hi guys... Sorry i'm a newbie here..
I'm doing all motor for my car using B18c GSR block and B16a cylinder head...
Currently i'm using jun oversize valves which are 1mm oversize intake valves and 0.5 oversize exhaust valve... Please guide me to choose the right camshaft for my car?? Because my friend used the same oversize valves like mine and he used the jun type 3 camshaft then he ran it but the engine blew when the vtec's on.. the valves were bent...

My friend said I have to use camshaft that have big overlap... Is it true??

Please help me....

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ichikers &raquo;</TD></TR><TR><TD CLASS="quote">Currently i'm using jun oversize valves which are 1mm oversize intake valves and 0.5 oversize exhaust valve
My friend said I have to use camshaft that have big overlap... Is it true??
</TD></TR></TABLE>
The opposite is true. You need less overlap to reduce the chance of valve to valve contact.

 

the only real way to know is to check the vavle to valve clearance.. it depends on how the valve job was done, etc

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JDogg &raquo;</TD></TR><TR><TD CLASS="quote">it depends on how the valve job was done, etc</TD></TR></TABLE>
So true. I had a head that the porter sunk the valves into the head to allow for oversize valves, but the flow numbers sucked.

 

I have a question.. Is the head ported? What are your goals with this engine? Do you have a larger stroke or bore?

 

Yeah the head ported and also have been milled a few mm... My goal is to get as big as it can get but also can run as a street car...

I have stock stroke and oversize .5mm bore...

I'm planning to go for toda B.. Is it safe for my car?

 

I would ditch the oversized valves on an 81.5mm bore.....

 

why? my piston clearance is still safe for using the oversize valves. The thing that i concerned is the valve to valve clearance if I use higher camshaft..

 

small bores shroud big valves, the valves cant flow b/c the cylinder walls block the flow.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JDogg &raquo;</TD></TR><TR><TD CLASS="quote">small bores shroud big valves, the valves cant flow b/c the cylinder walls block the flow. </TD></TR></TABLE>

Exactly.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by b19coupe &raquo;</TD></TR><TR><TD CLASS="quote">So true. I had a head that the porter sunk the valves into the head to allow for oversize valves, but the flow numbers sucked. </TD></TR></TABLE>
interesting, so how the flows numbers on the oversize valve head compare to the standard size valve head, the reason why I ask is because that's how I did my head to accomodate the oversize valves and it flow great

 

as long as you have a big enough bore and its done right big valves can flow great... but there are people that have made 270+ hp on stock size valves .. soooo yeah

 

270 hp on stock valves is easy... with the right turbo.

 

well, I'm not talking about big bore/stroke motor with oversize valves head, as b19coupe stated that his head porter sinked the oversize valves into the seats (which is what I did to my head and I know how much it folws) in order to keep a good valves to valves clearances, which resulted in not good flows numbers.....I'm assuming this flow numbers is attained from the flow bench, which flows numbers measured at 1/2 inches lift and so on.....so my question is how is the oversize valves head flows numbers compare to standard size valves head ON THE FLOW BENCH with the same amount of lift, NOT how it is perform on different displacements engines...