These hydraulics lifters are fantastic. What they do is basically make your camshaft a variable duration cam. The intended purpose of these lifters is to make your engine idle better if you have installed a high performance cam. So if you have a 270-280 deg cam, I would say at a guess it would idle at about 800RPM and a bit rough at that and there would be no low down torque. Add these lifters and the engine will idle much better at a lower RPM, have better idle vacuum and have more low down torque.
How does it do this? Basically the lifter bleeds off valve lift and duration at idle. Depending on how you adjust them it will reduce cam duration between 10-15 deg and valve lift by .030". So if you have a 270deg cam these lifters in practice will make you cam a 255deg cam at idle which is close to stock. So you get all the benefits of your near stock cam at idle and low engine speeds but once the engine revs up, the bleed down is greatly reduced the full high performance cam is restored at about 3500RPM.
Another advantage is you can install a bigger cam than you first wanted but didn't because of the disadvantages of poor low down performance, high fuel consumption, rough idle etc. These lifters can allow you to go approx 10- 15deg more in duration without the side effects. I have fitted about 6 sets of these lifters in various engines. I sold one set to a customer that purchased a 280deg cam which brought it back to about a 265deg. This made it possible to couple up to an auto transmission without fitting a high stall converter. I sold several sets for the purpose of hiding that the engine had a cam fitted. The lifters reduced the cam specs to near standard, however a standard car was no match at the lights. There is however a rather obvious way of telling there is something different about the engine when it idles. The lifters rattle like a solid cam, but I tell all the users to say their lifters are stuffed when someone asks. That way they don't know it has a performance cam fitted.
Now here is something different. I fitted a set to my standard 6cyl XE falcon as an experiment. I have an article on how cams work on my site, so I won't cover it in detail here, but suffice it to say, the smaller the cam the better the engine idles, the better fuel economy you will get, low speed torque is increased and the engine has more vacuum. The down side is you lose all top end performance. WOW what a difference to a stock motor these lifters made. It was very responsive on the throttle and I blew every stock falcon away at the lights and I got heaps better fuel economy around town and better economy around the 80KPH all because the cam duration and lift were reduced. The ticking didn't bother me, it sounded cool, everyone thought I had a solid cam or as I used to say my lifters were shagged.
I thought these lifters would be gone by now, but they are still selling. Now they have roller lifters available and a few variations to the original lifters from the 80's. Go to their website, there you will find lots of info about them and how they affect engine management systems in modern engines. The link opens a new browser window, or right click into a new tab.
