Camshaft Timing
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Teching In
Joined: Feb 2009
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From: Va Beach
Camshaft Timing Problem: Peak horsepower is at 5400 rpm with an LS9 cam that is retarded 2*.
History: When I first built this engine back in 2015 I installed a used GT-9 camshaft (215/247 duration @ .050 lift - .629/.656 lift with 1.7 rocker 121 CL ). I will admit I didn't degree the camshaft like i should have but I used the stock timing marks as my guide so I didnt think it would be off and if it was, it wouldnt be by much. Im trying to locate the old dyno sheet to verify but I believe I had the same low peak rpm issue im having now.
After reading up some more on that camshaft I decided I would rather have something a little easier on my valve train so I swapped in a stock LS9 cam. When I did the install I also installed a hex-adjust double roller timing gear, an Innovators West crank pulley and I cut my timing cover in half so I could utilize the adaptable feature on my cam gear if I needed to without having to take the crank pulley off. Also, since I didn't want to remove the engine I kept the crank sprocket I had on there (could that be part of the issue). When I installed it I lined up the two timing marks and then retarded the cam by 2* with the hex adjust bolt to try and get my horsepower curve a little higher in the rpm range.
I recently swapped the MP112 for a TVS2300 and when I got it dynoed I noticed that my peak RPM was at 5400rpms. This seemed low to me so I did some research and the general consensus is that a stock LS9 cam should be peaking in the low 6k (6100-6200rpm) range.
This morning I took the top half of the timing cover off just to verify when the timing marks and adjust key were positioned and they were exactly as I had set them. At this point im at a loss for why my hp peak is so low, especially, since I would expect with retarded timing the peak should shifter to the right and not the left. Looking for suggestions at this point because im missing out on about 50rwhp. Thanks.
History: When I first built this engine back in 2015 I installed a used GT-9 camshaft (215/247 duration @ .050 lift - .629/.656 lift with 1.7 rocker 121 CL ). I will admit I didn't degree the camshaft like i should have but I used the stock timing marks as my guide so I didnt think it would be off and if it was, it wouldnt be by much. Im trying to locate the old dyno sheet to verify but I believe I had the same low peak rpm issue im having now.
After reading up some more on that camshaft I decided I would rather have something a little easier on my valve train so I swapped in a stock LS9 cam. When I did the install I also installed a hex-adjust double roller timing gear, an Innovators West crank pulley and I cut my timing cover in half so I could utilize the adaptable feature on my cam gear if I needed to without having to take the crank pulley off. Also, since I didn't want to remove the engine I kept the crank sprocket I had on there (could that be part of the issue). When I installed it I lined up the two timing marks and then retarded the cam by 2* with the hex adjust bolt to try and get my horsepower curve a little higher in the rpm range.
I recently swapped the MP112 for a TVS2300 and when I got it dynoed I noticed that my peak RPM was at 5400rpms. This seemed low to me so I did some research and the general consensus is that a stock LS9 cam should be peaking in the low 6k (6100-6200rpm) range.
This morning I took the top half of the timing cover off just to verify when the timing marks and adjust key were positioned and they were exactly as I had set them. At this point im at a loss for why my hp peak is so low, especially, since I would expect with retarded timing the peak should shifter to the right and not the left. Looking for suggestions at this point because im missing out on about 50rwhp. Thanks.
Thread Starter
Teching In
Joined: Feb 2009
Posts: 33
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From: Va Beach
That's good to know. The articles and threads I read about the LS9 never mentioned if they installed it "straight up" or not. I'll admit my knowledge about how the whole valve timing thing works is fingernail deep but everything ive ever read suggest that a retarded cam raises the rpm band while advanced timing raises low end torque. I guess I could advance it and see how it goes...after all that's why I got the hex-adjust and cut the timing cover.
Thread Starter
Teching In
Joined: Feb 2009
Posts: 33
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From: Va Beach
It was suggested to me that I may be experiencing spark blowout and that my gap (.035) might be excessive for the boost levels im running (20psi). As a first step, mechanically, im going to regap the plugs (NGK TR6) to .025 and see if that does anything.
I wouldn't advance the cam with a blower, especially a PD blower like that. It has plenty of cylinder filling at low rpm as is.
Really I would copy what gm did with the cam. People make really high power with that cam as is and just porting the snout on the OE blower.
What's your exhaust setup like? Is it able to breathe at high rpm? What about the intake tube/filter setup.
I don't look at a lot of pd blower dyno sheets but aren't they known for falling off up in the upper rpm range?
Really I would copy what gm did with the cam. People make really high power with that cam as is and just porting the snout on the OE blower.
What's your exhaust setup like? Is it able to breathe at high rpm? What about the intake tube/filter setup.
I don't look at a lot of pd blower dyno sheets but aren't they known for falling off up in the upper rpm range?
