Cam only LS7 dissapointing dyno numbers
Cam only LS7 dissapointing dyno numbers Spent the afternoon at Arrowlane getting my rail tuned after the cam swap and am disappointed with the power it made.
Here are the details:
LS7 GM crate motor with Diamond pistons and head studs
GM Cup Cam #8086
90mm Throttle Body
Camco 1 3/4 header
S4 Trans
Rail made 412HP and 431TQ to the wheels. My tuner has done lots of other LS7 rails and most make 500+. I know someone with this same cam and he made 525 to the wheels.
Chris spent about 6 hours with me and we are both perplexed at the low HP. He suggested I get a Fast 102 TB and bring it back. I couldn't be happier with the service I received but am disappointed with the power my engine made. Anyone have a suggestion on what might be wrong with my combo?
Complete cam specs:
88958606 Roller Camshaft Gen 3 Showroom Stock Design --
This hydraulic roller camshaft for RPO LS1 or LS6 was designed for showroom stock road racing. It requires the use of 2002 and later LS6 hollow stem intake valves P/N 12565311, hollow stem - sodium filled exhaust valves P/N 12565312, and valve springs P/N 125565313. It features .570�intake and exhaust lift, 251 degree exhaust duration at .050 and 239 degree intake duration at .050.
Technical Notes:
Center line of intake lobe means M.O.P. or maximum open point, determined across nose of lobe.
Lobe flank is not symmetrical - for best torque set intake to TDC@105 degree and for best poer set intake to TDC@106.5 degree.
Cam timing @ 0.050 tappet lift (timed @106 degrees intake to TDC)
Exhaust opens @ 51 degrees and closes @ 20 degrees with duration at 251.
Intake opens @ 12 degrees and closes @ 47 degrees with duration at 239.
Here are the details:
LS7 GM crate motor with Diamond pistons and head studs
GM Cup Cam #8086
90mm Throttle Body
Camco 1 3/4 header
S4 Trans
Rail made 412HP and 431TQ to the wheels. My tuner has done lots of other LS7 rails and most make 500+. I know someone with this same cam and he made 525 to the wheels.
Chris spent about 6 hours with me and we are both perplexed at the low HP. He suggested I get a Fast 102 TB and bring it back. I couldn't be happier with the service I received but am disappointed with the power my engine made. Anyone have a suggestion on what might be wrong with my combo?
Complete cam specs:
88958606 Roller Camshaft Gen 3 Showroom Stock Design --
This hydraulic roller camshaft for RPO LS1 or LS6 was designed for showroom stock road racing. It requires the use of 2002 and later LS6 hollow stem intake valves P/N 12565311, hollow stem - sodium filled exhaust valves P/N 12565312, and valve springs P/N 125565313. It features .570�intake and exhaust lift, 251 degree exhaust duration at .050 and 239 degree intake duration at .050.
Technical Notes:
Center line of intake lobe means M.O.P. or maximum open point, determined across nose of lobe.
Lobe flank is not symmetrical - for best torque set intake to TDC@105 degree and for best poer set intake to TDC@106.5 degree.
Cam timing @ 0.050 tappet lift (timed @106 degrees intake to TDC)
Exhaust opens @ 51 degrees and closes @ 20 degrees with duration at 251.
Intake opens @ 12 degrees and closes @ 47 degrees with duration at 239.
Yes. This cam was recommended by the tuner. I went to him before touching the motor and told him I was considering a cam swap and tune. He recommended this particular cam saying it would not require a valve spring upgrade and I would pick up 60-70 hp. I wish I had dynod it before the cam install. At this point I want to rule out any other potential issues. The tuner did tell me that he "maxed out the injectors". I believe the injectors are stock LS7's.
Trending Topics
aren't ls7 injectors around 36-39 lbs or so ? they can make mid 5xx before going static I thought. with that said if your fuel pressure is steady @ 58 psi and it peaking where it does,there is a problem obviously somewhere. is the trans/stall shot ?
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Yes. This cam was recommended by the tuner. I went to him before touching the motor and told him I was considering a cam swap and tune. He recommended this particular cam saying it would not require a valve spring upgrade and I would pick up 60-70 hp. I wish I had dynod it before the cam install. At this point I want to rule out any other potential issues. The tuner did tell me that he "maxed out the injectors". I believe the injectors are stock LS7's.
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Yea, I'm running 48 lb injectors and I'm only at 68% cycle at my power level. No way 42 lb ones should be maxed out at op's power unless he has a huge Drive train loss. I loose 19% through my drive train. I can't see him loosing more than 25% even with an auto
This is in a sand rail with a Mendeola S4 Transaxle running 934 CV's through mid boad hubs. The axles/cv's run at a 17 degree angle. Most of the sand rail experts I know estimate 25% drivetrain loss.
Yes 58psi. We put a snap on fp gauge on it for the last dyno pull to make sure we were not losing pressure.
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A 25% loss would put you around 550hp at the crankshaft. That is still to low. So maybe a combination of the dyno and your drive train loss being higher than you thought.
By the way what tires were on it when you dyno'd. Also what gear was the transmission in during the dyno pull? Was this with 91 octane gasoline?
By the way what tires were on it when you dyno'd. Also what gear was the transmission in during the dyno pull? Was this with 91 octane gasoline?
A 25% loss would put you around 550hp at the crankshaft. That is still to low. So maybe a combination of the dyno and your drive train loss being higher than you thought.
By the way what tires were on it when you dyno'd. Also what gear was the transmission in during the dyno pull? Was this with 91 octane gasoline?
By the way what tires were on it when you dyno'd. Also what gear was the transmission in during the dyno pull? Was this with 91 octane gasoline?
4th gear (1 to 1)
4:86 rear gear ratio
91 octane
front engine accessories are alternator and howe power steering pump
no emissions
4 into 1 headers with camco shorty muffler
After the dyno session I took it to the dunes and broke an axle. When I pulled the axles I discovered that two of the CV's were worn out/binding and my midboard wheel bearings were shot. I suppose this could account for a few HP lost.
On the last dyno pull (the chart above) we removed the air filter. The air intake does have a 90 deg bend a few inches from the TB.
You're showing a power peak at 5,500rpm that takes a dive after 6,000rpm. That's not right. Either cam is installed wrong, or your valvesprings aren't up to the task. Your headers are small, but that shouldn't stop you from running it up to 7,000rpm.
I pulled it apart and verified that the cam was installed dot to dot. I do not have a degree wheel. I suppose the cam grind could be off from the manufacture. The valve springs are the originals. Not sure how many hours are on them. Sand cars have no odometers so there is really no way to tell.
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The gear ratio is not dyno friendly and neither are those tires. That being said you should still be putting down more power. What type of air intake system are you running? That would be from the throttle body to the airfilter.
It has a 3 1/2" tube that makes a 90 right off the TB then straight for about 12 inches and another 90 to a 10" K&N filter.
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