|The MGA With An Attitude
PP-101 -- WHERE TO START
When You Want To Kick A Little Asphault
Consider italics here. It has been ten years since first issue of this article, so a few tweaks may be reasonable by now. Newer notes here will be in italics.
Okay, so you knew it wasn't going to be one of those "build a hot engine" stories right out of the box, didn't you? It all starts with a couple of innocent sounding questions, and then it can escalate to a fever. But we don't really want this to involve those obscene amounts of money, do we? At least not in the beginning.
At 09:39 PM 11/8/98 EST, GMGoodman@aol.com wrote:
>"Saw the mail about the sport coil---would like a little bolt on pep if possible, but have been nervous about a hotter spark ---- old valves, guides and all."
First the quick and easy answers. Lucas Sport coil for 40K volts, open the spark plug gaps up to .035, and you'll have all the reliable spark you need. It might not add much to the top end performance, but it'll never miss a beat and will be easier to start. All other ignition parts can remain stock.
>"Also thought of running some real high octane but have same concern.....am I nuts, can these things cause some damage?"
Not nuts, and not damaging either. But if you just switch from regular gas to premium, you probably won't notice much difference except for the size of the fuel bill. Premium pump grade fuel has a higher octane rating than regular grade, but the function there is to prevent preignition (spark knock and detonation). As such, those expensive octane modifiers added to the fuel actually make the fuel a little harder to ignite, so it doesn't fire off from the heat of compression alone, but will wait until it gets the ignition spark. Premium fuel may also have just a little less energy content, but it can make up for that in efficiency if used in conjunction with higher compression ratio or more spark timing advance.
Start by setting the spark timing at 20 degrees BTDC at idle with a strobe light. I think that translates to about 12 to 15 degrees static timing. It sounds like a lot for an MG, but your car will really appreciate it and will reward you accordingly. Note: Dynamic timing (with a strobe light) may be different than static timing due to mechanical advance kicking in at some engine speed below the speed where you set the idle. If mechanical advance starts at 700 rpm, and you set idle speed to 1000 rpm, you might have 5 degrees mechanical advance at idle speed. In this case 12 degrees dynamic timing at idle speed could be the same as 7 degrees static timing.
A better method for setting timing is to disconnect the vacuum, then set dynamic timing around 32-34 degrees BTDC at 3500 rpm (or whatever speed is required to max out the mechanical advance). You can do this using a set-back timing light or by filing some extra timing marks on the crankshaft pulley in 5 or 10 degree increments. When you set max timing for road speed like this, the idle timing may not be exactly what you had in mind, but a slight tweak on the idle speed screw should make it idle well around 900-1000 rpm. Find more about spark timing in the Ignition section.
If the engine pings at 2500 rpm under hard throttle, put in premium grade pump gas, about 97 octane. If it still pings, back off the timing about 2 degrees. If it still pings, clean the carbon and all sharp edges out of the cylinder head and try spark plugs one grade cooler. If it still pings, do a compression check. If you get 175 psi you have flat top pistons and/or a shaved head, in which case you may need fuel in the range of 100 to 104 octane. Where you find that stuff depends a lot on where you live.
Another thing you can do right up front to optimize performance on the cheap is to get the tire pressure right for the type of driving you intend to be doing. This applies equally no matter what kind of tires you drive on. Figuring out what the best pressure might be could take a while, but it's quite effective and not particularly expensive. For more than you thought you wanted to know about tires and tire pressure, read up on the Magic Shoe Polish Tricks.
So far your bolt-on pep is on the cheap. Beyond that you need to ask and answer a few questions about how you want to use the car. If you want hot wheels for street use, you might like a fast street cam or mild road cam, larger carburetors, exhaust headers, and maybe a lighter flywheel and competition clutch. Of course you would also be spending more on tires after all that. If you want to go autocrossing with SCCA, or any other organized competitive driving for that matter, do not start with the purchase of a hot camshaft, because it will kick you right out of two racing classes. For any serious competition your first investment should be a copy of the rule book for the organization you would be competing with. Just one wrong part installed on your car can throw you into a class you didn't intend to be in, and where your car may not be competitive.
Your first well learned lesson in performance should be that the best bang for the buck will come from improving the driver. This can yield large returns for a very small investment in materials More importantly, if you don't improve the driver first, all the money you might be willing to throw at car parts could be for naught and may never get you to the winner's circle. The best prepared car in the world will not win with a poorly prepared driver. You should discover very early on that driver skill and finesse must go hand in hand with performance enhancements to the car. While it's easier to buy performance parts, it will be cheaper (and initially more productive) to improve your driving skills.
To that end, your first investment in performance should be a trip to a local autocross event (or more appropriately several of them). This will not only hone your driving skills, but will also give you a better idea of what adjustments or modifications you might like to make to your car, and in what particular class you might like to compete. For the least impact on your wallet, get some practice and do the investigation and make the decisions first before you start spending a lot of money on the car. Now turn the page and learn the pertinent basics of autocross preparation.