Stumped on my 383 - carb to EFI lost power, been chasing it for a few years now.
07-14-2015, 10:17 AM
#1
Stumped on my 383 - carb to EFI lost power, been chasing it for a few years now. Very long story - but I've had a 383 LS1 in my boat for a while now. It started off with a carb and was swapped over to EFI a few years back. Immediately after the swap I was down on power compared to the carb. I've been racking my brain for a while trying to figure out how to get it back. It had a Fast 90 on it from a few years ago up until this past weekend. Then it was swapped over to a Super Victor EFI and Accufab 4150 TB (mostly because a Super Victor and 850 Demon worked well on this motor). Long story short...not sure what I'm doing wrong here. The regulator is an Aeromotive 13129 - I have it set right now at 58psi. When idling, it will stay at 58 - at WOT it will fall to about 54 psi. The regulator is connected to the Accufab. I realize that a different cam and heads (or obviously forced induction) would get me some power...but I'm more after the power that I had, and now do not. I'm not sure if this is due to something I changed, something that is a simple fix that is staring me in the face, or if I just need to go back to a carb.
Engine specs:
LS1 block - advertised as 11:1 CR
Eagle 4" crank
Eagle H-beam 6.125" rods
JE pistons -2cc
Gapless rings
MTI Stage 3 241 heads - 64cc chamber - 2.055/1.6 valves - flow 310 cfm intake/225 cfm exhaust @ .600
Cometic gaskets - unknown thickness
Bullet hyd roller cam - 238/244 @ .050; .600/.600 lift; 113 LSA, 109 ICL
Yella-Terra ultra light rockers
45# injectors
Aeromotive 13129 regulator
Magnafuel MP-4302 pump
No MAF or O2 sensors
The desired (and likely highest) rpm is approximately 6000 rpm. Maybe up to 6100 rpm. With an 850 Demon/Performer RPM the engine would turn 5700-5800 rpm, and with the 850 Demon/Super Victor the engine would turn 5900-6100 rpm. Currently with the Fast 90 and the Super Victor/Accufab 4150 it will flash to 6200 rpm on launch, but as the pump loads it will get pulled down to 5500 rpm. Depending on which impeller chart you choose to believe, this is somewhere between a 50-80 hp loss.
Engine specs:
LS1 block - advertised as 11:1 CR
Eagle 4" crank
Eagle H-beam 6.125" rods
JE pistons -2cc
Gapless rings
MTI Stage 3 241 heads - 64cc chamber - 2.055/1.6 valves - flow 310 cfm intake/225 cfm exhaust @ .600
Cometic gaskets - unknown thickness
Bullet hyd roller cam - 238/244 @ .050; .600/.600 lift; 113 LSA, 109 ICL
Yella-Terra ultra light rockers
45# injectors
Aeromotive 13129 regulator
Magnafuel MP-4302 pump
No MAF or O2 sensors
The desired (and likely highest) rpm is approximately 6000 rpm. Maybe up to 6100 rpm. With an 850 Demon/Performer RPM the engine would turn 5700-5800 rpm, and with the 850 Demon/Super Victor the engine would turn 5900-6100 rpm. Currently with the Fast 90 and the Super Victor/Accufab 4150 it will flash to 6200 rpm on launch, but as the pump loads it will get pulled down to 5500 rpm. Depending on which impeller chart you choose to believe, this is somewhere between a 50-80 hp loss.
Last edited by FormulaZR; 07-14-2015 at 03:03 PM.
