Rocker ratio on SBC

I was told that SBC`s like 1.5`s on the intake and 1.6`s on the exhaust.
Any opinions?

I think it really depends on the application. That's one of the reasons that you can buy dual pattern cams these days, at least taht's what I was led to believe.

I believe that the ratio is 1.5 on both intake and exhaust. Big block rockers can be used for a 1.6 ratio...I think.

Vince

Big block rockers are 1.7 and too long for a small block.

Running 1.5 I, and 1.6 E could better. It depends on your camshaft, valve sizes, cylinder head flow, exhaust sytem, induction, etc. The only real way is to know is to try it and see what happens.

Depending on the cam sometimes we will swap between 1.5 and 1.6 rockers on our race car.Sometimes the 1.6s on the intakes sometimes just on the exhaust.


Smokey Yunick used to modify the 1.7 big block rockers to work on smallblocks.It was alto of work though because he had to move the rocker studs to a differnt location.

I have 1.6s right now. I was thinking of trying some 1.65s on the exhaust with the 1.6s, and then trying them on the intake the other way.

Chevy,according to their Power book did some rocker testing and found the best setup is;
Cylinders 1,2,7 and 8 get 1.7:1 inlet and 1.65:1 exhaust.
Cylinders 3,4,5 and 6 get 1.65:1 inlet and 1.6:1 exhaust.
That was on a 358ci smallblock built to NASCAR specs a tad
over the top for the street, and it all depends as well on the rest of the setup.

The conventional setup if you're going to use unequal ratios is 1.6 on the intakes and 1.5 on the exhaust. It boosts the area under the curve on the intake without over-scavenging the exhaust.

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BSE Racing Engines

The 1.6's on the exhaust would increase the low end torque, horsepower on the intakes.