I'm about to order valve springs for my new setup.

I have a hydraulic Comp Cam 292H (PN 12-213-3)

Flat Tappet Lifters (Federal Mogul)

The cam card suggests a 986-16 spring for a 1.5 ratio rocker. That would
give me 0.501" lift at the valve.

I'm switching over to 1.6 ratio rockers and need to change springs for clearance.

The springs I am considering are: Comp Cams 990-975 Dual Springs

They have an open pressure of 340 lbs. @ 1.150"

By my calculations, that would be 0.550" lift (1.7" installed height).

My max valve lift would be 0.534" (or 1.16" open height).

Questions:

1. Is the open pressure rated at the open height, or at the bind height?

2. Since I'm not lifting to the open height, I'm guessing the open pressure will be
slightly less. Am I looking to screw a lifter, or shave a lobe with that much open pressure?

Thanks for your thoughts,
Tino

 

http://www.compcams.com/Technical/Cu...ML/340-349.asp

Learn to use that!

The 987 with a installed height of 1.800" and 120lbs on the seat will go to .600 lift so you don't need to change springs.

It's always best to break in a flat tappet cam on small ratio rocker arms since it will put less pressure on the lifter face.

Bret

 

had alot of fun with that cam in the very first SBC i did when i was a kid. break out the vacuum can[we manged without one but brakes sucked at idle]
Anyway we ran the isky equiv. of 987 springs no problems, no float.And yes, we did wipe the lobes off the cam before that due to improper valve springs[too stiff and didnt remove inner or use break in arms] .Hey, first motor's for learning right?




QOUTE;"Welcome to the Internet where everyone's a mechanic & has a 10 second car." awesome sig BTW.

 

I should have mentioned, that cam has been broken in already. I used the
292H last season.

After studying the flow data for my SP II heads, I realized 0.501" valve lift
wasn't doing the job.

I am changing the springs and rockers only, in addition to a stud girdle to keep
the valve train happy.

Thanks for the chart and the recommendation. I was looking for a spring with
the same installed height as my current spring. After seeing the numbers,
the 987 will be less harsh at my open height.

As for the 292H cam, I'm very impressed with the performance. Idle is weak,
and my vacuum dropped 10 in./hg. from my Crane Energizer cam.!

 

look at isky and crower too for springs--i not bashing comp;ive got comp cam,Rs, and springs,but sometimes you find a spring profile slightly better suited to your needs.
FWIW,my 292 liked less ""lash"" than other mild hyd.,about 1/4 to 1/3 turn after barely reaching resistance.Hyd's at the limit of float like just as much setup prep and lash maint as solid flats in my exp.
In my[more than humble] opinion, a girdle is not necesary at that lift level, ive been to .650[roller] on SBC before i noticed a difference;but that's on my trusty 36wide *** type dyno..Accepted lift is around .6 for a girdle according to most mainstream pros.
I used 7/16 studs whenever possible to help control flex on what a guy who did a little bit of research once called "a mickey mouse valvetrain"

Some of the pros here might have different opinions on girdles or hyd. setup, but hey, they get paid to do it,so i'd go with their opinion.
Best of luck w/ your setup.

 

I normally set my pre-load to a maximum of 0.020" which equates to less than a quarter turn.

My valves are set every season since this is a summer car only.

Question about valve height.
If I opt to install a spring @ 1.8", will my current stock valves accept that
height?

I can't seem to find any info on maximum spring height. I do recall a value
of 1.750", but I don't know if that was a maximum.

http://www.sallee-chevrolet.com/Worl...nII_Heads.html
http://store.summitracing.com/defaul...h.asp&x=27&y=9

 

I guess it's not a big deal because the pressures with the 987 @ 1.7, or 1.75
are still favorable.

n/m

 

I want to learn a little more about spring dampers.

When and why would you consider using them?

I've read a few articles on the 'Net regarding what a dampener does,
but not WHEN it's absolutely a requirement for the application.