some Valvetrain questions

[98evoIIIpwr]

Ok so Im rebuilding my head again. I have a set of BC 280's, BC springs, retainers and some port work.

My question is. I want to take the head down and get more extensive port work done in the bowl's and what not. I havent purchased new valves yet but know that i want to go with an oversized valve.

What are the benifits to running bronze valve guides. I see people writing about them and saying "you should do them". But why? I know stock guides are steel,but that doesnt help me at all.

Basically, I want to purchase oversized valves and new guides. Is it worth while to go with a larger valve and if so why???? should I buy the bronze guides over the steel?

For what its worth, my mods are in my profile and im looking to get around 550hp to the wheels. I know a stock head flows well but with the cams im running im almost obligated to upgrade everything else.

Thanks for the input in advance.

Ron

 

[Defiant]

Bronze guides lubricate better than steel ones do. In the 4G63T motor, the arrangement of the rocker geometry subjects the valve stem to very slight sideways thrust, so the steel valve guides survive well.
The "why" to ask may be better-aimed at the idea of porting a forced-induction's intake system.

 

[dwdsm]

Def bronze valve guides..but why an oversized valve??? I have read that the benifits of the extra air flow are nullified by the surface area that the air has to travel...So if you can save the money.. Concentrate on air velocity by keeping Neckdowns to a min..

 

[98evoIIIpwr]

Well, my decision to go with oversized valves was based solely on the fact that the pricing was the same. I would have to assume that there is some benifit to them as most high performance cars run them. Although speculation, it seems to be working for them.

Thanks Defiant, as simple as the answer was I was oblivious to the reason behind running them. With that said, Ill go ahead and order some

BTW I ended up getting Si nitride 1mm O/S valves. Could I mention that MAPerformance has been very helpful and considerate to me with my purchases thus far. I highly recommend them.