How much lift can these heads take?

[LT-102]

Installing a new cam later this year and am concerned about the increase in lift. I have a set of 487X heads and will be going to .514 lift. Will I need to have the pushrod slots elongated? Anybody running these heads with this much lift?

[mikep]

A lift of .514 signifies a few things. One is that you are going to a longer duration cam which will in turn shift your power band upwards so you will be revving the engine much higher than the pressed in studs were designed to handle. .514" is also close to the limit most stock diameter valve springs were designed to handle. Many are rated at .550" but what does that mean. It means that you will bind at over .550" Thats all fine and dandy but as we have already stated you will be turning the engine faster you will having a much greater possibility of floating the valves and when those springs bind.... out come your studs or worse. Time to have the heads cut for screw in studs . Since you have screw in studs might as well get the guide plates . That will eliminate the need for elongating your pushrod slot. a Few other things. You should check your piston to valve clearance. Anything over .500" should have at least either special hi tension valve springs with special raised retainers . They dont cost that much but give you another .050" before you get into sring bind .... or larger diameter valve springs but that will involve some additional machine work.. I wouldnt go to double springs until you get to .550" as they can cause some lifter and lobe problems with street engines.

[LT-102]

Thanks mikep for your response. I will be using the valve springs recommended by the cam manufacturer, "Comp Cams". I wasn't for sure to go to screwin studs and you have answered that question also. Thanks again.

[bigjimzlll]

Hi...I would have the spring pockets enlarged,even if you stay with stock diameter springs now, in the future you can upgrade easily..elongate the pushrod holes and use guide plates and studs...be wary of comps suggestions on valve springs..im guessing they want you to use 981-16...they would be just borderline with those lifts...im doing basically the smae thing as you are...I went with 2.02-1.6 valves..single springs good to .600 lift..and had them checked for coil bind...the are good for a lift of .530..im also going to use a stud girdle..
Jim