Orange67Dart
Active Member
Just wondering what anyone thinks about doing a mixed ratio setup on my 340 X heads. My engine builder suggested this to make more torque. 1.6 intake 1.5 exh. ( or somethinglike that ) No parts have been ordered yet.
Mixed ratio roller rockers?
- Thread starter Orange67Dart
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Arco440
Well-Known Member
Look into the Rhoads lifter i use them in my 440 and im very happy.It basicly does the same thing.
alan627b
Well-Known Member
Arco, Have you been smoking the drapes?
Bleed down lifters change the rocker arm ratio? Is your set magic? Mine don't. They bleed down at low rpm effectively reducing the duration the engine sees for more vacuum, but they don't change effective valve lift. Especially not at anything above low idle.
He's thinking of putting a 1.6 rocker on effectively increasing lift and/or duration, the exact opposite effect of Rhoads and other bleed down lifters. He's looking to make more torque across the entire RPM range.. If I'm wrong, please correct me, Orange dart.
Orange Dart, mixing rocker ratios is a fairly common thing.. make sure to check piston to valve clearances at max lift so there is no interference... if you have a competent machinist/builder who knows how to do his work it shouldn't be a problem.
Some of the experts will chime in soon I'm sure.
Alan
Bleed down lifters change the rocker arm ratio? Is your set magic? Mine don't. They bleed down at low rpm effectively reducing the duration the engine sees for more vacuum, but they don't change effective valve lift. Especially not at anything above low idle.
He's thinking of putting a 1.6 rocker on effectively increasing lift and/or duration, the exact opposite effect of Rhoads and other bleed down lifters. He's looking to make more torque across the entire RPM range.. If I'm wrong, please correct me, Orange dart.
Orange Dart, mixing rocker ratios is a fairly common thing.. make sure to check piston to valve clearances at max lift so there is no interference... if you have a competent machinist/builder who knows how to do his work it shouldn't be a problem.
Some of the experts will chime in soon I'm sure.
Alan
swinger340
Well-Known Member
Ive seen the opposite done. 1.5 intake and 1.6 exhaust on stock or mildly ported X O U or J heads. Usually the exhaust flow #s are a pretty far cry from 75% of the intake flow #s. Easier to buy a duel lift/duration cam.
Valvebounce
Well-Known Member
I've heard of guys running bigger ratio arms on the ex valves to compensate for nitrous.
dusted72
Thanks Hemiroid!!!!
I would say that it could be possible with 1.6 on the exhaust. It seems that our heads struggle in the exhaust flow area. At least on stock heads.
It depends on how the cam is ground, cubic inch size and how good or bad the cylinder head flows. Sometimes there's a benefit from 1.6s on the intake side only, similar to the way a roller cam usually has more lift on the intake side. Just like everything else, it is all dependant on the entire package.
moper
Well-Known Member
In a race engine, with the package well engineered to make power at a specific rpm range, there are advantages in using a faster rocker on the intake or exh. For the vast amjority of street or mixed use engines, using the lower rocker ratio is the smarter choice for longevity, and specify the cam to get the lift and duration you want. Rocker ratio can have a small affect on valve motion. But they wont make or break a street engine. You can have a much greater affect by chosing the right cam.
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