Which roller rocker ratio?

[nastynavy]

I have a stock set of GN1 alluminum heads and need to buy some roller rockers for them. I have a 220/224 cam, ported intake, 20 over Wiesco pistons, k-1 rods, good crank and a 67 bb turbo. I am trying to figure out whether to use a 1.55 ratio or a 1.65 ratio. Any help would be great. Thanks,

 

[FastRegalWE2]

Im running GN1'a, 215/220 with 1:55 Scorpion roller rockers
You have to keep in mind PTV clearance if you go bigger. Do the math and see what the new lift would be.
Im also running Diamonds and they have recess for big lift cams but I didnt see the need to run larger than stock ratio on mine

 

[Alky V6]

The 1.65 will eek out a little extra valve lift for a little better breathing. You have to do the math with your setup to tell if it is worth it or not. Usually, it's good for a tiny bit more HP.

 

[turbobose13]

Go with the 1.65, I have them on my car and you will pick up a little HP.

 

[49-blues]

What about 1.55s on the intakes and 1.65s on the exhaust-i ve heard of people doing this for better exhaust flow to spool up turbo alittle better.

 

[Alky V6]

What about 1.55s on the intakes and 1.65s on the exhaust-i ve heard of people doing this for better exhaust flow to spool up turbo alittle better.

You could experiment and try it both ways, see what you get. I would guess though, that you would end up with 1.65 on both intake and exhaust.

 

[Mike Licht]

I do not think the extra lift will help much on an unported head. You will also have to be carefull about coil bind with a 1.65
Mike

 

[nastynavy]

Thanks for all the responses guys. I will call you tomorrow Mike and order some rockers. Thanks,