Optimizing a 460ci stroker
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Joined: Feb 2018
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From: Lawrenceburg Ky
Brer Rabbit, I have the same 4.250 stroke engine as you but with better heads, bigger cam, bigger intake, and a 105mm throttlebody. As expected I make quite a bit more power than you but even so I still flatline at 6500. I talked with Erik at HPR who built my 468 and he said these motors want as much air as you can give them and switching from my carbon pst/105mm throttlebody to a CID Intake/4500 throttlebody will give me 50-60 more rwhp and extend my rpm range a bunch. Do a google search for HPR 468 and read the various threads and you'll see what I mean about the more air the better for the 4.250 stroke motor.
Last edited by BigDaddy97; Sep 18, 2021 at 07:05 PM.
I agree with ddnspider yes the intake upgrades will help but not the cause of the engine coming to a stop like that at such a low rpm range and then tank. We all know stock ls3 head go over 7000 no problem on almost every engine I’ve seen so a worked 460 should smooth sail right past 7000k. You have to have a problem either mechanically and maybe something stupid in the tune that not right. If Andrew is tuning it hard to believe it’s the tune though.
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Brer Rabbit, I have the same 4.250 stroke engine as you but with better heads, bigger cam, bigger intake, and a 105mm throttlebody. As expected I make quite a bit more power than you but even so I still flatline at 6500. I talked with Erik at HPR who built my 468 and he said these motors want as much air as you can give them and switching from my carbon pst/105mm throttlebody to a CID Intake/4500 throttlebody will give me 50-50 more rwhp and extend my rpm range a bunch. Do a google search for HPR 468 and read the various threads and you'll see what I mean about the more air the better for the 4.250 stroke motor.
Thread Starter
Joined: Nov 2001
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From: Chicago, IL
Hey BigDaddy, based on the info shared on Brer's car, what do you think it could make on pump 93? He's gonna check compression, if it's on the high side might be interesting to try E85 or a can of race gas what do you think?
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From: Lawrenceburg Ky
Last edited by BigDaddy97; Sep 18, 2021 at 09:09 PM.
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Verdad Gallardo TECH Regular
Joined: Feb 2018
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From: Lawrenceburg Ky
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Small problems before the major stuff as you wouldn't see the real Difference...with a intake upgrade
Engine this Big would like a 6500 TB but the problem going this Big is not Having IAC and wanting a street car ..
Engine this Big would like a 6500 TB but the problem going this Big is not Having IAC and wanting a street car ..
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The only thing that I can think of that would cause that bad boy to be down on power that much with nothing broken could be that both coil harnesses might be flipped backwards. The ones that plug directly into the coils. Purple wire to #1 and red wire to number 2 and laid out accordingly. Worth a shot to check. Usually they break up slightly over 6000 rpm but who knows. The intake may be holding it back a little, but not that much.
Thread Starter
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From: Chicago, IL
He's trying to keep a balance of having a nice street car he can cruise in with his dad (who bought the GTO new!), and running decent at the track. Not easy to achieve, but let's see what happens with the TB. Brer the FAST intake you have, does it have the changable runner setup?
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Joined: Feb 2018
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From: Lawrenceburg Ky
That's not bad at all, I'm sure we'll chat about whenever we next hang out.
He's trying to keep a balance of having a nice street car he can cruise in with his dad (who bought the GTO new!), and running decent at the track. Not easy to achieve, but let's see what happens with the TB. Brer the FAST intake you have, does it have the changable runner setup?
He's trying to keep a balance of having a nice street car he can cruise in with his dad (who bought the GTO new!), and running decent at the track. Not easy to achieve, but let's see what happens with the TB. Brer the FAST intake you have, does it have the changable runner setup?
Last edited by BigDaddy97; Sep 19, 2021 at 03:10 PM.
Thread Starter
Joined: Nov 2001
Posts: 45,312
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From: Chicago, IL
From talking to you guys and few others I know, I think the suggestions are:
If he wants to step it up:
- What valve springs, what installed height, maybe sure not valve float?
- FAST shorter runners just a good general move
- NW 103 TB, a good general moved, has been ordered
- Depending on compression, consider running E85 or race gas
- One long time friend wonders if there is a spark issue, I don't think there was but I'll add it here
If he wants to step it up:
- More cam
- CID intake + 4500 TB
- 2" or more headers
fast runners I have the long runners in now, I also have the next size shorter runners available to put in. the plan is to do the throttle body and log a few runs on the good old Edens expressway after some street driving. Then trying to hit the Dyno where I can swap runners and see what works best.
TECH Regular
Joined: Feb 2018
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From: Lawrenceburg Ky
I have the long runners in now, I also have the next size shorter runners available to put in. the plan is to do the throttle body and log a few runs on the good old Edens expressway after some street driving. Then trying to hit the Dyno where I can swap runners and see what works best.
On The Tree
Joined: Jun 2019
Posts: 184
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From: HTown, Texas
Is there any chance the throttle isn't opening 100%? I knew a guy that had an issue with swapping a DBW pedal and control module into an older car and it wasn't reading 100% opening. He gained like 50whp from getting that fixed lol.
