" GRUMPY?
I have some AFR 195 competition port heads with the upgraded springs from AFR (I think the spring upgrade is P/N 9018). I was assured by AFR that these springs would handle anything my mild street combo could throw at them. However, I chose to use a comp cams 280 XFI cam. I have been told this cam sets the valves down very hard/quickly. Even when I first put the heads on the car, it would float the valves at about 6500. Now, after 18 months or so, I can't rev the engine past about 6000 without floating the valves.
I'd rather just swap out to some stronger valve springs (something that won't crush a stock replacement hydraulic lifter) but if there isn't a suitable spring option that will get me to 7000 reliably, I'm not opposed to swapping the cam to something that sets the valves down a bit slower and makes the springs job easier.
Thoughts and recommendations are greatly appreciated, thanks"
http://garage.grumpysperformance.com/index.php?threads/lifter-weights-and-its-effect-on-rpm.16731/
heres a similar engine, notice that without a rev kit power falls drastically above 6000rpm, and even with a rev kit they don,t push a hydraulic roller to 7000rpm, its already having power fall off by 6500rpm, BUT thats a 500rpm improvement in the power curve. if you want to reliably spin an engine past 6000rpm a solid roller cam will do that provided its used with the correct matched valve train and springs
you have two basic problems, the first ones that HYDRAULIC tappet cams are not designed to nor will they reliably operate at 6500rpm-7000rpm NO MATTER WHAT the cam manufacturer may tell you, any time your looking to spin 6500rpm plus with a f hydraulic cam your really in SOLID LIFTER TERRITORY and should use a solid lifter cam and a rocker stud girdle or shaft rockers
next many COMP cams cams have lobe designs that have acceleration rates and result in lofting the valves or loss of valve train control ,that are at the limits of valve control, Id suggest talking to several manufactures about a solid lifter cam (preferably a roller solid lifter design)
what most guys over look is that by the time you add enough valve spring load rate to control a hydraulic lifter at 6500rpm your really in solid lifter rpm ranges, a REVE KIT on a HYDRAULIC ROLLER CAM IS A BAND-AID APPROACH
ID ALSO POINT OUT THAT A ROCKER STUD GIRDLE ADDS A GOOD DEAL MORE STABILITY TO THE VALVE TRAIN
viewtopic.php?f=70&t=4836&p=13219&hilit=indexing+plugs#p13219
next
your cams designed to max out at well under 6500rpm
http://www.compcams.com/Company/CC/cam- ... =1111&sb=0
the second ones that your current cam and heads both max out below 6500rpm
http://www.rbracing-rsr.com/runnertorquecalc.html
viewtopic.php?f=52&t=333
CHECK WITH SEVERAL CAM COMPANYS but your more likely to find something like this cam below works at 6500rpm
I have some AFR 195 competition port heads with the upgraded springs from AFR (I think the spring upgrade is P/N 9018). I was assured by AFR that these springs would handle anything my mild street combo could throw at them. However, I chose to use a comp cams 280 XFI cam. I have been told this cam sets the valves down very hard/quickly. Even when I first put the heads on the car, it would float the valves at about 6500. Now, after 18 months or so, I can't rev the engine past about 6000 without floating the valves.
I'd rather just swap out to some stronger valve springs (something that won't crush a stock replacement hydraulic lifter) but if there isn't a suitable spring option that will get me to 7000 reliably, I'm not opposed to swapping the cam to something that sets the valves down a bit slower and makes the springs job easier.
Thoughts and recommendations are greatly appreciated, thanks"
http://garage.grumpysperformance.com/index.php?threads/lifter-weights-and-its-effect-on-rpm.16731/
heres a similar engine, notice that without a rev kit power falls drastically above 6000rpm, and even with a rev kit they don,t push a hydraulic roller to 7000rpm, its already having power fall off by 6500rpm, BUT thats a 500rpm improvement in the power curve. if you want to reliably spin an engine past 6000rpm a solid roller cam will do that provided its used with the correct matched valve train and springs
you have two basic problems, the first ones that HYDRAULIC tappet cams are not designed to nor will they reliably operate at 6500rpm-7000rpm NO MATTER WHAT the cam manufacturer may tell you, any time your looking to spin 6500rpm plus with a f hydraulic cam your really in SOLID LIFTER TERRITORY and should use a solid lifter cam and a rocker stud girdle or shaft rockers
next many COMP cams cams have lobe designs that have acceleration rates and result in lofting the valves or loss of valve train control ,that are at the limits of valve control, Id suggest talking to several manufactures about a solid lifter cam (preferably a roller solid lifter design)
what most guys over look is that by the time you add enough valve spring load rate to control a hydraulic lifter at 6500rpm your really in solid lifter rpm ranges, a REVE KIT on a HYDRAULIC ROLLER CAM IS A BAND-AID APPROACH
ID ALSO POINT OUT THAT A ROCKER STUD GIRDLE ADDS A GOOD DEAL MORE STABILITY TO THE VALVE TRAIN
viewtopic.php?f=70&t=4836&p=13219&hilit=indexing+plugs#p13219
next
your cams designed to max out at well under 6500rpm
http://www.compcams.com/Company/CC/cam- ... =1111&sb=0
the second ones that your current cam and heads both max out below 6500rpm
http://www.rbracing-rsr.com/runnertorquecalc.html
viewtopic.php?f=52&t=333
CHECK WITH SEVERAL CAM COMPANYS but your more likely to find something like this cam below works at 6500rpm
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