choosing the right 350 chevy setup

[capitan828]

hi, I'm new to the boating world and recently purchased an 82 sea ray with a 260 mercruiser. The engine is waterlogged and needs to be replaced. it was raw water cooled and i don't want to risk putting money in it and end up regretting it since its got a few years on it. so I'm gonna replace it all together. I have a couple options for rebuilding another engine. I have two engines lying around, one is a 350 from a 80something 2500 chevy and the other is a vortec 350 from a 96 tahoe. the one from the 2500 was a good running engine that had a top fire and the vortec was running poorly with misfires but should still be good. i don't know how well the engines mix and match together so thats why I need advice from people that know more about it than i do. obviously i want to keep cost down since I'm gonna be doing all the work myself. which ever engine i end up choosing I'm gonna rebuild myself or at least freshen up. can i use the the complete vortec long block or will it have issues since it will be going into a carburated application? what kind of intake manifold would i need? if the 2500 happens to be a four bolt main, could i use it and put the vortec heads on it?

 

[joewithaboat]

Re: choosing the right 350 chevy setup

If it is in good health, use the vortec... It will have better heads, roller cam, light weight pistons, one piece main
Get an Edelbrock 4 barrel alum intake (for vortec heads) and a marine carb
You should switch out core plugs to brass, and use the felpro marine head gaskets.
Should be a good bit more HP than you had before.

 

[Scott Danforth]

Re: choosing the right 350 chevy setup

if you want a bit more grunt while your in the engine, upgrade the cam. there are a few companies that have some really good marine cams out there. i went with a comp cams 262 grind myself.

 

[capitan828]

Re: choosing the right 350 chevy setup

Do all the bolt on accessories from the 82 350 bolt right on to the vortec engine? Mechanical fuel pump, v pulleys alternator, and so on? I don't want to make too many modifications because they equal $$$$!

 

[Scott Danforth]

Re: choosing the right 350 chevy setup

the vortec engine will not have a mechanical fuel pump area machined. you can have the machine shop machine it, or you can switch to an electric fuel pump. other than that, the accessories will bolt on. you will need a vortec specific intake for the vortec heads (different bolt pattern and intake ports).

 

[81 Checkmate]

Re: choosing the right 350 chevy setup

Im thinking the engine coupler and flywheel are different from a one piece (96) to two piece (80's) rear main seal?
Just some info to check on!

The Vortec would be the way to go if you can do it.

 

[joewithaboat]

Re: choosing the right 350 chevy setup

flywheel will also be different! So in summary... you will need a flywheel, new intake (vortec specific), maybe a carb, electric fuel pump. Everything else should work when swapping generations.
Good luck!
Be sure to use your original style water pump, I know some of, if not all, the late model serpentine pumps are reverse rotation.

 

[Scott Danforth]

Re: choosing the right 350 chevy setup

the flywheel is a basic gm truck manual flywheel. your local salvage yard may have one for under $25

 

[81 Checkmate]

Re: choosing the right 350 chevy setup

the flywheel is a basic gm truck manual flywheel. your local salvage yard may have one for under $25

Then you have to consider the flywheel housing which containes the back motor mounts!

Just more to think about.

 

[RogersJetboat454]

Re: choosing the right 350 chevy setup

Then you have to consider the flywheel housing which containes the back motor mounts!

Just more to think about.

Shouldn't be any troubles with that as a direct bolt on.

OP needs to match the (tooth count) flywheel he picks up to what his block will accommodate for a starter. Some blocks are drilled for both the cross bolted (168 tooth flywheel) and strait bolted (153 tooth flywheel) starters. Some are not, and drilled specifically for one or the other starter. If the engine he uses is a true Vortec block (such as the one that has the plastic timing cover), there is a chance it may not have a provision cast into the side of the block for a mechanical fuel pump. The OP should honestly plan on using a suitable marine electric pump. If this boat is going into salt, the OP should ensure that the core plugs are brass, and the head gaskets are marine grade.

 

[81 Checkmate]

Re: choosing the right 350 chevy setup

So he posibly could bolt the orig flywheel and housing from the boat motor to new vortec motor providing the starter teeth are a match?

 

[capitan828]

Re: choosing the right 350 chevy setup

It seems like its gonna be too much of a hassle to use the vortec engine. I think I'm just gonna go with the non vortec. I'm not really looking for hi performanc. I want affordability and above all reliability, since if it breaks down in the ocean I won't have the option to get out and push! Can I use any intake manifold for the engine? Or does it need to be a marine/expensive one?

 

[RogersJetboat454]

Re: choosing the right 350 chevy setup

So he posibly could bolt the orig flywheel and housing from the boat motor to new vortec motor providing the starter teeth are a match?

Flywheel housing, yes.
Flywheel, No, if it's a flywheel from a 2 bolt main engine, it will not fit a 1 piece RMS vortec.

 

[RogersJetboat454]

Re: choosing the right 350 chevy setup

It seems like its gonna be too much of a hassle to use the vortec engine. I think I'm just gonna go with the non vortec. I'm not really looking for hi performanc. I want affordability and above all reliability, since if it breaks down in the ocean I won't have the option to get out and push! Can I use any intake manifold for the engine? Or does it need to be a marine/expensive one?

Find out about your 80 something block. If it's a '86 or newer block, it will be a one piece like your Vortec. Even if it is, it's not the end of the world, it would just mean that you need to get a matching flywheel and coupler for it. You should be able to use your mechanical fuel pump with it.

If you want to mix and match, you could use the vortec heads off the 96 engine off your 80's engine with a little bit of consideration. You will need self aligning rockers to make it work, and the correct Vortec manifold.

Speaking of which, you asked about the manifold. Since you are running this in salt, it's probably best you consider an iron intake manifold. If you want to get fancy, they do sell aluminum manifolds with bronze lined water passages. If you want to be cheap, you can use an aluminum manifold, but be prepared to change it out every couple years. Would just be easier to go with the iron intake.

 

[capitan828]

Re: choosing the right 350 chevy setup

Find out about your 80 something block. If it's a '86 or newer block, it will be a one piece like your Vortec. Even if it is, it's not the end of the world, it would just mean that you need to get a matching flywheel and coupler for it. You should be able to use your mechanical fuel pump with it.

If you want to mix and match, you could use the vortec heads off the 96 engine off your 80's engine with a little bit of consideration. You will need self aligning rockers to make it work, and the correct Vortec manifold.

Speaking of which, you asked about the manifold. Since you are running this in salt, it's probably best you consider an iron intake manifold. If you want to get fancy, they do sell aluminum manifolds with bronze lined water passages. If you want to be cheap, you can use an aluminum manifold, but be prepared to change it out every couple years. Would just be easier to go with the iron intake.

I am going to install a full closed cooling system. I want this thing to last a long time so I'm gonna invest the extra cash for the full system kit. So would I be able to use any aluminum intake manifold without having to do any modifications to it?

 

[RogersJetboat454]

Re: choosing the right 350 chevy setup

I am going to install a full closed cooling system. I want this thing to last a long time so I'm gonna invest the extra cash for the full system kit. So would I be able to use any aluminum intake manifold without having to do any modifications to it?

Yep, you can use an aluminum intake as long as it matches the heads you use.

'55-'86 use the old common intake. '87-'95 uses an intake similar to the older one, but the bolt angles for the center 4 bolts are different then the older manifolds. '96+ Vortec heads use their own specific manifold, bolt count and angle have no resemblance to the two older manifolds. All should be available in aluminum.

 

[joewithaboat]

Re: choosing the right 350 chevy setup

Also... check your 96 block
Some of the mid 90,s blocks were also drilled to use a mechanical pump (even though they came in a fuel injected vehicle). I have one that came from a fuel injected truck that is drilled for the fuel pump rod and just plated over.
You really need to further investigate the two engines you have (rear mains, flywheels, fuel pump rod bore, starter patterns etc.) the the year model wont always tell the full story.

 

[capitan828]

Re: choosing the right 350 chevy setup

Also... check your 96 block
Some of the mid 90,s blocks were also drilled to use a mechanical pump (even though they came in a fuel injected vehicle). I have one that came from a fuel injected truck that is drilled for the fuel pump rod and just plated over.
You really need to further investigate the two engines you have (rear mains, flywheels, fuel pump rod bore, starter patterns etc.) the the year model wont always tell the full story.

Yea, tomorrow I'm gonna go and pull both engines and find out exactly what i have.

 

[capitan828]

Re: choosing the right 350 chevy setup

So how much more power do you guys think the vortec will produce compared to the other engine, seeing as how it will still be carbureted. Also, would the vortec be more fuel efficient than the older engine?

 

[Bondo]

Re: choosing the right 350 chevy setup

So how much more power do you guys think the vortec will produce compared to the other engine, seeing as how it will still be carbureted. Also, would the vortec be more fuel efficient than the older engine?

Ayuh,.... All else equal, 'bout 20hp...