Cylinder head and cam specifications?

[crusher]

Has any one cc'ed the 3a cylinder head? The 4a cylinder head?
Does anyone have the cam specs for these two engines?
I just purchased a Chevy Nova with a 4AC and I am considering re-building with a eye on performance. The goal would be 100HP AL-25 six speed 4WD.
Any specifications, or experience in building 4AC engine would be greatly appreciated.

[Petros]

I recall from an earlier thread on this topic that the head assemblies are almost the same, they use the save valve part number, etc. The main differance in 3ac and 4ac is displacement, specifically the bore dia, since the stroke is the same.

All of the performance parts for the 3a and 4a engine are interchangeable, getting 100 hp would not be easy with either engine (very costly), mostly because of the small intake valves and obsolete head design. Starting with a 4a engine gives you more displacement, going to flat top pistons would raise the compression ratio for more power (but that means premium fuel), and either using the Delta Cams regrind (about $60 exchange), or a more expensive new shchinder cam shaft, weber carb, plus a header and 2" exhaust is about all you can get. That would give you perhaps 85 hp. Going to oversized valves (with new seats) and a full port job might get you 5-10 more, at a lot of expense. There are few other tweaks, but they yield very small increases.

I have also found when you push that engine design that far you end up with a number of other problems like blown head gaskets, warped heads, etc. The head can not take that kind of alteration. You can get more hp with less cost by adopting a stock fuel injected 4AFE engine, or even more power (but also more effort) a 4AGE engine to the Tercel. You get better reliability, more hp, better fuel economy, and can use regular gasoline. There are lots of threads on this topic.

Good luck.

[teranfirbt]

After having done work to my old 22RE (cam, exhaust, intake, throttle body, stand alone fuel injection, minor head work) and then doing an engine swap (basically stock 2RZ-FE) in my Celica, I'll say that the engine swap route tends to be more difficult in the short term, but cheaper and more reliable in the long run when comparing power outputs.

Looking at the 3A-C, I'd say the key points of restriction lie less in the head itself, but more in the intake and exhaust. A header with full exhaust and decently designed intake with a Weber would probably bump power up to the 75-80 hp range if done right, and fuel injection would probably net you another 5 hp. Granted, that's just a guess based on how horrible the intake and exhaust are designed. Next summer I plan on building a nice header and full exhaust for mine, so we'll see how that goes, and at some point she'll be getting converted to Megasquirt and multi-point injection... Personally I'm looking more for mileage and drivability than power, but I figure 75 hp and 40-45 mpg freeway isn't an impossible goal with that setup if tuned properly.

[Petros]

how are you going to go to multi-port fuel injection on a 3ac? Custom intake maniold? You might as well adapt a 4afe head to the 3a block, or just go the full 4afe engine. The 4afe engine is well suited to he Tercel, it was designed for economy and it has a high torque curve, and is fairly easy to adapt. Your efforts will be much simplified if you go with a distriburtorless ignition (either aftermarket or from a wrecking yard off of a '94 or newer Tercel) so you do not have to cut a hole in the fire wall. Since you are making a custom header, you might as well do it for the 4AFE head with it much better design 16-valve design. You will get more power, better economy, and more reliability. I have a spare 4afe head I will sell you for $35 (it needs to be rebuilt, valves reground, etc.) and you will need the intake manifold, throttle body, fuel rail, etc. But well worth the effort. I was considering building up a "3AFE" with it, but if I do it I will likely just get a whole car to cannibalize for parts.