Has anyone actually dynoed gains from shaft mount rockers?
02-28-2008, 10:14 PM
#1
Registered User
Thread Starter
Join Date: Apr 2000
Posts: 1,444
Has anyone actually dynoed gains from shaft mount rockers?
I see plenty of quotes where people "have seen" 15, 20, 30hp gains
from switching to shaft-mount rockers of the same ratio (from roller rockers)
but I have yet to see any proof.
Has anyone actually done a back-to-back dyno test? (SOTP dynoes don't count)
from switching to shaft-mount rockers of the same ratio (from roller rockers)
but I have yet to see any proof.
Has anyone actually done a back-to-back dyno test? (SOTP dynoes don't count)
02-29-2008, 08:09 AM
#4
Registered User
Thread Starter
Join Date: Apr 2000
Posts: 1,444
02-29-2008, 09:36 AM
#5
Registered User
Join Date: Nov 2005
Posts: 61
It might be difficult to get the valvetrain geometry correct on aluminum LT1/4 heads with SBC rockers/guideplates because of slightly different valve spacing. Shaft-mounts are easier to set up correctly and can worth power and reduce wear in cases like that.
02-29-2008, 11:04 AM
#7
Registered User
Join Date: Sep 2004
Location: Lantana, TX
Posts: 1,872
In my limited experience the gains to be had with switching to shaft mount rockers are because of improper valvetrain setup to begin with, not because of some magical bearings or incredibly light components. I believe that if you use offset stud mount rockers and set up the valvetrain properly then you won't see any significant gain. The gains come from people switching from pro mags, cranes, etc. to shaft mounts which isn't a fair comparison.
02-29-2008, 11:50 AM
#8
Banned
Join Date: Oct 2006
Location: Goochland, Va.
Posts: 4,974
02-29-2008, 12:07 PM
#9
Moderator
Join Date: Dec 1969
Location: Buffalo, New York
Posts: 10,745
I someone provides the car, the parts, and will install the shafties I can get the testing done on a Dynojet. Has to be like ratio to like ratio, etc. and I would need a release about damage, blah blah, blah and also permission to use the results on a web site for advertising purposes, etc. If we asked a maufacturer to provide the parts, I bet they wouldn't because I bet they know that they do not make any more power, at least on the typical bracket or street/strip car. Hell, you could offer to pay for them IF they made more than a trivial power difference (more than ~1% or so) and they wouldn't do that either.
Rich
Rich
Last edited by rskrause; 02-29-2008 at 12:10 PM.
02-29-2008, 01:16 PM
#10
Registered User
Thread Starter
Join Date: Apr 2000
Posts: 1,444
I someone provides the car, the parts, and will install the shafties I can get the testing done on a Dynojet. Has to be like ratio to like ratio, etc. and I would need a release about damage, blah blah, blah and also permission to use the results on a web site for advertising purposes, etc. If we asked a maufacturer to provide the parts, I bet they wouldn't because I bet they know that they do not make any more power, at least on the typical bracket or street/strip car. Hell, you could offer to pay for them IF they made more than a trivial power difference (more than ~1% or so) and they wouldn't do that either.
Rich
Rich
All we need is someone to donate parts LOL yeah ... probably not gonna happen.
Worth a shot though, that's how I got the NRT H/C package for my 95
03-01-2008, 10:42 AM
#12
Registered User
Join Date: May 2004
Location: Bay Area, CA
Posts: 2,001
As I think it has been said quite a few times on here, the "gains" from switching to a shaft mount system are minimal if your stud mount system is of good quality and the geometry is correct. You also are not going to see gains if you are running a hydraulic roller, unless your geometry was way off to begin with. We just recently switched a customer over to shaft mounts on his super production racer not for power gain (there was none - dyno verified) but because we wanted to save valve guides, his off-set lifters and valve spacing was causing side-loading of the valve that only an off-set shaft mount system would fix. The Crower Enduro II off-set rockers were not helping much because the rigidity was not there. Now if you are building a motor from scratch, I think the shaft mounts are a good investment to look into because once you price all the components needed for a stud mount system it's pretty comparable. Shaft mounts are hard to setup wrong if you follow the directions, stud mounts take some knowledge and practice to get them to work as best possible.
03-03-2008, 12:50 AM
#13
Registered User
Join Date: Feb 1999
Location: Montville, NJ, U.S.A.
Posts: 661
Here is an article on Jesel's website pertaining to shaft mounts vs. studs on a small block Chevy: http://www.jeselonline.com/v2/index.php?categoryid=52
What no one has mentioned so far is that shaft mounts (I know that Jesel does, not sure about other brands) correct the not so great valve train geometry on a SBC. If you have a SBC with heads that have even further valve spacing than stock, its even more reason to go with shaft mounts. Remember, this is on a small block Chevy. Shaft mounts don't pay such dividends as say on a LS series motor. This issue along with many other improvements were made when the motor was designed. As MachinistOne said, if you are building a motor from scratch, they are worth looking into. The price is comparable by the time you buy the rockers, studs, guide plates, and a girdle. As far as power increases, my engine builder has seen 20 to 25 HP on a small block Chevy build. I have run both setups on my motor. It started out with a stud mount, then I upgraded to shafts. I used to be someone that was completely against shafts on a street motor. After my experience, my view is totally different.
Nick
What no one has mentioned so far is that shaft mounts (I know that Jesel does, not sure about other brands) correct the not so great valve train geometry on a SBC. If you have a SBC with heads that have even further valve spacing than stock, its even more reason to go with shaft mounts. Remember, this is on a small block Chevy. Shaft mounts don't pay such dividends as say on a LS series motor. This issue along with many other improvements were made when the motor was designed. As MachinistOne said, if you are building a motor from scratch, they are worth looking into. The price is comparable by the time you buy the rockers, studs, guide plates, and a girdle. As far as power increases, my engine builder has seen 20 to 25 HP on a small block Chevy build. I have run both setups on my motor. It started out with a stud mount, then I upgraded to shafts. I used to be someone that was completely against shafts on a street motor. After my experience, my view is totally different.
Nick
03-03-2008, 08:40 AM
#15
Registered User
Join Date: Sep 2004
Location: Lantana, TX
Posts: 1,872
What components are you guys buying where the price is comparable between stud mount versus shaft mount? When I do the same comparison on my BBC, the shafties cost about $1K.
Pro Mags - $300
ARP Studs - $35
Guide Plates - $25
Comp Girdle - $200
Jesel SS Shaft Mount - $825
Pro Mags - $300
ARP Studs - $35
Guide Plates - $25
Comp Girdle - $200
Jesel SS Shaft Mount - $825