Lawhead

iTrader: (14)

Since I've been doing the whole "wanting to build my motor" and stuff and research. I've seen on a lot of the cams Llyod Spec's he keeps the lift numbers pretty close to each other. So what thinking with the CC306 with the 1.7 Roller rockers on the intake side and the 1.6's on the exhaust side and would keep the the lift numbers really similar also you hear it debated that the rocker changes change more then lift but I always thought it was Lift and Lift only.

230/244 .578/.576

Any advantage in this? Assuming the heads on the car I have will benefit from the added lift but in this case we just say they will and pretty sure they can due to the numbers it had produced.

Just Curious if anyone has ever done this or think it would be help. I mean any help is good I've seen the 1.6 to 1.7 comparisons on a stock car but of course that was on both sides. What you guys think??

Wicked94Z

iTrader: (26)

It'll pick up some power, yes. It will change the duration and lift that the engine sees at the valve. LT1s like a quick intake lobe so you're going in the right direction.

Lawhead

iTrader: (14)

Thats what I was thinking as well that it should pick up some power but just a matter of how much.

And Nice play on words there....lol

Wicked94Z

iTrader: (26)

lol typo fixed.....

Lawhead

iTrader: (14)

Thought it was clever I would have claimed that to be what i actually said haha

nitrous2fast

iTrader: (2)

if you are doing this on a stock LT1 head (ported or non-ported) I would put the 1.7 on the exhaust side. The problem with a lot of gm heads is that they can get the air in effectively, but have trouble getting it out. this is why you see a lot of cam grinds for a stock head with much more exhaust duration than intake.

Also many grinds do incorporate this flow imbalance and increase the duration of the exhaust lobe to compensate. Many times matching ratio rockers are best. Only after the engine is running/tested can a judgement be made to whether you NEED more of either...guessing as to whether split ratio rockers will improve your vehicle's performance before any real data can be recorded/analysed is not very smart.

Wicked94Z

iTrader: (26)

with the CC306, an increase in exhaust ratio will further decrease torque as the exhaust events occur too early as it is. Since pumping losses are not a concern with a decently ported stock casting under 7000 rpm with the CC306, you'll likely see no benefit up top from the ratio increase. As I already said LT1 responds very well to quick (and early) intake valve action as a nature of the induction design. It has nothing to do with max lift, it has to do with the lift area that the engine sees at the valve (duration x lift).

nitrous2fast

iTrader: (2)

well adding to the early intake you also get a late intake too.... the cylinder can't build pressure until the intake valve closes. Thus losing more compression....

If the cam was the 503 then yes i would put the higher ratio on the intake, but with 306 the intake valve closing at 73* ABDC adding a even later event is not going to help.

Wicked94Z

iTrader: (26)

what happens to DCR when you increase VE? That's the reason you snap the intake valve open.

nitrous2fast

iTrader: (2)

Increasing VE is determined by much more than intake duration and lift.... intake closing is much more important than intake opening. The 306 has the intake valve closing way too late as it is, which is why it makes so much of it's power in the high rpms. adding to the intake is just gonna push that curve up even more... for a 355 with the stock-style heads just leave the 1.6's in OR change the intake to 1.5 and exhaust to 1.6's.. you would widen the power band and still retain the high rpm power this cam is known for.

gregrob

iTrader: (8)

Uhhhhh...... lol

Lawhead

iTrader: (14)

Well then.

Puck

iTrader: (17)

The 1.7s will have the effect of making the intake lobe seem more aggressive, which is what the lazy 306 needs.

The 306 was not made for LT1 heads at all, so what characteristics are ground into it do not apply. I think that 1.7s will help more on the intake valve then exhaust with it.

Personally I would just run a different, properly specced cam on 1.6s, but if you already have the 306 or are set to run it then the 1.7/1.6 combo will help over the 1.6s.

Lawhead

iTrader: (14)

Yeah the 306 is in it and a complete long block. So not wanting to change cams. I might do some back to back track outings see if it helps