wanted to know if anyone knows how much more hp/tq you get from jumping from 1.5 rr to 1.6. cam specs with 1.5 rr are 218/224 .495/.503 112 LSA. jumping from 1.5 to 1.6 would bring my lift to around .528/.535. how much more rwhp do you think i'd get from just jumping to 1.6 rr to achieve that lift? thanks guys

 

prolly 4-9 hp,could be more depending if your combo needs the extra lift and duration

 

not enough for you to notice, but it should be more and the 1.6 rockers most likely will be better than factory pieces.

 

Putting rockers with a consistent, repeatable ratio in there is worth several HP.

The difference between quality 1.5s and 1.6s is quite small on a typical stock motor, because the valve opening isn't the engine's bottleneck.

With your mods, there may be a little more difference. So if you're buying rockers anyway you might as well go for the higher ratio. You should definitely get 1.45" diameter valve springs put into your heads though, even if you go with 1.5s; with 1.6s, you'll be risking destruction if you don't.

 

I have also heard of using 1.6 ratio rockers on just the intake or the exhaust to gain either more low or high RPM power. Is this true??

That's what the guy building my engine said he may end up doing, depending on dyno results.

 

That's a fine tuning thing that must be done on the dyno; it's nearly impossible to predict how a given setup will react. The heads especially, and the exhaust system, are the biggest factors that determine that.

In any case, you will almost never get "more power", either at higher or lower RPMs, by using less valve lift. Rather, what you are doing, is trading off power for valve train longevity. In racing, especially long round-track racing like NASCAR, everything in the engine is stressed to the absolute limits of its endurance; if they find that they can reduce the stress a little bit without slowing the car down, they'll do it.

In a street car, especially one with stock heads and a stock induction system on it, and a cam with such low lift as that one, it doesn't really apply. The lift will help out, on both valves, at all RPMs. Just use the right valve springs so you don't break parts.

 

OK - Maybe I missed the meaning of the above. Please clarify this for me.

Assuming a non-stock induction,heads and cam, and using proper springs - it still woudn't make sense use 1.6 RR on the intake or exhaust only?? Or would increasing lift on both give me more power throughout the whole range? Just not sure if I'm reading your answer correctly.

Thanks RB!!

BTW, It does make sense to me that if my exhaust system is a bottleneck, opening up the exhaust valve further would show no gains....let's assume no bottleneck exists...intake or exhaust.

 

i bought comp cam 986 springs... wouldnt that be enough for that lift on 1.6 rr's? i just want to replace the factory rr's with either 1.5 or 1.6's... seeing that 1.6 would yield more power for the same price, im heading my decision towards them.

 

alot of people will use 1.5 rr's on the intake side and 1.6's on the exhaust to make the to squeeze every last hp out of the deal because the 1.6's are supposed to be over kill for most motors unless u are putting some serious hp numbers out. so i have heard

 

Yes, those would be good.

 

OK, since no one could answer my question above (or didn't want to), I again went through a search which left me as confused as before.

Looks like to me overall a split ratio setup may or may not improve performance, and if it does, it could be as little as 4 HP up top or 40 HP.....I guess I'll see when it gets on the dyno at the end of this month. Sorry, wasn't trying to take over the post, just had an interest in this also since I'm in the middle of having a new engine built. The guy will be tuning it on the dyno anyway...

Don't worry, I'll share what I found out.