LS9 camshaft timing

Problem: Peak horsepower is at 5400 rpm with an LS9 cam that is retarded 2*.

History: When I first built my (forged 5.3 with Stage II PRC heads, 1 7/8" headers, MP112) 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. I'm 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 dynode (475rwhp/530rwtq) 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.

Quote:

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Originally Posted by theone61636

Problem: Peak horsepower is at 5400 rpm with an LS9 cam that is retarded 2*.

History: When I first built my (forged 5.3 with Stage II PRC heads, 1 7/8" headers, MP112) 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. I'm 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. Visit AutoGuysLand to review what should rpm be when starting car in case you may concern. 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 dynode (475rwhp/530rwtq) 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.

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Hope this link can help you although it belongs to gen 4:
https://forum.hptuners.com/showthrea...-If-Interested

There are a lot of things that can shift the hp peak to a lower rpm. If you'll post your tune and a datalog, it'll help us help you.

A few things to look at...
Did the datalog indicate any knock retard?
Did the boost fall off at upper rpm? Was the belt slipping?
Did the AF ratio go rich or lean at upper rpm?

Quote:

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Originally Posted by Ricardowelch

Hope this link can help you although it belongs to gen 4:
https://forum.hptuners.com/showthrea...-If-Interested

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Thanks, I had actually read that one but it didn't mention anything about where they degreed the cam. It was interesting to note their peak RPM was 6250 though which is where I was expecting mine to be.

Quote:

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Originally Posted by kevin87turbot

There are a lot of things that can shift the hp peak to a lower rpm. If you'll post your tune and a datalog, it'll help us help you.

A few things to look at...
Did the datalog indicate any knock retard?
Did the boost fall off at upper rpm? Was the belt slipping?
Did the AF ratio go rich or lean at upper rpm?

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I will download the tune tomorrow and upload it. I'll have to ask the tuner for the boost vs torque graph but he didn't indicate that he noticed any belt slip during the dyno. I'll also have to ask him for the AFR graph as well. Thanks for pointing out some areas I should be checking. Someone else mentioned I need to verify the throttle blade is opening all the way so im going to try to do that tomorrow as well.

It was suggested to me that I may be experiencing spark blowout due to excessive plug gap (.035) and the amount of boost im running (20psi). So as a first step, mechanically, ill regap the plugs (NGK TR6) to .025 and see if that helps.

^ for that kind of boost i would go even colder plug and gap around .028