LQ4 Rebuild - Q's about Cam
12-18-2016, 09:58 PM
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LQ4 Rebuild - Q's about Cam Hi Everyone, I've been lurking around on your site for the last few days, and have learned a lot about my first CSB. I have a few questions specific to my situation. I've tried to include all pertinent info, but if I've left something out, just ask. Thanks in advance for any guidance / clarification you can provide.
Truck:
04 2500HD 4x4 CCSB 6.0L /4l80e / 4.10 175k miles
Back Story: (skip if you're not interested - go to"Goals")
Purchased an abused truck in March;oil pressure "stuck" around 20 psi (according to dash gage). Suspected stuck pressure relief valve.Added seafoam to motor oil, changed 600milater with 10w-40 and added seafoam again. Pressures rose to 20psi @ idle,around 35 @ 2500 RPM after oil changed - lasted a few hundred miles.
Oil Pressure has now droppedto 4 psi @ idle, 14 psi @ 2500 RPM (measured with mech. gage) - Low OilPressure chime on whenever engine idles. Changed oil to 20w-50 + smoke stop to increase viscosity; didn'tincrease oil pressure.Sound of RodKnock present from bottom of engine through both wheel wells, not fromengine bay, immediately following oil change. Let engine idle for 5 minutes; nochange in noise or pressure.Droppedoil pan, flex plate doesn't appear to be cracked; Rod endplay seemed okay (haveyet to measure, but nothing obvious)Checked a single rod bearing - no obvious signs of excessive wear(weather permitting, I'll take a photo to verify with you).Was attempting to pull a main cap, then windkicked up, blew sand and grit into crankcase - have decided to pull motor andperform rebuild.Truck was a bit dodgyanyways.
Goals:
Truck is mainly used for towing/hauling, so increase in torque and throttleresponse is desired. Have decided bestroute is a cam and possibly 799 heads.The heads will depend on what the rest of the rebuild ends up costing.
I want to:
Maintain emissions
Good quality idle, minimal lope.
Improved torque focused in 1000 - 3500 RPM range
Questions:
It seems most refer to valve overlap at .050 duration; and that a lowpositive number is max to minimize lope, i.e. 10. Is this correct?
I've also read that I need around -10* overlap to maintain emissions - alsocorrect?
Out of the cams I'm looking at; all have quite a bit negative overlap, so I'm wonderingif I'm being too conservative with cam selection?
Two that I'm considering:
CompCam 54-452-11: adv. dur266/270,@.050 212/216,lift .520/.524,LSA 115+4.
I calculate adv. dur. overlap at 38*, and @.050 -16*, stated RPM 800-5200
VHP080 adv. dur 272/280, @.050210/218, lift .551/.551, LSA 116+2
adv dur 43*, and @.050 -18* stated RPM 1400-5800
I'm not sure it's significant, but VHP advertises @.004 on their website,CompCam is the traditional .006.
Additionally, would either of these benefit from a mild port & polish(diy) of the heads? I'm concerned thatthey may not be aggressive enough to justify it, and may negatively affect intake velocity.Also, I’ll be installing a rebuilt trans, butI don’t think I can change the TC without voiding the warranty, so stall will be 2600.
Truck:
04 2500HD 4x4 CCSB 6.0L /4l80e / 4.10 175k miles
Back Story: (skip if you're not interested - go to"Goals")
Purchased an abused truck in March;oil pressure "stuck" around 20 psi (according to dash gage). Suspected stuck pressure relief valve.Added seafoam to motor oil, changed 600milater with 10w-40 and added seafoam again. Pressures rose to 20psi @ idle,around 35 @ 2500 RPM after oil changed - lasted a few hundred miles.
Oil Pressure has now droppedto 4 psi @ idle, 14 psi @ 2500 RPM (measured with mech. gage) - Low OilPressure chime on whenever engine idles. Changed oil to 20w-50 + smoke stop to increase viscosity; didn'tincrease oil pressure.Sound of RodKnock present from bottom of engine through both wheel wells, not fromengine bay, immediately following oil change. Let engine idle for 5 minutes; nochange in noise or pressure.Droppedoil pan, flex plate doesn't appear to be cracked; Rod endplay seemed okay (haveyet to measure, but nothing obvious)Checked a single rod bearing - no obvious signs of excessive wear(weather permitting, I'll take a photo to verify with you).Was attempting to pull a main cap, then windkicked up, blew sand and grit into crankcase - have decided to pull motor andperform rebuild.Truck was a bit dodgyanyways.
Goals:
Truck is mainly used for towing/hauling, so increase in torque and throttleresponse is desired. Have decided bestroute is a cam and possibly 799 heads.The heads will depend on what the rest of the rebuild ends up costing.
I want to:
Maintain emissions
Good quality idle, minimal lope.
Improved torque focused in 1000 - 3500 RPM range
Questions:
It seems most refer to valve overlap at .050 duration; and that a lowpositive number is max to minimize lope, i.e. 10. Is this correct?
I've also read that I need around -10* overlap to maintain emissions - alsocorrect?
Out of the cams I'm looking at; all have quite a bit negative overlap, so I'm wonderingif I'm being too conservative with cam selection?
Two that I'm considering:
CompCam 54-452-11: adv. dur266/270,@.050 212/216,lift .520/.524,LSA 115+4.
I calculate adv. dur. overlap at 38*, and @.050 -16*, stated RPM 800-5200
VHP080 adv. dur 272/280, @.050210/218, lift .551/.551, LSA 116+2
adv dur 43*, and @.050 -18* stated RPM 1400-5800
I'm not sure it's significant, but VHP advertises @.004 on their website,CompCam is the traditional .006.
Additionally, would either of these benefit from a mild port & polish(diy) of the heads? I'm concerned thatthey may not be aggressive enough to justify it, and may negatively affect intake velocity.Also, I’ll be installing a rebuilt trans, butI don’t think I can change the TC without voiding the warranty, so stall will be 2600.
