Building a 350 sbc from a marine engine...need opinions on direction
01-28-2014, 10:40 AM
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Building a 350 sbc from a marine engine...need opinions on direction Hi Guys,
I owned a 30 foot express cruiser since new in 1999. Unfortunately, the boat suffered a top side fire resulting in a total loss. I bought the boat back and savaged a ton of parts off her. I maintained and ran the boat...never ran her hard.
Included in the salvage was the two Mercruiser 350 mag mpi 300 HP engines. Both are believed to be LH rotation with the counter rotation taken care of via the transmission. These engines where replaced with new long blocks from mercury 110 hours before the fire.
Here's what I have:
880 block
906 Vortec heads
Cam - Merc Part No 431-811658 Duration @ .050: 197 intake, 207 exhaust Valve lift in inches: .430 intake, .450 exhaust Lobe centerline degrees: 106 ATDC, 112 BTDC Lobe Separation Angle in Degrees: 109
Merc 861422A 5 Intake...Intake is good I am not sure that the throttle body is. Also the injectors wire harness was burnt and I will be replacing the injectors.
Overall condition:
Block:
Heads:
Intake is good, but I am not sure that the throttle body is. Also the injectors wire harness was burnt and I will be replacing the injectors. Distributor and coil are bad
Originally, I wanted to install the ramjet intake kit, a custom ecm, tune, and harness. The stock cam appears close to the ramjet cam which I believe the specs are 196/206 @ 0.050", .431"/.451", 109 LSA.
Other thoughts are the install the LT4 Hot Cam...prep the heads for 1.6 rockers. and come up with a efi option. I do not want a carb.
I will be having the mains converted to 4 bolt.
I will be installing this into a 2005 Jeep Wrangler LJ with a 4L80E trans. This is not a daily driver and strictly a toy. I am looking for around 400+ hp and 400+ torque. Use will be two track cruising, jeep night cruises, and most important...sand dunes and maybe sand drags. I would like to build it capable of adding some nitrous later.
I am looking for all suggestions.
Thanks, Steve
I owned a 30 foot express cruiser since new in 1999. Unfortunately, the boat suffered a top side fire resulting in a total loss. I bought the boat back and savaged a ton of parts off her. I maintained and ran the boat...never ran her hard.
Included in the salvage was the two Mercruiser 350 mag mpi 300 HP engines. Both are believed to be LH rotation with the counter rotation taken care of via the transmission. These engines where replaced with new long blocks from mercury 110 hours before the fire.
Here's what I have:
880 block
906 Vortec heads
Cam - Merc Part No 431-811658 Duration @ .050: 197 intake, 207 exhaust Valve lift in inches: .430 intake, .450 exhaust Lobe centerline degrees: 106 ATDC, 112 BTDC Lobe Separation Angle in Degrees: 109
Merc 861422A 5 Intake...Intake is good I am not sure that the throttle body is. Also the injectors wire harness was burnt and I will be replacing the injectors.
Overall condition:
Block:
Heads:
Intake is good, but I am not sure that the throttle body is. Also the injectors wire harness was burnt and I will be replacing the injectors. Distributor and coil are bad
Originally, I wanted to install the ramjet intake kit, a custom ecm, tune, and harness. The stock cam appears close to the ramjet cam which I believe the specs are 196/206 @ 0.050", .431"/.451", 109 LSA.
Other thoughts are the install the LT4 Hot Cam...prep the heads for 1.6 rockers. and come up with a efi option. I do not want a carb.
I will be having the mains converted to 4 bolt.
I will be installing this into a 2005 Jeep Wrangler LJ with a 4L80E trans. This is not a daily driver and strictly a toy. I am looking for around 400+ hp and 400+ torque. Use will be two track cruising, jeep night cruises, and most important...sand dunes and maybe sand drags. I would like to build it capable of adding some nitrous later.
I am looking for all suggestions.
Thanks, Steve
01-30-2014, 03:55 PM
#2
i can't see your pics at the moment,
i would ditch all the mercruiser crap on the motor- the distributor, intake and everything above. you said your goal was 400+ hp/tq and also said nitrous later. if your goal is anything over 350 i'm pretty sure you will not get there on a typical 19x/20x cam unassisted with 93 octane gas. I thought most late model merc 350's had flat top pistons but the compression ratio was around 9.5:1 at most which will hold you back from your hp/tq goal. however, you might want to reconsider your hp and torque goal and what rpm's you want that to happen at. you can achieve close to 400 lb-ft of torque with a 20x/21x sized cam and you'll have much more torque under 3000 rpm but it'll fall off quickly at 4000-5000 rpm thus less maximum hp. when you have goals of 400+ hp for the 350 c.i.d. then that requires higher rpm which requires a larger 23x cam and as a result the torque at lower rpm is reduced. and you'll also need better heads than those vortecs, and then you might as well get a set of aluminum heads.
as for efi setup i'm not too knowledgable and haven't followed things like that in a while. I wouldn't use the merc efi because that's programmed for loads seen in a boat which is different than the varying loads the motor will see in a car/truck. you don't have crank and cam reluctor wheels so i think that might limit you, but i would look for something that incorporates both the ignition/distributor with the efi setup for it to be optimal. I thought holley came out with a plug and go efi system that i though i read was supposed to be good.
i would ditch all the mercruiser crap on the motor- the distributor, intake and everything above. you said your goal was 400+ hp/tq and also said nitrous later. if your goal is anything over 350 i'm pretty sure you will not get there on a typical 19x/20x cam unassisted with 93 octane gas. I thought most late model merc 350's had flat top pistons but the compression ratio was around 9.5:1 at most which will hold you back from your hp/tq goal. however, you might want to reconsider your hp and torque goal and what rpm's you want that to happen at. you can achieve close to 400 lb-ft of torque with a 20x/21x sized cam and you'll have much more torque under 3000 rpm but it'll fall off quickly at 4000-5000 rpm thus less maximum hp. when you have goals of 400+ hp for the 350 c.i.d. then that requires higher rpm which requires a larger 23x cam and as a result the torque at lower rpm is reduced. and you'll also need better heads than those vortecs, and then you might as well get a set of aluminum heads.
as for efi setup i'm not too knowledgable and haven't followed things like that in a while. I wouldn't use the merc efi because that's programmed for loads seen in a boat which is different than the varying loads the motor will see in a car/truck. you don't have crank and cam reluctor wheels so i think that might limit you, but i would look for something that incorporates both the ignition/distributor with the efi setup for it to be optimal. I thought holley came out with a plug and go efi system that i though i read was supposed to be good.
