Engine Tuning

This winter I was planning on rebuilding the engine, as the rings are going and the head was never rebuilt for unleaded. So while I have it all apart and out of the car, I thought it my be wise to start from square one. I also see this as a chance to tune the engine for some more power. I thought 200hp would be a nice round number, but I am not sure how involved it would be to produce that kind of power.

I've seen B engines that were bored to 1950cc. This seems like a good start for more power and would also keep the engine looking original. Would this be a good place to start or is this too large of a bore and am I inviting trouble?

If you want 200 hp from a B engine send it to Tom B with a blank check. He is one of the very few people who could build such a creature. A rover v8 would probably be cheaper. a 3.4 chevy v6 swap certainly would

First thing to do is get a copy of Peter Burgess' book, "How to Power Tune the MGB 4-Cylinder Engine". Peter is an acknowledged guru of the B engine. You'll find that 200 ponies is a bit much for a B engine, at least without going to a supercharger. Making horsepower is not hard, but keeping it driveable is. You could probably hit 175-200 horses at the flywheel, but it would have to have such a radical cam that it would not idle at all, and probably wouldn't run at under 3500 RPM.

There's been discussion on the GM V6 ... what kind of power does that generate? Are they easy enough to come by and install?

You are inviting trouble. 1950 pushes the limit for boring. Some blocks come out ok, others go through the wall and you then have a boat anchor. And the only substitute for cubic inches is cubic dollars.

I don't think you're going to get 200 ponies out of an unblown B motor. Maybe Tom can coax 'em out, but that's voodoo beyond my knowledge.

If I were seriously planning on building a 200-horse B engine (which I want to do, some day), I would leave the bore alone, or maybe just slightly overbore. No way would I go to 1950, because you're really straining the block.
I'd put an 8-port crossflow head on it and a supercharger. Should produce about 200 horses. Build carefully, keep the compression low to reasonable, and it should be pretty solid and reliable, too, if you can make the bottom end hold up. I'd also seriously look at installing an aftermarket FI system on it, such as the megasquirt, to make sure I wasn't running into lean conditions ('charged motors hate lean conditions) and squeeze a few more hp out.

But what I'm describing would easily cost as much or more than just swapping to a more powerful motor, whether that's the V8, a V6, or something like a Toyota 4aGE.

Don't overbore your block, it's a pure waste and you can't gain enough by doing it to tell you've done anything. Tom B can coax all the power out of a B engine that can be had and keep it streetable at the same time. Damn few mechanics can do that, fewer still will leave you with a reliable engine for years to come while producing that power.

I could get you 135-150 streetable HP out of a B motor. You go over that and your not going to be able to drive it around town. It will get real expensive real quick though. The engine will need to be balanced, lighten, stress relieved, and blue printed. The head will need to be ported with rim flow valves. The valves are $40 a piece. Of coarse it would be camed up and the cam indexed. I use billet steel cams with lighten cilled iron lifters, and crane push rods. Figure around $700 for cam, lifters,push rods, and ajustable gear.You will need a set of HS 6's and a header with free flow exhaust. That's another $1000. All in all your looking at a $6000 power plant.

Tom, for clarity's sake, that's rear wheel horsepower, right?

yea

Check out the new Moss super charger with a good well built engine.

matt...1950 is fine...look in on the MGOC technical questions, and if you bore, fully balance, and use flat top pistons with a 270 cam and alloy pistons take about 3/4 pounds out of the flywheel, you will get real superise for power.....also mill the head and port the intakes and exhaust to the max....a good header with a 45 dcoe weber..peco/ansa exhaust...now you are talking 9 or 10 to one compression and while you are at it...put in a good borg and beck clutch (competition) 'cause you will need it in the sprins when you blow the doors of the v 8 's you will have power to weight and they only have torque. Happy trails.

Jerry, don't get his hopes up. He's not going to get 200 horses out of a normally aspirated B motor. If he bores out to 1950, then he's stuck.. can't go any further.
And running flat-top pistons with a milled head is going to be a lot more than 9:1 compression. Wasn't stock 8.8:1?