Weekend Engine Research and Comparison

Being away from Jakarta where all of this project is being done, i can only imagine and assume things to help me answer some questions lurking inside my brain. So whenever i get a chance to be in Jakarta, i tried my best to spare some time to do a research in order to satisfy myself with answers derived from actual hands-on experience.

I had both of my engines, the old 4A-C and its replacement, a smallport 4A-GE, at home yesterday. I took this chance to do a comparison on these two. Here's some stuff i learned last weekend. I hope this would also help you if you're doing something similar.

Q: Can a pilot/spigot bearing from a 4A-C fit to a smallport 4A-GE?
A: Yes, effortlessly.

As you may have known, being a FWD engine, originally a smallport 4A-GE is not equipped with a spigot/pilot bearing. A spigot bearing is required so that a RWD gearbox input shaft can match to this bearing and be kept spinning in place, thus avoid ruining your input shaft's oil seal and subsequently, avoid oil leaks. A 4A-C has this bearing on its flywheel. Now, if a pilot bearing from a 4A-C can be directly put inside a smallport 4A-GE, you'd save yourself from having to find out what size bearing fits the replacement engine. You simply bring your old bearing to a shop, get an identical-sized new one and slam it to your 4A-GE. See below comparison pic which shows you that both have same outer bearing circumference. By the way, what do you call that "slide ruler" i am holding in the pic? lol.
This pic also tells you that 4A-C flywheel will not fit a smallport 4A-GE crankshaft as the number of bolts holding the 4A-C flywheel is different compared to that of a smallport 4A-GE (6 bolts vs 8 bolts).
Bonus Pic! Here's a closeup of the pilot bearing on the 4A-C. You can see the bearing markings which would hopefully help you on the bearing identification.
You can see "6001 RS" marking there. A quick google will give you detailed info on the bearing. That is a 12x28x8 sealed ball bearing, meaning it has 12 mm inner diameter, 28 mm outer diameter and 8 mm thickness. Wow.. now I know that bearings and oil seals are identified in a similar manner! It's always inner diameter x outer diameter x thickness, in mm.

Let's move on to the next question.

Q: Can i use 4A-C sandwich plate and starter motor on a smallport 4A-GE?
A: Yes!

First off, why do we need to bother swapping the sandwich plate and starter motor? Well, a smallport 4A-GE's starter motor is positioned on the wrong side of the block which is on the intake side (well, mine at least.. i found out that Dereck's smallport has it on the correct side) so it won't match Charmant's gearbox bellhousing. Hence, you need to relocate it to the correct side: the exhaust side. More info on this, read my previous post on Daihatsu Charmant 4A-GE conversion guide.

Yesterday i compared the gear teeth spacing on both flywheels and luckily they have same spacing! This means a starter motor from a 4A-C can also spin a smallport's flywheel. Also the studs and holding bolts hole positions for the sandwich plates are the same. So, yes the sandwich plates are also interchangeable. Here's some pics though i am not sure these would explain my conclusion. First pic is a smallport flywheel and the second one is 4A-C's part.Next question..

Q: Can a 4A-C Clutch assembly (clutch plate & pressure plate housing) fit a smallport 4A-GE?
A: Yes

I took the 4A-C clutch assembly off the flywheel and successfully fit it to my smallport 4A-GE. As simple as that. Here's a pic of the 4A-C pressure plate housing installed on smallport's flywheel.
So now you know that you can get a 4A-C clutch set when doing a RWD smallport 4A-GE conversion.

Q: Do i need to make a fuel return line if i am going to do fuel injection on my Charmant?
A: That depends..

In an EFI system, fuel is pressurized to a constant value so that the ECU can calculate precisely how long to open the injectors in order to supply certain amount of fuel to each cylinder. With constant pressure, the longer the injector opens, there's always more fuel injected. The fuel pump must always supply more than the injected fuel to keep the pressure constant. This means that there should be a return line to the tank to channel back any excess fuel. Hence there should be at least two fuel lines between the tank and EFI engine, the supply and return lines.

Being a n00b that i am, i thought carb'd cars don't have such return line (only supply line only, single fuel line between the tank and carb'd engine). Discussing about this with Dereck and seeing my engine bay myself, i now know i was wrong. Our 4A-C engines have cam-driven fuel pumps which would pump more fuel with increasing RPM. This way, there's no way to shut down the pump when too much fuel is supplied. Hence, there should also be a fuel line to channel back any excess fuel to the tank! See a pic of 4A-C fuel pump below..
From the pic above, the line connected to "R" is the return line. This confirms that there's already two lines going between the engine and fuel tank. So if you're going to install an EFI system (or like me, swap the engine with a full EFI smallport 4A-GE), you don't have to fabricate a new fuel line.

.. or do you?

There might be a problem in using the original fuel lines when swapping to higher output EFI engines. The lines might not be big enough to supply more fuel for higher horsepower engines. If i am not mistaken (yet another thing i need to check myself when in Jakarta next time!), the supply line in our Charmant is 8 mm while the return is 6 mm. I am not sure if 8 mm is enough to supply fuel to my smallport 4A-GE. This is why the decision to fabricate new fuel lines depends on your application.

Anyway, new fuel lines or not, don't forget that you need to replace any flexible hose along the lines with the ones specified for fuel injection. EFI exerts higher fuel pressure to the lines and keeping the original flexible hoses is just asking for trouble. You might as well throw Molotov cocktails to your car, less trouble same result.

I have more pics on my hard drive so if you need any more related to this topic, just inform me and i'll check.