Boring the block, how much HP increase?

[predator5100]

How much horse power will this add if any. The reason i aksed is i rebuilt the engine and proted my heads, three angle valve job, as well as bored the block over i have a 3.4 and someone says it probably added more horse than i think.

[ July 30, 2002: Message edited by: Magnus ]</p>

[Magnus]

Lets look at the math here first.

3.4 specs:
Bore : 3.62 in
Stroke: 3.31 in
Cubes : 204.4 ci

With a .020" bore

Bore : 3.64 in
Cubes: 206.7 ci

So you increase in cubes by 2.3ci. Rough estimate, 1HP/ci. However the gain should be over the whole curve.

So figure you picked up ~2hp and ~2tq. Thats at the flywheel though.

I don't believe minor bores in our engines are really worth HP. I believe they are more of a cure for cylinder scars and uneven bores.

Hope this helps.

- Keith

[3.4 slow to go]

have the piston tops, combustion chambers & valve faces thermal coated :cool: while they're accessable.

[Arctc Wolf]

You will get roughly 1 hp per cubic inch of displacement increased and the gain will be over the entire power curve. A larger bore usually contributes to more of a hp gain that torque as well as better breathing at top end. Of course, the bigger the original bore is anyway, the larger the displacement increase. The thermal coating slow 2 go mentioned will help increase the burn rate inside the cylinders, reducing hydrocarbon emissions as well as raising the detonation threshold. These both help in the final tuning of the car and add a layer of added protection to your motor.

[predator5100]

Thanks for the help hmm so will milling the heads do anything for me at all

[3.4 slow to go]

raise compression some, depending on how much is machined. Have either the intake face of the head or the intake itself machined the same amount to keep proper alignment. also keep an eye on valvetrain geometry if going to 1.6 rockers.