Engine Swap

78 Midget, 1500 engine, daily driver, even in Oregon rain. Already runs pretty OK; mild cam, UK 9:1 pistons, Webber. As you know, gear ratios leave a lot to be desired over 60 mph, regardless of engine performance. I'm well aware of the non-availability of a 5-speed for the 1500 engine. I know dollars make a lot of decisions. I've not seen any information on the ability to put a 1275 with 5 speed conversion into a '74 thru '79 Midget. I see the obvious changes on the exhaust system, wiring harness, throttle cable, heater inlet air hose. What am I missing? and I may be missing a lot. Motor mounts? Drive shaft? Transmission tunnel? It is my understanding that the structural body of the pre and post '74 didn't change much.

I have a good core 1275 that I picked up to put into '60 Bugeye that is on an engine stand rotisserie for floor replacement. That project will go on for a couple of years. Meanwhile, why not build the 1275, add a 5-speed, and put into my daily driver.

Any thoughts are appreciated.

May I suggest that you swap in not just the Datsun 5 speed but the Datsun A 15 engine that bolts right up to it. With the BL 1500 car all that is needed is to fab motor mounts, and buy the trans mount. Also fab exhaust and modify oil pan. For the intake you can make one as I have done or purchase the twin SU manifold.
Of course if you have a use for the 5 speed/1275 combo down the line... go for that.

Kurt

I agree with Kurt for the most part, but I would build the 1275 over the A15 for 2 reasons. It would give you a chance to find out if the performance is what you are looking for and put you a step ahead on your Bugeye project. I've never driven a 1500 Midget or one equipped with an A15, but I understand the personalities of the two (1275 and 1500) are really different. I personally like an engine I can rev the snot out of without it sounding like its going to blow up, but everybody is different.
Good luck, Rut

The 1275 is a pretty straightforward swap in a 1500 car. My race car is a '78 running a 1275.

You'll need to noodle about with the clutch hydraulic line and I'm not sure if you intend to keep the 1500 radiator (I did, but it takes some funky hose routing).

And although the 5 speed can be nice, you can get essentially the same effect with a low (numerical) final drive (the 3.7 that is used in later 1500 cars). Much easier, cheaper and quicker to do than a trans conversion.

The stock ribcage trans that comes with the 1275 is a very sweet shifting unit and combined with a normal 1275, it can easily handle the 3.7 gears.

Nial,
what years did they use a 3.7 rear end? Would his '78 have one or did they make '78s with 3.9s?
thanks, Rut

I'm thinking the cutoff was oct of 78 for a 3.7, but that is just from memory.

Yeah, my '78 originally had the 3.7 gears.....I'm not sure when they started that either.

All good information. Much appreciate your combined knowledge. Aeronca65t, very interesting that your race car is a '78 with a 1275. Its been my understanding that the '74 and later is heavier and suspension raised/poorer. Loosing the bumpers helps with weight, and I assume your suspension is radically changed for race. Gives me encouragement.

My modifications are pretty modest. I really just took the low-cost approach on suspension.

When I needed to re-arc the leaf springs in the race-Spridget (to lower it) about 8 years ago, I used a two pound sledge hammer and "worked" them down cold. This is a time-consuming but perfectly legitimate way to change the arc on leaf springs. I does not change the load bearing of the spring appreciabley. The "anvil" I used was an old 1500 Spitfire engine block ("perfect!" ). I just placed the spring over one of the open bores and hammered the arc back flatter (a little at a time). Anyway, all that hammering got old quickly, so I built this little setup (see below) to re-arc the leaf springs on my cars. You could also just use a hydraulic shop press if one is available. When bending, I stay away from the center hole and just bend back the outer half of each leaf. I mark the spring in 1" increments and bend a little at a time. It's not a quick job, but it's easy to control and it works great. The bottle jack is a 6 ton unit ($25 at Walmart) and I needed it anyway for my new van. The other stuff is just scrap I had around.





You can also drop the rear a bit with this setup.

https://https://www.mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=57068


For the front, I used longer bolts to replace the bolts that hold the spring seat (#48) to the wishbone (#3) and I added spacers between the seat and wishbone (see picture below). This drops the car. I made spacers on a lathe but you could also just use a lot of washers. If you add a 1/2" spacer between the spring seat and the wishbone, the front of the car will drop about 1".

If you are going to build a 1275 anyway, go for that. A 1275 will propel a BE very nicely. You can check your diff ratio with a putty knife, flash light, and a contortionist body! As you look aft the ratio is stamped on the flange of the diff at about 10 O-clock. If you have the 3.7 then, I agree with Nial, standard 4 speed and 1275 will work nicely.

Kurt.

Nomad, Thanks for the info on the location of the differential ratio. I was a little surprised by what I found. The stamp is on the casting (as opposed to the flange itself) and is in two levels. When viewed from the wheel well, it is visible at about 10 O-clock. The top two digits are 11. The lower two digits are 41. There is no decimal point as best as I can tell, and it is quite clean. This isn't close to 3.77, or 3.9. Therefore, I'm wondering if I have the right numbers. The numbers are clear and not mistakable. If anyone has input at to the meaning of these numbers I would be thankful.

[h=2]41 / 11 = 3.72727273[/h]
You already have the 3.7 rear...so you should be good to go.