how do shaved pistonheads increase car performance in a carburettor engined car?

Question

I have an 8 yr old Suzuki Swift (Esteem in India) Its not an fuel injection car..n Im told thats better from a performance enhancing point of view cos it can be tweaked a lot more..Im planning to shave the Pistonheads and add a free flow exhaust..can somebody please explain clearly how they will help and what happens to the mileage as well..please explain in as much detail as you can....

Answer 1

shaving the pistons lowers the compression.. shaving the head increases the compression. an increase will produe more power. but be sure you have a machine shop that knows how much to shave do it. there are alot of dynamics like valve clearance and fuel to consider.. if the compression goes up alot , say to 11 to 1, you will have to use a higher octane fuel.. in the U.S. it would be 93 octane.. where u r I am not sure. Horsepower comes from fuel mixture in and exhaust out. the ways this happens is thru the intake, head and the camshaft, and the exhaust is opened up to flow freer. sounds like ur exhaust is done, while you have the head off, have it ported and flow tested.the reason to flow test is u want all the ports to flow as close to the same as possible. especially if u port them out..you may see if there is an intake valve that is bigger that can be installed.. in the U.S. we improve the heads by milling, porting the exhaust ports and putting bigger valves in certain heads, mainly small block v8, like the chevy and the ford heads will take a 2.02 inch intake and a 1.6 inch exhaust. the exhaust has to be smaller or the gasses will not leave at an efficient rate. but matching the ports on the intake and heads helps. u can polish the intake ports in the heads. since u r carbureted, do not polish the intake runners . reason is the fuel atomizes better on a porous surface. as an experiment, use a piece of sandpaper and put water on it and blow , it will spread out flat.. use a piece of glass with water and it will roll in beads. this is important to know since fuel vapor burns not liquid fuel..hope this info helps..

Answer 2

You are on the right train of thought by removing a carefully measured amount of material from the cylinder heads but there are several things to consider before having this done:
What is the present compression ratio? If you are near 9.2 -9.6 now, any increase in compression is most likely going to force you use higher octane fuel. I could be entirely wrong hears why: Some gasoline engines can tolerate higher compression ratios because of the internal shape of the combustion chamber. Generally speaking 4-valve per combustion chamber cylinders do not have the usual wedge (may cause detonation) shape and shrouding of the valves. The air-fuel mix comes in and out more efficiently in 4-valve chambers. Here's a head scratching for instance: The Duratec Ford 3.0 24 valve V6 double overhead cam motor (4valves per cylinder) has a 10.0 compression ratio and runs fine on 87 octane fuel. Usually any wedge shaped chamber will detonate, ping and knock.

Let's talk about your cylinder head for a moment. Its very important that the combustion chambers have no sharp edges or casting irregularities anywhere. We'll talk about how that's done later. The intake manifols should be perfectly matched to the cylinder head the intake runners must be straightened and the valve guide boss supports narrowed. The intake ports do not need to be polished.

Todays top NASCAR cylinder heads haved cylindrical grooves machined around the ports starting at the opening all the way to the valve seat. This is done to tumble air and fuel to keep it mixed in as small particles as possible. The valves should be unshrouded on the back walls of the head. The exhaust valve bouls must be cleaned up and straightened. Again, the valve guide bosses must be narrowed and contoured.

If I were you when the head or heads are off the motor have the chambers checked for cubic centimeter volume (cc'd) They should all be the same volume. Well before you have the cylinder head planed measure the valve open to piston clearance with modeling clay. You should have no less than .040 clearance with the head installed.

Call around to find a race porting service you will gain more power by touching up the ports and chambers than removing stock off the head. If you do both you will have a winner.

Porting services have very specific tooling, flap wheels carbide burrs, air grinders and some have specialized CNC machines to replicate ideal flow patterns.

Answer 3

I could be wrong but I think what you are referring to is is shaving the heads. Taking material off the heads will reduce the combustion chambers sizes, creating higher pressures on the compression stroke. In turn making a more violent explosion when ignited by the spark plugs. Which creates more power, but at the risk of detonation. You will have to retune your car, back off the timing. Detonation is when the excessive pressure in the combustion chamber ignites the gasoline before the spark plug gets a chance to. And since the piston is still on it's way up when this occurs it's very damaging to your engine. It sounds like nuts and bolts rattling in an empty coffee can, unmistakable.

Answer 4

When you shaved the heads, or mill the heads as it is sometimes called, you are in effect, increasing the combustion ratio. The higher the ratio the more power you have. This will also give you a chance to straighten out the heads. You can also bore the cylinder walls out to increase the cubic displacement.

Answer 5

Funny

Answer 6

shaving the piston heads will lower your compression and power, shaving the cylinder head will increase your compression and power but you will also have to burn premium fuel. you wont notice much increase unless you also add a performance camshaft and rejet your carb.

Answer 7

shaving piston heads will give you higher compression which will result in more power. as far as i know you use the same amount of gas, and you getting more power. its like that with racing lawn mowers anyway