Fitting Bigger Valves in a YB
#3
10K+ Poster!!
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?
I expect at your power levels big valves will be of benefit. Do you lose torque lower down with bigger valves?
#4
PassionFord Post Troll
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
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
Last edited by smiley; 02-04-2015 at 06:33 PM.
#7
cossie fan (unluckerly)
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
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#8
PassionFord Post Troll
Thier ya go mate whoever wrote that i posted is talking shit you dont need one
#10
10K+ Poster!!
Would make sense on na engine as there is no boost to push the air in
#11
PassionFord Post Whore!!
#15
PassionFord Post Whore!!
#16
Happily retired
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.
#18
Happily retired
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