first off .. my head flow #s

lift Int Exh
100 74 51
200 144 113
300 206 161
400 253 193
500 281 214
600 301 227
700 309 235

currently i run the CC306 with 1.6 RRs getting .544 and .576 lifts

I can swap my rockers for a set of crane adjustable ones and set the intakes to 1.7 (leaving exh on 1.6) resulting in .578 / .576 lifts

would 0.034" extra lift on the intake yield enough extra flow to result in any noticable hp ?

 

Looking at lift numbers it SHOULD produce some more hp. Usually going to a higher ratio will kill some lower end but give you more top end HP. I suppose this would be true of our cars, thats how it works for a regular small block at least.

 

Yes you will gain some useable HP and TQ.

Even still you arent even comming close to using the full potential of those heads. You could always keep the 1.6 rockers and get a new cam ground that would suit the heads better for less money if you install it yourself.

 

the rockers would be a free trade with my pro mag 1.6s ...

I will go with a massive lift cam after my engine rebuild .. as i run close to 12:1 C/R with 2.05 / 1.6 valves so running a 700 lift cam would be asking for trouble ... im sure i can get away with .578 on the intake as my exh is running that much lift on higher duration ...

I know i should get a custom cam to make full use of my heads .. but i thought the rocker swap would give me a decent bump in NA power then why not (considering its free)

 

if it's free, then do it. It's just labor.

Your not going to gain a ton here. 5hp is my guess, but it will be some.

Side note:

The P/V clearance issues stem mostly from duration, ramps and LSA. NOT MAX LIFT. The piston is so far down the bore at max lift that it's not even close. It's during the overlap period when the piston is coming back up to TDC that you get the P/V very close. The problem is assocaited with big lift cams because most of the time they are big duration cams too.

Don't feel stupid though. I've had to mention this to people who do know better but never thought about it.

Bret

 

The only reason why im double thinking this "rocker trade" is that the crane adjustable rockers dont have a roller tip... they have this curved plate on their tip where the valve stem has contact.. they are only roller fulcrom (sp?)

has anyone ever used these rockers ? any good / bad things about them ?

 

When you say "swap" do you mean like a trade or just changing them out for the Crane 1.7's?

If not you could just buy a set of Crower 1.7's with the full roller tip. Worth swapping to see if you gain anything but like Bret said, I don't expect much.

-Mindgame

 

i mean trade them for my 1.6s

i dont want to put 1.7s on my exh valves as their lift is already at .576 with 1.6s ..

the ones i would be trading for are adjustable (1.6 - 1.65 - 1.7)