HI. I am slowly starting to work on my 817 heads, got the Comp Cam 268, which is 230 degree duration at .050, and .520 lift. Both my machinist, and the guy on the phone at Comp. Cams recommended their single spring with damper, part No. 941-16. So, I bought them. THey require a 1.750 space to run in, which will give me 130 lbs. spring pressure at that length. When I got them, I noticed how they were somewhat longer than my old springs, and smaller in Dia., both O.D., and I.D. My machinist told me how to measure from the top of my stock retainers, down to the spring pocket, then subtract the thickness of both the retainer flange and the umbrella flange. I did all that, double checked several of the valve locations, and got 1.683 consistently. Which means these new springs would be squeezed .067 shorter than they are meant to be. Doesn't sound too good to me. So, I go to my machinist, tell him what I've got, and he sells me some Crane brand keepers, 7 degrees, which are supposed to gain me added spring height. I just installed and checked a few, and they only gained me .005-.010. Still not good, in my book. I called Comp. Cams, and the guy asked me if I needed 7 or 10 degree keepers. Does anyone out there know which degree keepers the 409 uses???? All Comp. Cams has, is the taller (.050), height keepers in 10 degrees, but not 7 degrees. Seems like maybe my only other choice is getting the valve pockets machined deeper. BTW, I am going with screw in studs. ANy thoughts or suggestions on this matter. Feels like I'm kinda backed against the wall with this stupid problem, but I'm glad I found it now, and not later. Thanks for any input! Brian and his 60'.
Valve spring Operating Length???
- Thread starter 60biscayne
- Start date
CDNpontiac409guy
Banned
It's an ONGOING problem, Brian. These stubby valve spring installed heights, but using BBC valve lifts and valve train weights.... One fighting the other for sure.
Without a doubt, that 941 spring, installed at the factory 1.68"-1.70" height, is going to have WAY WAY WAY too much pressure for that cam profile.
In a perfect world, you need 110-115 pound on the seat, and around 275 open.
In a 1.25" diameter single configuration, that spring does not exist. Looking in the catalogue though, if you're willinbg to go to that "beehive" design, it appears that P/N 26981 would be darn near perfect. I personally have not warmed-up to that style of spring.
Alternatively, P/N 981 may do the job at 1.68/1.70" installed height. 105 pounds may be a little light on the seat though. If you're going to a high quality, light weight roller rocker, it may be just the ticket.
Max RPM expected ? 5500-5700 ?
Definitely looks better than the 941.
Just my thoughts. I deal directly with Comp Cams a few times every week.
Without a doubt, that 941 spring, installed at the factory 1.68"-1.70" height, is going to have WAY WAY WAY too much pressure for that cam profile.
In a perfect world, you need 110-115 pound on the seat, and around 275 open.
In a 1.25" diameter single configuration, that spring does not exist. Looking in the catalogue though, if you're willinbg to go to that "beehive" design, it appears that P/N 26981 would be darn near perfect. I personally have not warmed-up to that style of spring.
Alternatively, P/N 981 may do the job at 1.68/1.70" installed height. 105 pounds may be a little light on the seat though. If you're going to a high quality, light weight roller rocker, it may be just the ticket.
Max RPM expected ? 5500-5700 ?
Definitely looks better than the 941.
Just my thoughts. I deal directly with Comp Cams a few times every week.
Aubrey, " I deal directly with Comp Cams a few times every week." Wow, Aubrey,, business must be great!!!!!! 
Beehive springs
THanks, Aubrey, for the tips. WE are going to be using Roller Rockers, and don't plan to spin the motor over 6000, Max, so I think i may check into the Beehives. I'm just learning about them now!! Brian.
THanks, Aubrey, for the tips. WE are going to be using Roller Rockers, and don't plan to spin the motor over 6000, Max, so I think i may check into the Beehives. I'm just learning about them now!! Brian.