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Old 10-13-2014, 08:08 PM
mhenesian mhenesian is offline
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Join Date: May 2002
Location: Livermore/CA
Age: 73
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Default COMP 925 springs too soft ? 440 Source Head problems

Hi Friends,

it's been a while since I posted anything, although I check this site frequently.

We (son and I) built a new 10.5 to 1 440 motor for drag racing in one or our '69 Roadrunners (0.030" over Ross #82008 flat top pistons, stock forged crank, forged 440 source rods with 7/16" ARP wave lock bolts, decked, balanced and blueprinted, reconditioned 440 Source heads, 3/8" Isky #1623 pushrods, M1 single-plane, Holley HP carb, etc..) but I'm sorry that I used COMP 925 springs on the heads with the Lunati Voodoo cam (287/297 advertised degrees, 242/252 at 0.050", 0.533/0.552" lift). TECH machine in Livermore,CA did all the head work, machine work, balancing and short block assembly (we are very happy with their work). At the track the motor pulls very hard to 5200 RPM, then just flattens out in power. It feels like it's on the rev limiter or running out of gas ! At 5800 RPM it picks up again, but by then we are so freaked out we just shift into the next gear. At the 1/8th mile we just hold on in 3rd gear at 5600 RPM until past the 1/4 mile mark. Very uncomfortable for bracket racing a Mopar - not having that awesome top-end power. The motor should easily pull past 6500 RPM with the Voodoo cam, big valve heads, M1, MSD Ignition, MSD distributor, etc...

From the "old" days, it feels to me that the valves are floating or at least bouncing off the valve seats causing a loss of dynamic compression and power. It must be that the COMP springs are doing a bad job of controlling the valve motion.

To make matters worse, we discovered that the 440 Source roller rockers had completely worn out the "hardened and polished" 440 Source rocker shafts. The little rollers dug into the shafts about 0.005~ 0.015" and formed nice little channels, some with flat spots. 440 Source does not have an explanation for the excess wear. So we put back the old tried and true Mopar HD stamped rocker arms and shafts, and old Mopar 5/16" pushrods, and got back around 30 HP (based on 1/4 mile trap speed). The valve float is not as pronounced but the power still seems to drop off before it should.

We are very frustrated with COMP and 440 Source. The COMP catalog specifies the 925 dual with damper spring for all their mechanical cams, and even their retrofit hydraulic roller cams. The COMP 924 spring ( 114 # at 1.900", 347 #/inch) is specified for the hydraulic cams, but the 925 is stiffer (111 # at 1.900", 395#/inch) and should cover all the hydraulic cam choices. I'm thinking we should have used the COMP 929's (140 # at 1.900", 437 #/inch) or 953's (148 # at 1.900", 474 #/inch) These spec out more like the old Mopar dual P2806077 (green/purple stripe 115 # at 1.900", 530 #/inch ?) which are today >$25/spring. Say what ?

We did not degree in the Lunati cam, just installed it straight up. This should not be the problem as the motor pulls hard from 2500 to 5200 RPM. Ignition timing is 16 to 18 degrees initial with 34 to 36 total running 91 octane Sunoco unleaded,

Any suggestions ?
Thanks
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Old 10-16-2014, 04:32 PM
mhenesian mhenesian is offline
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Join Date: May 2002
Location: Livermore/CA
Age: 73
Posts: 171
Default

No comments from the Mopar drag race community ?

I'm (almost) sorry I didn't use my old '933' hemi springs (single springs w/dampers, 110 # at 1.900", 430 #/inch) on the 440 Source heads, and stick with the Mopar '509' cam or COMP's Nostalgia Plus PP292H grind (247/254 degrees at 0.050" lobe lift on 108 degree lobe centers, 0.509 lift). I never had a valve float problem on cast iron heads with these obsolete '933' springs.

Mark
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