I looking into new valves for my build and found some valve sets. But if i get .5 mm or 1 mm over stock, will they fit right in or will it need a port or bore or something?
And for a turbo should i get high comp? or stay with standard compression valves?
I orginally planned on building just the block so i didnt do much research on head components so i just need some quick info on this question!
I can't give you any firsthand information on this, but I've read that oversized valves are for people who want to push the threshold of 500hp or more. The main reason you want them is to increase the cubic feet per minute (CFM) of air that your engine inhales and exhales. But just putting new valves in won't increase this, you're going to have to send in your head to get the valve ports enlargened to fit them. Usually, you're going to have to send the valves with them to get it seated just right too.
I'm just speculating at this point, but if you have a big turbo with oversized valves on the H22, I would imagine the lag time would be enormous and although you might be happy with top end power, your spool up time would kill it for you and you'd be unhappy overall. If you're still shooting for the 350 to 400whp, you might be better off leaving the valves stock size, but upgrading them to a good aftermarket kind known for high boost applications.
Remember, the stock valvetrain and head flows very well from the factory, so this all might be unnecessary until you get your numbers.
Are you planning to do everything all at once on this engine or see what you get with a certain amount of mods and go from there?
Oh and as for your response on if you should stay with high compression or not, the answer is more complex than this but here's the gist...
If you're going to run high compression on a forced induction motor, you can only run a limited amount of boost unless you start using gasoline with a very high octane count. Only tuning will tell you your threshold on this setup and the limit of the power you can make based on listening for detonation (which will come alot sooner with F/I and high compression)
If you're going to run low compression pistons on a forced induction motor, this increases your ability to turn up the boost and still be relatively safe.
For those with alot of knowledge reading this, I base this on the pricincple that the timing settings would remain the same on both motors.
Ultimately the pros of F/I and high compression together is a faster spool up time and more power through the power band. The cons of this are a ceiling put on your power unless you start using higher octane fuel which could, depending on your tune, force you to not have a street car anymore.
The pros of an F/I and low compression motor is safer tune, more room to turn up the boost and a larger amount of power to be made in the top end. The cons include turbo lag up the as$ and low amounts of power in the low end.
It's up to your driving style and requirements to dictate what you do.
I've never heard of lower compression valves to be honest. If you have, where did you get your info from?
But yes, if you get oversized valves, your original valve holes have to be enlargened to fit them. This is a very delicate machining process finished with a 3 or 5 angle valve job.
And I'm not necessarily saying high compression is better than low compression or vise versa, it all depends on your driving style and personal opinion.
On the skunk2 website, there are diferent choices of valves, standard comp and high comp.
I have heard of it either so im just going to get supertech valves. But thanks again for your help man!
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