does anyone know what exactly is different on a 305high output rather than just a stock 305?

 

Depending on the year:

Cam, exhaust, compression, fan, gears, air cleaner, carb & dist calibration

Things that are the same: heads, intake

 

its an 84 TA what do you think is differnt on it than the regular 305

 

Doesn't matter too much what I think, but I'll tell you about the reality.

Everything in that list, except maybe the air cleaner. The Z28s got the dual snorkel cold air system; but the Birds had no room for it. I'm not sure what they got.

In the Camaro the L69 was "rated" at 190 HP, compared to 145 for the std 4-barrel. It may or may not have been "rated" the same in the Birds, I don't know.

 

It is rated the same in T/A's, but I read that the heads on the HO motor are different in this book. I don't remember what it's called but it's about all Firebirds from 67 to 2000. He says they have better breathing heads or something to that effect. I'll get the name of the book later.

 

I don't care about the book, don't need one. I was there.

The heads are the same. They are usually 416 casting with 1.84"/1.5" valves; and some people have reported finding 601s in theirs. Same valve sizes.

Ignore the book. Look at the cars instead.

 

The HO engine had up to 50 more horsepower than the base LG4 305. It also had a redline of 6000, when the LG4 had a 5000 redline or something. The HO was built with better parts too, like an aluminum intake (Some LG4s got it too, but not all), a more aggressively tuned ECM, stronger connecting rods, lightweight flywheel for the 5-speed, performance gears instead of highway gears, and a truckload of other stuff.

The 305 HO was designed to be a performance engine, the LG4 was only used so you'd be able to say you had a V8. It was never meant to go fast. The HO motors are pretty good performers. They would put a Corvette of the same vintage in its dust. Its been proven faster than a same-year Corvette many times.

 

So the valves and everything are the same size?

 

Yes, the valves are the same size considering as how the heads are the same size, as RB stated. Same springs and what not as well.

I think the HO got flat topped pistons (with valve reliefs?) versus the non-HO's dished pistons.

 

Yup, the different pistons were what gave the HO higher compression. But they started using the same pistons in the LG4 in its later years; 86-up or something.

Heads and valves are the same. The book is wrong.

 

The 84 L69 305 TAs had effectively the same thing. Instead of an electronically operated second snorkel, they had an electronically activated cowl hood. The signal would open a flap behind the metal grate at the rear of the cowl. The air came into a channel, then passed into the air cleaner through a connector on the top of the filter assembly which was.

 

Here are some pics

84 L69 305

 

Yup, you got the cowl induction hood.