Chevy rebuilds
 

"Wayne.B" wrote in message
...
On Mon, 05 Nov 2007 09:26:15 -0800, Capt John
wrote:

About five years ago I had a shop I've been dealing with for years
build me 300 hp 350's, completely remachined, new sheet metal, pistons
rings cams, bearings timing gears and chain, oil pumps, ect.

I'm sure there are people who can get that kind of power but it can't
be easy or durability/operability is compromised in some way. If it
was easy Mercruiser would be doing it and they're not.
One of the challenges is maintaining low end torque while you hop up
the high end. Another issue is what happens to durability if you have
to run at 5000 RPM to get the 300 hp.

I have a 6.2L MPI (about 373 cid) that Mercruiser rates at 320 hp, so
300 hp out of a carburated 350 is a bit of a stretch.

Not really. My 350 MPI engine is rated 330 hp.
http://www.michiganmotorz.com/Marine...07+replacement)
315 hp. But they are Vortec base engines.

Chevy rebuilds
 

Notice the MPI? That measn multiport injected. Not carburated. He said
carburated.

"Calif Bill" wrote in message
...

"Wayne.B" wrote in message
...
On Mon, 05 Nov 2007 09:26:15 -0800, Capt John
wrote:

About five years ago I had a shop I've been dealing with for years
build me 300 hp 350's, completely remachined, new sheet metal, pistons
rings cams, bearings timing gears and chain, oil pumps, ect.

I'm sure there are people who can get that kind of power but it can't
be easy or durability/operability is compromised in some way. If it
was easy Mercruiser would be doing it and they're not.
One of the challenges is maintaining low end torque while you hop up
the high end. Another issue is what happens to durability if you have
to run at 5000 RPM to get the 300 hp.

I have a 6.2L MPI (about 373 cid) that Mercruiser rates at 320 hp, so
300 hp out of a carburated 350 is a bit of a stretch.

Not really. My 350 MPI engine is rated 330 hp.
http://www.michiganmotorz.com/Marine...07+replacement)
315 hp. But they are Vortec base engines.

Chevy rebuilds
 

The 400's have siamesed cylinders so they are not very popular in the marine
world. They have cooling problems right where the cylinders meet which is
also right where head gaskets tend to blow out on small blocks.

The stroked 383 is a pretty good configuration but don't expect miracles.
It is just a slightly longer stroke and 33 more cubic inches.

The basic problem is still that the small blocks really like to make hp with
rpm's and there is a limit to what you can do to get hp at low rpm with
them. It's an unavoidable problem when combined with a big heavy boat.
That's why higher displacement is really the way to go in a big boat.

I think the op is gone anyway.

"Capt John" wrote in message
ups.com...
On Nov 3, 1:27 pm, Wayne.B wrote:
On Sat, 03 Nov 2007 10:57:15 -0700, wrote:
I have a 32' Luhrs Sportfisher. Currently with Chrysler 318 engines.
I have 2 Chevrolet 350 4 bolt marine engines, one standard, one
reverse rotation. I would like to find out what spec. and what parts
I need to build these engines to 280 to 300 hp on carburators. The
boat weights 17000 lbs. It is my understanding I need foot lbs. of
torque more than rpm. Anyone know if there is a guide or book? Anyone
with information. Thanks in advance.

The most I've seen from a carburated 350 is 260 hp. You can get 300
to 320 with multi-port fuel injection, maybe more. With 17,000 lbs of
weight you'll be a lot better off with 454s or even bigger. My old
Bertram 33 weighed 21,000 and it was only a marginal performer with
350 hp 454s.

I had 350's with carbs and 300 hp, it's not difficult. A better choice
is to make those 350's into 383's, plenty of torque at low RPM's and
still light weight. Even better, if you can find them, small block
400's. But to do any of this you need a good engine shop that knows
marine engines. Their's so many choices of heads, valve sizes, cam
shafts.

About five years ago I had a shop I've been dealing with for years
build me 300 hp 350's, completely remachined, new sheet metal, pistons
rings cams, bearings timing gears and chain, oil pumps, ect. Bottom
line, $2500 each, I'd probably bet their about $3000 each now. The
best thing about 350's are the parts are cheap!!!

Chevy rebuilds
 

"jamesgangnc" wrote in message
...
Notice the MPI? That measn multiport injected. Not carburated. He said
carburated.

"Calif Bill" wrote in message
...

"Wayne.B" wrote in message
...
On Mon, 05 Nov 2007 09:26:15 -0800, Capt John
wrote:

About five years ago I had a shop I've been dealing with for years
build me 300 hp 350's, completely remachined, new sheet metal, pistons
rings cams, bearings timing gears and chain, oil pumps, ect.

I'm sure there are people who can get that kind of power but it can't
be easy or durability/operability is compromised in some way. If it
was easy Mercruiser would be doing it and they're not.
One of the challenges is maintaining low end torque while you hop up
the high end. Another issue is what happens to durability if you have
to run at 5000 RPM to get the 300 hp.

I have a 6.2L MPI (about 373 cid) that Mercruiser rates at 320 hp, so
300 hp out of a carburated 350 is a bit of a stretch.

Not really. My 350 MPI engine is rated 330 hp.
http://www.michiganmotorz.com/Marine...07+replacement)
315 hp. But they are Vortec base engines.




I said mine was the MPI. The link is to a 315 hp carbed motor. And the
400's sucked in cars also, the cooling left a lot to be desired.

Chevy rebuilds
 

"Calif Bill" wrote in message
...



I said mine was the MPI. The link is to a 315 hp carbed motor. And the
400's sucked in cars also, the cooling left a lot to be desired.


Ahem. GM built two different "400's". The first was unique to Pontiac,
was a big block and was used starting in 1967 in the GTO. It was a slightly
bigger version of the 389 but had improved heads with larger valves for
improved breathing.

The "other" 400 ci, to which you are most likely referring, is a bored small
block and indeed, had some problems.

Eisboch

Chevy rebuilds
 

Calif Bill wrote:
I said mine was the MPI. The link is to a 315 hp carbed motor. And the
400's sucked in cars also, the cooling left a lot to be desired.

a person could probably use a 400 on a fresh water system with no much
problem with cooling, but the blocks are thin, like it was factory
bored about as far as one would want to take it.

I never was impressed with the 400 Chevy.

Chevy rebuilds
 

"Eisboch" wrote in message
...

"Calif Bill" wrote in message
...



I said mine was the MPI. The link is to a 315 hp carbed motor. And the
400's sucked in cars also, the cooling left a lot to be desired.


Ahem. GM built two different "400's". The first was unique to Pontiac,
was a big block and was used starting in 1967 in the GTO. It was a
slightly bigger version of the 389 but had improved heads with larger
valves for improved breathing.

The "other" 400 ci, to which you are most likely referring, is a bored
small block and indeed, had some problems.

Eisboch


Forgot about the Pontiac 400.

Chevy rebuilds
 

The cylinders were cast joined to each other all the way down so it could be
bored bigger. That reduced the cooling flow around the cylinders.

"Tim" wrote in message
ups.com...

Calif Bill wrote:
I said mine was the MPI. The link is to a 315 hp carbed motor. And the
400's sucked in cars also, the cooling left a lot to be desired.

a person could probably use a 400 on a fresh water system with no much
problem with cooling, but the blocks are thin, like it was factory
bored about as far as one would want to take it.

I never was impressed with the 400 Chevy.

Chevy rebuilds
 

The link just says "invalid serach conditions" A 300+ hp carburated 350 is
reasonable though. The vortex heads are pretty good.

"Calif Bill" wrote in message
...

"jamesgangnc" wrote in message
...
Notice the MPI? That measn multiport injected. Not carburated. He said
carburated.

"Calif Bill" wrote in message
...

"Wayne.B" wrote in message
...
On Mon, 05 Nov 2007 09:26:15 -0800, Capt John
wrote:

About five years ago I had a shop I've been dealing with for years
build me 300 hp 350's, completely remachined, new sheet metal, pistons
rings cams, bearings timing gears and chain, oil pumps, ect.

I'm sure there are people who can get that kind of power but it can't
be easy or durability/operability is compromised in some way. If it
was easy Mercruiser would be doing it and they're not.
One of the challenges is maintaining low end torque while you hop up
the high end. Another issue is what happens to durability if you have
to run at 5000 RPM to get the 300 hp.

I have a 6.2L MPI (about 373 cid) that Mercruiser rates at 320 hp, so
300 hp out of a carburated 350 is a bit of a stretch.

Not really. My 350 MPI engine is rated 330 hp.
http://www.michiganmotorz.com/Marine...07+replacement)
315 hp. But they are Vortec base engines.




I said mine was the MPI. The link is to a 315 hp carbed motor. And the
400's sucked in cars also, the cooling left a lot to be desired.