Replace 305 (5.0LX) with 350 (5.7L)

[gjcombs]

All,

It's another post on repowering, so I apologize ahead of time. Here's what I need to know:

1. Can I use the parts from my 1994 5.0LX engine on a marine 5.7L long block?

2. Can I use the same Thunderbolt Ignition?

3. Is it worth going to a 350 versus the gain in weight of the engines and HP?

4. For a 1994 engine, should the one I have be a one-piece rear main seal?

5. Can I use the same outdrive (Alpha One, Gen II, 1.50R) gear ratio in going to a 350?

6. Any suggestions or answers that I am not asking the questions yet about, but should be?

Thanks.

 

[Bt Doctur]

Re: Replace 305 (5.0LX) with 350 (5.7L)

Yes to all

 

[John_S]

Re: Replace 305 (5.0LX) with 350 (5.7L)

You should consider going with vortec heads for another 30hp. It will require a new intake manifold, and maybe some adjustment to your 4brl carb.

 

[gjcombs]

Re: Replace 305 (5.0LX) with 350 (5.7L)

You should consider going with vortec heads for another 30hp. It will require a new intake manifold, and maybe some adjustment to your 4brl carb.

Should the 305 parts be compatible with a vortec 350?

Should a vortec long block come with heads and intake manifold?

 

[John_S]

Re: Replace 305 (5.0LX) with 350 (5.7L)

Should the 305 parts be compatible with a vortec 350?

Should a vortec long block come with heads and intake manifold?

Long blocks typically come with the heads, but not the intake.


The following are things to check, be it vortec or non-vortec:

- If it has a plastic timing cover, a different engine circ water pump is needed to clear it.

- If new engine has a roller cam, your distributer needs the melonized gear.

- If new engine has a roller cam, and mechanical fuel pump boss, you need a fuel push rod for a roller cam.

- If new block does not have mechanical fuel pump boss, need electric fuel pump system.

- While the location of sbc ports hasn't changed, the spark plug location/angle has changed slightly. Check you exhaust manifold part number, to a gen+, or standard head 350. If there is any question on condition of existing manifolds, just get new ones.

- Thermostat housing must fit and hoses clear other items.

- Bracketry attached to intake bolts, if any, would need modification or change for vortec intake.

- If you have a "stove" style choke, need to convert to electric choke for vortec.

- Need a 350 harmonic balancer.

- Carb tuning from 305 to 350 or 350 vortec.

 

[gjcombs]

Re: Replace 305 (5.0LX) with 350 (5.7L)

Follow up:

I have a manual choke Qjet 4bbl. What if I want to go to an electric choke? I am thinking an Edelbrock 1410. Should the wiring harness have leads already?

 

[John_S]

Re: Replace 305 (5.0LX) with 350 (5.7L)

Follow up:

I have a manual choke Qjet 4bbl. What if I want to go to an electric choke? I am thinking an Edelbrock 1410. Should the wiring harness have leads already?

The edelbrock 1410 is calibrated for BB. It will need to tune it (rods/jets/springs) for the 350. The 1409 is tuned for 350. Not sure if you have a wire in your harness, but if powered from icm, you probably need to run a wire to alt that would have full voltage and current.