valve train explanation wanted

[poppa]

What does 1.5 or 1.6 mean when talking valve and rocker set up??? Is one better than the other? Which is stock?

[Musicman]

Lift Ratio... 1.5 is stock... 1.6 gives a little extra, opening the valve a little bit more, but can sometimes lead to pushrod clearance issues where the rods pass through the head due to the change in geometry... no big deal though, just a little extra grinding if this is the case. Most folks stick with the stock 1.5 ratio however, and use a bigger cam if they want extra lift.

[Chryco Psycho]

the rocker multiplies the cam lift , the cam lift is around .300 , with a 1.5 rocker you get .300x1.5 = .450 lift at the valve
with a 1.6 rocker you get .480 at the valve .
.300 X 1.6 = .480
The factory rockers are not very accurate , usually 1.45 range

[68pplcharger]

The rocker ratio (1.5 or whatever) is the distance from the centerline of the fulcrum(center of rocker shaft) to the point of contact at the valve divided by the distance from the centerline of the fulcrum to the point of contact of the pushrod. That is where the mathematical ratio comes from that gives you your "lift ratio" or "lobe lift multiplier".

[poppa]

How do you know which ratio to go with? Can you get the rockers and then a cam or is it better to get the cam and then the rockers? Does anything else need to be thought over first? Thank you

[Chryco Psycho]

More lift can be free power , but it depends on the ability of the port to flow more air with more valve lift , at some point the port stalls & more lift will not allow more air flow as the valve essentially becomes invisable to the air flow . More lift can also shorten valve spring lift & may require stronger valve springs .
The main consideration is piston clearance , you need to be sure more lift is not going to cause the psiton & valve clearance to become inadequate

[poppa]

Thanks for the reply. I plan on doing a stroker (512 or 528) with the Stealth heads,would the 1.5 ratio be a good choice for this? I was kind of leaning towards a Comp xe  284h. I would like to have the ports done some,not something too much. I have to check on these items as I have power brakes.

[elacruze]

Unless you have a very specific reason for using something other than the stock ratio, use the stock ratio. Cams and springs are designed to work a certain way, and if you change the valve lift you change dynamics of the springs and increase the load on all the components, and potentially run the risk of overcoming the springs' ability to keep the valves under control. AFAIK all stock Mopar rockers are 1.5:1 ratio.

Adjustable rockers and correctly measured pushrods are preferred over stock, but not mandatory for mild builds.

[Chryco Psycho]

I would use something other than Comp for cams , they are designed for Chevs for the most part Crower & Lunati can offer you a beter design tailored to work in Mopars
Not sure at what lift the stealth heads stall + there is a Super Stealth with should be a better fit on a 512/528" but you should have lots of clearance up to .610 lift with 1.6 rockers , I have been using 572/586 lift solid grinds very similar to street roller grinds in the strokers we build