5.0 5.7 Vortec heads

pennyduke

Petty Officer 2nd Class
Joined
Aug 29, 2009
Messages
119
I have a 1996 5.7l Vortec engine I pulled from my Suburban 1500 with a spun bearing. Will the heads from this truck motor fit on my 1993 Mercruiser 5.0L motor to try to increase HP.

I also wanted to thank everyone for all the help at the begining of summer. My boat ran great after all your help. I'm still only getting 28 mph and want more power for next year. Thanks, Mike
 

Bifflefan

Commander
Joined
May 27, 2009
Messages
2,933
Re: 5.0 5.7 Vortec heads

They will probably fit, Im a Ford guy. But they are most likely exactly the same heads.

If your only getting 28 MPH with a 5.0 you got other issues.
 

Alpheus

Lieutenant Commander
Joined
Aug 3, 2009
Messages
1,757
Re: 5.0 5.7 Vortec heads

They will bolt right up to the block, but you need a new intake manifold to match the heads...
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
70,465
Re: 5.0 5.7 Vortec heads

Will the heads from this truck motor fit on my 1993 Mercruiser 5.0L motor to try to increase HP.

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...
 

John_S

Rear Admiral
Joined
Jun 21, 2004
Messages
4,269
Re: 5.0 5.7 Vortec heads

Along with what Bondo said, 305 heads are usually 58cc where 5.7L vortecs are 64cc. That would lower the compression and reduce power as well.

With a big boat, just rebuild that truck 5.7L and put it in with most of the marine parts from the 305.
 

pennyduke

Petty Officer 2nd Class
Joined
Aug 29, 2009
Messages
119
Re: 5.0 5.7 Vortec heads

So it sounds like the head swap won't work. My next step was to rebuild the 5.7 truck motor like Imported_John_S mentioned. Will I need to change the Cam? Also can someone recomend a performance Marine Intake for it?
 

TilliamWe

Banned
Joined
Dec 21, 2004
Messages
6,579
Re: 5.0 5.7 Vortec heads

The cam from the truck engine would work in the boat application as well. But wouldn't you want to replace the camshaft/lifters due to age, anyway?
 

Alpheus

Lieutenant Commander
Joined
Aug 3, 2009
Messages
1,757
Re: 5.0 5.7 Vortec heads

Like I said the 350 Vortecs will bolt right on your 305 block. Been there, done that on my old Camaro.

The problem was keeping the compression ratio close to stock.

The stock compression is 9.3:1 using (305-5.0) 58cc heads.

If you go up to(350-5.7) 64cc heads (Vortecs) then use Felpro embossed shim gaskets then you'll stay at 9.26:1 compression ratio. You just have to make sure the deck on the block is true, as well as the heads.

Having said that, you will probably not want to run those type of head gaskets on a raw water cooled engine if you run in salt water. If you choose to use stock thickness head gaskets for marine use you will lower your compression ratio enough that the extra HP gain from the heads will become negligible. But they can and do bolt up...
 

zbnutcase

Commander
Joined
Sep 19, 2009
Messages
2,055
Re: 5.0 5.7 Vortec heads

I'm for rebuilding the 5.7 and droppin her in...
 

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,454
Re: 5.0 5.7 Vortec heads

I believe they are the same. The part numbers for the heads between a 5.7 and 5.0 are the same in the Volvo and Mercruiser parts lists at least. Both 5.0 and 5.7 each have 2 part numbers listed and they are identical for each motor.
 

John_S

Rear Admiral
Joined
Jun 21, 2004
Messages
4,269
Re: 5.0 5.7 Vortec heads

I believe they are the same. The part numbers for the heads between a 5.7 and 5.0 are the same in the Volvo and Mercruiser parts lists at least. Both 5.0 and 5.7 each have 2 part numbers listed and they are identical for each motor.

The standard 305 heads were 58cc and had smaller valves. I believe they had recessed/dished pistons. I am wondering if the 305 vortecs, if they do use 350 heads, are they running a flat-top piston to match with the larger chamber?

I still vote for the rebuild 350, though. :)
 

FLAT RATE

Cadet
Joined
Mar 25, 2010
Messages
18
Re: 5.0 5.7 Vortec heads

The Votrec heads flow better and they will fit on the 305 but you will need to use a new intake manifold. I put the Vortec heads on a small block that was stroked, has 9.1 compression and then went with a marine cam to get the power I wanted to move a big heavy boat. Best thing I ever did, gets the boat on plane with only 1/2 throttle and don't have to use the trim tabs and it seems like a completely different boat. Went with more prop and gained a bit more speed as well with out the hassle of converting to a big block, it idles smooth and is good on fuel. I vote for rebuilding the 350, using the vortec heads, good cam and quality parts and you won't be sorry.
 

spdracr39

Lieutenant Junior Grade
Joined
Aug 30, 2010
Messages
1,238
Re: 5.0 5.7 Vortec heads

As has been said before " nothing replaces cubic inches". If you have big boat syndrome you need the bigger 5.7 anyway so why keep patching the 5.0?
 

GLENN M

Petty Officer 1st Class
Joined
Aug 14, 2010
Messages
204
Re: 5.0 5.7 Vortec heads

you put a 350 head on 305 the intake runners are way bigger so you will lose air velosity [speed] combustion chamber way bigger you lose compresion engine will be dog.bore size on 350 4 inch 305 3 7\8 inch you will shroud valves all that work to lose all bottom end power go with 350 magic number for power is 4inch bore
 

Alpheus

Lieutenant Commander
Joined
Aug 3, 2009
Messages
1,757
Re: 5.0 5.7 Vortec heads

intake runners are way bigger so you will lose air velosity [speed]

Wrong!!!

Do your homework and read the other posts. This has been asked and answered. As stated above the part numbers for the heads are the same...


The part numbers for the heads between a 5.7 and 5.0 are the same in the Volvo and Mercruiser parts lists at least. Both 5.0 and 5.7 each have 2 part numbers listed and they are identical for each motor.
 

Aloysius

Chief Petty Officer
Joined
Aug 21, 2010
Messages
484
Re: 5.0 5.7 Vortec heads

Reread bondo's post. Other Chevy heads are different between 305/350 for this reason..valves hitting the cylinder walls. However, vortecs don't use real big valves from the get-go, so the same head MAY work on both, but you'll still have the shrouding issue.

I've never understood why GM produces these 2 virtually identical engines. Only explanation..they can charge more $$$ for a 350..which is ALL profit.
 

unclepete2o

Cadet
Joined
Sep 13, 2010
Messages
8
Re: 5.0 5.7 Vortec heads

On your camshaft selection go with an RV cam, I assume your just going to use the carb set up. An RV cam will give you some good low end grunt and the top end will be decent as well.

Also If your super ambitious, bore .30 over, will make it from a 350, to a 355 ish. That engine will really sing, and if all done right and not over carbed, you will easily throw off 275HP, as long as your lower unit is up to the task.
 

redjmp

Chief Petty Officer
Joined
Mar 16, 2005
Messages
536
Re: 5.0 5.7 Vortec heads

Wrong!!!

Do your homework and read the other posts. This has been asked and answered. As stated above the part numbers for the heads are the same...

10239906 12558060 12558062 are the "real" vortec heads that everyone wants. The '906 casting has a hardened exhaust seat that reduces flow so you might want to stay away from that one if you want pure performance but the hardened seat is preferred for regular marine applications.

The 5.0L also came with vortec heads 12558059 but they are different totally than the "real" ones for a 5.7L. Similar but different. Combustion chamber is smaller and not heart shaped for starters, runners are slightly different as well.
These are the heads you get from GM when you buy a 5.0L in a truck.
And they are the correct size for a 5.0L, 58cc

I am surprised that Mercruiser uses the 350 heads on the 305 as they are not the same.
Gm marine engines use the 059 casting afaik.
I sure hope so as I have a set ready to bolt onto my 898 along with a performance products manifold and edelbrock 4bbl.


But I agree with the other people and recommend that you rebuild the 5.7L with the marine stuff from the 5.0L.
Good for about 60 more hp.

You will need to reprop and/or change gears in your upper unit though.
 
Top