5.0 5.7 Vortec heads

[pennyduke]

Re: 5.0 5.7 Vortec heads

I'm going to start tearing down the 5.7. I'm also gonna go with the RV Cam and bore .30 over and would like to use a high performance Intake. Can someone recomend a Cam & Intake Package?

 

[John_S]

Re: 5.0 5.7 Vortec heads

FWIW: Assuming roller cam, you can usually find the GM cam that is used in 350 Mercs for less than any aftermarket. You will not be able to go with much more lift than that, unless you also modify the heads. Being this is a heavy boat, wouldn't try to go for too much "high perf" stuff. Staying closer to stock, might be better. An Edelbrock Performer Vortec Intake should be fine. If raw water cooled and boat in salt or brackish water, will need bronze lined water passage or other treatment. If you are running a bravo drive, give more considereration to building a 383 stroker, than a hi perf 350.

 

[pennyduke]

Re: 5.0 5.7 Vortec heads

The Boat is heavy. I think thats why the tired 5.0 can't keep up. The boat does have a closed cooling system. I'm also going to replace the cast manifolds and risers with a new set of Aluminum ones. I mostly boat in fresh water and hardly ever get to salt water.

imported_John_S- I'm running an Alpha 1 gen 2 outdrive. Do you know how much horsepower it can handle?

 

[Tail_Gunner]

Re: 5.0 5.7 Vortec heads

Nope,... The valves are bigger/wider on a 350, because the cylinder bore is larger...
The valves will/ might hit the edges of the cylinders...
If they don't hit, they'll be shrouded, 'n not breathe properly....

Basically, 350 heads won't go on a 305, 'n 305 heads don't work on a 350...

Bingo...With that said they can be made to work.. But its a combination of pistons tops and cyl compresssion.. even the right gaskets.

 

[TilliamWe]

Re: 5.0 5.7 Vortec heads

...
imported_John_S- I'm running an Alpha 1 gen 2 outdrive. Do you know how much horsepower it can handle?

300hp at the prop. More if you are careful. Torque help kills them too, but not from a 5.7.

 

[John_S]

Re: 5.0 5.7 Vortec heads

imported_John_S- I'm running an Alpha 1 gen 2 outdrive. Do you know how much horsepower it can handle?

Merc stops using them with engines over 300HP, but it is the torque that kills them. Merc tried some low hp 454's with alpha drives. Didn't last long on heavy boats. A heavy boat needs the toque to get on plane.

So, if your drive is in good order, and staying with alpha, probably best to stay with the 350.

 

[TilliamWe]

Re: 5.0 5.7 Vortec heads

Merc stops using them with engines over 300HP, but it is the torque that kills them. Merc tried some low hp 454's with alpha drives. Didn't last long on heavy boats. A heavy boat needs the toque to get on plane.

So, if your drive is in good order, and staying with alpha, probably best to stay with the 350.

John, I will have to disagree with you slightly. My dad owned one of those Heavy boats with a 454(330hp)/Alpha (gen 1), and the drive did last, a long time. 12 years +, as a matter of fact. That's what I meant by being careful, which he was. No full throttle starts, no trying to jump wakes, and no pulling back on the throttle, then punching it wide open.
So I would have NO problem putting a 383 in front of an Alpha Gen 2. But Penny, in your case, rebuild the 5.7 to be a torquer and you'll be FINE. You don't have to put in a 3.75" stroke crank if you don't want to. You could, though, if you want to.
Whatever you do, don't try to make the 5.0 into something special. It's just not worth it.

 

[John_S]

Re: 5.0 5.7 Vortec heads

John, I will have to disagree with you slightly. My dad owned one of those Heavy boats with a 454(330hp)/Alpha (gen 1), and the drive did last, a long time. 12 years +, as a matter of fact. That's what I meant by being careful, which he was. No full throttle starts, no trying to jump wakes, and no pulling back on the throttle, then punching it wide open.
So I would have NO problem putting a 383 in front of an Alpha Gen 2.

There are a number of people that run 383's with alphas, and they seem to last, but most of those have been in lighter, or go-fast type boats. Good input on the 454/alpha, but most owners did not know they had to baby it. If the OP can control their right hand and the right had of anyone that will be driving it, then they could consider it. Without knowing the OP's planned use, but knowing it is a heavy boat, a bravo would be a better choice. To me, going with the extra torque of the 383, but then having to ease into it, you are loosing most of its advantage in a heavy boat. ie getting on plane faster, vs top speed, which is usually not the goal with that type of boat. It is JMHO, and it is OK to have a different one.