Swapping heads on an 86 3A engine

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My tercel:: 1986 Tercel 2wd Hatch

Swapping heads on an 86 3A engine

Post by F4ctor » Thu Dec 20, 2018 6:33 pm

Recently I bought a 1986 Tercel 2WD hatchback with a 3A and a 5 speed manual. My intent is to eventually upgrade this car for racing, capitalizing on its light weight, but for now I’m just repairing the 3A on the cheap. I did some digging into other A series engines and am attracted to the idea of swapping a 4A-L or 4A-F or similar head for more power cheap and easy. My question is does anyone have definitive info on what heads can be swapped on a 3A? I’m not trying for a huge build right now but I’d like to get at least 80hp so if anyone has ideas please let me know. Thanks

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My tercel:: '84 Tercel4wd w/extensive mods
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Re: Swapping heads on an 86 3A engine

Post by Petros » Fri Dec 21, 2018 3:28 am

Welcome to the forum!

the 3a engine is not really suitable to increase the hp. I did it on several rebuilds on mine and gave up on it. the head is not suitable to gain hp, the head gaskets become unreliable, those 8 small valves limit air flow and performance.

The short block is very durable, it is the head that is poorly suited for higher hp. best thing you can do is do a whole 4age engine swap. all the hard points bolt up, and you have to fabricate a new exhaust header on the other side of the engine. You could swap out the 16 valve 4age head on to the 3a, but why? the whole engine is better suited to the increased hp. you can either rig up EFI with the 4age, or get a set of side draft carbs for it (more costly but easier to install than EFI). The 4age has been tweaked up to 450 hp, the rest of the car, including the trans, will not likely handle that much hp. No way to get a 3a anywhere near that high.

The easiest swap is the 4ac, which is almost identical to the stock 3ac except it is 1600 cc instead of 1452 of the 3a. It is a simple bolt on swap without having to fabricate any special parts or adapters. It also has an improved more durable head design around the combustion chamber. You can tweak more power out of it without the head gasket problems. you can install the webber carb and a Delta cam in it, and get decent power without worry for failed head gaskets, and not spend too much money on it.

Good luck! Keep us posted on your progress
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)

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My tercel:: '86 SR5 4WD, 5AFE, lifted rear, 195/70/14 tires
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Re: Swapping heads on an 86 3A engine

Post by teranfirbt » Tue Jan 08, 2019 4:14 am

One thing to watch out for on racing is the transmission, it's definitely not a serious unit that'll withstand a the abuse of racing if it's not in tip top shape. It's worth the time to do a full teardown, inspection, and bearing replacement (if they're worn) before you put any serious track time on it. You will need to also inspect the differentials for correct pinion to ring gear engagement and lash.

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