310 and 330?

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03-25-2002, 11:33 PM

#11

Blackhawkdn

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Is the 454 your refering to a magmun or is it the 454 that is the 7.4l, both 454's but different engines

03-26-2002, 03:26 PM

#12

Revelocity

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Referring to the GM L-29 7.4 MPI 340crank /310 prop HP engine - not the 454 magnum.

03-26-2002, 04:37 PM

#13

WETTE VETTE

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The carb 7.4L is 330 HP at the crank, and 300 at the prop. The injected 7.4L is 340 HP at the crank, and 310 at the prop. In actuality I think they are the same motor, but the injection is worth about 10 HP. Right? How much is the price difference between these motors?

03-26-2002, 08:17 PM

#14

crmax

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the heads are differnt on the 7.4 mpi they are the oval but use the vortech tech to burn the fuel better.

Ive heard the intake was bad also, I think there is a shop that ports and mills them

03-26-2002, 09:58 PM

#15

checkmate981

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I have heard same thing on the Intake plenum as well .Just remember that the 310 mpi has the little rods ,cast crank,and cast pistons.The block is a gen 6 4 bolt mains same as newer 454 mag mpi.Cam is milder.
Dave

03-26-2002, 11:07 PM

#16

crmax

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I would like to get 50-75 more hp and Ill be happy with the motor any more than that Id move up to a differnt motor

03-27-2002, 05:13 PM

#17

Madmax

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Not trying to advertise, but i've got a Mark VI Magnum roller cam that would slip right in with no spring changes or anything. I was always gonna do this to my motor, and never did. It's brand new. You can contact me offline if your interested. On a desktop dyno program, it indicated it would make about 30hp at 4500rpm than the stock mpi cam. The specs for both are:

Stock cam that you have:

.480 lift intake
.483 lift exhaust

206 duration intake
211 duration exhaust

119 centerline

The mercruiser magnum cam specs are:

.483 lift intake
.483 lift exhaust

224 duration intake
224 duration exhaust

115.5 centerline

The springs in the vortec heads are good to .500 lift, and the roller lifters just swap right over to the next cam, so other than tearing your engine apart, it'd be a no-brainer. I'm not sure how the computer would react to the new cam. That's the uncertain part....????