T Series Information

Toyota T Series motor information, V1.1

This represents a compilation of what I used to know about the T series engines. This is also the first revision since 1997! Since moving to EFI, I have since forgotten most of it.... However, I have left it here on my page for those of you who don't want to go into the modern world, IE, fuel injection. I am definitely not the expert here, I am just repeating what I have either tried or what I have heard of done.

What I don't know: Other links...

First of all...Fuel delivery...Carbs...

These engines, even without internal modifications, could use more fuel delivery in the high revs. The stock Aisin carburetor and header are not worth your time above 4000 rpm if you are serious about performance. Many people will disagree over which is better as a replacement, Weber or Mikuni, but everyone agrees that just about anything is better than the stock Aisin unit. I had a Weber 32/36 progressive on mine for a year or so. Although a bit pricey for my collegiate budget at $278., I have found that it was well worth what I paid. Below 1500rpm there is a noticeable gain, and above 3000rpm the free-flowing nature of the carby is very discernable. Passing at speed is greatly helped, as is high rpm driving. This unit is a downdraft, not a side draft; The side draught carbs show even more gains. I now have experimented with a set of side draught SU HS4 carbs on my spitfire (Feb 2002) and can tell a lot of difference at 4500+ RPM between the down draft Weber and side draft SU types of carbs.

The general power theory says that low end torque is obtained by high fuel/air velocities, and horsepower is gained through high mass flow of the fuel/air mixture. In either case, turning hard corners after mixing fuel with air (IE, Weber DGV) is a bad thing.

The stock fuel pump can be replaced with a higher output one for increased pressure and better reliability at higher than stock delivery rates, but this does nothing when you still have the stock carb. My Weber did not require anything more than the stock pump; However the dual Mikuni side draughts on a fire breathing monster most certainly would. The easiest way to tell if you need more fuel delivery capacity is to see if you are leaning out at high rpm... If you have an oxygen sensor (mine originally did not, but I have a manifold on that does have a O2 sensor- from a 81 corolla) you can measure the voltage coming from the wire. Westach makes a very nice analogue gage, of which I have bought for my Spitfire. There are many different links to devices which use a LM3914 dot/bar display IC. As the corolla was a low budget college project and I didn’t know enough then to do anything about it, I never bought or made a gage.

The intake manifold can be given a slight polish, but not too much. A smoother than stock finish will allow for more fuel to reach the cylinders, but a too- smooth polish will not keep the fuel properly atomized and it will clump and not burn completely. The amount of polishing to do is more an art than a science, and if you have any experience in this field then please go ahead and tell me about it. Supposedly the perfect intake port looks like a lightly sandblasted tube. Never was worth my time to try, as there were always more pressing issues and ways to get power.

Next, Exhaust

The addition of aftermarket headers is probably the most beneficial thing that you can do for your engine. The stock headers do not allow for much in the way of flow. TRD makes a high quality header; It is also impossible to find anymore. When changing a header you also are going to need to change your exhaust, as it will do nothing alone. Of course, the same is true of the other way around- with larger piping everywhere but the header, you still are not going to realize the potential of your engine. Do the whole system. With a catalytic converter from a Nissan Sentra and a free-flowing turbo muffler, I will be all ready for a header set and more horsepower. The final word of advice is this: use stainless steel, as opposed to aluminized pipe or regular steel. While more expensive, it will LAST. The restrictions of the stock exhaust system are most noticeable above 4200rpm. The car seems to lose power and no longer picks up as well; It hits a barrier of sorts where the power output is no longer increasing. My corolla uses a stock exhaust (stainless) from the cat back, and a modified front pipe from the 4A-GE to the cat. For what I use the car for, it’s perfectly find. If I were silly about power, it would warrant a change. I’ve used the pacesetter header on my Spitfire and am relatively happy with it. However, of the two copies I have, one is very good, the other came from the factory not quite right, and I have spent a lot of time trying to make it right. As with anything else, you get what you pay for.

Then, ignition

The X700 ignition system from Crane has been getting high marks for its reliability and some comments about increased performance. While running around $80-120 US, it is worth the money if you are replacing your points system. If you have a stock ignitor with electronic ignition, don’t expect any differences. MSD makes some very nice programmable ignition units which allow you to set your own timing curve. If you have the money ($450-700) this is the way to go. However, don’t expect big gains unless you have done something silly to the engine. In the Spit, since I had points the X700 gave more reliability and hence a performance value The distributor can be replaced; There are blueprinted units but I have heard that the 1972 2T-C distributor was a very good one, relying on mechanical advance instead of vacuum for a curve. This should be very easy to pick up in a yard if you know what to look for.

If you are really going for all out performance, consider investing in a aftermarket ECU. These units, made by many manufacturers including Haltech, Electromotive, SDS, Motec and Accel, really give you total control over your motor. You can set timing advances, fuel maps, pretty much everything. However, they run from $400 to $4000 and you usually get what you pay for. This is the ultimate mod that you can do- change your carbureted T series (or other, for that matter) to a EFI setup. FWIW, swap in a 4A-G and avoid the hassles. DOHC is the way to go, pushrods are inherently limited.

Engine modifications

The engine itself can be modified, of course. The pistons, rods and cam are all good in stock form for all but the most serious of rebuilders. The head can be replaced with a high compression type from a pre 1974 2T-C motor. These are supposedly Yamaha designed units, with the same mounting locations, albeit missing smog fittings. (Oh, shucks.) The cam from the 1972 model year 2T is also a good one to have due to the slightly more aggressive lobes (less in the way of smog regs that year). The steel piston rings can be replaced with molybendium rings, as they will wear longer and provide more service. Of course, better bearings than stock can be located and if really wanted, either a prelube or a dry sump system can be installed for the increased oil lubrication of all moving parts. Finally, a radical cam can be installed, which would up your performance even more. Again, evaluate the cost of hop up parts versus a complete different engine. Spending $5000 on a hot 3T-C versus ~$1400 on a 4A-GZE….

What it all means...

Basically, it all comes down to what you want to spend and what kind of performance you will be satisfied with. If you just want a mild street brawler, then stick with a bolt on carbie and perhaps a set of headers. If you want an all out race machine, be prepared to invest serious amounts of time and money into a fast but possibly unreliable machine. I personally want something in the middle, so I am swapping a 4A-GE into my car, and perhaps later replace that with a 4A-GZE. Something to keep me happy and fulfill my needs (without killing my pocketbook!!)

Last updated Feb 19^th 2002