Inliners International Forums General Discussion Engines Ray Bell/ BMC 1275cc engines

Ray,

You recently mentioned something about having experience with BMC engines, a while back. The last one I worked on was in about '62, so I'm not familiar with them. I was wondering if you could give me some advice?

I have an opportunity to buy the complete drive train from a Morris Minor, including the 1275cc engine, 4-sp transmission and rear differential, at a decent price. I have heard the engine run and drove the car around the block. There are no leaks, or unusual noises, and the engine, (with a Holley-Webber carb/after-market header, but no drastic modifications) is surprisingly peppy.

My plans are to maybe install the whole set-up in my Crosley coupe.....at a later date. (Will run the stock engine while I'm getting the suspension, brake and body work done)

I also have a Datsun 1200cc engine, with a 4-sp Transmission that I could use. Of course, I'd have to buy the Morris differential, because the Crosley has a very weak, torque-tube differential.

The Datsun engine will have to be rebuilt, but I could install and drive the car with the Morris engine, just like it is. Buying the BMC set-up would also be cheaper than rebuilding the Datsun.

So, which route would you go? Thanks ahead of time for your input. Dennis

I've overhauled a couple of 1098's and found them to be a very simple engine the 1275's were the same as I under stand it. No oil to the rockers (vapor) and no rear main seal.(labirinth) Mine were in a 65 Sprite with SU's. For sizing I'm sure the BMC will fit easily not sure with the Datsun. A rear from a Sprite/Midget is narrow and mounted on leafs. They had 4.22 gears and we also found some 3.70's. My normal fuel milage was over 40 on the road and 35 in town if this helps.

It would be really cool to get on of these real modern computor controled DOHC, convert it rear wheel drive and use all the controls. Good Luck

Thanks, Jimmy 6.

Yes, that information does help.

For the first time in my life, I'm building a car that I don't intend to use as a dual purpose vehicle. (drag race/street)I'm gearing toward something that doesn't use a lot of fuel, but will be unique and fun to drive. A comfortable cruising speed of 65 mph, while getting good economy, is my goal. 40 mpg would be fantastic! I'm comparing between the most desirable attributes of the Datsun and BMC drive trains. Since the Crosely has it's original engine, I can drive it while deciding which of the more powerful engines I'm gonna ultimately end up with.

Thanks, Dennis

Frankly, I'd prefer the Nissan 1200. It's a much more modern basic design and has an alloy head, so it's lighter and I'm sure it's oversquare.

The 1275S engines in my racing days were stretching to get 130hp, the Nissans with similar mods (like the Corollas - another option) would get 145hp. I would like to go with the SU carbies, however. They're nice, need no tuning once set up and give good power and excellent economy.

With the Nissan you might also find a 5-speed gearbox. They came in some models. Another possibility, though rare, was what was called a GX head, which had better porting.

BMC rear ends had 3.78, 3.90 (very rare competition model), 4.22, 4.55, 4.875 and 5.125:1 ratios. There is a similar spread of ratios among the Nissans, but harder to find the lower ones (which I'm sure you don't want).

The narrowest Nissan rear would be from the Datsun 1000 of the mid-sixties, I'd think. Again, Corolla would be an option. These are strong and light, though maybe a tad heavier than BMC axles. Most certainly less prone to troubles, however.

If you do use a BMC rear, get sealed bearings for the semi-floating setup, DO NOT use the tab washer under the big nut (they hammer themselves thin over time and let the nut come loose), but use Loctite instead. It would be a course of wisdom to polish the radius inside the axle flange as that's a point of failure, and if you have access to a machine shop it might be good to neck down the axle to the inner diameter of the spline to give it some compliance so it won't break so readily.

The best insurance against breaking axles, however, is to have the rear suspension set up so it neither lifts rear wheels or lets them bounce too much.

All of that said, either would be satisfactory for your state purposes. 65mph would be well within the bounds for cruising, though wheel size and gearing have to be considered. That fifth gear in the Nissan box would be a definite plus here, though they do adapt easily to the Morris engine.

Thanks a lot, Ray.

I talked to a fellow in yesterday who mirrored your remarks, stating that the Datsun would be a much better choice. He's a Nissan mechanic and has had experience racing 1200/1300/1400 and 1500 push rod Nissan engines. He claims they're almost bullet-proof.

That's good enough for me...I'm going for the Datsun engine/transmission. Now, I have to locate a rear end.(The guy with the BMC engine will not separate the drive train)

I know where there's a wrecked Volvo with a pair of SUs on it. I believe it's a '70 model and I can get the carbs cheaply. I have no idea what size the Volvo engine is, but should I grab them while I have a chance? I have a manual somewhere for SUs, but haven't used them before..

Those SUs would be too big, I'd think... they will be at least 1.5", possibly 1.75". You need to find a pair of 1.25" (Sprite) to have an ideal setup for what I imagine you'd like to use the car for.

Look out for Corolla rear ends, and you might consider Suzuki or Daihatsu mini van units too.

I'm going to use a Holley-Webber...picked up a nice one today. Will fabricate my own adapter.

We rarely see Daihatsus here, but Suzuki Samurais are a possibility. Thanks for the tip, Ray.