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Discussion Starter #1
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.
 

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How much boost psi?
What was the correction on the dyno? (bad dyno cal which is like every shop I've ever worked with)
RPM match the roller speeds? (clutch slipping)
Picture of dyno sheet with afr on the bottom?
Check to make sure tb opening up?
Did you change pushrods when you went from gt9 to ls9 cam?
 

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Discussion Starter #3
20psi, don't know about the correction factor, don't know about roller/vs rpm match but the tuner didn't indicate that there was any clutch slip, the dyno sheet I have doesn't show AFR so i'll have to see if I can get it from the tuner. I'll hook up my HPT and verify that the TB is opening all the way vs what it's registering. No change to the pushrod length between the two cams. I did measure for length when I did the initial install and i'll double check the length pushrod I used tomorrow and post it.
 

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HOLY SHITBALLS! 475rwhp on 20psi???!!???!!?? There is something not right there. I was gonna say plugged cats, but you have none.

I think I have an idea. Whats your spark plug gap? at 20 psi, it better be around .025
 

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Discussion Starter #8
What valve springs are you running? How many miles on them?
PRC .660s dual valve springs with probably 5000 miles if that.
HOLY SHITBALLS! 475rwhp on 20psi???!!???!!?? There is something not right there. I was gonna say plugged cats, but you have none.

I think I have an idea. Whats your spark plug gap? at 20 psi, it better be around .025
Hmmmm, ill have to check. I don't think I have them gaped that closely though.

btw, you missing out on more that 50hp dude.
Yeah, I know. That's why im very interested in figuring out what's going on. haha.

Can you post dyno sheet? Where was peak torque?
499190
 

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Something definitely big happening at 5k killing your car's power. Regardless of what cam you have the engine curve should not make a right angle.

Are you logging misfires? Would guarantee ignition system is at fault if fuel is right. Maybe too cold of plugs or too big of gap like mentioned above.
AFR of this pull would help a lot maybe fuel pump running out of capacity to supply enough fuel.
Also a time log of ignition timing in the engine. Could be knock/low oil psi pulling a ton of timing.
 

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Discussion Starter #11 (Edited)
Here's the #1 spark plug. NGK TR6. Gapped at .035...the coloring of the plug looks fine. Still working on downloading the tune. I have to download HPT to to my new laptop then I'll pull it from the ecu. Based on what you all are recommending I'll pull all the plugs and regap them to .020. if the spark was really being blown out would it really manifest itself the way my dyno results suggest?
499194
499195


Edit: After doing some research on the Cobra forums it looks like a lot of high boost PD guy gap their plugs around .025 so ill start there and see if it has a positive effect.
 

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Yes it would and .035 is a very big gap from what I see others running with an identical plug and psi.

One thing I want to say however is that your car should be throwing out misfires codes like crazy during the pull. I'm thinking flashing cel, engine sounding like total shit coughing etc. Were you there when the car was getting tuned? I just don't understand how this gets back to you "tuned" unless the tuner informed you there was an issue.
 

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Discussion Starter #13
Yes it would and .035 is a very big gap from what I see others running with an identical plug and psi.

One thing I want to say however is that your car should be throwing out misfires codes like crazy during the pull. I'm thinking flashing cel, engine sounding like total shit coughing etc. Were you there when the car was getting tuned? I just don't understand how this gets back to you "tuned" unless the tuner informed you there was an issue.
Unfortunately, no, i wasn't there during the dyno sessions. I do get random misfire codes, but only when i spin the tires in low gear. Regular driving is fine and higher speed highway pulls seem fine as well but i haven't actually done any data logging. I'll regap the plugs, put the engine back together and start logging runs to see if we can identify what the issue is.
 
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