1.5 or 1.6 ratio how to choose?
- Thread starter hwy2
- Start date
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The answer is "it depends". I always choose a camshaft based on the rocker I am using, not the other way around. In other words, choose a camshaft with the lift at the valve you want with the rocker you have now. Otherwise, it's kinda a "band aid" for a camshaft that doesn't have the lift you want. If that makes sense.
Im adding to upgrade as suggested. I have .513 lift cam now hyd roller. Im building a 392. I think I can stand some more lift if thats what is gonna happen to get roller rockers. It did not start off as this build it was going to be a .040 over 318 with heads and a cam.
Then get the 1.6s if that's what you want. If I HAD 1.5s already, no way would I spend on the 1.6s.
I have stock stamped regular old rockers
Then the world is yours! lol
Since you have nether A D your using speedmaster heads, where do the heads ports start to loose flow? I, myself like to lift the valve as much as possible or at least to where the maximum amount of flow happens in the head. This is not always possible but I try.
There isn’t a lot of power to grab unless the build is at a minimum, a pretty hot build or race build. But there is power there.
If the flow curve of the cylinder head tops out at .580, lifting it beyond that on a street car doesn’t really pay off. If your cam is a .500 lift, then adding another .030 helps a little.
Same again if it’s a .550 lift and you add .030 or .035 more.
Coupled with a longer duration, at the higher lifts, the engine starts to breath in pretty deeply.
Just be sure the valve springs are up to the increased lift & lift/close rates, check with the cam grinder to be certain, & be sure the installed ht./seat load is what's specified.
Yes and also be SURE to check retainer to guide clearance!
Not they you wouldn't check everything out with 1.5 ratio rocker, but the use of 1.6 ratio rockers requires even more through inspection. Pushrods start getting close and sometimes require clearancing on the heads. When you play with geometry it may also require shaft spacers and for sure will require different pushrods. It just not a simple upgrade. Personally I would have stayed with the 1.5 ratio.
Tom
Tom
Sometimes more ratio helps and sometimes it doesn't. I spent a few thousand dollars proving this.
https://www.motortrend.com/articles/trying-find-extra-power-rocker-arm-testing/
https://www.motortrend.com/articles/trying-find-extra-power-rocker-arm-testing/
Andy, you're a true asset to the site. Thanks for that very informative article!
Before you spend the money for 1.6 rockers, get with 3B to correct the geometry. It is well worth the money.
3B Engineering, they have a sheet to fill out and supply parts to get the rocker arm geometry corrected.
Hyper_pak
Old School Chrysler Fan
Not to hijack the tread, but how does the 1.5 vs 1.6 effect the duration numbers?
Or does it.
Or does it.
j par
Well-hung Member
The stock speedmaster Springs have plenty of clearance for what you are doing and plenty of clearance for the push rods with 1.6 to 1 rockers or at least I do...
But always check...
After that DON'T OVER THINK IT...
People get so caught up in all the guru comments..
They end up spending too much money on things they don't need...
But always check...
After that DON'T OVER THINK IT...
People get so caught up in all the guru comments..
They end up spending too much money on things they don't need...
Higher ratios add duration at the higher lifts points. Adds more area under the curve.
This is how it works. The camshaft will have a lobe lift of .333. But the rocker will alter the amount of lift by the amount of its ratio. If the rocker was a 1:1 ratio, you would have .333 lift at the valve.
A 1.5 X .333 = .4995 or just round it up to .500
A 1.6 X .333 = .5328 or just round it up to .533
The addition amount of lift is not fixed, nor is the intensity since another cam may have a different lobe design. Also, as A stat left a link that should be read, just because a rocker says it has a certain ratio doesn’t mean that’s the lift that will appear. In addition, where the rocker is placed in the saddle and how long or short each end of the rocker is will effect the overall lift. Then there is the geometry of it all. The same rocker not well placed will ether give more or less lift until corrected.
What you’ll find in rockers are a lot of differences that a casual eye will miss but once you start looking closely, ohhhhh boyyyyy can they be very different. To the point you’ll scratch your head saying, “WTH is going on here?!?!”
I needed a crazy off set on my Edelbrock heads, that were milled by the way, which causes more issues in geometry for the rocker.
The rockers are the Hughes engines 1.6 rollers.
And this may make the lobe appear fatter. It will intensify the cam. But just a little bit. Lobe dependent.
Depends on the lift. A higher rocker arm ratio won't change the advertised duration much, but it can easily double or triple the duration at the higher valve lifts. Of course, those events happen very, very quickly so it might not have much effect on power.
On my 511 race engine I would pick up about 10 hp from 1.85 rockers on the intake rather than the usual 1.80 rockers. The 1.80 rockers picked up a bunch of power from 1.50 rockers. My 470 pump gas engine didn't pick up power from 1.50 to 1.70. I ended up using the 1.65 T&D rockers on that engine since they were the nicest rockers but they didn't add any power over the cheapest set of 1.50 rockers that I tried.
Thanks. That was back in the days when I had a cushy side gig writing for Motor Trend. They would pay me $1500 for the article and the vendors would send me the parts at a discount or sometimes for free. I had to do all the labor and pay for the dyno time, but I usually broke even once I cashed the check from Motor Trend and sold a few of the used parts. So it wasn't really a job, more like a hobby that paid for itself.
With the math 1.6 x .513 = .825? Is that the total lift.
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