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Thank you all for the great input. Seems I picked not the best cam for a stroker. I have an adjustable cam gear. Will it help to adjust from IVC 44.5 to 49
Thank you all for the great input. Seems I picked not the best cam for a stroker. I have an adjustable cam gear. Will it help to adjust from IVC 44.5 to 49
It'll help, but not be a cure-all. you retard the IVC, you move the powerband, yes. But also you retard the EVO, which will also fight your ability to rev. What I expect this will cause is you'll peak higher, but fall faster past peak.
Personally, I would get something with a bigger intake lobe and less split as spanks has suggested. 16 degrees of split is unnecessary. 10 degrees split is plenty unless you plan to rev past 8000. I would be thinking in the 240/250 range. call it 111 + 2 for kicks and giggles.
That said, your graph looks very valve-floaty to me. If you have the time and inclination, I suggest shimming the valve springs so that peak lift is within .050" of coil bind to help with those harmonics. Not knowing your cam specs, my guess is you're in the 0.620-0.640 range on lift? Also, if you can stomach it, consider a set of 3/8" pushrods vs 5/16 for stiffness.
It'll help, but not be a cure-all. you retard the IVC, you move the powerband, yes. But also you retard the EVO, which will also fight your ability to rev. What I expect this will cause is you'll peak higher, but fall faster past peak.
Personally, I would get something with a bigger intake lobe and less split as spanks has suggested. 16 degrees of split is unnecessary. 10 degrees split is plenty unless you plan to rev past 8000. I would be thinking in the 240/250 range. call it 111 + 2 for kicks and giggles.
That said, your graph looks very valve-floaty to me. If you have the time and inclination, I suggest shimming the valve springs so that peak lift is within .050" of coil bind to help with those harmonics. Not knowing your cam specs, my guess is you're in the 0.620-0.640 range on lift? Also, if you can stomach it, consider a set of 3/8" pushrods vs 5/16 for stiffness.
His graph is a simulated dyno chart from G-force measurements. Actually one of the better simulated dyno sheets I've seen. I've tried making them from HPTuners data before and they never turn out that well.
I agree though - it simply needs more intake duration for the cubes, and retarding the cam won't fix that. Summit racing sells some great cams at a low cost, and you could sell your cam for nearly the same money.
You could get this and maybe if you feel like doing it adjust it 1-2 degrees retarded on your cam sprocket. There are stroker specific cams out there from Cammotion and BTR that will be a bit larger in duration, but for $269 you would have to find something used to even come close to that price point.
@ spanks13. Thank you for your cam proposal. Will definitely plan a cam change.
Again my strange dynochart now in WHP compared with other projects. I am still wondering about the low WHP in my 403 LS2 stroker. The WHP are at least 10% below my expectations. Especially the lower output compared to the standard LS3 with less ci and smaller 225/236 cam.
I understand your comments to the low peak numbers because of IVC 44.5*. Is this really the reason for only 450WHP.
I checked also fuel with WB and saw AFR of 12 during WOT. Will change AFR to 12.8. WOT timing is 25*.
I agree you should be able to match closer what the LS7 is outputting.
Rod mod ls3 intake is a substantial gain especially above 6000 rpm. Timing, my 402 w/ ls3 heads made more power up to 30* timing. I ran 28* on the street and it was within a couple hp of 30* and was safer vs knock. Our pump gas LS3 and 415 with LS3 heads also makes the most power at 28* all on 91 octane at >11:1 compression. Leaning it from 12:1 to 12.8:1 will only be fractional horsepower, maybe a couple.
Are your headers 1 3/4 or 1 7/8"?
Your stroker kit was for flat top pistons right? I've seem NA 400" strokers built with dish pistons and they never perform well.
Would you ever have a chance to get it on a real chassis dyno? Where did you record these G-force runs? Same road and conditions between all cars?
What are your cam specs, not just the 'stage 3' part.. I see they have a stage 3 LS3 cam that's 231/247.. that would be small for a stroker that you are trying to rev out to 7200. I am running a 403" LS2 in my Corvette, and I'm running a 239/247, and that is pretty mild in many people books (its a street car, didn't want stupid amounts of chop/surging).
If the exhaust components you have are good (good quality headers, and the gutted cats aren't a restriction, and the pipe layout is good), then the 2.5" is probably costing you in the range of 15-20 hp. Not enough to only make that much at the crank. LS3 heads and pretty much any LS3 intake normally should support 600-650 crank hp.
Got a dyno plot?
Just curious, what LSA is that 239/247 cam ground on?
Graph is choppy AF. What is your valvetrain setup. Springs, lifters, pushrods, etc
Totally agree with the choppy graph. Looks like an alligator's *** (been in Florida too long!) Something is up with the valve train or cam. Even with undersized exhaust, it should be a lot smoother graph than shown.......
I agree you should be able to match closer what the LS7 is outputting.
Rod mod ls3 intake is a substantial gain especially above 6000 rpm. Timing, my 402 w/ ls3 heads made more power up to 30* timing. I ran 28* on the street and it was within a couple hp of 30* and was safer vs knock. Our pump gas LS3 and 415 with LS3 heads also makes the most power at 28* all on 91 octane at >11:1 compression. Leaning it from 12:1 to 12.8:1 will only be fractional horsepower, maybe a couple.
Are your headers 1 3/4 or 1 7/8"?
Your stroker kit was for flat top pistons right? I've seem NA 400" strokers built with dish pistons and they never perform well.
Would you ever have a chance to get it on a real chassis dyno? Where did you record these G-force runs? Same road and conditions between all cars?
I'd look into figuring out your valvetrain first. By the way that graph looks you either need to shim the springs or get different ones and install them correctly.
Not to take anything away from any of the really smart people in this thread, but someone is ALWAYS going to recommend another cam.
Yes a given cam is going to peak earlier in a larger engine, but it still should carry the power out past peak, not fall off a cliff.
The choppy graph is the result from calculation out of G-forces from street runs. All the comparison cars graphs are similar. Need to get it asap on a real chassis dyno.
I realized also from HP-tuners logs compared with a C6 Z06 some strange MAP readings. Not sure about the reason. Intake turbulences ? Valvetrain issues ? old 98ECU ?
Choppy map readings are an issue. Also, though, the degrading map reading. Your intake is not keeping up. i.e. - air filter too small or plugged, intake tract too small, throttle body too small, intake manifold too small. Your may is in the low 90's at WOT. There's ~10% just fixing that.
The eratic map readings are most likely the sensor itself. the map will get choppy from engine weirdness, but mostly that's closer to idle. A real chassis dyno will reveal if you have valvetrain issues.
05-24-2022, 06:34 AM
