Cesar Ablao
Super Veteran
Heres what im waiting for. How much does this head cost? Sorry i cant post a picture right now, im just using my cellphone.
Head Jvt Big Valve Head
- Thread starter Cesar Ablao
- Start date
Cesar Ablao
Super Veteran
sir kiram let me borrow your pic.
Here it is, the JVT big valve head!
We contacted sir mon regarding this, but unfortunately, he doesnt have the price for this yet!
Here it is, the JVT big valve head!
We contacted sir mon regarding this, but unfortunately, he doesnt have the price for this yet!
Cesar Ablao
Super Veteran
i think big valve head upgrade is advisable for bore kits 62mm up. just like raider 150, it has 62mm bore so the recommended valves is 19-22. stock head and valve is just fine for 59mm below.
bhek_21
Super Veteran
Okay. Because I remember a friend of mine went to a very well known mechanic here in Pasig and told him that big valves is not required unless your engine is high comp even if the engine bore is 63.. His engine bore is 63mm but the mechanic didn't recommend him to change to big valves because he is not high comp.. just my share..
Cesar Ablao
Super Veteran
Maybe hes just telling you that its ok to use stock head and stock valves to big bores.
bhek_21
Super Veteran
No bro.. He is not recommending to use big valves if your engine is not high comp even if your engine bore size is 63mm..
Cesar Ablao
Super Veteran
Ok bro. Anyway, lets just wait for the updates for this jvt head. Im very interested with this.
bhek_21
Super Veteran
The mechanic you are referring, what is the name of shop? 
albert_manio
New Member
im using 57mm vixion block. but i dont know what's the number of my compression. how will i know whats compression ratio of my block.
Kenneth Roy M. Caberto
New Member
jetron.....
Francisco N. Maristela
Veteran
guys, below is a rough computation on your compression ratio considering there are no changes in the head (Shaving, jackup, high comp piston and polishing). Porting doesn't increase compression.
Stock LC135
Combustion Chamber Volume = 134.4cc/10.9(Compression Ratio)
= 12.33cc
Vixion Kit Compression (57mm piston dia)
= 149.78cc/12.33cc
= 12.14 Compression Ratio
91Octane above recommended
62mm kit = 177.2 cc/12.33cc
= 14.37 Compression Ratio
95octane rating recommended. Po
65mm kit = 194.78cc/12.33cc
=15.80 Compression Ratio
(Big Head upgrade, or polishing is not recommended but a must to prevent knocking) Polishing increases the head volume.
Compression ratio 2:1 3:1 5:1 10:1 15:1 20:1 25:1 35:1
Pressure ratio 2.64:1 4.66:1 9.52:1 25.12:1 44.31:1 66.29:1 90.60:1 145.11:1
Stock LC135
Combustion Chamber Volume = 134.4cc/10.9(Compression Ratio)
= 12.33cc
Vixion Kit Compression (57mm piston dia)
= 149.78cc/12.33cc
= 12.14 Compression Ratio
91Octane above recommended
62mm kit = 177.2 cc/12.33cc
= 14.37 Compression Ratio
95octane rating recommended. Po
65mm kit = 194.78cc/12.33cc
=15.80 Compression Ratio
(Big Head upgrade, or polishing is not recommended but a must to prevent knocking) Polishing increases the head volume.
Compression ratio 2:1 3:1 5:1 10:1 15:1 20:1 25:1 35:1
Pressure ratio 2.64:1 4.66:1 9.52:1 25.12:1 44.31:1 66.29:1 90.60:1 145.11:1
Kenneth Roy M. Caberto
New Member
sir,, i think when we increase the diameter of piston / bore; our combustion chamber volume also increase.
Francisco N. Maristela
Veteran
Nope. Combustion chamber is calculated during the top dead center. no matter how much you increase your piston diameter, it will not increase the combustion chamber unless you have allowance or decrease in the the top dead center.
Kenneth Roy M. Caberto
New Member
sir combustion chamber means the space between cylinder head and top of piston. Distance between top of piston and head remains the same but the diameter of the combustion also increase which means volume also increase. i have also read some threads about vixion kits that once you used it; your engine become low compression.
lpsnipie_67
Super Veteran
The actual size of the combustion chamber is the volume left clear of the cylinder head when both the intake valve and the exhaust valve are closed, and the piston is at the top of its cycle. A smaller combustion chamber produces a higher compression ratio and hence will produce more power. Higher compression also created higher temperatures. The size of the combustion chamber can be changed either by boring the cylinder head or by changing the shape of the piston head.
I hope that helps answer the question!
I hope that helps answer the question!
Francisco N. Maristela
Veteran
THanks Bro. Absolutely right!
Kenneth Roy M. Caberto
New Member
tha
thanks for further explanations sir,, which make it clear that we increase the size of the bore also increases the combustion chamber volume.The actual size of the combustion chamber is the volume left clear of the cylinder head when both the intake valve and the exhaust valve are closed, and the piston is at the top of its cycle. A smaller combustion chamber produces a higher compression ratio and hence will produce more power. Higher compression also created higher temperatures. The size of the combustion chamber can be changed either by boring the cylinder head or by changing the shape of the piston head.
I hope that helps answer the question!