Headers for my MG Midget

[mickri]

I did the math for ideal primaries and collectors. 1 3/8 tubing is the ideal size for the primaries on this engine in a stock configuration. The length should be 33.5". No way to get the ideal length. The collector is slightly bigger than ideal and the ideal size out the back is 1 7/8 OD. It is better to be slightly under size for a street engine than to be over size. That is why I am going with a 1 3/4 OD back to the muffler.

On the number 4 cylinder a 2.5" radius won't fit. There is only 3.5" from the head to the foot well. On all of the other cylinders if you use 2.5 radius bends the header will run into a frame rail and the inner fender well. There is only 6.5" from the head to the center of the slot. The only place that I could use a 2.5" radius bend would be on the last bend going down to the collector. This is just a street car. The main consideration is to get the exhaust somehow to the back of the car.

If I could use 2.5 radius bends I would. And I would have a better header. I did a design with 2.5 radius bends only to discover that it would not fit in the car. Doesn't do much good if it won't fit in the car.

 

[westerner]

Easier than welding and if it fails I could always weld it.

Ya, I don't know about that. It will be a molecular level clean-up to get all the glue out enough to get a good weld.

 

[pontiac428]

Makes sense to me! I think the Corolla transmission is a good idea. Would make the car much more fun. What kind of HP does it put out, and what is the vehicle weight?

 

[RandyWilson]

We used to get two pipes under the car with LCB headers. It took a while to realize you aren't going out the stock exhaust route. I have a touch of experience with that platform, having built several G and F prod race cars. Still have the last F/P 1275 in the back room, complete with 1987 RunOffs tech stickers.

While I strongly feel you would have been better served with a built 1275 (80-100 HP drop in). Don't shy away from having to pull the steering column. On a '65 without the collapsible column, it's not that hard to slide it back. If it wasn't for the horn switch, one bolt and you can slide the hole shaft right up and out of the mast jacket.I did that on my builds How often do you have to change starters, anyway?

 

[mickri]

I briefly thought about a 1275 and if my car had come with a 1275 I might have gone that route. But it had the original 1098 frozen solid and a smooth case transmission. There were some holes in the transmission from battery acid dropping on it. By the time you figure the cost to buy and build a 1275 and then get a 5 speed conversion you are somewhere north of $5,000. Probably a lot north. I'll have around $1500 in the toyota swap with a reliable 75 to 80 hp and a 5 speed. My total cost in this car will be $2,500 to $3,000 all said and done. Although not often I have had a starter go out when far from home and did the R&R by the side of the road. I always carry a tool kit with me. Been doing that since high school. And the exhaust still has to go out in the same place.

75 hp in a 1500 lb car that handles like an oversize go kart will be more than enough excitement for me.

 

[RandyWilson]

One thing about Midgets (and Minis for that matter) is you don't really need a starter. Give it a bit of a shove, hop in, and dump the clutch.

 

[Mini Cooper S]

I'm more of a British car purist, and I believe that a 1966 Midget with a proper BMC engine of whatever displacement will always be worth far more that one with an engine swap, however, it is your project and by all means pursue whatever inspires you. Let's face it, half the reason that we do projects like this is because it's in our DNA to do weird stuff! (This coming from a guy that put a 327 Chevy with a Muncie 4 speed into a 60's vintage Toyota Land Cruiser!) That said, don't be intimidated by the header. My son, with a lot of work, crammed extra large primaries and secondaries into his Vintage racing Triumph GT6 The unequal length primaries are not going to be a serious detriment to a street engine.
Good luck and have fun.

Richard

 

[mickri]

Spent some time this morning trying to see how many of the 1.5 radius bends I could replace with 2.5 radius bends. I am down to five 1.5 radius bends and all of the bends coming off the engine are now 2.5 radius. The number 4 cylinder is a question mark as to whether the 2.5 radius bend will fit there. I think that I can now order everything that I need to make the header. I am going to get one extra 1.5 radius bend just in case I need it for the number 4 cylinder. I didn't add up the length of each tube. The lengths should still be within 1".

I am making the flange out of 3/8 by 2" 1018 flat bar and should have it done today.




Edit: More work this morning. I was able to replace the two 1.5 radius bends on the #2 tube with one 2.5 radius bend and the one 1.5 radius on the #1 tube with one 2.5 radius bend. That gets me down to two 1.5 radius bends on the #3 tube.

 

[mickri]

The exhaust flange is done.



Here is the narrow slot that the header has to fit down into. You can see the little hole where the exhaust pipe has to exit the engine bay.



My latest on the header design.

 

[pontiac428]

I missed the detail that you are using a 3TC engine, for some reason I thought it was the Toy transmission only. The motor you have selected is an interesting choice considering what's happened with engine technology since that engine came out. I agree 100% that power to weight is all that matters (I build small vehicles for that reason), but I can't fight the urge to try for more performance (I want to stuff a Mazda KL-DE and Megasquirt into everything). Are you planning on carburetors or EFI? I bet a pair of side-draft DCOE carbs would be a hoot, but EFI would really be the way to do it. If budget is everything on this project, then you're already off to a great start.

Edit: The Toyota 1.8 is small enough to run Hayabusa throttle bodies (they're cheap) if you want a hot EFI conversion.