At what BHP level should you be looking at fitting bigger Inlet and or bigger Exhaust valves?
Is it based just on BHP or are there other considerations?

Cheers Rich

 

Anyone?
Feel free to discuss.

Rich

 

I guess some depends on what head work has been done, size of turbo and pressure of boost then the cams too. I.e. Are the valves the limiting factor or is something else restricting flow?

I expect at your power levels big valves will be of benefit. Do you lose torque lower down with bigger valves?

 

Found this mate

The standard cylinder is very good. It can support up to 350bhp without modification. For 350-500bhp the valves can remain standard but the ports need to be enlarged to 22.5mm on the intake side and 23mm on the exhaust. For 500bhp+ the valves can still remain standard but the ports need to be made even larger, 25mm inlet and 24mm exhaust and this works well with BD16 inlet cam and BD15 exhaust or BD15 inlet and BD14 exhaust. For 600bhp+ port need to be taken to 26.5mm inlet and 25.5mm exhaust. At this level the valves are becoming restrictive so bigger item need to be fitted. For bigger valves, bigger cams are required and this means further machining of the head

 

I don't have them & have more Power than most.

 

Thread closed

 

With the power and torque rod had and the way it came in its safe to say if he didn't have them put your money towards something else. But I guess ultimately you can only take the advise of who you use to build your engine. Be it wrong or right

 

Thier ya go mate whoever wrote that i posted is talking shit you dont need one

 

So we're going with you don't need larger valves at any point when tuning a turbo'd YB and I presume they are only necessary for the N/A boys?

Rich

 

Would make sense on na engine as there is no boost to push the air in

 

800hp or above you will start to have gains and losses going bigger.

Mark

 

Cheers Mark so is Rod's new spec going to have larger valves?

Rich

 

No it will not.

 

So you can easily run 1000bhp with standard valves?

Good to know

Rich

 

We havent easily done a 1000hp yet and most likely be very hard.

Mark

 

Wow!! that would be good.


As with all engines its a compromise. We could fit bigger Valves, larger Ports & a wild exhaust cam but it would do nowt below 6k. Its about Gains & Losses. We want a road engine not a drag engine & that will be tough.
The head has .25mm bigger Ports & a stage wilder exhaust cam. We hope to follow the existing curve up to 6k then the Huge Airpump we strap to the engine will be asked to puff circa 4bar ( 58psi) to increase the Torque above 6k. If we see 656ft/lb at 8k the Dyno WILL show 1000bhp. The Maths don't Lie but it may be hard to achieve.

 

I used the word "easily" flippantly but what I was trying to convey is there is no need for larger valves on pretty much ant turbo'd YB application.

Rich

 

That's correct.