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Discussion Starter · #1 ·
I'm asking this for a friend. He has a 2000 explorer bottom end with afr 165 heads. He has a f303 cam for it that he was gonna use 1.6 rockers on to bring the lift down to 512 i believe. since the explorer block has no dish at all, just valve reliefs i'm almost positive he is going to run into PTV issues. Can someone clear this up for me?
 

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Total valve lift has nothing to do with PtV issues, the valves are at full lift when the piston is >1.6" below deck. Anytime you upgrade with an aftermarket camshaft you always need to check for PtV......and so does your friend. :)
 

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Discussion Starter · #5 ·
thanks, i'll give my friend the info. Does anyone have experience with a combo like this though? any problems? I really don't think the cam is going to work with the explorer pistons
 

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so called "explorer pistons" are not really anything different than anything else.

I dunno why you referr to the pistons as having "no dish", ...but that they have eyebrows...

.....the valve ,...when it hits the piston,... is only concerned with the "eyebrow relief"...

weather there is a dish or no Dish, means nothing to the amount of clearance that is there for the valves when the cam is at overlap and piston near top dead center.

the amount of DISH is only to correct the amount of COMPRESSION that is computed with the various chamber size volumes of each head.


essentially,
you need to convert one pair of the stock roller lifters "into a solid" with little washers or a piece of wood inside instead of the spring and then assemble it all together and see just how much valve to piston clearance you end up with when both valves are opening and closing.

when using ANY aftermarket head such as what you have,
you must also check the rocker geometry via a adjustable pushrod .....( another complete post topic in itself )

when you change / optomise the rocker wear path via a change in the pushrod length,..this can change the amount of piston to valve clearance..
when the CAM is "timed" differently...( aka INDEXED differently) ...this will change the amount of piston to valve clearance...
 

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once again,

the cam should be "TIMED" with a degree wheel
and then
the rocker geometry must be corrected with a different pushrod BEFORE you can make any assesments about if there is adequite piston to valve clearance....
 
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