Volvo Penta 7.4GSi engine questions

[cobalt252]

I'm looking at a 1999 Cobalt with a Volvo Penta 7.4GSIPEFS engine (s/n Engine 4110199747 and Out Drive 4112061762).

This 7.4GSi engine is rated at 405bhp, which is almost as much as the V-P 8.1GI and GXI category, with a displacement of 7.4l vs 8.1l.

Most 7.4l engines are rated at about 320bhp.

What is unique about this engine. How did VP do this?

 

[Scott Danforth]

my 7.4 liter motor is putting out close to 500hp.

nothing special, cams, heads, fueling, etc.

only mildly built BBC's put out 320BHP. you can get that from a 5.7 without any trouble

 

[alldodge]

MY opinion, the 454 MPI (7.4 GSI) produces 405 at the crankshaft and 385 at the prop, just like the Merc

The TBI L29 was 310 at the prop
The MPI LX with oval port heads was 320 to 330 at the prop

 

[cobalt252]

MY opinion, the 454 MPI (7.4 GSI) produces 405 at the crankshaft and 385 at the prop, just like the Merc

The TBI L29 was 310 at the prop
The MPI LX with oval port heads was 320 to 330 at the prop

That's useful information.

Question: how do you get more HP out of a TBI L29 (454 7.4l Gi) without going crazy on modifications etc. I hear Volvo makes it difficult.

 

[Scott Danforth]

different cam and a re-flash of the ECM and different exhaust. or get rid of the stock fuel injection and go with a carb to bypass the re-flash of the ECM

here is the L29 with a comp cam XM284HR marine cam

http://www.superchevy.com/how-to/en...power-on-a-junkyard-454-with-simple-cam-swap/

or bolt on a supercharger

https://www.cpperformance.com/c-821-whipple.aspx

to get a good amount of power, you would be cheaper to sell what you have and buy what you want (either at the motor level or the whole boat level)

 

[QBhoy]

MY opinion, the 454 MPI (7.4 GSI) produces 405 at the crankshaft and 385 at the prop, just like the Merc

The TBI L29 was 310 at the prop
The MPI LX with oval port heads was 320 to 330 at the prop

Not sure the VP he has is equivalent to the mpi of big power on the merc version ? Would it not have to be a GXi for that ? Gi usually means tbi not mpi (gxi)

 

[alldodge]

Not sure the VP he has is equivalent to the mpi of big power on the merc version ? Would it not have to be a GXi for that ? Gi usually means tbi not mpi (gxi)

Not a VP expert but everytime someone ask a question about one, I go to marine parts europe and bring the motor up. The 7.4 GSI comes up as a MPI and appears to have the intake with the long runners and would match up to the 502 heads

https://www.marinepartseurope.com/en/e-volvo-penta-271-7.4GSIPEFS.aspx

 

[QBhoy]

Not a VP expert but everytime someone ask a question about one, I go to marine parts europe and bring the motor up. The 7.4 GSI comes up as a MPI and appears to have the intake with the long runners and would match up to the 502 heads

https://www.marinepartseurope.com/en/e-volvo-penta-271-7.4GSIPEFS.aspx

I don’t know much about the big blocks to be fair. Just know the 4.3, 5.0 and 5.7 gsi are equivalent to efi merc. The gxi on those engines is the mpi equivalent