3 bearing block and shell clamps for it, but that is all.

My questions are to the engine builders:

1. Are there any parts on a 1500 B series, that will help me build up my 1800 B series, considering I currently just have the block and main bearing shell housings. I'll be looking for a new crank, rods, pistons, head and cam.

2. Is the sump from a 1500 the same as an 1800 3 bearing?

3. Are the pushrods and any accessories similar?

4. Is the front duplex chain area the same?

5. Should I be looking for a 5 bearing B series engine to rob parts from or a 1500 B series engine or both?

I'll get there in the end, but I just thought I'd pick your brains here first, before studying many books including Lyndsey Porters B series engine build book.

Martin
Martin

Martin

I will let some of the more technical-able users respond to some of the finer parts of your question. I installed a 5-bearing engine and was able to use nearly all the external bits (oil pipes, filter assembly {modified to spin-on}, distributer, carbs, manifold, duplex timing gear, water pump, generator etc). Important also to use the 1500 front plate as it is drilled differently than the 1800 for the engine mounting brackets.

Hope this helps

Steve
Steve Gyles

Hi Martin. You can rebuild and install the 3 bearing 1800 engine. But if you are planning on high performance modifications, and are looking to obtain a substantial increase in horsepower, the 3 main engine is probably not the best way to go! The 5 main bearing engine has a much stronger lower end, and is a much better platform for high performance endeavours. The 5 main bearing engine also has a proper metal/rubber rear main oil seal. Cheers! Glenn
Glenn

Many thanks for the responses so far.

I can see I need the 1500 front plate for engine mountings to line up.

More questions:

1. Is the rear oil seal a scroll type like the 1500?
2. Does a 1500 sump fit an 1800 3 bearing?
3. I think the 1500 pushrods are smaller on a 1500?
4. I seem to have read somewhere, reccomendations for special can followers?
5. If I get standard 1800 pushrods, is there anything in the way of lightening I can do?
6. One good thing about the 3 bearing 1800 is the tacho takeoff. Has anyone ever drilled out the 5 bearing 1800 to fit the mechanical tacho?
7. Some engine tuners will claim a 3 bearing engine can spin faster due to less friction area on bearings? Any comments here, apart from it is not as strong? Has anyone ever broken the crank on their 3 bearing engine?

Martin

Hi Martin, I built a 3 brg for my 1600 'A'. These are my suggestions.
You will need the correct crank, I think the rods are the same as a 1622, check the parts no's,
a 285 or 717 cam will be OK, the timing gear is the same, I used later MGB pushrods and followers, you will need a MGB head with the bigger inlet valve and modify the block to clear the valves. I lightened the flywheel to 20lbs, I'm not sure if your starter position will clear the block, is it high or low? The water pump is different and will be very close to your radiator ( I had one modified ). You might have to change the oil fed rocker post, the sump is different. I used my engine for 2 years, it went very well apart from the oil leak from the rear crank scroll, apparently the 1800's are worse than the 1500/1600's. I've now installed a 5 brg 1892cc with a few performance mods, which doesn't leak oil, if you want more cc's the 5 bearing is the way to go

Terry
Terry Drinkwater

Hi Martin. A friend managed to break a 1600 (3 main) crankshaft about 15 years ago. When I rebuilt my 1500 engines, both crankshafts were bent, and had to be straightened on large hydraulic pressed before they could be machined! I suspect that bending of the 5 main crankshaft would be less likely, since it is better supported, and has less "whip". Cheers! Glenn
Glenn

Terry

I stand corrected. I did put a different water pump on my 1800 block. Just been to look in the garage and the old pump is still on the 1500 engine on the garage floor! However, the blades on the 1800 are still a good inch from the radiator. I seem to remember that I had the choice of two lengths of shaft on the pump.

Steve
Steve Gyles

Terry,

How good is tickover with the 285 0r 717 cam and are there any significant power gains?

Regards...John
J Bray

I had a 3 main 58 1500 break the crank right behind the first main brg and counter weight. Was in Glenwood canyon heading back to Denver in the November snow. Engine ran but with one heck of a knock. Got dragged by a Ford pickup truck all the way home. Darn near froze to death.
R J Brown

Terry, I am interested in your comments.

I've always thought about B 3 bearings because its an almost bolt on change. The concerns I have with a 5 bearing B are:

1. There is no mechanical tacho drive takeoff. Can you drill out the blanked area on a 5 bearing and machine in a mechanical takeoff as per a 3 bearing ??

2. How can a 5 bearing mount on the front mountings. Any changes here?

3. How can you interface the rear engine to clutch and gearbox of the A. I have read many articles, only to confuse me. I understand a 5 bearing B flywheel is larger than a 3 bearing. Plus if you have gone for a complete B gearbox and clutch, does the gear lever come up in the same position and how do you interface to the splined driveshaft? Did you make a special rear gearbox mount if you did this?

Many thanks.
Martin

Hi Steve - the 3 brg water pump is different to a 5 brg, which as you know, there are 2 different lengths, they are not interchangeable.

Hi John - both cams have a lumpy tickover, the 717 has less tappet niose but the 285 gives more power ( in my opinion )both give the same amount of torque ( again in my opinion I don't want to upset Piper or Kent Cams! ) Both rev more than a standard cam or a 714


Martin - I used a 18v block, sadly there is no mechanical tach takeoff. I agree that the 3 brg block 'looks' the same, a trained eye could tell the difference.

The front plate from your 1500 will fit a 5 brg

You will need a rear engine plate available from Peter Gambol of Hi-Gear Engineering in the UK, a early 5 brg inertia starter flywheel, again available from Peter (I think)these are getting had to find in the UK, It will fit your gearbox

Regards terry
Terry Drinkwater

I terry

I had a 1622 block and a 1800 block (ex a Land Crab) side by side yesterday. The casting at the end of the camshaft tunnel is different, and it does not appear that a tach drive can be fitted.

On the 1800 the chamber is smaller, and there is less metal on the exterior where the drive enters the block.

fwiw

Ian F
Ian Fraser


I terry = Hi Martin
Ian Fraser

Martin. I spoke about converting my MGA, when finished, to an MGB engine with the Moss peole at a car show I attended. They recommended going with a five main bearing motor for one simple reason--they were having problems getting parts made for the 3 main bearing engines. They suggested that the parts problem will get worse over the years and that a five main bearing motor should, because of the larger number produced, should have a longer use life with access to better quality parts at a lower price as compared to an MGA or MGB three main bearing motor. Do not know if this is still the case today, but might be worth factoring in to your evaluation process.

Like Terry, the early 18V engine is my choice as being the best to install. Doug Jackson's website, something like www.mgamgb.com has some good information on MGA engine swaps and the use of alternate transmissions.

Les
Les Bengtson

Guys, the easiest engine to instal in the MGA is the 3 main MGB and it is a slightly more powerful and freer running engine to boot.

Use the entire MGB engine except for the front and rear engine plates. Use the front transmission cover from an MGB installed on the MGA trans with an MGB diaphragm clutch.

The 1500/1600 crankshaft is garbage. The 1622 is stronger, and the 3 main B is stronger yet, with thicker mains. You won't have any problem with it in an MGA, and I say that from racing and blowing up every version of these engines for the last 32 years.

You can make a 3 main B look exactly right for the MGA - look at the one in my 62:

http://www.rhodo.citymax.com/i/non-rhodo/engine2.jpg

http://www.rhodo.citymax.com/i/non-rhodo/engine1.jpg

http://www.rhodo.citymax.com/i/non-rhodo/coupe-may21-05.jpg

Took it to a couple of shows after I repainted it and no one noticed any difference - thought it was a stock 1622.

Bill
Bill Spohn

Many thanks for all your comments and info.
Having decided to go 3 bearing; I have a 3 bearing block with bearing cup holders and will get this dipped soon. Ancillaries shouldn't proove a problem on the market place etc.

I'm setting this up for a fast road with a 285 cam.
Any ideas on where to obtain a 3 bearing crank, conrods and pistons. should I be using a special manufacturer on the pistons and rods??

Martin
Martin

Hi Martin

I've got a 3 brg block 1840cc, complete, less the head and cam etc, its only done approx 3000 miles since a complete rebuild, I have also got a spare crank which I think is serviceable. Are you interested? I live near Weston Super Mare in Somerset. Email me off board

Terry
Terry Drinkwater

Some great info. I think I missed the answer. Will an MGA oilpan fit the 3 Main MGB engine? I have heard that these engines are quite strong. the only parts that might be hard to find would be the crank and rods. the part number for rod bearings for an MGA and for the 3 Main B are the same.I cross referenced my MG catalogs from Moss, and the engines share some same part numbers. Moss offers an aluminum flywheel for the MGA, and it is the same part number for the aluminum flywheel for the 3 main MGB. Same flywheel bolts, and possibly the oil pump. you can call Venolia Pistons, and they can make you a set of pistons in about two months for four hundred and fifty dollars. You can have cranks and rods made, but you have to pay.
ASH Andrew

The 3 main MGB engine shares oil pump, oil pan (as far as I can recall), head, camshaft and connecting rods with the 1622 engine. The flywheels are interchangeable but you'd have to drill some new holes of you want to use the diaphragm MGB clutch on an MGA flywheel (highly recommended - be sure to also get an MGB front trans plate and fork).

No need for special rods and don't bother with expensive alloy flywheels for the street.
Bill Spohn

This thread was discussed between 26/09/2005 and 03/10/2005

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