300 HP Crossfire engine?
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1st Gear
Joined: Aug 2019
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300 HP Crossfire engine?
What’s best and most reliable way to get 300+ HP from the Crossfire engine in my ‘84 ‘Vette? I want to up daily driving performance hopefully without going to forced induction. No nitrous thanks!! New intake manifold, port and polish job, new cam, larger throttle body, up fuel pressure or go to bigger injectors? Headers and/or exhaust? Some combination of these?
Can I do this with bolt-on mods, maybe for less than two grand?
Can I do this with bolt-on mods, maybe for less than two grand?
Last edited by Chromis; Aug 3, 2019 at 02:05 AM.
Safety Car
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From: Mission Viejo CA
Team Owner
Joined: Aug 2004
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From: Park City Utah
What’s best and most reliable way to get 300+ HP from the Crossfire engine in my ‘84 ‘Vette? I want to up daily driving performance hopefully without going to forced induction. No nitrous thanks!! New intake manifold, port and polish job, new cam, larger throttle body, up fuel pressure or go to bigger injectors? Headers and/or exhaust? Some combination of these?
Can I do this with bolt-on mods, maybe for less than two grand?
Can I do this with bolt-on mods, maybe for less than two grand?
*Port the bejeesus out of your stock intake or buy a "Renegade" intake or use an Offenhauser or Edelbrock Cross ram intake with a custom lid.
*Headers and dual exhaust
*Injectors/fuel pressure/timing to "feed it what it wants"
^This should get you to ~250-260hp or so. I actually had a friend who had this combo, minus the headers and was making about 250 horse.
*Ported heads, or heads
*Mild cam
^Should get you to 300 hp or so. If you can tune the ECM (tune the stocker or swap to a '7747 ECM) you could get a lot more radical with cam selection and cruise right on by 300 hp easy, with CFI.
Below the intake it's a SBC. The intake's Achilles heal is the runners are too small in cross section. Port the hell out of them or get a Renegade/Offy/Edelbrock Cross ram intake to fix that. The BENEFITS if the CFI intake are that it's a nice, mid-length runner intake, so it's not RPM limited by it'a architecture, like TPI is. Get the runners bigger, and you got a good intake.
.
Last edited by Tom400CFI; Aug 4, 2019 at 12:12 PM.
Safety Car
Joined: Sep 2004
Posts: 3,953
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From: Mission Viejo CA
Tom's got some good suggestions, but don't waste your time trying to modify those stock "624" heads. Here's some info for you, if you want to stay with (economical) iron heads. Of course, aftermarket aluminum heads would be a big help, but would probably bust your budget. Most aluminum heads don't have the exhaust crossover ports, if you want to retain the '84 EGR valve.
Drifting
Joined: Jun 2018
Posts: 1,402
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From: Brisbane Australia
C4 of Year Finalist (performance mods) 2019
I’m doing a dyno run on mine next Wednesday so I can report back on what sort of HP alloy heads, cam, renegade and EBL ECM can deliver. The mathematics says you can’t make 300hp with two 61 pound injectors running at 13psi so I will be interested to see how much HP my crossfire makes. Depending on Wednesday’s results I might end up parallel plumbing my throttle bodies replacing the injectors with 454 80psi ones and installing an external regulator. The next step after that in boring out the throttle bodies to 2”.
Team Owner
Joined: Aug 2004
Posts: 21,543
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From: Park City Utah
^That's more work than the same 300 from the CFI system^
As a guy who's "been there and done that", I can save you a bunch of time and effort here:
1. Parallel plumbing does nothing. It's a total waste of time. It's treating an psychological problem, not an actual one. Same goes for the external regulator. It's eye candy, but doesn't do anything that the stock one can't or do (that it needs to).
2. You need 454 injectors
3. 2" TB's aren't needed and don't make any diff @ this hp level. All the bigger TB will do is make the throttle more sensative/responsive off idle. Which isn't a bad thing necessarily, but that's all/what it will do.
.
1. Parallel plumbing does nothing. It's a total waste of time. It's treating an psychological problem, not an actual one. Same goes for the external regulator. It's eye candy, but doesn't do anything that the stock one can't or do (that it needs to).
2. You need 454 injectors
3. 2" TB's aren't needed and don't make any diff @ this hp level. All the bigger TB will do is make the throttle more sensative/responsive off idle. Which isn't a bad thing necessarily, but that's all/what it will do.
.
Last edited by Tom400CFI; Aug 6, 2019 at 10:10 AM.
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From: New Jersey
Drifting
Joined: Jun 2018
Posts: 1,402
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From: Brisbane Australia
C4 of Year Finalist (performance mods) 2019
^That's more work than the same 300 from the CFI system^
As a guy who's "been there and done that", I can save you a bunch of time and effort here:
1. Parallel plumbing does nothing. It's a total waste of time. It's treating an psychological problem, not an actual one. Same goes for the external regulator. It's eye candy, but doesn't do anything that the stock one can't or do (that it needs to).
2. You need 454 injectors
3. 2" TB's aren't needed and don't make any diff @ this hp level. All the bigger TB will do is make the throttle more sensative/responsive off idle. Which isn't a bad thing necessarily, but that's all/what it will do.
.
As a guy who's "been there and done that", I can save you a bunch of time and effort here:
1. Parallel plumbing does nothing. It's a total waste of time. It's treating an psychological problem, not an actual one. Same goes for the external regulator. It's eye candy, but doesn't do anything that the stock one can't or do (that it needs to).
2. You need 454 injectors
3. 2" TB's aren't needed and don't make any diff @ this hp level. All the bigger TB will do is make the throttle more sensative/responsive off idle. Which isn't a bad thing necessarily, but that's all/what it will do.
.
thanks for the tip Tom.
Team Owner
Joined: Aug 2004
Posts: 21,543
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From: Park City Utah
Look at people spending other people's money! 
Totally. I bored my own TB's. Back in the day, I'd heard that you could got 2.03" (53mm) w/o cutting through the walls. Well, I went 53mm and was left with huge gaping holes in the walls. 
I made new walls with moldable epoxy, re-bored them again, then honed them smooth, then radiused the transition at the inlet side, so it was smooth. I installed 53mm plates and put it all together. It ran great, but didn't get me squat for power -at that power level. CFI-EFI did back to back on his car and gained nothing from the larger TB's.
I never wasted my time on the parallel plumbing, regulators or any of that. I threw in a 255 lph fuel pump (when I needed more fuel), and made my stock regulator adjustable, set it and it ran great.
I made new walls with moldable epoxy, re-bored them again, then honed them smooth, then radiused the transition at the inlet side, so it was smooth. I installed 53mm plates and put it all together. It ran great, but didn't get me squat for power -at that power level. CFI-EFI did back to back on his car and gained nothing from the larger TB's. I never wasted my time on the parallel plumbing, regulators or any of that. I threw in a 255 lph fuel pump (when I needed more fuel), and made my stock regulator adjustable, set it and it ran great.
Intermediate
Joined: Jun 2016
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From: Houston area
Dart Heads (do not exceed 180 intake runner size), , ported and gasket matched intake, 1.6 roller rockers , Crane 2040 PowerMax cam, long tubes, x pipe and 375 gears. All on the stock computer. TPI fuel pump. She ran low 13s around 106 with bad traction
Drifting
Joined: Jun 2018
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From: Brisbane Australia
C4 of Year Finalist (performance mods) 2019
Look at people spending other people's money!
Totally. I bored my own TB's. Back in the day, I'd heard that you could got 2.03" (53mm) w/o cutting through the walls. Well, I went 53mm and was left with huge gaping holes in the walls. I made new walls with moldable epoxy, re-bored them again, then honed them smooth, then radiused the transition at the inlet side, so it was smooth. I installed 53mm plates and put it all together. It ran great, but didn't get me squat for power -at that power level. CFI-EFI did back to back on his car and gained nothing from the larger TB's.
I never wasted my time on the parallel plumbing, regulators or any of that. I threw in a 255 lph fuel pump (when I needed more fuel), and made my stock regulator adjustable, set it and it ran great.
Totally. I bored my own TB's. Back in the day, I'd heard that you could got 2.03" (53mm) w/o cutting through the walls. Well, I went 53mm and was left with huge gaping holes in the walls.
I made new walls with moldable epoxy, re-bored them again, then honed them smooth, then radiused the transition at the inlet side, so it was smooth. I installed 53mm plates and put it all together. It ran great, but didn't get me squat for power -at that power level. CFI-EFI did back to back on his car and gained nothing from the larger TB's.I never wasted my time on the parallel plumbing, regulators or any of that. I threw in a 255 lph fuel pump (when I needed more fuel), and made my stock regulator adjustable, set it and it ran great.
Le Mans Master
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From: New Jersey
My regular is adjustable and I tried a walbro 190 litre per hour pump but I couldn’t get the pressure low enough. I blew out the return line with compressed air but I’m not sure what the problem is. I have a new return line but I haven’t fitted it yet. Anyway that’s a tale for another thread and another time. I like the idea of just changing to 80# injectors but I thought that they had to be different flow rates to compensate for pressure drop (although thinking about that it doesn’t make a lot of sense).
Drifting
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As I x4 L83 owner I found this very helpful, always been surprised that its not a sticky here also?
L83 Tips
L83 Tips
Le Mans Master
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From: New Jersey
At 80lb/hr you're using almost 50% more fuel at 13 psi (and 90ish duty cycle) so if the 84 pump is tapped out 13psi on the 64s then it'll drop pressure on the 80s. Otherwise regulated restriction is constant unless you're running enough fuel to build up tons of head... ie the return is too small for the flow rate returning.