wanna lower compression to 9.5:1...what parts are needed? It's a FI build.

 

NO one know's.....wow!
besides piston what else?

 

5in thick head gaskets!!! Lol just kiddin, kids don't try that at home

 

new aftermarket heads with larger combustion chambers....

 

then tune the flux-capacitor

 

Basically you choose between a head with a big chamber or a piston with a dish. Have you committed to a piston or head yet?

 

the heads will be ported but what should i make sure they focus on when it comes to porting heads!

 

Im definitely doing both ported heads/piston..what dish piston should i go with? This will be a 355ci forged build

 

combustion chamber work will increase the volume and effectively reduce CR. also a thicker head gasket in conjunction would help. but loosing a full point is a lot.

How much boost are you planning on running?

 

i have a p1sc i wanna run either 12psi or 15psi more and likely 12psi

 

You might just need a -10cc dish..

Can you get 93 or is 91 your only option?

 

i have a 76 that carries 100 octane.I was gonna run 91 for my weekend cruises and c16 for my races events.I would like to do a 100 octane tune but dont have enuff fill-up station in my pch cruise routes!my 91 comes from chevron or 76 only..

 

You need to decide on something and then make the rest fit..
You said the heads would be ported but never said what the heads were.

 

stock aluminum heads.

 

So if i get the right pistons then i dont have to go extreme on the head porting then right?

 

Reducing the compression ration of an engine for turbocharging/supercharging applications is done with dished pistons. As you will have this engine apart, surely you're having an engine shop do some work for you. They need to CC your heads to determine they're exact displacement then they'll tell you what size dished pistons you'll need for the boost level and fuel you'll be using. Input from the Procharger may be needed by the machine shop.

This is not something you can just guess about or take a poll here for. You need to have this calculated correctly as you proceed with the engine work.

 

Not entirely..... the combustion chambers get cleaned up when ported but time is taken to not take a bunch of material off to keep the volume close to the same. On being FI the heads can be ported much more than a typical street port because the supercharger is going to push the air in instead of the vacuum of the cylinder. When a positive pressure is applied the flow dynamics change. Thus porting characteristics change. Also something to think about... When you change the amount of restriction the air has to go through to get to the cylinder, the boost pressure is going to change. For ex. if you have a air flow of 400cfm and pressure of 10lbs, then you port the heads and still only flow 400cfm the pressure may now be only 8lbs. Now that doesn't mean that you lost HP/torque. it just means that your intake system is working more efficiently. You should have gained power.

The reason I say this is because with stock heads/cam the stock block could hold about 10-12 lbs boosts. (depending of fuel used) now if you port the heads and install a better cam (for your app.) the stock block may be only capable of handling 8 lbs now. (actual results may vary, just used as an ex.)

Now if you drop the compression and add more boost, lets say 20lbs, your going to need a bunch of stuff like fueling, and ignition changes also. just a FYI.

Just saying this to show that 12lbs on a stock block is NOT the same as 12lbs on a setup with ported heads and a nice cam. The requirements to run safely are different. something to think about when going for XXlbs of boost

 

You don't need to do too much head porting when using a power-adder as you are. A nice clean up and port matching would be nice. A good set of valves and valve job is needed-spend some money here. A boosted engine may need higher intake valve spring rates. The boost will try to keep the intake valves open.

 

greatly appreciated guys...members like you keep tech alive!!!!

 

Who is porting your heads for you? I would hope they have a clue about this and should be able to help you out.