My cammed LT1 is a dog on the dyno...HELP!
04-05-2011, 10:30 AM
#1
My cammed LT1 is a dog on the dyno...HELP! Hey everybody, just had a very disappointing day at the dyno, I recently had the motor rebuilt with new rings, bearings, oil pump, gaskets, Lunati Voodoo 60121 (219/227 515"/.530"), 1.6 CC magnum Roller rockers, beehive lunati valvesprings, 52mm TB, CAI, mid-tube headers, gutted cat, Magnaflow exhaust, lt4 knock module....also replaced wires, plugs, coil, cap and rotor...needless to say it should put out a hell of a lot more than a measly 241 RWHP AFTER a dyno tune
The baseline was 232 RWHP 
Others with the same/similar combo (cam is very similar to LT4 hotcam) make an easy 320-340 RWHP....WTF is wrong with my motor? The power curves were very smooth and followed the stock hp/torque curves except mine is 50-60 HP less than stock everywhere and mine revved to 6500 instead of 5800....a freaking stock Impala SS put down 260 on this same dyno and a Z28 made 295 so something is definitely wrong here when my cammed 6sp car is 20-50 hp less than STOCK.
The dyno tuner said my sensors were operating normally and it was NOT pulling timing....WTF...he said it's probably something "weird" like somebody put the cam in wrong and it's bleeding compression and I should start with a leak down test....my buddy is doing that for me this weekend...we'll see if more bad news is to come. The guy who rebuilt the motor has worked at a Pontiac/Buick dealership as a mechanic for 30 years; and was familiar with LT1s and has rebuilt many. On top of my lack of power issue it's been getting 10-11 MPG witch I started another thread a couple weeks ago about. Any ideas on where to start looking for my "missing" 80-90 HP? I'm getting discouraged on this LT1 and the spare LS1 I have laying around for my other car (99 Firehawk) is looking more and more tempting to banish my LT1 troubles forever...HELP!
The baseline was 232 RWHP Others with the same/similar combo (cam is very similar to LT4 hotcam) make an easy 320-340 RWHP....WTF is wrong with my motor? The power curves were very smooth and followed the stock hp/torque curves except mine is 50-60 HP less than stock everywhere and mine revved to 6500 instead of 5800....a freaking stock Impala SS put down 260 on this same dyno and a Z28 made 295 so something is definitely wrong here when my cammed 6sp car is 20-50 hp less than STOCK. The dyno tuner said my sensors were operating normally and it was NOT pulling timing....WTF...he said it's probably something "weird" like somebody put the cam in wrong and it's bleeding compression and I should start with a leak down test....my buddy is doing that for me this weekend...we'll see if more bad news is to come. The guy who rebuilt the motor has worked at a Pontiac/Buick dealership as a mechanic for 30 years; and was familiar with LT1s and has rebuilt many. On top of my lack of power issue it's been getting 10-11 MPG witch I started another thread a couple weeks ago about. Any ideas on where to start looking for my "missing" 80-90 HP? I'm getting discouraged on this LT1 and the spare LS1 I have laying around for my other car (99 Firehawk) is looking more and more tempting to banish my LT1 troubles forever...HELP! 
04-05-2011, 10:47 AM
#4
Yea, the tuner seems pretty knowledgeable about tuning LT1's; he has tuned many; his name is John at Sigma Six dyno services in Concord NC; the car already had a PCM for less tune by Bran Herter....John was able to pick up 11 HP from the PCM for less tune by richening the AFR at WOT. As for as the preload, I will have to ask my buddy who just adjusted my valves before the dyno tune...(I don't know what I'm doing when it comes to internal engine mods). I don't have a scanner to upload the dyno chart...I'll ask the gut to email it to me and see if I can post it later
Yea, he's gonna let me go back to run it again on the dyno once I get this sorted out (HOPEFULLY)
Yea, he's gonna let me go back to run it again on the dyno once I get this sorted out (HOPEFULLY)
04-05-2011, 11:38 AM
#5
Yea, the tuner seems pretty knowledgeable about tuning LT1's; he has tuned many; his name is John at Sigma Six dyno services in Concord NC; the car already had a PCM for less tune by Bran Herter....John was able to pick up 11 HP from the PCM for less tune by richening the AFR at WOT. As for as the preload, I will have to ask my buddy who just adjusted my valves before the dyno tune...(I don't know what I'm doing when it comes to internal engine mods). I don't have a scanner to upload the dyno chart...I'll ask the gut to email it to me and see if I can post it later
Yea, he's gonna let me go back to run it again on the dyno once I get this sorted out (HOPEFULLY)
Yea, he's gonna let me go back to run it again on the dyno once I get this sorted out (HOPEFULLY)
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04-05-2011, 01:18 PM
#9
04-05-2011, 02:25 PM
#14
but i do agree with everyone else, start with the easiest, which is rocker adjustment.
Last edited by draggin97s10; 04-05-2011 at 02:35 PM.
04-05-2011, 03:09 PM
#16
I doubt he screwed up the correction factor on the dyno...my seat of the pants dyno tells me it's making less power than my stock except for headers 1999 LS1 Firehawk (322 RWHP)....even when the LT-1 car has 4.10 gears. I guess my buddy and I get to tear down motor again this weekend and check rockers, valve adjustment, and leak down test....what a PITA! 
04-05-2011, 04:18 PM
#18
I'd start with an objective power measurement, like a 1/4 mile trap speed. There is too much that can go wrong on a dyno dynamics machine to take it as the word of God. Did he say what the max injector duty cycle was? With that, the injector size and fuel pressure we can figure out roughly how much power it makes as well.
If it traps slower than stock or isn't using as much fuel as stock, then you can start checking compression, banana up the tailpipe and whatnot.
If it traps slower than stock or isn't using as much fuel as stock, then you can start checking compression, banana up the tailpipe and whatnot.
