HardcoreABN said:So I finally had the latest build of my engine tuned yesterday and the numbers were waaay lower than they should be. It was tuned by Mayhem Motorsports in Raleigh, NC and made 475/450. I was expecting hp to be in the 525-550 range.
Specs on the engine:
2000 Corvette Z51, M6 T56, 3.42 3 rib diff
402 LS2 (4.005" x 4.0")
- Callies Compstar crank/rods
- Wiseco pistons/rings, -8cc dish
- GMPP CNC LS3 heads with Comp Cams 921 springs (installed height verified), milled .036"
- Cometic 4.085" .045" thickness head gaskets
- 11.5:1 or so compression
- Comp Cams 875 lifters with (I believe- I can't find my notebook) .020" preload
- Comp Cams 7795-16 Hi-Tech pushrods, 7.375" measured for .020" preload
- Comp Cams 235/250 .621/.595 115+4 spec'd by Martin @ Tick
- LS3 intake/LS2 throttle body
- return style fuel system conversion
- Holley billet rails
- Aeromotive 13101 regulator set at 58psi plumbed after the fuel rails
- all Fragola PTFE braided stainless lines
- stock GM fuel supply line
- 60# Deka injectors
- KB BAP set to turn on at 4" of vacuum
- Melling 296 oil pump
- Edelbrock Victor water pump
- under drive pulley
- MSD plug wires
- NGK TR55 plugs
- LS7 MAF in a 4" housing mounted at the throttle body
- Vararam
- Comp Cams billet tensioner
- ARP rod bolts, head studs, and main studs
- AIR delete
- LG Motorsports Street Series 1 3/4 headers 3" collector
- Corsa dual 2.5" Tigershark exhaust
- no cats
Driveability was great from what little I drove it. After I got home from the tuner it sat until this morning when I blew a power steering hose- which will be here Thursday and will be installed on Friday morning.
I honestly do not know where to look. I was told by the tuner that I need larger primary tube headers and that they would net me probably most of my missing hp because LS3 port heads need a larger exhaust than cathedral port heads.
I want to be clear- I am NOT, in any way, bashing ANY of the companies whose parts are in it or have done work to it.
Here is they dyno sheet
The lifters are http://www.summitracing.com/parts/cca-875-16
The head flow numbers are from GM- they are GMPP CNC heads.
I did not have the valve seats touched since the heads were new- I just had them milled to bring the compression back up. 69cc chambers with dished pistons = no compression lol
Clutch is a Monster level 3 with about 15,000 on it. Definitely NOT slipping lol.
What do you mean by "Did you take open measurements after the instal when checking geometriesand clearances? "
I need to get a new compression tester, mine won't work on metric heads lol
I got the 525-550rwhp number after discussions with the guy who specced my cam. I gave him all the data on the build and gave him my goal of 525-550rwhp while being streetable enough for a DD and that won't chew up valve springs. He specced the cam to get me there.
Right now I am leaning more towards an exhaust back pressure issue or possible valve float due to the lifters/push rods not playing well together.
I also plan to get the car in the air and do back pressure testing on the exhaust and verify push rod length requirements and preload- soon as I get the TT CTS-V out that I am rebuild the trans. Sorry for the delayed response, been really busy the last week or so.I did end up doing a compression test.
1 - 175
2 - 175
3 - 170
4 - 170
5 - 170
6 - 160
7 - 175
8 - 172
Average compression ratio is 170.8 which makes all cylinders within the ideal 10% margin.
I have not been able to get consistent EGT readings with the IR temp gun, which is frustrating me. once I get the car back together I will dig into it some more, measuring spark burn, ect....and comparing cylinders.
GM Engine Vin Codes
Anyone going out looking for a 4.8L or 5.3L Truck based LS engine that has already been removed from the vehicleBeware, Because unless you can look into the spark plug hole with a scope or little camera to see the top of the piston or insert a wire and run it across the piston surface to feel if it's dished or a flat top It's hard to tell the difference between those two. However if you look for the 8th digit in the VIN It will tell you most everything you need to know.
1999-2006 Trucks, Vans & SUV
4.3L, VIN. X or W(2003+) (8th digit)
6.0L, VIN. U (8th digit), (LQ4) Trucks, Vans and Denali
6.0L, VIN. N (8th digit) (LQ9) Escalades & SS Silverado
4.8L, VIN. V (8th digit)
5.3L, VIN. T (8th digit, opt LM7)
5.3L, VIN. Z (8th digit, opt L59)
5.3L, VIN. B (8th digit, opt L33 05+ HO Aluminum and Iron Block with 243/799 heads)
2007+ Trucks
classic body style, 6.0L, VIN. U (8th digit, opt LQ4), Compressed Natural Gas and Gasoline
classic body style, 6.0L, VIN. N (8th digit, opt LQ9)
classic body style, 4.8L, (VIN. V, 8th digit, opt LR4)
classic body style, 5.3L, VIN. T (8th digit, opt LM7)
classic body style, 5.3L, VIN. Z (8th digit, opt L59)
classic body style, 5.3L, VIN. B (8th digit, opt L33)
classic body style, 4.3L, (VIN. X, 8th digit, opt LU3)
new body style, 5.3L, (VIN. 0, 8th digit, opt LMG)
new body style, 5.3L, (VIN. J, 8th digit, opt LY5)
new body style, 5.3L, (VIN. 3, 8th digit, opt LC9)
new body style, 5.3L, (VIN. M, 8th digit, opt LH6)
new body style, 6.0L, (VIN. Y, 8th digit, opt L76)
new body style, 4.3L, (VIN. X, 8th digit, opt LU3)
new body style, 4.8L, (VIN. C, 8th digit, opt LY2)
5.3L
2003-04 GMC Truck Envoy XL
2003-04 Isuzu Ascender
2003-04 Chevy TrailBlazer EXT (all with VIN "P", 8th digit)
2005-06 (all with VIN "M", 8th digit)
lets look at some basic facts, engines need to breath efficiently, have a near ideal fuel air ratio, and minimal exhaust flow restriction to make good power.
the GM/GMC law suit on active fuel management engines
watch these video's, there's a great deal of info you might not know, info that should affect your choices and options you may want to avoid on used vehicles that lack of that info can easily affect the potential engine life span and expected durability issues there's a very serious built in...
garage.grumpysperformance.com
youll need the fuel/air ratio to be in the 12.5-12.8:1 range.
the dyno power curve suggest the engine combo stops breathing efficiently at about 5400rpm,
that could be exhaust back pressure (likely)
or not enough cam duration on to wide a LSA(likely)
OR the injectors maxing out (likely)
or a combo of all three, or it could be valve train control, fuel supply or ignition issues (a bit less likely but check obviously)
your COMP CAMS 235/250 duration on a 115 LSA is less than ideal in a 402,in my opinion.
Id have selected something closer to a 240/245 on a 112 LSA, with about a .660 lift, but obviously talk to several cam suppliers not just your builder and yeah 170 psi is LOW for 11:1 compression
http://schneidercams.com/270rsbcsolidroller-3-1-1-2-1-1-1-1-1-1-1-1-1-1-1-1-1-1-2-2-1-1.aspx
Center Counterweight Ls Series Cranks
Using Dart's CCW (center counter weight) Crankshaft in OEM LS blocks I found this info that might be useful posted elsewhere by 0HP RESEARCH https://www.summitracing.com/parts/sum-g3611?seid=srese1&gclid=EAIaIQobChMImeipnJCr9gIVRkKGCh2ZtAgcEAQYBCABEgKizfD_BwE keep in mind the stock LS crank is...
garage.grumpysperformance.com
http://forum.grumpysperformance.com/viewtopic.php?f=56&t=1166
http://forum.grumpysperformance.com/viewtopic.php?f=69&t=10416&p=43246&hilit=+ls3+cams+test#p43246
http://www.hotrod.com/how-to/engine/1507-1968-camaro-461-inch-rhs-ls-engine-build-and-dyno/
http://www.superchevy.com/how-to/project-cars/sucp-0805-ls-engine-power-packages/
http://forum.grumpysperformance.com/viewtopic.php?f=52&t=10450&p=43597&hilit=using+graphs#p43597
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