What is the advantage to using a higher ratio rocker arm such as 1.6 v 1.5 ? and can they be used on a stock engine ? Engine in question is a Pontiac 400.
>>>They add about .30 thousands to the Lift of the cam ,,IE; a 5.00 lift would be a 5,30 lift ,,NO added duration tho ,,just lift ,,might help a stocker ,,but not much ,,mainly for hi er performance motors that need a tad more ,,
You'll see less than a 10 hp gain. Additional pressure will be introduced at the lifter crown/cam lobe interface, so while the motor might operate just fine with the springs it has at 1.5, using 1.6 rockers might put it over the edge due to the shorter lever length from pushrod cup on the rocker to the axis at the stud and could result in a lifter crown goin' south on you. This is ***uming a flat tappet cam. My best advice.....don't. Save the higher rocker ratios for when you replace the stock arrangement with a roller cam. You can get away with it then.
yeah keep it stock for now or what are your plans those heads need work to change the studs for 1.65 rockers?
The pushrod holes must be elongated towards the stud or the pushrods will rub the head to use 1:65 rockers. A tool used to be available to do this or use a die grinder, either way the heads will have to come off. It would be easier to put another cam in it with the additional lift. If it has an 068 cam in it now it is a very good street cam, a Summit racing 2801 has the same duration as an 068 with the extra lift built in, a good deal for $60. You'll also want to upgrade to some better arp rocker studs, the stock ones are hollow and will break. Plus you'll want the valve train adjustable. I used the comp roller tip 1:52 on my 670 heads.
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