Teddy Posted May 16, 2004 Report Share Posted May 16, 2004 Hey all Well, now I'm thinking on the lines of Cams ! when u say (from nicks car) - 42/88 what is what... is the 42 like the time it opens, and the 88 is the closing time? And I'm on ebay, lookin at this... Click Me and the seller has got " Sure Cam MZ16 Profile, duration 239 deg @ .050", .450" valvelift, 105 lobe centres " Wtf ! Any 1 lol Quote Link to comment Share on other sites More sharing options...
Super Jamie Posted May 16, 2004 Report Share Posted May 16, 2004 this is getting into pretty complex territory to understand how a cam works, you need to understand how the 4 strokes of a combustion engine work. read these first http://auto.howstuffworks.com/engine.htm http://auto.howstuffworks.com/camshaft.htm http://www.enjoythedrive.com/content/?id=25288 http://www.chevyhiperformance.com/techarti.../148_0405_lobe/ cam timing is listed in this order. inlet valve open, inlet valve close, exhaust valve open, exhaust valve close. when there are two timings, assume the cam is mirrored for exhausts. another way of saying "42/88" would be "42/88, 88/42". sometimes you get cams that are slightly different, i recently did a grind for someone that's a "21/61, 63/19" duration is the amount of time, measured in crankshaft degrees, the valves are open for. a higher duration cam makes more power up high, and less down low. a smaller duration cam makes less power up top, but more at lower rpm. nick's cam has about 310 degrees of advertised duration, mine has about 270, stock is like 246. advertised duration is measured usually from when the valve opens, sometimes at .006, sometimes at .004. people think measuring from .050 gives a more accurate idea of a cam's profile, i beg to differ, the entire ramp rate of the lobe makes the difference (ramp rate being how fast the valve opens and closes) overlap is the amount of time both valves are open, a certain amount of this is good, as the vacuum of the exhaust causes more intake charge to be sucked into the cylinder. you don't want too much overlap, or you needlessly suck good intake charge out the exhaust, wasting power and fuel. nick's cam has like 84 degrees of overlap, stock is 32, mine is 50 lift is how high the cam opens the valve, more is better, but you can run into problems with coils binding (the valve springs run out of room to compress) or hitting the valve stem. a good lift for a worked k motor is about .400. i don't know how much you can run before you start needing to change things, but i reckon .450 would be getting close, if not past it also be aware that there is "camlift" and "valvelift". the rockers on these motors open the valves 1.5 times more than the cam pushes them (one end of the rocker is longer than the other), so .100 camlift is .150 valvelift, and so on. this is called having 1.5 ratio rockers. a common performance trick on v8s is to put in 1.6 or greater ratio rockers for more valvelift as for that specific cam, i'm not too good at reading durations at 050, but it drops power everywhere with my engine so i wouldn't use it, there are better profiles out there. it's also overpriced, a grind anywhere will cost you about 100 bucks if not less, and you can get k motor parts for free everywhere Quote Link to comment Share on other sites More sharing options...
Teddy Posted May 16, 2004 Author Report Share Posted May 16, 2004 nick thats a great idea - "It shal be named Project Special K" ! hehehehehe Quote Link to comment Share on other sites More sharing options...
Teddy Posted May 16, 2004 Author Report Share Posted May 16, 2004 wow - another good write up supa jamie ! I'm really starting to understand so much more thanks 2 ure smashing effort on the forums - i beta get u a x-mas prezzy this year lol !! THANKS!!!!!!!!!!!!!!!!!!!!!!!! P.s - i now understand cams with a chunk more confidents !!!! Quote Link to comment Share on other sites More sharing options...
Super Jamie Posted May 16, 2004 Report Share Posted May 16, 2004 i keep playing around in dyno2000 trying to make a good motor with that cam, but it just doesn't happen. it's the bloody wierdest grind i've ever seen! even with 13:1, twin 45 sidedrafts, huge valves, huge extractors and superb head porting i can still get mine and doug's to make few more horsepower, noticably more torque and still be streetable but that's only a computer program. every other top-end grind i have closes in the 70 degree range, giving the motor SOME compression i'm so interested to see how different your car feels with the weber and a 25/65 :) Quote Link to comment Share on other sites More sharing options...
Super Jamie Posted May 16, 2004 Report Share Posted May 16, 2004 project special k, thats classic :) love it Quote Link to comment Share on other sites More sharing options...
Teddy Posted May 16, 2004 Author Report Share Posted May 16, 2004 heheheheh :) Quote Link to comment Share on other sites More sharing options...
Super Jamie Posted May 16, 2004 Report Share Posted May 16, 2004 this makes me think now, if i built another K motor for street, i'd use a slightly milder cam. ivan tighe has a grind (tighe 112) that's a 20/60 with heaps of lift, it still makes a fair bit of power, peaking at 6500rpm, and about 10% more torque than a 25/65, which is already a fairly nice torquey cam to drive around with having a big 7500rpm power peak is fun, but the thing sounds like its going to shake apart above seven, and i don't like holding it at high rpm because of crankcase blowby and oil getting trapped in the head. you should get one of these cams teddy :) Quote Link to comment Share on other sites More sharing options...
Super Jamie Posted May 16, 2004 Report Share Posted May 16, 2004 They obviously made this cam for some reason....The reason will remain unknown until we can work out why the feck its got such a big overlap... its not even that, tighe's stage TEN speedway grind has 312 degrees duration too, but it's a 50/82 84/48. 88 degrees inlet valve close give the thing like, TWO crank degrees to compress what little air fuel is left in the cylinder i don't get it either. maybe someone made it because the nsw rta won't let you put a 12a in a ke20/25 and they really REALLY wanted that ported rotor sound in their oldcorolla :) Quote Link to comment Share on other sites More sharing options...
Teddy Posted May 16, 2004 Author Report Share Posted May 16, 2004 having a big 7500rpm power peak is fun, but the thing sounds like its going to shake apart above seven, and i don't like holding it at high rpm because of crankcase blowby and oil getting trapped in the head. you should get one of these cams teddy :) lol - i just want my motor to look stock as all hell, but to have a bit more power - lets face it - i live in a hilly area, and my car doesnt excatly like the hills, althou 2nd gear @ 4,000 up a hill isnt too bad, (anything above 4000 and muma beside me starts to make more noise than the car) heheheheh But yea, what cam do u think would best suit my car if i had the 4:1 extractors, 2" exaust, 3K big port Inlet manifold and head.. :S Quote Link to comment Share on other sites More sharing options...
Super Jamie Posted May 16, 2004 Report Share Posted May 16, 2004 tighe 112 - 20/60. it's got something like 425 or 435 thou lift, pretty high but you could still use it with stock 4k valve gear (you'd want at least new stock springs tho) Quote Link to comment Share on other sites More sharing options...
ke1x Posted May 16, 2004 Report Share Posted May 16, 2004 if you run an early 3k bigport head you may have trouble with this much lift. the early heads have the valve stem seals in the retainer, which sort of reduces the amount of lift available, compared with later heads. if you change to later guides and the valve stem seals that clip onto the guides, it shouldn't be a problem. the 3k bigport heads were standard on later 3k equipped ke10s through ke20s. 3k-b heads have 2 extra water galleries, going into the inlet manifold. the next cam i buy will be a tighe 112 20/60 to go in bec's ke16 which has a stocky ke70 4k-c atm. seems to be the strongest cam up to 7 grand with dyno2000. for street driving torque is good. Quote Link to comment Share on other sites More sharing options...
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