transwiz

iTrader: (26)

I have a set of 317 heads that I bought and was planning on some porting and milling on them. I bought some stainless intake and exhaust valves for them.
(ferrea) and was planning on a valve job.
They are the stock size valves 2.00" intake and 1.55" exhaust.Can I install 2.02" intakes and stay with the 1.55" exhaust since the 1.57" are only 2 thousands of an inch bigger would that effect performance? Do I have to go with 1.57 on the exhaust.

KCS

iTrader: (20)

You don't have to go to 1.57" on the exhaust, 1.55" exhaust valves will work fine with 2.02" intake valves.

96capricemgr

iTrader: (1)

why do you want to change valvesize atall?

wildcamaro

iTrader: (15)

Let me get this straight you want install 2.02 over 2.00 intake valves, but don't want to install exhaust because they are ONLY 2 thousandths bigger? Am I missing something?

96capricemgr

iTrader: (1)

Well besides the fact it is 2 one hundredths each as in BOTH there is the fact that larger valves aren't really going to be worth the expense without professional level porting and even some professionals like stock size.

Betting he just likes the sound of 2.02 because that was all the rage 40 years ago............

KCS

iTrader: (20)

That's not fact, that's an opinion.

transwiz

iTrader: (26)

I was told that with my car I was looking at about 10 horsepower difference at the wheels with 2.02"/ 1.57" vs 2.00"/ 1.55". I was going to send the heads in to West coast cylinder heads for some porting.If you notice my signature I am running 2.08" intakes which I was told are redundant unless I have more cubes and are spinning it over 7k.It won't pass smog so I am going to change heads to be able to pass smog.I don't want to loose any horsepower. If I can stay with the same horsepower I will be happy.
Trying to make sure a make the right decision before the heads are on the car.

KCS

iTrader: (20)

Why won't it pass smog? Maybe a cam swap would be better?

96capricemgr

iTrader: (1)

I would agree a cam is a more likely smog issue than heads.
Far as valve size since you are having them professionally ported why ask here ask the vendor.

transwiz

iTrader: (26)

Cam is a baby cam 224/224 561/561 @115. I was told it was the heads.The heads i have
on now were set up for a stroker motor and not a 346.I was told that I would get more power with a different set of heads with 2.02".

Always2Slow

iTrader: (8)

This is the most backward thinking I have encountered. Bigger valves will make more power 100% of the time, UNLESS you are shrouding the valve badly in the chamber or bore or you create flow problem as a result of not having the port structured in a way to support the new valve. Even if your coefficient of discharge drops with a the large valve and it flows more you will pick up.

KCS

iTrader: (20)

If the heads are too big, then appropriately sizing the ports for the RPM and displacement will be a good thing. With the bigger valves, the cam acts bigger than it would with a smaller valve, which is why I would have swapped the cam. By going with smaller valves, you're effectively making the cam smaller.

wildcamaro

iTrader: (15)

Always2slow, I'm not familiar with the coefficient of discharge...could you explain?