Engine Swap Question

[Petros]

I bought some flat top pistons for the 3ac a few years ago, seems the 4ac should be out there somewhere. I do not think the 3ac flat tops are available anymore.

flat tops are not really necessary unless you are going for 12 or 13 to 1 CR. you are starting at 9.5 to 1, over boring .040" and milling off .04" off the head raises the CR about a half point each, you will be in the 10.5 CR range than, and I would not go any higher using pump gas (must use premium at that high a CR already). the head gasket will not tolerate any more, and I would highly advise going to a 4ac before you get anywhere near 10.5 on the 3ac engine, you will have nothing but trouble with it. That 3ac head will not tolerate much tweaking, I have spent 3+ years trying to get more reliable power out of it, and I gave up. It is not suitable for higher output, it is a waist of time.

go 4ac, or even better 4age or 4afe, but do not push the 3ac too far or it will become unreliable very quickly.

[overs10ded]

Hello Petros, bringing this back up again as I am now faced with this question. The ol' 3a in my wife's 86 fwd wagon is really burning the oil, about 350 miles per qt! No leaks either, all out the exhaust! Getting noisier too. Anyway today my wife found a guy that has a 4a engine for $400 and says it's "good"! He has a good reputation so I think I'll go that route but like your advice. Anything I need to know about the swap? I don't know exactly what 4a it is yet but the guy told my wife it would work for her 86, replacing the 3a. Thanks in advance Petros!

[Petros]

that is an easy swap, but you will have to swap over a lot of external parts (in fact, likely all of them, maybe even the water pump). The engine mounts, the oil pan and oil pick up, the alternator and power steering pump and the mounts, the intake and exhaust manifold (along with the carb and all of the emissions equipment), all have to be swapped over on to the 4a long block. you will also have to swap over the 3a flywheel (install a new clutch while you are at it, and a new rear seal). if you have time you might see if you can get a machine shop to remove 4 lbs off the 3a flywheel and have it reblanced with the new clutch assembly.

You might consider putting in a new front seal and timing belt since the engine is out (unless you know it is a recent belt and seal), these are inexpensive and easy to do with the engine out. you will likely have to swap over the front pulley anyway. Though this can be done later in the car, not a big problem to do a timing belt with the engine in the car. It is just better to have the engine all set up with new seals and timing belt. the rear seal must be done with the engine out, and you might as well replace it since you have to pull the 4a flywheel off anyway.

it is a fair amount of work but the good news is it will all bolt up no problem, no adapters or special parts to fabricate. When you are swapping the oil pan and oil pick up (they have to go with together, they are not interchangeable separately), you can pull off the number 3 and 4 connecting rod cap and inspect the bearing and crank journals to verify the bearings are good. Journal should be smooth and shiny, not streaks or scored. the Bearings should be even, clean and smooth, any wear should be even. Do one at a time, put them back on exactly the way it came off (do not swap ends with it), and torque it to factory spec.

the 3a to 4a swap is the easiest engine up grade you can do, it gives it much needed little extra power, and it is a more durable engine (less issues with the head gasket). Though you may sacrifice a mile or two per gallon in fuel economy, mostly due to the fact that when you stomp on the pedal you actually feel acceleration, so you want to do it more often.

good luck.

[overs10ded]

Great news Petros, thanks!! So use all the 3a assys and the pan & sump on the 4a, correct? And my weber 32/36 will use the same adapter? OH that will go with the swapped intake!! I'm excited now!! right on the main caps! If I pull the head and find it is oe spec, how much can I mill for 92 octane? Also, where do you suggest taking meat off the flywheel? Thanks again!!

Good times!
Bruce

[jimcrazy]

i have my 4a ready to go in just trying to find a free Saturday to do it, not a cheap swap if you start adding it up I went overboard, water pump, all seals including valve seals, valve cover and oil pan gasket,thermostat, spark plugs,timing belt, clutch kit, lighten the flywheel 3 pounds, new rad ,upper and lower rad hoses,air filter,couple of u-joints for the drive shaft and oil and antifreeze. roughly about $600.00 canadian

[overs10ded]

OHHH THAT LOOKS NICE!! Right on the cost, but if I have to put that money into the 3a also anyway I'd like the extra 100cc! I hope this engine is decent, that is the question!! Good luck with your 4a!!

Good times!
Bruce

[jimcrazy]

that's the way I feel to,this motor only has about 60000kms or 36000 miles on it, when I had the valve cover and oil pan off both were spotless inside,the oil pan had a magnet in the bottom of it and not a spect of metal on it, hope it runs well

[Petros]

no need to pull the main bearing caps, pull only the number 3 and 4 connecting rod caps to inspect the condition of the bearings. the connecting rod bearing get starved of oil first, if they are good than the rest are good. Even if you need new connecting rod bearings, it is rare that the mains would be bad unless the whole engine is trashed.

also, no need to pull the head, save the trouble unless you know it needs a head gasket. It is no more or less work to pull the head when it is in the car anyway. Be sure to use the procedure to replace the head gasket over in the repair guides section.

If you take 0.040" off the head it raises it about one compression point. i.e. from 9.5 to 10.5. Personally I would stay with the stock 9.5 cr unless you need to pull the head and resurface it anyway, 0.020" should raise it to about 10.0 CR, which will run on premium 92 octane pump grade fuel no problem. you can run premium pump gas up to about 10.5 CR in my experiance, without any issues.

best place to remove weight off the flywheel is off the outer edge and the back, the furthest to the outside edge you remove the weight the more effect it will have on reducing the rotating inertia. have the face resurfaced too, gives you a fresh clutch surface and also takes some weight off. Do not worry about taking too much off or making it weak, it is plenty strong and heavy. Ignore any advice from "know it alls" who will tell you it is not good to take too much off, they are ignorant. the 3a flywheel is heavier than the stock (and far more powerful) 4a, 4afe, 4age and 7afe flywheels (I have weighted them). and performance flywheels weight about half as much as the stock 3a flywheel, which are designed for much higher horse power engines. When I worked for a fully sponsored racing team, the 1000 hp turbocharged 3 liter race engine used a clutch and flywheel combo that weight only eight pounds complete (it was all titanium).

the only good thing about a heavy flywheel is you will be less prone to stall the under powered engine on a botched shift, typical of beginner drivers. Which is why I suspect Toyota choose to put such a heavy flywheel on their entry level car. To help marketing to beginner drivers, both the equivalent honda and Nissan cars had more power and lighter flywheels, so the beginner would find the Tercel easier to drive.

[overs10ded]

Thanks Petros! Great information!! The clutch only has about 10k on it and I surfaced the flywheel then with a new clutch/pp but I'll cut the flywheel down with the engine swap. This is my wifes car but she is good on the clutch and I think she will be fine once she drives a bit to get used to the different feel of the lightened flywheel. However I am interested at looking at the flywheel, clutch, and pp after this last 10K. I'm sold on the 4a, now to negotiate a trade!! In my twenties I built a '73 vw type III fastback w/2.0 ford (100hp+) conversion that I had a aluminum flywheel made with a hardened steel insert, weighed 10#s and I beat that car as a dd for 3 years and was still fine when I sold it! Just have to watch clutch slippage-quick engage clutch techniques to keep heat down.

Good times!
Bruce

[overs10ded]

Will my 3a distributor work in the 4a? This engine is missing the distributor, the mounting flange looks close! The guy says it "has had some work done but was running strong" so I'll get it home and take a look. Traded a older mitsubishi diesel 5spd w/ 4x4 transfer for it! Value 3-400$us for either in my book! Of course, this will be a budget swap (I hope!)! Meanwhile I'll keep on keeping this thing on the road!
Both are "C" engines.

Another question; Will the 3AC head work on the 4AC? They look the same on the outside at first peek (on a picture lol)!

Good times!
Bruce

[teranfirbt]

Heads are the same, distributors as well.

[Petros]

distributor is the same no problem. the head is similar but not quite the same, it will bolt on, but there are a number of slight differences. The 3a and 4a have the same compression ratio, but the 4a has a larger bore. this means the compression ratio would go way up if you put a 3a head on a 4a engine.

Also, on my 4a the head has improved coolant circulation with a slightly different water jacket in the head, the 4a is more durable and less prone to warpage from overheating than the 3a in my experiance. Some other versions of the 4a have bosses on them as if you can drill for putting in port injection.

I would not swap a 3a head on to a 4a unless you have no other options.

[overs10ded]

OK! Thanks guys! Well the 4a looks good! I pulled #3 con rod cap and crank looks really pretty good, bearing shows wear but not excessive, the timing belt looks new, plugs arent bad. I'm not pulling the head! Things look too good to warrant that at this time and my budget is happy about that! Thanks for all the info and help!!

Good times!
Bruce