SBC exhaust manifold comparison.

[suprf1y]

The bottom manifolds are the ones to use.

Some useful info here

https://www.castheads.com/manifolds-car ... manifolds/

[Newold1]

You would not see 5 HP difference between the two manifolds at best. You'll see no torque difference between them. Use your time to and money to do other things to the engine and systems and you'll gain more torque but don't expect big changes. What do you really need, pulling power for towing with torque increases, or are you after better economy? It's an El Camino, basically a car with a long open trunk, not a bigger pickup truck.

[rfoll]

From what I saw on the Castheads site, the log type manifolds with the Y pipe are the way to go. If I stay with the 305 engine, I may consider headers. Truthfully, the 305 is fine for my purposes. Actually I am quite impressed with the amount of low end torque, and as a smaller engine, economy should be better than a 350. I don't anticipate doing much towing, although it has a large receiver type hitch welded on the back. I'm sure if I scratch build a 305 I can improve torque with carful parts selection and modifications. Otherwise I have the fresh 350 from the wrecked El Camino. I only got 1500 miles on it before the accident.