imported_rosco
Seaman
- Joined
- Oct 12, 2006
- Messages
- 68
Re: 1988 Merc 7.4 Oval Port?
in 1988, mercruiser used TRS drives on their performance engines. they required a seperate transmission. really tough. i know,. i did my best to destroy a couple.
the oval port heads are the base engine heads. designed for trucks mainly. later on, they switched all their big blocks to square port heads. they made basically one engine whose only differnace was the cam shaft, carb, and compression ratio. it significantly reduced the cost of production and still allowed performance options.
but mercruiser didnt do it, GM did. infact, mercruiser doesnt make engines, like volvo penta and every one else, they buy the marine long block from GM or ford or crysler, and add their acessories to them.
the alpha drive is a very good and dependable drive. it has been around for a very long time, and will work on anything from a 4 cylinder to a 250hp small block v8.
it was never designed to handle the beating a big block will deliver. even your base model engine. 454s are tanks. they deliver a ton of torque.
my advise, upgrade to atleast a bravo one. or replace the engine with a small block.
as far as the "magnum" series goes, it is a name they gave just about anything that was an upgrade from the base engine. for instance, take a carburated 454 base engine, add EFI to it, and now its as 7.4 "magnum" EFI, MPI, whatever. same engine with a performance upgrade of some type.
all of GM.s big block marine engines are now the high performance build. forged pistons, forged rods, square port high performance heads, 4 bolt mains with windage trays. the only differances are the cams, compression ratios(pistons), and fuel system(carb,EFI,supercharger) which give them differant names.
for instance, the punched out 502 that has 540 cubic inches and a whopping 600 hp on pump gas is called the "bull dog". odly, they are discontinuing the 502 engine. in stead it will be replaced by a punched out 454, the new 8.1. probably to save production costs, now they will only be producing "one" big block engine in several configurations.
its sad, the 502 is a monster. alot of bang for the buck. over 100 more hp than the base 454 and over 100ft lbs more of torque on regular pump gas. there will be a fwe around in rebuild shops for a few more years, but after that, it will dissappear forever.
either upgrade the drive, or downgrade the engine if you want a dependable system that will take a bit of abuse.
in 1988, mercruiser used TRS drives on their performance engines. they required a seperate transmission. really tough. i know,. i did my best to destroy a couple.
the oval port heads are the base engine heads. designed for trucks mainly. later on, they switched all their big blocks to square port heads. they made basically one engine whose only differnace was the cam shaft, carb, and compression ratio. it significantly reduced the cost of production and still allowed performance options.
but mercruiser didnt do it, GM did. infact, mercruiser doesnt make engines, like volvo penta and every one else, they buy the marine long block from GM or ford or crysler, and add their acessories to them.
the alpha drive is a very good and dependable drive. it has been around for a very long time, and will work on anything from a 4 cylinder to a 250hp small block v8.
it was never designed to handle the beating a big block will deliver. even your base model engine. 454s are tanks. they deliver a ton of torque.
my advise, upgrade to atleast a bravo one. or replace the engine with a small block.
as far as the "magnum" series goes, it is a name they gave just about anything that was an upgrade from the base engine. for instance, take a carburated 454 base engine, add EFI to it, and now its as 7.4 "magnum" EFI, MPI, whatever. same engine with a performance upgrade of some type.
all of GM.s big block marine engines are now the high performance build. forged pistons, forged rods, square port high performance heads, 4 bolt mains with windage trays. the only differances are the cams, compression ratios(pistons), and fuel system(carb,EFI,supercharger) which give them differant names.
for instance, the punched out 502 that has 540 cubic inches and a whopping 600 hp on pump gas is called the "bull dog". odly, they are discontinuing the 502 engine. in stead it will be replaced by a punched out 454, the new 8.1. probably to save production costs, now they will only be producing "one" big block engine in several configurations.
its sad, the 502 is a monster. alot of bang for the buck. over 100 more hp than the base 454 and over 100ft lbs more of torque on regular pump gas. there will be a fwe around in rebuild shops for a few more years, but after that, it will dissappear forever.
either upgrade the drive, or downgrade the engine if you want a dependable system that will take a bit of abuse.