I had some piper regrinds 264-s installed in my tuned 9a engine which i'v run for 3k before removal from car. Today i removed cam cover to inspect cams, measured the lobes and they were all slightly different. Also measured diameter of lobes(end to end) and found that overal diameter is allot less than standard items, as much as 3mm Surely this will mean less lift=less power? Compared inlet cam to standard, mild 9a item and it showes more duration but 2mm less lift Also compared exhaust cam with standard kr cam(same as 9a) and this also showed 2mm less lift, well confused now . Shuld they be like this or not?
If they are re-grind you'll find the sizing quite a bit different from the standard cams. If you mic from side to side, which is the base circle you'll find that this can be 2mm+ smaller than a standard cam. By doing this you gain lift. ie. standard B/S is 38mm. Standard lift about 10.5mm. So your overall height of the lobe will be 48.5mm. So, if you lose 2mm off the B/S your lift will then become 11.5mm(2mm off the B/S is 1mm of the radius at the bottom of the lobe) they will then grind in a new ramp, flank and nose radius to achieve the desired duration. So yes they are ok, although not to put a downer on things but re-grinds are never going to be as good as a ground blank. But certainly cheaper. Hiope this is of some help Edited by: Hotgolf
Lobe heights, or mor to the pointthe overall lobe length from base circle to the radius should be the same on all the lobes of that particular cam. If their not theres a problem. Got any pics?
No pics my computer older than rado . To be honest dont think you l be able to tell by pics alone due to very small differences. I still cant grasp fully how can a cam with overal smaller lobe diameter open the valve as much as cam with longer lobes . Valve length still same. And if base circle diameter 2mm smaller does it mean valve springs will have less tension when closed? Sorry hotgolf but this area is not to clear to me Edited by: sambo
This isn't really that hard to grasp, but I know what part your getting lost with. First off forget about the width of the cam, just concentrate on the overall height. If you got 10mm at the bottom of the lobe(valve closed) and 20 at the top(valve open) you have 10mm lift. Easy. If you hade 10mm all roundthe cam is round and you wouldn't lift the valve. So if you remove 1 mm from the bottom you now have 9mm at the bottom (the gap will be taken up by either the hydraulic lifter or re-shimming) but still 20mm at the top so the difference is now 11mm, so you have 11mm lift. Whenever you remove material from the bottom the extra gap is always taken up with the lifter or shimming. So that when the cam turns your not taking up gap first(well apart from pre-set .2 or .4mm factory clearance) But, when you take material away from the base circle, you increase the ramp angle of the lobe, you will increase the speed that the valve opens, but also the speed it closes, so you lose duration. To gain back the duration you will need to then add more lift, which inturn creates a viscous circle. You will also alter the way the cam works which could really mess things up. Hope this is a bit better. Don't take it a gospel but its pretty much what you need to know.
Cheers hotgolf, that makes sense! I will still give them a good check over for uneveness on lobes. Do you think these cams will be good enough for 45mm itb-s as they are going on soon?
Just done some measuring and found thah base circle diameter is 3mm smaller, and calculated lift, its 10.5mm on inlet and exh and 264 duration. There is some differences in some of the lobes but not as bad as i thought. Do you lads think cams will be good enough for 45mm itb-s? If not what spec cams should i use? Thanks
KR/ABF cams for use with ITBs.. Graham Scott managed 202BHP & 165lbs/ft @ Stealth with his K-Jet & Schricks... Myself & IanB both pushing 160lbs/ft too..... I wouldnt automatically assume hotter cams make for a gutless rev monster just because Gary didnt get quite the result he wanted..
Gary and Tubthumped both tried Schrick cams in their cars. Both were total pony to drive on the road afterwards. Ok if you drive everywhere at 6500+rpm. But running TBs can get away with wilder cams as far as im aware.
Thats what i thought cos you can map the engine more precisely, i just wonder what spec would be best compromise for power and torque because i want both
TB's definitely give a smoother torque curve, but that is more down to the fact that the ECU is mapped.. I wouldnt say the TBs give significantly more power/torque than a "fully" sorted K-Jet version though. (IanB/Graham Scott) I may gain a few BHP over them with miles & a tweak here & there but no more.. Seems bizarre that the cams have worked so well for Ian/Graham, but not Gary & Craig. The only additions their cars have are 4 branches & some serious RR setup time... I cannot personally see the logic in spending 2K+ on a TB conversion to hold power & torque back using standard cams..
throttle bodys are like the icing on top of the cake of all other modifications, it really is the last step, once everything else is sorted only then should you be thinking of TB`s
Like i said everything else is sorted i just wonderd if piper regrinds with 10.5mm lift and 260 duration are good enough for itb-s on my engine? wanted to establish this before maping the ecu to avoid need to swap cams and map again because it would be unnecessery cost
