[Walt Fricke]

Tweeks - just about anything you do will affect drivetrain life/reliability. Unless you seldom use much of the extra power, in which case it might have been more economical to rebuild a stock motor to stock specifications, and tranny too.

However, I suppose it just isn't possible (and certainly isn't wise) to flog things as hard on the street as on the track, where wide open throttle is the name of the game. The more tweeked a track motor (or dual purpose) is, the shorter the time between rebuilds of something (rod bearings especially). 40 hours is a figure you often hear for race motors, though a whole lot of us run ours at least triple that (perhaps not wisely).

If you want to run higher compression (as you will have to do to make the kinds of power you aspire to), be sure to twin plug the heads. But I don't think you can expect to get 100 FWHP limiting the revs to 7,000. You'll need to be able to spin up to 8,000 or close to it, especially if you keep to a CR you can make work with pump gas. That means a HP peak around 7,600. The factory 2.8s developed their peak HP at 8,000.

My favorite low buck 915 is a 7/31 with the gearset out of an 8/31. Just swap out 4th and 5th (the others are the same) in a 7/31 box and save yourself setting the differential up (me, I did it the other way because I had an 8/31 box). While you are in there be sure to install one of the one piece bearing carriers in place of the two separate ones Porsche used. A 2.4 or '74 mag case box saves weight, and those boxes have a steel insert cast into the area where those two big bearings go already, making the tranny sideplate perhaps the weak point of the mag case (which you can deal with by using a late 3.2 side plate or an aftermarket reinforced design). Mike is considering the fact that the 7/31 is a weaker gearset than the 8/31. But swapping in all the gears (you can move 3d to 4th - it makes a nice 4th, and changing 1st isn't really worth it, so I guess all really = three, but they will not be stock/less expensive gears) is going to raise the price. How much do you want to pay?

I once ran a short box and a long box on my track car, depending on the track. I got pretty good at swapping (maybe 2 hours out and back in by myself), but that gets old. I also had both a 2.3 and a 2.7 I swapped back and forth. That got old as well, though not as old as tranny swapping.

You ask about cost. Well, you won't achieve your goals starting with your 3.0 for less than the cost of a 3.6 transplant, I'll wager. Have you asked a machine shop what they want to twin plug heads? Not astronomical, but it is not $100. Or what special valves cost? Even brand new stock ones - look at what Pelican sells them for as a reference. Cheap as chips is relative, as you know speed costs money. I gather it just costs us a bit less than it costs Mike on the other side of the pond. Use the power of the internet to price out trick parts and head work costs - they are out there.

Since you say you can't afford the 3.6, here is a suggestion: the late Euro 3.0s were real screamers. In Porsche Club racing they are bumped up a class from the US spec 3.0s, and their competitors say they should be put up two classes. Find the heads and intake from a '78-79 US 3.0. (or swap your '81 for a '78/9) Buy new Euro/ROW 9.8/1 pistons (and probably cylinders, as chances are the old ones are worn or are Alusil). Maybe get a 964 or reground set of cams. Replace the stock rod bolts with Raceware or ARP. Put on SSIs (or find a stock '74 exhaust) and a muffling system of your choice. Build this engine (you will learn a great deal I suspect you do not yet know) and run it with whatever transmission you have. You'll have great fun. If you aren't an old track hand, you will not need more horsepower than stock to begin with anyway on the track - it will just cause your crashes to be more damaging if you try. And while the Targa has a whole lot going for it in the grin department, it is not the optimum base for a track car (unless you weld in a full cage, which greatly narrows the gap).

Not what you want to hear, but there is no getting around the costs involved even if, as I assume, you do all the engine assembly yourself.

Walt Fricke