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I recently installed a BTR Stage 3 cam (231/244 .630"/.615" 112.5+2.5) and a set of PRC 225 as cast heads from Texas Speed on my C5. I upgraded the fuel injectors to 42# since the stock ones were nearly 25 years old. I am in an emission control county where I have to pass a visual and a scan. I left the stock manifolds and cats on the stock H-pipe.
The car dynos at 360 WHP.
The car does pull nicely north of 3000 RPM all the way to 6700, but I really thought I was going to do a little better than this. While I realize LTs are a critical component to building a 400+ WHP outfit, I did think I could hit 380 or 390 without them.
So my question is, would upgrading my stock LS1 intake and TB make a difference here? If an LS6 picks up like 5-7 WHP or a Fast 92 with an LS2 TB takes me to 10-12, I would say no. But with my heads and cam, even on a stock exhaust, would that Fast make 20 or 25?
Not sure I understand your cam choice. Your cam is designed for a high rpm range, yet your intake and exhaust are designed for a low-mid rpm range.
Why did you elect to mismatch your cam?
I guess the idea was to do the internals first since they were the most expensive and hardest to install. Then I would start adding bolt-ons to support the cam. But I am not seeing where either an intake or full exhaust pick up a 75 to 100 more HP like the cam says it can make. Does a FAST 92 really pick up 25 like Fast says it does? I would think LTs would add maybe 30, no cats maybe 5-7?
I just wonder if I add that FAST or a ported LS6 intake I will see enough difference to spend the money.
the stock shortys and cats are KILLING the rest of the mods. it needs to breathe or you aren't going to make jack for power. actually that's already the case lol. if you do intake you NEED the exhaust.
I guess the idea was to do the internals first since they were the most expensive and hardest to install. Then I would start adding bolt-ons to support the cam. But I am not seeing where either an intake or full exhaust pick up a 75 to 100 more HP like the cam says it can make. Does a FAST 92 really pick up 25 like Fast says it does? I would think LTs would add maybe 30, no cats maybe 5-7?
I just wonder if I add that FAST or a ported LS6 intake I will see enough difference to spend the money.
Right now you’re at about 405 crank hp, the same as a Z06 with a much smaller cam.
The single most important bolt on for your current cam would be headers, which won’t get past the inspection. Frankly, Id be surprised if that cam lope goes unnoticed.
Pouring money into the intake won’t fix the exhaust bottleneck. Either address that, or get a milder mid range cam that can live with the exhaust manifolds, and some lower rear gears that will launch it out of the hole.
Last edited by vette4fl; Aug 15, 2023 at 09:36 PM.
the stock shortys and cats are KILLING the rest of the mods. it needs to breathe or you aren't going to make jack for power. actually that's already the case lol. if you do intake you NEED the exhaust.
I don't know how I would pull that off. As soon as the I/M tech opens the hood, I would fail emissions. What about BBK shorties? They are CARB certified. BBK says they are worth 10-12 HP. Or are these tuned for the stock cam?
Right now you’re at about 405 crank hp, the same as a Z06 with a much smaller cam.
The single most important bolt on for your current cam would be headers, which won’t get past the inspection. Frankly, Id be surprised if that cam lope goes unnoticed.
Pouring money into the intake won’t fix the exhaust bottleneck. Either address that, or get a milder mid range cam that can live with the exhaust manifolds, and some lower rear gears that will launch it out of the hole.
Yeah, she does chop.. and on a cold idle, she does stink. After she's been driven up to temps it's not so bad, but my state is more concerned with tampering with exhaust than they are internals. As long as it scans clean and as long as it passes visual, the teenage kid that works there sticks your decal on and you're good for another year.
I know everyone rolls their eyes at shorties, but if I could snag a pair (maybe even used) and port the LS1 TB and Intake, would I be looking at 30 HP in gains? At 390 to 400, I would call that a win and sit pretty. I should sound grateful.. Like you said, I got a Z06 for half the money. But for less than another thousand bucks, I would do it for 390..
Yeah, she does chop.. and on a cold idle, she does stink. After she's been driven up to temps it's not so bad, but my state is more concerned with tampering with exhaust than they are internals. As long as it scans clean and as long as it passes visual, the teenage kid that works there sticks your decal on and you're good for another year.
I know everyone rolls their eyes at shorties, but if I could snag a pair (maybe even used) and port the LS1 TB and Intake, would I be looking at 30 HP in gains? At 390 to 400, I would call that a win and sit pretty. I should sound grateful.. Like you said, I got a Z06 for half the money. But for less than another thousand bucks, I would do it for 390..
Shortys are worthless. I’ve had them and it was a waste of money. Your cam needs headers and a good tune and nothing else is going to compensate. Your alternative is having two sets of exhausts to swap out for exams. Honestly…in your situation it might be better to just cut bait and just get a more suitable cam.
A healthy upgrade from a Z06 level would be something like a 218/226 .550 to .590 lift 114+3 cam. No noticeable lope, strong under the curve range. Strong pull to mid 5000 rpm’s and hold power through low 6000’s. Backed by 3.90 or 4.10 gears could run higher 11’s. Not bad for an inspection state.
Call a cam outfit like CamMotion and be straight with the exhaust limitations and they will help you navigate this.
Shortys are worthless. I’ve had them and it was a waste of money. Your cam needs headers and a good tune and nothing else is going to compensate. Your alternative is having two sets of exhausts to swap out for exams. Honestly…in your situation it might be better to just cut bait and just get a more suitable cam.
A healthy upgrade from a Z06 level would be something like a 218/226 .550 to .590 lift 114+3 cam. No noticeable lope, strong under the curve range. Strong pull to mid 5000 rpm’s and hold power through low 6000’s. Backed by 3.90 or 4.10 gears could run higher 11’s. Not bad for an inspection state.
Call a cam outfit like CamMotion and be straight with the exhaust limitations and they will help you navigate this.
I wondered. All these companies post big gains on their parts, but I am finding none of them are realistic. Does this mean I wasted $2500 on the heads then? I guess I could have had my 241s sent off and got the same power with a smaller cam. I may do that still. Send them off to Texas Speed and sell the 225s. I just don't relish the thought of pulling half the car apart again to get that cam out.
Thanks for your thoughts here. I'm no mechanic, and it is hard to find sound advice on these things. I appreciate your candor.
I wondered. All these companies post big gains on their parts, but I am finding none of them are realistic. Does this mean I wasted $2500 on the heads then? I guess I could have had my 241s sent off and got the same power with a smaller cam. I may do that still. Send them off to Texas Speed and sell the 225s. I just don't relish the thought of pulling half the car apart again to get that cam out.
Thanks for your thoughts here. I'm no mechanic, and it is hard to find sound advice on these things. I appreciate your candor.
The 225 head is comparable in flow to a cnc ported ls6 head, but beefier. Hang on to those. A cam swap and good tune should do the job.
I feel the pain on a re-do. On the plus side, you already have new supporting parts in place, and it will go a lot faster second time around.
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LS1 upgrade intake 
