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Old 12-28-2009, 10:47 PM
421sd 421sd is offline
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Default comp cams 995 springs

i have a set of comp 995 springs on a set of heads and i am rebuilding these heads to put on a new motor. the 995 springs have lost about 10% of pressure. 100lbs seat load and 310 lbs open load. i am using an ultradyne 288/296 with 1.65 rockers. i am wondering do i need to replace these springs and if i do should i use the 995 springs or use crower 68405 springs? which is a better spring?

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Old 12-29-2009, 10:15 AM
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Depending on the lift you could simply shim the 995 springs to bring them back into spec.

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69 Bird w/1970 400 block(409 cubes), #64 heads, hyd. roller, Q-jet by Jeff E., original interior, ps, pdb, th350, and 3.73 gears. Pump gas, street driven muscle. 3800 lbs. race weight. Best, 11.39 @118, my son's car.

79 T/A w/463, Scat crank, Eagle rods, Icon pistons, Lunati solid roller, 262/270, KRE 325 heads,Northwind intake, QF950 carb, full interior, ps, pdb, th350, and 3.73 gears. Pump gas, 3650 lbs. race weight. 10.72 @ 126 so far... no tuning yet.
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Old 12-29-2009, 10:59 AM
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If all check within 5 lbs of each other you have room to shim them to 115lbs seat. They are good to .600 lift plus .060 clearance with book installed height.

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Old 12-29-2009, 04:56 PM
Steve C. Steve C. is offline
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421sd- If you know, what is the current installed height ? 1.700 as rated ?
Thanks.

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Old 12-29-2009, 06:30 PM
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Quote:
Originally Posted by Steve C. View Post
421sd- If you know, what is the current installed height ? 1.700 as rated ?
Thanks.
the current installed height is 1.7 as rated

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Old 12-30-2009, 11:15 AM
Steve C. Steve C. is offline
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Thank you.
That follows right in line what a Comp Tech Rep mentioned to me about a week ago. And yet others apparantly have seen the opposite, one example suggested with most stepped retainers, they are up near 140-160 @ 1.700".

Got to make you wonder if at a low spring pressure with these springs are they involved in any of these "lifter crashing" XE hyd flat tappet lobes

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Old 12-30-2009, 11:20 AM
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Post FWIW:

Steve I have checked hundreds of 995 springs and never saw a set over 120 on my 'Calibrated' Rimac Spring Checker. Hummmmmmmmmmm. Most were as stated or on the low side. Faster ramps require higher springs to keep the lifter on the cam at rpm. Having built quite a few track championship hyd cammed roundy round engines, Ya hera about float. Not the lifter 99% of the time it's not the right spring package.

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Old 12-30-2009, 11:32 AM
Steve C. Steve C. is offline
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When I stated "lifter crashing" I was refering to the title applied by some for the XE issue, precieved or not. I think it was on the Buick board first, but not sure. Your statement concerning the right spring package is more appropriate.


Pontiac Dude's comment about valve float reminds me....
I don't know how many like to read magazine tech articles but if interested the new Feb Chevy High Performance magazine has a good article about "Curing Valve Float with Lifters and Springs". You might glance at it while at the grocery store or book shop when it arrives on the newsstands. I subscribe and just got my issue. It's a 4.250 stroke BBC build using a hydraulic roller cam. By 5,700 rpm it was still making power but by 5,800 rpm it had a DIP and by 6,000 rpm it had all but fallen on its face ! With that Steve Brule at Westech Performance suggested the valvesprings may be too weak. Thus the changes were made and re-testing was done. While on the dyno they cleaned up the valve float issue, found an extra 40 hp in the process and extended the reach by 600 rpm.


Last edited by Steve C.; 12-30-2009 at 11:46 AM.
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Old 12-30-2009, 02:33 PM
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Steve. I agree. Most builders and/or hobbyist look at seat and never open. Or look at the rated open but that is at max lift.
Most builders with street cars never get near this open pressure, (and even some race engines are done wrong) thus the open is a lot less then they think. Then of course the engine will fall flat on it's face. I have seen even Professional builders use the wrong springs for the application and then the Cam takes the hit or bad rap.

Look at the E-head spring and rating. That is at .600 lift. Now check it on a spring tester at the cams final lift with the rocker ratio one is gonna run. Then rpm range the engine/heads/intake/exhaust and cam are rated for. People slap stuff together and never take into account a lot of little things that makes one combo run and the same next have issues.

Just because one is a Professional engine builder doesn't mean they know what they are doing or you wouldn't have posts about this and that.

Best case senerio is to find the spring that will coil bind about .060/.070 away from your lift with the pressures you need. Or at least get close. Not always possible but if it's just a daily driver or rarely or never see's the track the spring package can be more forgiving.

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Old 12-30-2009, 05:10 PM
Steve C. Steve C. is offline
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The subject of distance from coil bind in this thread might be of interest:

http://forums.performanceyears.com/f...highlight=coil

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