Split ratio rockers?
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Split ratio rockers?
I need some opinions on rocker ratios. I'm gathering parts for a 393 (399) stroker. 3.85 crank,.060 hyper pistons,Edelbrock rpm manifold and 750 carb, stock cast iron smog heads, self ported and polished with 1.94/1.60 valves. I'll have about 10:1 CR and plan on running a Speed-Pro CS1231R flat tappet hydraulic cam : adv.dur 290 int/300 ex.- 214/224 @ .050 with 112 lobe seperation. Basically a hot streeter. I am shopping for roller lifters and have a choice between 1.7, 1.6, and a 1.6/1.7 set. I am thinking 1.6 is what I want, but right now I can pick up a set of 1.6/1.7 for a pretty good price. There is not a big price diff. in any of them, though. Whatcha think?
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Joined: Feb 2005
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From: Noth Georgia
1.6 is stock, 1.7 will net more lift with the same duration (under the curve) but will also run closer to coil bind.
for THAT cam, in THAT engine, I would go 1.7/1.7, that should keep you neer 1800-4250 rpm powerband.
on the other hand, you'll probably run out of head well before cam, so 1.7I/1.6E would also work.
a stock 400 has larger ports and valves 2.06/1.66 and runs around 282/292; 204/214; .484/.510 to net 1800-4000 rpm powerband
If possible, get a second opinion from someone with dyno software, they could tell you the difference better heads would make.
for THAT cam, in THAT engine, I would go 1.7/1.7, that should keep you neer 1800-4250 rpm powerband.
on the other hand, you'll probably run out of head well before cam, so 1.7I/1.6E would also work.
a stock 400 has larger ports and valves 2.06/1.66 and runs around 282/292; 204/214; .484/.510 to net 1800-4000 rpm powerband
If possible, get a second opinion from someone with dyno software, they could tell you the difference better heads would make.
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