Cylinder Heads?

[blackviper]

At 10 lbs of boost, will getting a set of ported heads increase cylinder pressure or just increase the motor's efficiency? Will they create additional stress on the already on the ragged edge stock internals?

 

[BigRed460]

Increase cylinder pressure.

 

[blackviper]

I've been told that increased cylinder head efficiency may actually decrease boost. How does this affect the cylinder pressure? I know that horsepower theoretically generates more stress on components but does volumetric efficiency create the same?

 

[RedSrt007]

I've been told that increased cylinder head efficiency may actually decrease boost.

This is correct, a GOOD set of heads (Strykers, etc..) will increase efficiency and may/usually decrease boost if the input (blower) cannot feed it properly (too small). We have had a few cases where people put strykers on the roe setup and boost goes from 12# to 9-10#. If you can compensate for the better efficiency, you can gain big numbers.

Flow numbers are not the only characteristics when looking at aftermarket heads. Flow design, Port and chamber design, [SIZE=-1]maintaining air velocity throughout ports, etc....


[/SIZE]

 

[rottenronnie]

I've been told that increased cylinder head efficiency may actually decrease boost. How does this affect the cylinder pressure? I know that horsepower theoretically generates more stress on components but does volumetric efficiency create the same?

Increased cylinder pressure is all that more power really is.
Find ways to increase V.E. and increases in torque generally follow.
Horsepower is just torque measured over time.
It is generally best to use a lower static c.r. and let either the turbo or supercharger build cylinder pressure than have a high(er) c.r. and let the forced induction just "top it up" so to speak.

Does that answer your questions?

 

[rottenronnie]

Flow numbers are not the only characteristics when looking at aftermarket heads. Flow design, Port and chamber design, [SIZE=-1]maintaining air velocity throughout ports, etc....


[/SIZE]

So true.
There is a lot of emphasis placed on the big numbers when it comes to flow in aftermarket or ported o.e.m. heads; especially at peak lift where the valve spends VERY little time. QUALITY of flow however is rarely discussed or the flow numbers in the range that really matters.
My Striker stuff should be here this week. I am anxious to install it.

 

[Silverback]

The short answer is your boost will decrease, and your power will increase due to more air, i.e. oxygen will be in the cylinder.

 

[blackviper]

So my next question is if the boost goes down what negative effect if any will this have on the stock internals? Will the internals have more stress or bare more load?

 

[Ram From Hell]

So my next question is if the boost goes down what negative effect if any will this have on the stock internals? Will the internals have more stress or bare more load?

If anything, your engine will have it easier. The reduction in pressure equates to a drop in temperature, hence a reduction of the risk of detonation. NOTHING is harder on the rotating assembly than detonation.

 

[blackviper]

So from what I gather so far, adding ported heads is not going to put the engine's bottom end any closer to coming apart. Is this correct?

 

[TNVIPER]

George..you are trying to side step the issue...the more power you put in each cylinder the greater chance of lower end failure....ported heads add power...more stress on the whole drive train.....that smaller pulley is already probably a death sentence for your lower end...may be tomorrow...may be 15,000 miles from now...but it will happen.....unless you just baby the throttle...like that will happen..

 

[RedSrt007]

More Power/TQ = Stress on parts

Cylinder pressure = Stress on Parts

Win / Win Situation

 

[JTS VENOM PERFORMANCE]

If you are going to the expense of installing pistons, there is no reason not to install rods, and if you are that far, then a big safety factor is doing billet mains, after machine work and purchase it will only add another $1200

 

[blackviper]

I guess I'll hold off on the heads till I build the bottom end. Thanks for the feedback.

 

[Silverback]

If anything, your engine will have it easier. The reduction in pressure equates to a drop in temperature, hence a reduction of the risk of detonation. NOTHING is harder on the rotating assembly than detonation.

Sorry Eric, wrong answer.

If you reduce the restriction in the intake system the boost pressure goes down. But with the reduced restriction you are able to get more air into the cylinder, hence more power, and more stress on the lower end components.