Engine Tech: Combustion Chamber Modifications for MORE POWER!

COMBUSTION CHAMBER MODIFICATIONS:

1. Install oversize valves if the engine has a bigger bore size. Installing bigger valves with stock bore size will just pinch and shroud intake flow around the valves closest to the cylinder wall.
2. Exhaust valves should be unshrouded as much but not as much as the intake valves.
3. Match the combustion chamber sides to the cylinder wall with out making it bigger than you have to!
4. Keep the combustion chamber CCs. at a minimum. A smaller combustion chamber yields more compression for a given piston.
5. Polish the chamber so it prevents the build-up of carbon and reflects heat back to the piston! ( Heat is Power).
6. If you have to choose between an open and a close chamber here is the difference: An open chamber will probably flow more on the flow bench. If you want to raise flow benches buy this heads! A closed chamber will probably flow less but has a much effective chamber and ‘BURN’ characteristics . Also requires less dome to achieve the same compression ratio! (more power with a flat top and smaller chamber)
7. The Valve affects the flow! The Valve Margin also plays into the mix. A thin margin creates a hot spot on its radius and screws up the flow off the valve and seats.

CASE IN POINT: When all is said and done with your ‘tricked’ heads make sure you pay attention on this! If your best power was achieve with 36-38 degrees of ignition timing before you modified the heads! And now you went faster but your timing requirements ended at 42-44 degrees you are in trouble! You have lost COMBUSTION EFFICIENCY and the added timing requires the engine to work against itself and its called NEGATIVE TORQUE! The engine has to work against the added 2 to 6 degrees more of crank angle at the time of ignition… If your new combo required less ignition timing to make more power, buy your engine builder a big SAN MIGUEL and give him your favorite Princess!!! LOL

NOTE: PRO-STOCK engines and NASCAR powerplants requiring 28 degrees of IGNITION TOTAL TIMING is an indication of an effective combustion chamber design! This is achievable by the combination of swirl and tumble flow in to the port, as well as some combustion chamber induced swirl. also a non-intrusive effective dome. The best piston is a flat top. When combined with high compression due to a compact chamber….

4 VALVE:

1. 4 valve breathes well but its drawback is its reduced flame propagation. Due to the absence of Quench! (some import heads have a quench pad and this is desirable in a normally aspirated engine or one with nitrous oxide).
2. On some 4V heads, the tumble situation of the heads reduces- instead of enhancing the flame front! This can be corrected but requires machining the heads and utilizing a custom piston with an extended quench pad. This is most beneficial on normally aspirated engines….

Questions? send us a message and we can post it or keep it confidential… Thanks Ben Alameda