It's been done, of course, a 200hp IO360 into a Cheeth/Tiger. But it's a lot of work. Fletcher Aviation put together a Tigerized Cheetah with a 200hp IO360 and a 3-bladed prop. They used a stock Cheetah cowling with an inlet enlarged to 4 times it's normal size. The air-box on this prototype was so large it would have to be removed to change the oil !

When they flew it, it was only as fast as a good Tiger. Certainly not worth the time and money to make the conversion worth while. This was due, in part, (based on my knowledge of fluid dynamics) to the enormously large intake. The spillage drag had to be enormous. Plus, there were other factors.

Disclaimer:  This was years ago. I may or may not have all the facts straight. Dave Fletcher bought Peter Otten's STC for his 200hp IO360 into a Cheetah. The thing about this STC is, you need to start with a Cheetah and convert the spar to a Tiger spar and then install the engine. Like the Fletcher version, this one requires a special air-box too; the difference is, this air-box is a lot smaller and uses a stock Cheetah nose bowl. BOTH conversions require the following (minimum) mods just to get the engine into the plane

1. The engine mount needs to be modified to get the IO360-C1C to fit

2. All new baffles need to be made

3. A new air-box needs to be made

4. All of the controls need to be relocated (Cheetah controls are in a different location.)

There is an IO360, albeit a 180hp parallel valve IO360, that will bolt right into a Tiger without any significant modifications.  You can reuse your stock engine mount, stock baffles, stock air-box, and, with the exception of putting a Prop control in place of the carb heat and changing the primer to an alternate air source, the controls all fit. And, yes, it has a constant speed prop. This IO360 will put out over 200hp with porting and polishing. It's also lighter than an angle valve 200hp IO360. In fact, with a light weight starter, the weight difference between the stock O360 and a parallel valve IO360 is negligible.

I started this project in 2012.  But, as all projects go, one thing lead to another and before you know it, all the wiring was changed, wire paths were changed, a new instrument panel was made, new avionics were purchased, the inside was stripped and painted with Imron, and on-and-on-and-on.  Here are the changes I've had to make so far:

1. Modify the airbox to match RSA injector servo.

2. Fabricate a new mount for the throttle cable to relocate the support 1/2 inch further up on the airbox.