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You've been getting good advice here, but I think some of it is too pessimistic. There are actually fairly well-defined steps up the power curve for your Sonett, which I think are as follows:
1) Get back to baseline: Before you do anything else, have the compression tested. If your compression is bad, nothing you do will add significant power; it will all leak out. If the compression is bad, you need to have it fixed before you do anything else. Also, check the basic tuneup stuff such as ignition timing.
2) Minimize parasitic losses: These are fairly cheap fixes if you're good at DIY. Replace your points with a PerTronix Ignitor so your timing will STAY where it's supposed to be. And if your car still has its original engine-driven cooling fan, consider replacing it with an electric one, activated by a thermostatic switch. The engine-driven fan eats power ALL the time, while an electric only steals power while it's running. Also, getting rid of the engine fan belt lets you put less stress on the wear-prone balance shaft gear. An electric fan is pretty easy to add on a Sonett III; there's plenty of room for a "pusher" fan in front of the radiator.
You can probably add both these fixes for about $200 total -- less if you're a good salvage-yard scrounger and can score an electric fan for cheap. They'll only add a couple of hp, but they'll help make your engine more consistent in its power output.
3) Improve breathing: This is the biggest bang-for-the-buck step you can take. Not only will it boost power noticeably, but (unlike some more radical upgrades) it won't hurt fuel economy in normal driving.
You need to address the breathing on both the intake and exhaust sides; if you only do one or the other, you won't realize the full benefit. On the exhaust side, the original Sonett dual system supposedly isn't bad, but you can do a bit better by adding the tuned Y-pipe system made by Motor Sport Services of Jamestown, NY. For street driving I'd suggest getting the two-muffler version; the single-muffler one is pretty loud. The tuning in this system will improve your power especially in the 3500 rpm-and-up area.
On the intake side, you've got a couple of choices for letting the engine inhale more easily. You can either find a 2-barrel intake manifold (no longer manufactured new, but used ones turn up for sale fairly often) and add a matching carburetor such as the Weber 32/36 DGV; or, you can buy a kit from Motor Sport Services that includes a modified manifold (you send in your old one as an exchange) and a professionally rebuilt Weber DCNF carburetor, along with almost everything else you'll need (except gaskets.)
Improving your intake and exhaust should increase your power by 20% or so, at a cost of about $800 to $1300 depending on how much you buy new and how much you scrounge. What's good about these upgrades is that they're all bolt-on, the engine can stay in the car, and you can do them with only hand tools provided you're reasonably good at wrenching.
4) Serious mods: I'd be inclined to draw the line at step 3, but if you really want to go beyond that you'll need to be prepared for some serious expense for machine work. Without pulling the engine, you can have the heads reworked for larger valves; if you don't mind yanking the engine out, you can replace the camshaft with a higher-performance item, have the cylinders bored for larger displacement, skim the block to increase compression ratio, etc. The downside to most of these (aside from cost) is that they make the engine more temperamental and more demanding in terms of maintenance, and you really have to ask yourself if that's worth it.
Even if you do all the tricks and spend all the money, roughly 120hp seems to be about the limit for what you can squeeze out of the V4 without turning it into a completely unstreetable race engine -- and as someone else said, at that level you also have to start worrying about upgrading the transaxle, clutch, brakes etc. To me it makes more sense to stop at step 3, enjoy your 20-25% power increase, and enjoy the car as-is.
Good luck and have fun...
posted by 68.227.170...
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