I'm installing a solid cam in my 350, a comp 12-221-5 (242/250@.050 w/.541/.567 lift using 1.6 rockers). Comp recommends the 987 spring, installed at 1.800.

I'm using my old stock heads for a year or so, until I replace them with aftermarket. So I don't want to machine the heads or replace valves. They currently have good 986 springs installed at 1.700 with standard keepers.

I can't get the 1.800 height. Best I can do is 1.750-1.760 using some .050 keepers that I bought. I called Comp today, and the guy didn't like me wanting to install the 987's at 1.750. He thought the seat pressure would be too high. He recommended that I use the 986's, and install them at 1.750 as the best compromise I can make to use my heads without machining.

My concern was, the new cam is a little more aggressive than the XE284 I'm replacing. It sounded wierd to me to want to use the same springs as the XE284, but at a taller installed height, and less seat pressure? Maybe it has somethign to do with a solid vs. hyd. cam? :confused:

What do you guys think of that advice? Is using the 986's at 1.750 a good compromise to using the 987's at 1.800 for that cam?

Thanks for any advice you may have... smile.gif

chris

Check Comps catalogue in their spring data section under springs by dia. Find a spring that will satisfy or come close to your requirements. Look at the spring rates and by combining a selected spring and shim you can probably get what you need......remember it doesn't have to be a Comp. spring ......K-Motion,Crane,Lunati,etc.,etc.offer springs that may better suit your needs graemlins/thumbsup.gif :do a little thinking,do a little research :cool:

Thanks Joe, smile.gif

I've never really looked at a spring chart before, that was very helpful. I noticed that the 986's I had were supposed to be at 1.800 as well.... the shop that did my heads put them at 1.700 :eek:

Which numbers are the most important? Seat pressure, open pressure, or rate? I mean, which one should I concentrate on the most? Also, how close to I have to be for the pressures? Is +/- 10 lbs ok? or +/- 20 lbs? Should I err on the heavy side or the light side? How about rate? I have no problem digging through spring charts, but I need a little better idea of what I'm looking for, besides dia. smile.gif Thanks again!

Chris

For a solid flat tappet cam you will want to have around 350# open, unless the cam is made on a billet core. Seat pressure of 150# will work. A spring with up to about 400# rate will probably work, but you have to check the numbers for both intalled ht and open ht. .

Since most of the stuff I work with are rollers you probably should work with rates close to what the manufacturer recommends.....probably plus or minus 20 wouldnt hurt but check other companies rates as well.....with a flat tappet use the min. required pressure to get the job done plus some margin for safety.I'm sure you can find a creative combination!

Isky makes a +.060" retainer. Never even thought about it, but could you use the +060 retainer AND the +050 lock? That might make for rocker clearance issues, but you never know . . .

Isky 295D's 135@1.75-.760. I think they're good to .580". But are expensive. See Wolfplace for them.

I was looking at these next springs for my next motor which will see positive intake pressure and needs more on the seat to cope.
You might try CC985 springs. Same size as 986's.(1.430) But more like 160 @ 1.75 and 330 at .500". They should drop 10 -15 lbs on break in.
Note: CC recommends the 985/986/987 as .500" max lift and then specs them for cams with more lift than that. The tech guy was a moron as most of them are. To much seat pressure! Lots of std core flat tappet circle track motors with 150 on the seat running around. Just need to keep it at 350ish over the nose to keep from wiping the cam.
And UDH specs about 140/340 for his similar solids on a BBC.

Thanks guys! I'm gonna take a look and see what I can find. Eric, I think you have a good point. I
m using Crane Gold rockers, and I better check rocker/retainer clearance. I thought it was pretty close before... better double check!

Also, good point on the max lift for each spring! I wonder why they spec that spring for that cam if the lift is too high? And they said it was ok to use 1.6 rockers as well? :confused:

Thanks again!

You might consider Elgin springs, PN ELG RV 1943X over at Midwest Miotorsports.
www.midwestmotorsportsinc.com (http://www.midwestmotorsportsinc.com)
1-800-262-5033

Spec's are:

Stock dia., .600" lift max.
Seat pressure = 125# at 1.80"
Open pressure = 360# at 1.20"
Coil bind = 1.15"
Price = $39.84 or kit at $54.99, (springs, retainers and keepers).

They are not high tech, but rather just a high lift version of the great old Z-, -142, spring IF they will meet your needs...

pdq67

I think I found one: Lunati 73949.

120 lbs @ 1.650 installed ht
320 lbs @ 1.100 (.550 lift - about my average)
.640 max lift
Rate 363 lb/in.

The 987 spring was 121/310 when installed to spec, so I think the lunati spring is perfect.

Now, I need to shim it .050 shorter than my nominal 1.700 with normal keepers. This is good for keeping my rocker/retainer clearance as nice as possible, instead of using offset keepers or retainers.

Does the shim go directly under the spring? Can you use more than one shim? Will the retainer I used on the 986's work with the Lunati springs? If you can't tell, I've never had to do any spring setup before (always just changed them for exactly what was in there before)... sorry about all the questions! smile.gif


chris

Thaks pdq... I think I needed a bigger dia spring to fit in the spring pocket properly. smile.gif

Yes, you can shim as you see fit generally and yes it goes under the spring,yes you can use more than one shim......put the thicker one on top....I new you could do this!.....I'm proud of you! graemlins/hurray.gif BTW the retainer may work...just compare the step dimensions to the spring

Thanks Joespanova! You've been a big help.

I think the comp retainer I have will work. The dimensions are very close to the recommended Lunati ones. And it looks like the spring will fit it just fine.

I just ordered the springs, and a shim assortment. I think in a few days, I'll be well on my way.... Now hopefully everything works out ok smile.gif Come spring time, that dragstrip better watch out...I want to see that 12.99!! :D

Chris

Godspeed my friend! graemlins/waving.gif