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It could just be done at that point. What intake are you running?
Are you mainly cruising the car and making rips on the street or are you also making track passes?
mainly cruise and making some rips on way out the way back roads. I’ll get to the strip sooner or later.
intake is the Dorman ls2, ported with a 92mm throttle body.
im running up to 24-25psi boost. I’m about back it down to 22ish. I’m afraid I’m playing with fire. Why:
-ls9 head gaskets with arp bolts, not studs.
-93 octane fuel with not meth injection (I had it in there but the pump went out and I haven’t fixed it yet)
I scaled the tune so I can control timing pretty high up in the boost range. I’ll look at my logs and tell you what I have it at for different levels)
-stock driveshaft, stock rear end, stock stubs, stock cv axles. I ride around on 275 nitto 555r2
It might be valve train related, but I doubt it. I only have btr .660 springs. with ls7 lifters, 11/32 .120 wall pushrods, max effort ws6store rockers, and a 232/248 .621 .611 cam. My limiter is at 8000 and it pulls hard all the way there, but I've got my shift point at 7200 rpm for regular street driving. BTR cathedral port equalizer intake with stock ls1 throttle body and 4 bolt adapter.
Only 20 psi at 7200 rpm, but will keep climbing after that as even though I'm hitting max recommended impeller speed the f1a-94 isn't done.
Below is a 226/232 cam through an LS6 intake and it is all done by ~6500. I think you need to get your cam inlet duration up into the 230's with a few deg of overlap (235/245-ish) to reliably move your peak HP into the 7,000's.
Thinking it's probably more intake related.
The Brute Speed FI cam I currently run is done by 6,400rpm according to the vendor but it will pull hard all the way to 7,500+rpm which I think is due to the single plane Vic. Jr. Intake and 105mm TB I'm running.
Wouldn't boost extend out the range of the intake/throttle body? I mean I'm running a stock unported ls1 throttle body on a 377 and it pulls as far as I'm willing to push ls7 lifters.
You can run an LS1/LS2/LS6 intake and stock TB well into the 7,000+ peak HP with a high duration cam - it was routinely done back in the early 2000's before aftermarket intakes became a thing with these cars.
If you don’t have a track (or don’t want to go to one). I’d get a draggy or something to see if revving it out is even beneficial. If you find it is, I’d look at back pressure next. Draggy would also let you see if your turbo is still making good power per added pound.
What lift is that cam? LSA? IVC?
If you over spring a combo and then put a small lift cam in it, it can throw off the open pressures. Then require shims to get it correct again. So if your springs open pressure is say 415lbs at .660 lift… it may be “under sprung” enough to cause issues at say .550 lift.
I like your old cam specs better, but Jack Roberts 8400+ rpm record 4.8 was only running a 227/233 @ 111 cam. (and it was advanced 5*)
Promod Pete’s green mustang turned 8400ish on a 5.3 with an untouched TBSS manifold as well. So don’t see either of those being a major bottle neck at 7400.
If you don’t have a track (or don’t want to go to one). I’d get a draggy or something to see if revving it out is even beneficial. If you find it is, I’d look at back pressure next. Draggy would also let you see if your turbo is still making good power per added pound.
What lift is that cam? LSA? IVC?
If you over spring a combo and then put a small lift cam in it, it can throw off the open pressures. Then require shims to get it correct again. So if your springs open pressure is say 415lbs at .660 lift… it may be “under sprung” enough to cause issues at say .550 lift.
I like your old cam specs better, but Jack Roberts 8400+ rpm record 4.8 was only running a 227/233 @ 111 cam. (and it was advanced 5*)
Promod Pete’s green mustang turned 8400ish on a 5.3 with an untouched TBSS manifold as well. So don’t see either of those being a major bottle neck at 7400.
100% agree I'm revving over 8000RPM with stock TBSS intake. you have to get the sweet spot of converter/gear/RPM. online calculators will get you close. but need to experiment.
Man, if only there was a device that you could use to actually see the power and torque curve of your setup. I mean, I know guessing is fun and all but... I've never understood the desire to rev something out so much if it's of no benefit. I get guys all of the time asking me if I can raise their rev limiter some more because they read about so and so on the internet and what they are spinning it to, then I show them their dyno graph with it being done at 7000 rpms.
I agree needs to be tested, I’ve had it go both ways.
Think there are a few instances where it helps to extend the shift point(s) even if power is falling off. Gearing and how far the converter drags a setup down is also a factor. Really noticable with a glide. I could feel my little setup falling on its face around 7200-7300ish… but extending the shift to 7500 picked up ET and trap speed in the 1/8 and ¼. 7800 picked up a tiny bit more.
If you aren't picking up, no reason to buzz it to the moon. I had a little rotary car that everyone told me to rev to 8k minimum. It would ET and trap faster shifting it at 6800. Any higher and it always slowed me down.
Man, if only there was a device that you could use to actually see the power and torque curve of your setup. I mean, I know guessing is fun and all but... I've never understood the desire to rev something out so much if it's of no benefit. I get guys all of the time asking me if I can raise their rev limiter some more because they read about so and so on the internet and what they are spinning it to, then I show them their dyno graph with it being done at 7000 rpms.
I only started spinning mine up higher because at 6,500rpm the converter wasn't coupling very good on the shift and the car just felt slow overall.
Plus I can feel it still pulling pretty hard even at 7,000rpm so it seemed to make sense, believe me, I wasn't too keen on doing it, but it made everything else happier.
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