Considerations for engine swap

[Century Arabian]

Hey guys, new to the forum but have posted here before. I recently had issues with my '96 5.0 XL back firing through the carb, traced it back to a seized #6 exhaust valve caused by a leaking riser/manifold gasket. Anyway, got word back from the machine shop today, mu heads are not reusable. The water jacket has corroded enough that it leaves very little sealing surface between the water and head bolt hole. They are now refurbishing a set of heads from a truck motor. Total cost for heads and gasket $1,317.90. This will get me on the water this summer anyway. The thing is this has got me to thinking what the internals of my block is like. I was thinking maybe I should be preparing another motor for a drop in over the winter. Just wondering what you guys would suggest for a replacement... Another 5.0 from the same era. 350 from the same era. How much issue would it be to use a newer 5.3lt, I can see where the fuel injection on the 5.3lt could be an issue. Could u use a carb on the newer 5.3s. Just looking for suggestions now, don't want to go too complicated, but a little more get up and go wouldn't hurt. The hull is a 1996 Century Arabian 21 ft. Any help would be appreciated.
Clyde

 

[alldodge]

If your in salt water, then be looking for a short block. Then put your heads on reman short block. Or get long block 5.0 or 5.7, would not use the 5.3 unless your doing a brand new drop in

 

[Century Arabian]

If your in salt water, then be looking for a short block. Then put your heads on reman short block. Or get long block 5.0 or 5.7, would not use the 5.3 unless your doing a brand new drop in

Thanks AllDodge. After doing a little research, guess all the electronics on the 5.3 would be a pain. 5.0 or 5.7 it is then. would the marine manifolds fir Vortec Heads. I'm thinking they would.
Clyde

 

[alldodge]

Your boat is a 1996 but I'm thinking you may have a 1995 motor (pre-vortec) since its an LX. Your serial number would need to be after 0F600999

If it is pre-vortec then some of your stuff won't work with a vortec (1996 and on) motor

 

[NHGuy]

Try to stop those guys rehabbing old heads. You can get new for less money unless the $1300 is installed.
And get a 5.7 engine, those Arabians are heavy, you can use the torque.

 

[Scott06]

For $3200 delivered you can get a new 5.7 base engine, swap all accessories from current engine (may need intake if not a vortec) . you can Never have too much power ...

 

[Century Arabian]

Your boat is a 1996 but I'm thinking you may have a 1995 motor (pre-vortec) since its an LX. Your serial number would need to be after 0F600999

If it is pre-vortec then some of your stuff won't work with a vortec (1996 and on) motor

AllDodge, I think you may be right, about me having a '95 engine. my serial # for the motor is 0F292223.

NHGuy....I do agree with you, I think my best option would be a 5.7 in the same age group. If I am not mistaken, GM switched to one piece rear main oil seal around 86 or so and the centerbolt valve covers in '87. So if I could pick up a 5.7 block between '87 and '95 everything should fit.
Glad you mentioned that the Arabian could handle the extra power, that would have been one of my next questions.

Now for another question, I am quite familiar with the cams used in street engines, torque verses horsepower, but if I picked up a regular 5.7 from an automobile, would I need to change the cam. I have a lobby cam in the 383 stroker in the vette, but I know i am giving up low end torque for top end horsepower. Just love the sound. lol.

Anyway, this is all good information keep it coming.
Thanks
Clyde

 

[Century Arabian]

Try to stop those guys rehabbing old heads. You can get new for less money unless the $1300 is installed.
And get a 5.7 engine, those Arabians are heavy, you can use the torque.

NHGuy, The situation I am in and time restraints, this for now is my only option. I work off shore on the east coast Newfoundland and our summer is pretty short. This with the engine happened two days before i came back to work and if I don't get something in play for when I get home, I only have three weeks off, my boating for this summer is done. I am going to get the 5.7 ready over the winter to be swapped out when I start having trouble with the 5.0 block. My brother has a 5.7 in his '87 cabin cruiser. We changed the motor in that a few years ago. Guess he didn't do a good job draining the block for winter, split the side out of the water jacket. Horrible job. Once again, thanks for the imput.
Clyde

 

[Scott Danforth]

count the number of holes in the intake

12 bolts is 1995 and older
8 vertical bolts is 1996 and later

brand new from GM heads for a 305 should have been under $700 a pair. gasket set about another $100

you cant use the new LT. it hasnt been marinized by any of the companies, so there is no way to use it.

you can build a brand new 350 or 383 for same price which is about $3000-$3200 (thats you buying new parts and assembling in your garage)

 

[Scott Danforth]

also, your 5.0 heads should not be used on a 5.7.

the small valves needed for the smaller bore limit flow, and the smaller chamber pushes the CR up on too high for marine use on the larger 5.7

on the other side, you shouldnt use 5.7 heads on a 5.0 as the intake valve is shrouded by the bore and the larger chamber drops the CR too much.

 

[Century Arabian]

count the number of holes in the intake

12 bolts is 1995 and older
8 vertical bolts is 1996 and later

brand new from GM heads for a 305 should have been under $700 a pair. gasket set about another $100

you cant use the new LT. it hasnt been marinized by any of the companies, so there is no way to use it.

you can build a brand new 350 or 383 for same price which is about $3000-$3200 (thats you buying new parts and assembling in your garage)

Scott, I assume you are talking US dollars here. Reconditioned 5.0 ltr here are $445.00 each. Gasket set $257.00. The price is what it is, I'm off shore, need the boat when I get in, ordering a new engine now would burn up the season, I only have three weeks off. Building a 5.7 on the off season sounds to me like a fun project.

 

[Century Arabian]

also, your 5.0 heads should not be used on a 5.7.

the small valves needed for the smaller bore limit flow, and the smaller chamber pushes the CR up on too high for marine use on the larger 5.7

on the other side, you shouldnt use 5.7 heads on a 5.0 as the intake valve is shrouded by the bore and the larger chamber drops the CR too much.

I did some research on the use of 350 heads on my 305, because i have a set of 350 marine heads from my brothers old block sitting in the garage. I have a 350 motor in my garage that came out of my '79 vette when I swapped to the 383. I was thinking something newer with a one piece rear main seal would be better. I don't know. That's the reason I'm here. Gathering as much information as I can directing me to make an informed decision. Getting the 5.0 running now for the rest of the season is priority. I will only get to use it for a couple of weeks then it's back to work for another three. After that it's fall up here in Newfoundland.
C

 

[Scott Danforth]

keep the ole 79 motor where it is

if your going to build up a reliable motor, go with at a minimum a post 88 roller block (make sure the keeper bosses are machined) and vortec heads (came out in 1996). a better solution would be either order a crate motor or build a motor like I stated.

have you checked with your local GM dealer in Newfoundland? check prices for a 1996-2000 5.7 truck block and heads and simply swap core plugs and head gaskets.

 

[achris]

...Now for another question, I am quite familiar with the cams used in street engines, torque verses horsepower, but if I picked up a regular 5.7 from an automobile, would I need to change the cam. I have a lobby cam in the 383 stroker in the vette, but I know i am giving up low end torque for top end horsepower. Just love the sound. lol...

As you aspired, top end HP is traded for low end torque. Boats need engines with as flat a torque curve as you can give it. Drives can't be pushed much beyond 5,500-6,000 rpm. So building a fire-breathing dragon that doesn't light the fuse until 7,000 rpm is a bit pointless.

The very best cam for a boat, is out of a truck.. Nice and flat, power from about 1,500 rpm, topping out around 4,600... Just like the cam Merc put in the engines.

Chris.....

 

[Century Arabian]

keep the ole 79 motor where it is

if your going to build up a reliable motor, go with at a minimum a post 88 roller block (make sure the keeper bosses are machined) and vortec heads (came out in 1996). a better solution would be either order a crate motor or build a motor like I stated.

have you checked with your local GM dealer in Newfoundland? check prices for a 1996-2000 5.7 truck block and heads and simply swap core plugs and head gaskets.

Scott, this is for sure the route I would want to take, 5.7 ltr truck motor, which leads me to an earlier question, will my marine exhaust manifolds fit vortex heads.
Another question, that may sound stupid to you but "Make sure keeper bosses are machined". what are you referring to here. I was concerned if the vortex heads were drilled to accept the accessories like alt bracket, coil and fuel filter.
Thanks for all the information.
Clyde

 

[Century Arabian]

As you aspired, top end HP is traded for low end torque. Boats need engines with as flat a torque curve as you can give it. Drives can't be pushed much beyond 5,500-6,000 rpm. So building a fire-breathing dragon that doesn't light the fuse until 7,000 rpm is a bit pointless.

The very best cam for a boat, is out of a truck.. Nice and flat, power from about 1,500 rpm, topping out around 4,600... Just like the cam Merc put in the engines.

Chris.....

Hey Chris, Just read your profile and noted your profession. I work with Oceaneering as an ROV supervisor, in Newfoundland, Canada.
Totally understand what your saying. As yourself and Scott stated, if I am going to swap for more power, newer 5.7 from a truck would be the way to go. Just a matter if my marine exhaust would fit the newer Vortex heads.
Thanks for all the help.
Clyde.

 

[Century Arabian]

Scott I also noticed you said to swap the head gasket, would you mind explaining this would be required.
C

 

[achris]

Current exhaust manifolds will fit. Intake will not. Vortec heads are drilled and tapped the same as non Vortec for accessories...

 

[achris]

Scott I also noticed you said to swap the head gasket, would you mind explaining this would be required.
C

Standard truck head gaskets are steel. Steel in sea water... Does not end with 'and they lived a long life'... Need to swap out head gaskets for 'non ferrous', ie, marine (felpro do a good set) and engine core plugs standard are also steel. Knock them out and put in either brass or stainless...

Chris....
(Working with Saipem in Egypt at the moment)

 

[Century Arabian]

Chris, Egypt sounds warm. We're still waiting for summer to show up here. lol.
O.k, that makes sense, I usually use the felpro gaskets for any rebuild. Fiber with the s.s. ring around the cylinder opening. Now still trying to figure out what Scott was referring to when he stated. "go with at a minimum a post 88 roller block (make sure the keeper bosses are machined) . Thanks again for all the help and stay safe at work.
Clyde