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#1
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Just curious: Any of you guys tried running the combination of 1.6 and 1.5 rockers on their small block. I was just wondering if this would give me more out of my Mopar purple .484 lift cam or if the benefits are nominal. I'm using the 587 stock heads on my 340. I forget which ratio goes where...someone refresh my memory. ART |
#2
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Usually the 1.6 is used on the intake side. It helps but not enough to be cost effective. Usually you have to buy a whole set of rockers just to get half.
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#3
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I have to disagree with you 1.5 on intake and 1.6 exh.,the exh,port's have more of a restriction on mopar heads .Some guy's just use a larger exh valve ,and some use a higher lift on the exh. side a duel grind .i see that alot on 6 cylinders I would go by what type of heads you are using and how small the exhaust port's are or are not.
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#4
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I'm still confused. Anyway, I've got a set of 1.5's (roller tipped), but was thinking of ordering the 1.6's for more lift. Then I had the thought that maybe I could serve myself better by using the split ratio.
I also thought it was 1.6 in the intake side, but wasn't sure. I hope someone else drops in to clarify. thanks, ART |
#5
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The best rocker combo depends entirely on the precise combination. I've seen lots of exhaust-restricted street cars pick up quite a bit with just higher ratio rockers on the exhaust, especially with nitrous. On the other hand, I've helped my friends with their ARCA car (Pontiac...Ugh!) and seen it pick up 1.5 MPH at Talladega with lower ratios on the exhaust, because of the less gas volume with the restrictor plate and less wasted energy opening and closing the valves. Go to a track like Atlanta, with no restricor plate and 9000 RPMs, and the car may respond to more ratio on the exhaust. An SB-2 GM resrictor plate motor is obviously a far cry from a streetable Mopar A engine, but you get my point. I tend to believe that if your motor gains anything from a rocker ratio change, you don't have the right cam to begin with. Most MP cams are a little lame in the lift department, considering their long duration, so higher ratio rockers may add some good power. Make sure your valvesprings are up to it, or you'll definitely be wasting your time and money and may well break stuff.
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#6
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I always believed that you could stager intake rockers too, for eg. putting 1.6 rockers on the ports farther away from the carb. and 1.5 on the closser ones. Can this be done effectivly.
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#7
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Krep,
That's interesting - never heard that, but I can see that it has merit. Maybe I'll just need to think about this a bit more. However, I will probably just go with the 1.6 ratio and sell my 1.5's. thanks guys, ART |
#8
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I've seen a few ARCA round track guys stagger the rockers on the corner cylinders, and it apparently helps for some applications. It seems this type of stuff is typically done by more serious racers who can afford lots of dyno time and a 5 gallon bucket of extra rockers. Like I said, if it helps that much you've got the wrong cam to begin with.
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