Roller Camshafts make a huge difference
Thread Starter
Instructor
Joined: Oct 1999
Posts: 217
Likes: 0
From: Houston TX
Roller Camshafts make a huge difference
Just got desktop dyno and plugged in my specs for my new 383. I wasn't too impressed because I was only getting around 375hp. This was with my Comp Cam Magnum 270 hyrdaulic cam. Then I started plugging in some roller cams. WOW! Huge difference in power! I was seeing 30hp gains with the same duration cam and an even larger torque gain. The converson to flat tappets to rollers is expensive but I think this mod is a better value than some head mods (using Sportsman IIs now). Has anybody seen a huge horsepower gain going from flat tappets to roller lifters?
Andrew
Andrew
Melting Slicks
Joined: Dec 2001
Posts: 2,025
Likes: 1
From: Billings MT
Re: Roller Camshafts make a huge difference (mastiff)
I belive they even mention it in the manual, but DD2000 overestimates the effect of a roller cam. They say for a normal roller to use flat tappet. Possibly 5hp more woudl be a correct assumption?
Hope that helps a little. :cheers:
Hope that helps a little. :cheers:
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
Re: Roller Camshafts make a huge difference (VETDRMS)
Cam for cam with the exact same ramps, one roller the other flat, yeh, maybe 5 hp saved from friction, if that....BUT
for the same duration/lift, the profiles of the ramps will be MUCH steeper, because the roller can follow the ramps, where a flat tappet would dig in and wear out very quickly.....
now having said that, most roller cams can give better overall lift and ramp charactoristics with out having to use insane spring pressures, and since average lift can be higher due to ramp design, overall idle charactoristics are much better for street driving....800 rpm idle with 425 ft lbs in a 350 ci engine ain't all that bad....wonderful street engine....
but to do that with a flat tappett, forgetaboutit....
now there is ONE thing....I do not like the idea of toggle type roller lifters for street use, there is what I think as a fairly obvious reason GM went to the double dee arrangement with retainers and that spyder spring retainer thing....longevity....
so IMO to do a roller engine correctly, go with late truck block and use factory setup.....do your own cam at that point...
GENE
for the same duration/lift, the profiles of the ramps will be MUCH steeper, because the roller can follow the ramps, where a flat tappet would dig in and wear out very quickly.....
now having said that, most roller cams can give better overall lift and ramp charactoristics with out having to use insane spring pressures, and since average lift can be higher due to ramp design, overall idle charactoristics are much better for street driving....800 rpm idle with 425 ft lbs in a 350 ci engine ain't all that bad....wonderful street engine....
but to do that with a flat tappett, forgetaboutit....
now there is ONE thing....I do not like the idea of toggle type roller lifters for street use, there is what I think as a fairly obvious reason GM went to the double dee arrangement with retainers and that spyder spring retainer thing....longevity....
so IMO to do a roller engine correctly, go with late truck block and use factory setup.....do your own cam at that point...
GENE
Le Mans Master
Joined: Nov 1999
Posts: 5,768
Likes: 3
From: San Diego CA
Re: Roller Camshafts make a huge difference (mastiff)
The Desktop dyno program specifically states that certain mild roller cams will be grossly overrated and that they should be entered as either hydraulic flat tappet or solid flat tappet - the two cams of identical duration and such will be much the same however since the roller can open and close the valve faster and ususally higher there will be some gains even with all things being equal - that includes the better idle and vacuum readings mentioned earlier.
