Gm847 Vs Compxfi 468
Gm847 Vs Compxfi 468 HI every 1,i need help choosing the next CAM,i have the cc305 with all the boltons,rear gear,ported heads & 3000stall,its time for me to go with a bigger cam.ive seen lots of threads about the GM847 but not alot on the xfi 468. i only drive my car once a week to race with it what do u guys recommend? 
There are a lot of threads on the xfi grinds. I have one myself and I love it. It's more aggressive than the 847 and has a lower RPM band. I think how big you want to go depends on how well your heads are ported. You might get more responses if you post the flow numbers.
OTOH, if you only race your car, you might first want to look at getting a bigger rear and a better wheel/tire combination. That will make you a lot faster as well.
OTOH, if you only race your car, you might first want to look at getting a bigger rear and a better wheel/tire combination. That will make you a lot faster as well.
Thanx alot for your response,im getting the LE2 heads soon to go with the xfi 468 cam,which i realy prefer.about gears i already have 4.10 ratio and 18"wheels with 285 wide tires so i dont have any traction loss issue.
What i want to know is this cam going to make more horsepower than the 847 cam??
What i want to know is this cam going to make more horsepower than the 847 cam??
Every setup will be different. If you want to make the most horsepower, you should really get your cam from Bret through Lloyd. However, I think the XFI cams make more power because they are a lot more aggressive. The 847 has some more lift, but I don't think it's that much more. Just make sure you get some beehive springs and set them up correctly. Bret has had trouble controlling the valves over the nose with the XFI cams, even with the beehive springs. You can talk to him more about that if you wish and he's much more knowledgeable than I am. I run some PSI springs that are beefier than the 918's which is what comp recommends for their cams, but there are plenty of other people running the 918's with the XFI cams and doing fine.
Also, I think you're giving up a good bit of HP with those large wheels and tires. I recommended a bigger rear end and tires so that you can cut down your track times, not necessarily just grip better.
Also, I think you're giving up a good bit of HP with those large wheels and tires. I recommended a bigger rear end and tires so that you can cut down your track times, not necessarily just grip better.
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I put down some impressive times several years back with the 847. I had an 11/1 383 with AFR 210's, a Victor Jr., and a Holley 750 in a full weight 3rd gen. The best time was 11.1 at 123 mph.
That said, the 847 has pretty lazy ramps. It's old tech and the new lobes are much more aggressive. The XFI 468 has more duration, more lift, and more aggressive ramps, so it will most certainly make more power than the 847. However, as Donnie said, these get tricky to set up the valvesprings right. I'd actually recommend an Extreme 236/242. Still more power than the 847, but easier on the valvetrain. You could even switch out the 3316 intake lobe for a 3196, which would put it at .585 lift with a 1.5 rocker rather than only .520.
Mike
That said, the 847 has pretty lazy ramps. It's old tech and the new lobes are much more aggressive. The XFI 468 has more duration, more lift, and more aggressive ramps, so it will most certainly make more power than the 847. However, as Donnie said, these get tricky to set up the valvesprings right. I'd actually recommend an Extreme 236/242. Still more power than the 847, but easier on the valvetrain. You could even switch out the 3316 intake lobe for a 3196, which would put it at .585 lift with a 1.5 rocker rather than only .520.
Mike
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Thanx guys for ur helpful info,i have Lunnati dubble coil springs w/dampers i think they will handle the lift on the xfi cam.
How can i contact Bret?do you guys have his e-mail or website?
How can i contact Bret?do you guys have his e-mail or website?
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Originally Posted by scorpion_z28
Thanx guys for ur helpful info,i have Lunnati dubble coil springs w/dampers i think they will handle the lift on the xfi cam.
How can i contact Bret?do you guys have his e-mail or website?
How can i contact Bret?do you guys have his e-mail or website?
I know he doesn't like those lobes because he has his own, and for other reasons. I would be careful using those springs on an XFI cam. They were designed for beehive springs which are much much lighter than those dual springs.
