|The MGA With An Attitude
BEFORE SPENDING $$$$, THINK ABOUT IT - PP-200
At 12:55 PM 4/23/03 -0400, Dave Handley wrote:
>".... for the MGA restoration .... Objective is for highway speeds pulling the little trailer, to drop the rpms on the highway but maintain 70 mph or so. There seem to be a lot of options or combination of options."
Yes, LOTS of options available, but way to easy to get carried away and go overboard. First be aware that very few modifications beyond stock configuration are economically justifiable. An overdrive gear ratio for instance will never save enough fuel or engine wear to pay for the conversion. So understanding that you would be laying out extra cash out of pocket for some performance or creature comfort or convenience (a.k.a. "luxury"), you need to answer a few questions before you jump to any conclusions or start spending money.
Are you looking for less noise, or more power, (or both)? Would you sacrifice some acceleration (autocross performance) AND hill climbing capability (especially trailer towing) for less noise during normal level cruising? Would it bother you if an engine or gearbox swap actually reduced the resale value of the car? Does it bother you that the car will most likely (99.9%) never be returned to original configuration after modification?
Keep in mind that no matter what you do to "improve" the MGA it will likely still not match the street performance of a new Honda Civic (let alone a Mazda Miata). You are starting with a 1950's vintage car built with 1920's technology. At best you may be updating some parts of it to 1970's technology level. And if you try to overcook the power output you can generate some driveability and reliability problems. The original design of the MGA makes a very reliable car when properly maintained, and the original combination of design features is a pretty good compromise for everything to work together well to make a fun sportcar. Almost anything you do to change it away from the original spec's will be changing the character somewhat, for better or for worse depending on your point of view, and it will never again be quite the same car as original. Such modifications are virtually NEVER returned to original configuration, and such argument is often flaunted only as a personal justification for making an otherwise objectionable modification.
The original intent and spirit of the MGA design does allow for some "manipulation" of the components. The car was built and intended to be driven in a spirited manner, moderately powerful (for its time), generally light weight (within certain cost parameters), and simple in form and function for low cost and low maintenance. These cars were often used for competition as well as for daily driving, and often served both purposes at the same time. The factory supplied a few alternate gear ratios for the final drive, a close ratio gearbox option, some engine upgrades during later production, and a few suspension upgrades. Competition drivers often installed additional aftermarket performance parts. All of this is within the original spirit of the car, and if done properly none of it should reduce the value of the car or make it any less an MGA.
Modifications generally "palatable" to the MG community at large would involve period parts and accessories (including some racing components). Tubular exhaust headers and Weber side draft carburetor are generally accepted on a race car (check the rule book of the race organization), but almost any change of intake and exhaust would be relatively expensive and only a marginal improvement to performance for street use (original carburetors are actually pretty good performers). In the spirit of improved technology over time, some more modern components are generally acceptable when used in the original spirit of the car. For instance, modern radial tires as long as they are not terribly oversized, uprated components in the clutch and braking system, almost any wheels that look nice as long as they fit properly, any combination of anti-sway bar(s) that you might find advantageous, uprated valving in the (original) shock absorbers, positraction differential, and almost any camshaft in the engine as long as it has a decent idle for street use. Any visible changes to the configuration may cost points in a concours car show, but otherwise this type of modification might actually increase the resale value of the car (slightly).
The next category of modifications involves substitution of non-period parts which are still MG parts and still bolt-in, such as the MGB 1800 engine, MGB front shock absorbers, MGB disk brake components. The MG community is about split down the middle on this issue, so these may detract slightly from the resale value of the car if you can't find the right buyer (makes it harder to sell the car for a good price). In light of the increasing number of recent 1800 MG engine conversions in the MGA cars, NAMGAR has recently acknowledged the enthusiasm for this modification by creating a car show judging class for this type of car. They call it "Modified MGA", and it has some specific limitations. This class allows substitution of almost any MG part into the car (even newer vintage parts) as long as it is a bolt-in installation not requiring any cutting or welding. In other words, they require it to be reversible so the car could be put back to original form relatively easily (even though this has seldom ever happened, yet). This show class only applies to the once a year NAMGAR national GT, and possibly an occasional regional NAMGAR chapter car show, but it does provide some "authenticity" and/or tacit approval to certain types of modifications. This usually applies to the installation of any MGB 1800 engine in the MGA, but generally requires the retention of the original MGA gearbox, because any MGB gearbox would require some cut and weld processing around the rear mount and tunnel.
The next step farther away from originality involves either period or more modern parts that have significantly different appearance than the original parts. Coil-over suspension parts, tubular shock absorbers, and a physically larger radiator would all likely reduce the value of the car some (except for a few performance enthusiasts). Any attempt at independent rear suspension would definitely be considered a hack job. Any non-MG engine or high-back seats from a Japanese car are a definite no-no and would reduce the value of the car about the same as leaving the seats out, because that's what it would cost to set it right.
Installation of MGB overdrive gearbox or some non-MG five (or six) speed gearbox might be less objectionable if it's done well. See Gearbox tech. This seems to fall into the category of "not there if you can't see it". A British Ford Sierra gearbox or even a Nissan (Datsun) gearbox may be palatable to most people if you don't hack the car up too much during installation, and the 5-speed units are generally easier to install than an overdrive (but more expensive). Any overdrive unit in the MGA will require some widening of the tunnel and some cut and weld of the frame for the gearbox mount, which usually detracts from the value of the car regardless of the cost of installation or the functional advantage of the conversion. This may not be a factor for you if you do not care about the resale value of the car (but be careful not to make it impossible to service). The early MGB 3-synchro overdrive gearbox will require less modification of the tunnel, but these units are relatively rare, making them moderately expensive, but maybe still less expensive than a 5-speed gearbox transplant. The later (wider) 4-synchro MGB overdrive gearbox requires a lot of modification to the tunnel, the frame, the hand brake installation, and generally leaves a very tight squeeze for the seats. It has been done, but I wouldn't recommend it.
A V8 engine conversion is extremely difficult in the MGA because of the narrow frame in the engine bay. I have only seen one V8 MGA that was ever done in a respectable manner, and that one involved widening the whole car by six inches and still didn't have any heater when finished. In other words, forget it. On rare occasion a narrow (60 degree) V6 engine is installed in an MGA in fairly reasonable form, and also occasionally a Mazda rotary engine, but these have a very narrow market appeal and will generally reduce the resale value accordingly. Some Volvo 4-cylinder engines may be a near bolt-in conversion, but would yield only a small improvement in performance while reducing the market value of the car.
The only non-MG engine in an MGA that ever brought a smile to my face was the installation of a Mazda Miata 1600cc twin cam engine into a MGA Twin Cam car. This sounds almost sacrilege, except that the car used started out as a badly rusted hulk with no drive train which might otherwise have been relegated to the crusher. The chassis and body was fully restored, and it received the Miata 5-speed gearbox along with the engine. Additionally it got the entire set of electronic engine controls and all emissions control parts from the Miata, so in the end it ended up being environmentally cleaner than the Miata because the MGA has less overall weight. The wiring harness was cut open and all unused wires removed. Then new wires were added as required to accommodate the new engine control parts, and the harness was rebound in the original MG tradition. They even installed some MG crested cap nuts on the valve covers for finishing touch. The entire installation was very clean and very professionally done, and candy to the eye. It did take two years to complete, and not much was said about the cost, but it did still say "-Twin-Cam-" on the body, and it did indeed have a twin cam engine.
>"Change the diff ratio and use early MGB 3.9 gears"
This is one of the easiest changes, and not very expensive. Not only is it invisible, but in fact the 3.909 gear set was an original factory option for the MGA (albeit quite rare in actual practice). I have procured an MGB 3.909 differential, and I intend to do this to my MGA quite soon [actually completed in late summer 2003]. The only technical problem here is Correcting the resulting speedometer error induced by the reduced speed of the propshaft.
>"Go to a Sierra 6 speed transmission, offered by Butch White in a 'bolt on kit'."
Big smile. Also $$$$$. While the adapter fixtures should have an indefinitely long life, the gearbox would eventually need servicing and replacement parts. Parts for this one should be readily available for the foreseeable future, just moderately expensive. Any time you do a conversion like this you need to maintain detailed and accurate records of the change so you will be able to find parts and have it serviced in the future. If these records should ever be lost, the entire conversion might become less than worthless on some future day when it needs service, and the owner might be forced to remove the entire gearbox including the adapter parts to install something else that could be made to work (like an original gearbox for instance). If you drive the car a lot, the new gearbox will eventually wear out and need servicing. If you don't drive the car much, that fancy conversion will appear to be very expensive by the mile, being a large out of pocket expense for very little use.
My personal solution to this is to keep the original gearbox in the car, get used to the normal engine speed, and smile at the traditional sounds emanating from the car. I can rebuild another engine and two or three gearboxes for the cost of one 5-speed conversion, and I don't have to lay out all of the money on day one.
>"Keep the 1600 engine and bore it out a little, put in the fast street cam you mention in one of your sections."
All in good fun, not terribly expensive, well understood, well documented, easily serviceable, and acceptably durable. See Rebuilding your engine from mild to wild. My only problem with the uprated engine is that it will now pull well past red line in top gear with the stock 4.3 final drive ratio. 6000rpm=102mph. I have had it once momentarily to 6400rpm in top gear (108mph) and still climbing nicely when I took my foot out of it. This is why I will now be changing [have changed] the final drive to 3.909 gears. That puts the red line (6000rpm) at 112mph, and perhaps the 9% reduction in torque at the rear axle will keep it from going any faster. The engine in this configuration comes fairly close to matching the output of the factory stock Twin Cam engine. Surprise! But I did say "stock". A slightly warmed over Twin Cam engine can do better.
>"Put in an MGB 3 main engine to work with some of the options above."
This is a bolt-in transplant, if you use the right combination of stock parts. See Transplanting the 1800 engine into the MGA All other things being equal, the 12.5% increase in displacement could yield 8%-10% more torque from 1500-3500 rpm. You might expect perhaps 5% more torque and horsepower at top end, limited by breathing restrictions. This means it could feel a little peppier for casual driving around town, but for serious foot stuffing competition like autocrossing at high engine speed the performance difference between the 1600 and 1800 block would be less significant. If this would involve the added cost of procuring an 1800 engine core before rebuilding, it's probably not worth it. Also there would be no difference in engine speed and little or no difference in noise level, engine wear, or fuel consumption. You might consider a slight advantage in durability to installing an 1800 5-main bearing engine, but then you lose the mechanical tachometer drive and need to use the 1964-1967 MGB electric tach. You may also notice a slight loss of throttle response (peppiness) due to the higher rotational mass of the heavier crankshaft.
>"The MGA that I end up with will look nice, and I don't mind it being a little off correctness (like the 3 main 1800 engine) but I don't want to make the major mods to a later 5 main, etc."
If you also use MGA carburetors and exhaust manifold, maybe no one would ever notice the 1800 engine. The MGB exhaust manifold with the long center branch and dual outlets is a very difficult fit in the MGA because of interference with the steering column. But it is a slightly better manifold, so that could be worth the extra effort.
As it turns out, the original MGA short three-branch exhaust manifold has just about the same performance level as the later MGB long-center-branch manifold, so there is very little to gain by trying to stuff the MGB manifold into the MGA. A tubular exhaust header is only a marginal improvement (sometimes no improvement at all if the tubes are too small), and it radiates more noise and heat in the engine bay. Exhaust system "enhancements" are best done only with a synergistic combination of other engine modifications.
>"So, could I ask you for your recommendations on what is better for consideration."
Sure. Start by forgetting about the idea that you're building anything with high performance. When the guy in the Miata in the next lane at the traffic light starts revving his engine, just smile and wave and let him use up his own tire rubber for no reason. Save the mildly spirited driving for the empty winding country roads, and the seriously spirited driving for the autocross course where you will be more evenly matched with other cars in a similar performance range. The best part about driving the MGA will be all the smiles and waves and compliments you get every time the car appears in public. The second best part could be all the pleasurable miles touring around twisty country roads or enjoying the mountains on a nice long road trip.
If you like pushing the car to the limits, you can get a very serious adrenalin rush and some well earned respect by matching or beating almost any other car at an autocross event when comparing index times. A set of sticky race tires and those magic magnetic numbers can make for a mystical transformation to the car similar to the results of donning Superman's cape. The real trick to winning at autocross is to not get tossed out of Stock class, so you can take full advantage of the time index factors. To that end, you might consider avoiding the 1800 engine, wide wheels and tubular exhaust headers. Keep a low profile and read the rule book before you spend big money on some mod that would put your car in another class where it wouldn't be competitive.
For functional purposes, building an engine with about 100 HP goes a long way towards improving the fun factor. That's enough to get you up hills at speed towing a small trailer, and allows it to keep up with the most spirited expressway traffic. 85-90 mph is a breeze, and towing the small trailer at 80 mph all day long is no big deal. If you build in more power than that you would probably need to lower the final drive ratio a LOT more to take advantage of the increased torque with slower engine speed, similar to the setup for a big 6 or a V8. But you won't get a lot more power out of these vintage four bangers without screwing up the driveability. A full race engine with 1800 block, ported head, larger carbs and full race cam might put out 145-160 HP, but you're looking at a $6000 price tag for the engine work, would have horrible idle characteristics, wouldn't be much fun on the street, and in a pinch might still get stroked by a new Miata or a BMW M3. If you were thinking about 140 for regular street use, then you should probably be thinking about a non-MG engine transplant.
I can personally recommend the Fast Street Camshaft installation. That alone (when properly timed) can boost your ego and fun factor enough to make more serious modifications seem almost pointless (unless you're going into competitive racing). For larger displacement to make much difference you need lots more cubic inches. To get any really big performance gains with small displacement you need a different drive train and suspension package with decades newer technology (like take the easy way and just buy a new Miata).