what is a 3A-S engine?

[Starbug]

The head and valve cover are not the same as a 3A, 3A-C, 4A, or 4A-C. The 3A-S valve cover and head are shaped differently, they have gentle curves instead of being straight on the sides where they mate together, and the gasket does not match up and seal against a normal straight 4AC head. I can't find any information on it anywhere, even wikipedia. I ask because I have what I thought was just a regular 3A sitting in my garage. While cleaning the valve cover off, I saw the sticker on it said 3A-S. Ok whatever, probably just refers to emissions equipment installed on a normal 3A.... so I sent it off to be powder coated blue to match my car. When it came back, we attempted to install it on my 4AC and realized that it didn't match up at all. Closer examination revealed that both valve cover and head were not the same shape as either a regular 3A or 4A engine or their California emissions equipped versions.

Has anyone ever heard of this engine? It seemed to be just as slow and underpowered as any other 3A or 3AC back when it was still in the '83 Tercel 4wd wagon it came from. So it's not a more powerful version or anything.

[Highlander]

The 3A-S is a JDM engine. My wife has one in her T4WD. It should have a dashpot on the back of hte head that actuates vanes in the intake tract. The vanes are supposed to give more power at low R's by reducing the flow area and thus maintaining the intake velocity to get better efficiency. My wife's does have more power than the other 3 (not including the one that I built and ported the head on) as well as good mpgs.

[shogun]

there are 3 3as engines that i know of (and own) there is the 3as which is the one with the swirl port, the scv which is the one that has a vacum activated valve in the intake, and 3asu which has the dual exit exhaust manifold and a dual variable ventouri carbs, the last one was rated at 90hp and 82 ft/lb

[Starbug]

Wow, very cool! Maybe mine was underpowered like a regular 3A because it was a tired engine that needed to be rebuilt? Perhaps with some TLC and a few new parts it would regain the better power it's supposed to have. How much hp is the 3A-S supposed to have? Would it be pretty close to the 90hp of the 3A-SU that Shogun mentions?

[4wdchico]

there are 3 3as engines that i know of (and own) there is the 3as which is the one with the swirl port, the scv which is the one that has a vacum activated valve in the intake, and 3asu which has the dual exit exhaust manifold and a dual variable ventouri carbs, the last one was rated at 90hp and 82 ft/lb

I did a search and found the page linked below with the vac diagram of the 3asu engine. That is one wild spaghetti system!

http://translate.google.com/translate?h ... rmd%3Divns

[shogun]

yea the vacum things of thate engine are a hot mess, that is why i took it off and went a ida 48 weber, but the car was gas guzzling so went back to the 32 36

[motownbrowne]

Mine has a 3a-s, which as I understand, stands for "swirl intake". Maybe supposed to have a little more power, but from my experience, not too much.

[Starbug]

Mine has a 3a-s, which as I understand, stands for "swirl intake". Maybe supposed to have a little more power, but from my experience, not too much.

So maybe mine was normal after all; it sure didn't seem to be any different than a regular 3A as far as the horsepower went.

[Petros]

swirl ports are supposed to improve low rpm performance, and typically sacrifice some top end power (which the 3a does not have much anyway). My 20R Toyota truck engine had swirl intake ports, I ground them out and open the port as far as I can make it, did not make any noticeable difference while driving it, but did improve the power out put.

[tercel4wdrules]

I believe only the twin-carb 3A-SU made something like 85-90 HP, which is what they should've all had, but a 3A-S isn't going to make that much power without the twin-exit exhaust manifold and better carb arrangement. The later 4A-C's also had the "wavy" valve covers like the JDM 3A variants.