yeah, I will be using the 9333, they just seem like a really soild gasket from all that I have read... and that even people with boost using them... and I'm hoping to never have to pull the heads on this thing in my life time... so I want something that will last...
but I did learn something... never heard of quench... but been reading up the last few days driving myself nuts... but this is the last engine I will be re-doing anyway...
so anyway... the gaskets came today... I unboxed them.. and 1 of them, it looks like the cardboard backer got bent.... so not sure weather to file complaint with rokauto and have them replace or not... it looks like it only bent the 2 ears on the gaskets... not sure if this would mean anything or not, but what do you guy's thinks, I have attached pic's...
I wouldn't lose any sleep over the slight bending. They're fiber gaskets. I doubt it'll be an issue once the heads are torque'd down.
Engine building really is a science to itself. There's "good enough" and then there's optimized. The less thought about things like quench distance, valve angle, valve seat angle (single, 3-angle, 5-angle, etc...), backcutting valves, blended ports, chamber polishing, hot spot elimination, port matching, piston-to-wall clearance, ring gap, ring thickness, oil ring tension, bearing clearances, windage, assembly weight, oil temperature, properly cleaning coolant and oil passages, valvetrain geometry, valve lash (with solid cams and lifters), oil viscosity, trans fluid temperatures (in automatics), and the many wonderful things about cam profiling that can mean the difference between an engine that just runs okay and one that pulls ahead of the rest and does so with more efficiency, less spark advance, and lower octane requirement.
---------- Post added at 04:12 PM ---------- Previous post was at 02:35 PM ----------
I'm bored, meds are kicked in, and I'm in a perfectionist hypomanic state at the moment so I'm going to do a brain dump. Enjoy it if you will. I just feel like letting it rip.
Only about 35% of the energy potential of the fuel burnt in the cylinder gets converted to rotational energy at the crankshaft. This is in part due to thermal losses to cooling of the engine and frictional losses in the engine, but a lot of it is because of poor fuel efficiency. This is caused by a number of things to include, but not limited to, poor compression, poor air/fuel homogenization, poor chamber design, cylinder fill dilution (residual exhaust still in the cylinder after the exhaust valve has closed), and wrong spark timing.
Contrary to popular belief, more spark advance is not a good thing. If you're having to advance the spark timing in order to pick up power, it means you're losing combustion efficiency. The ideal spark advance is 0 degrees. However, this is virtually impossible with current technology. The goal is to achieve peak cylinder pressure at 15-20*F after top dead center as this is when the piston/rod angle achieves the best leverage on the crankshaft. If the pressure peaks too soon, the piston can't get out of the way of the pressure surge and it causes piston rock/jarring in the bore and detonation, along with power loss. Peak too late and you give up power and response. In order to achieve this ideal peak pressure zone, we have to advance the spark and ignite the air/fuel mixture prior to the piston reaching top dead center to get the mixture burning. Modern, more efficient chamber designs like the pent roof chamber found in modern 4v DOHC engines are much more compact and efficient at burning the mixture, therefore burn the mixture faster, and require less spark advance to achieve the ideal pressure peak zone. When the spark ignites while the piston is still moving up the bore toward top dead center, excess pressure is created while the mixture is starting to burn. This excess pressure is working negatively against the engine's rotation robbing it of power and throwing away thermal efficiency. The more advanced the spark, the greater this effect, however the peak pressure zone advantage outweighs the negative effects. Hence why it's acceptable. It's not optimal, just acceptable.
A good example of this is your GT40P heads actually. They have a slightly more compact chamber (59-61cc) compared to standard GT40 and E7, E5, etc... heads found on the SBF engines. The spark plug is more conveniently angled toward the center of the chamber which allows the combustion pressure to expand away from the plug in a more even fashion. This is why the GT40P heads only require 28-32* max advance vs the typical 34-36* advance of other conventional SBF heads. A small change but every little bit helps.
The term quench is actually a bit misleading here it doesn't really "quench" anything like you would quench your thirst or quench a flame. It's quenching the air with fuel... or quenching the fuel with air... whichever. The process behind the term quench in this case is referring to the turbulent homogenization of air and fuel in the chamber. The quench distance is the distance from the top of the piston to the bottom of the cylinder head, including the head gasket thickness and deck height clearance. This is sometimes called the squish band. The purpose of tight quench distance is force the air/fuel in these areas of the cylinder inward toward the center of the chamber. This does a number of things. It creates a lot of turbulence which mixes the fuel into the air well allowing for a more even burn upon combustion. The air rushing across the top of the piston toward the chamber cools the piston a decent bit which is always beneficial. It keeps carbon from building up (as easily) in these areas as well. Anything tighter than about .045" quench distance will easily achieve this. From .045" to .060" is the gray area where some quench is achieved but not as well as it could be. Wider than .060" means very little to no quench achieved and instead just leaves pockets of air/fuel on the quench pads that can pre-ignite. This hostile range runs up to around .150" distance. Wider than .150" becomes safe again from detonation but without the response and efficiency that comes with proper quench. A lot of turbo engines run in the .150-.200" range to open the tuning window since air/fuel homogenization is already achieved with boost.
Tight quench, proper plug and plug location, and spark timing are all critical to getting most of the fuel that's being burned. You won't be doing much good to introduce more air and fuel to the cylinders when you already can't efficiently burn the air and fuel that's there.
Anything else you want to know or discuss, just ask. I love talking about this sort of stuff and could do it all day.