The while you are doing this you might as well Syndrome-gctid396384

[Guest]

I have a 1987 Ciera Sunbridge 2455 with a GM 305 (5liter) and a cobra out drive. The boat / engine has very little hours, but and I have a bad leak by the fitting on the bottom of the oil pain. I am a pretty good wr0ench but I cannot tighten the fitting enough to stop the leak.

Now I am faced with needing to pull the engine to fix the problem. So my while you are doing this you might as well do that syndrome kicks in. I do have a budget for parts (since I plan on doing all the work) is 3 to 4 K. In a perfect world I would like to spend around 2K on the engine upgrade, and around 2K on replacing the out drive

1st

The engine would you replace, (that will put me over budget unless I go used) or put new cam, pushrods and lifters , I have a brand new holly spread bore carb on the engine now. I would like to somehow increase the horsepower of my existing engine.

2nd

I will definitely replace the out drive; are there any good outdrives I can purchase that will keep me under my 2K budget?

[Guest]

You cannot increase usable HP on this engine. Putting in a cam and other items will make less usable power for this boat and engine. Don't do it.

You MIGHT get a bit of good HP by upgrading the manifold, I don't know what you have on there now, nor am I familiar with the spread bore carb. What is its CFM?

[2850Bounty]

You can indeed increase hp and torque by going to a LC Q/E style piston.

That, along with your other proposed upgrades, will increase performance.

Since you mentioned a drive replacement, another good bang for the dollar may be the OMC to DP-S conversion.

.

[Chief_Alen]

Low hour 5.0l i would keep it, throw on a 4 barrel. That alone will increase hp. Leave the cobra alone if it shifts good.

Got a mirror take a good look at the drain plug where exactly is it leaking from, maybe you stripped out the threads on the plug. There are other options before you pull the engine.

[Guest]

The Holly Spread Bore (650 CFM) carburetor is a replacement for the Factory installed Quaddrajet (Spelling??) carburetor.

What intake manifold would you recommend ?? I did not realize I could not increase the horsepower by changing the cams etc.

2850 Bounty: What piston, cam combination would you recommend? Would you also recommend an intake manifold, if so which one would you recommend ??

[2850Bounty]

mrrickb wrote:


2850 Bounty: What piston, cam combination would you recommend? Would you also recommend an intake manifold, if so which one would you recommend ??

mrrickb, I responded to your question earlier without much explanation, but to make a point regarding increasing power.

Yes.... you can pick up hp and torque by doing a q/e build, changing cam profile and intake manifold/carburetor.

However, the 5.0L will never produce the power/torque that a well built 5.7L will.

If you are going to do this, you may as well begin with a 5.7L cylinder block, cylinder heads and crankshaft.

5.7L bore/stroke = 4.000" X 3.480"

5.0L bore/stroke = 3.736" x 3.480"

The stroke is the same, crankshafts are not.

In many cases, you can actually build a 5.7L for less money than you can a 5.0L.

You mentioned Rochester Quadrajet. If you now have the Q-jet, there is no need to change the dual plane intake manifold.

A CFM calculator shows that a Marine 5.0L engine requires no more than 353.009 CFM @ 4k RPM.... and we don't run for long @ 4k RPM.

At the same RPM, a Marine 5.7L requires only 405.093 CFM.

The piston style that I'd use would be either a D-Dish, Low Compression Quench, or Reverse Dome style piston (depending on cylinder head chamber style).

The chamber size and desired static C/R will determine piston profile (i.e., dish volume).

Quench area is what we're after, and will be as close to .038" - .040" and we can get it.

These pistons can be bought in a good quality Hypereutectic material, yet they won't break the boat bank.

Nothing else to the build needs to change.

.

[Guest]

I found a brand new vortex 350 / 325 horse for around 3 k , will this most cost effective way to get to a 325 horse engine???

[2850Bounty]

mrrickb wrote:
I found a brand new vortex 350 / 325 horse for around 3 k , will this most cost effective way to get to a 325 horse engine???

That would be a good choice, but you'll still have the full dished pistons, unless it was custom built.

Also, look at the RPM at which the hp rating is taken.

I believe that these are rated at 5.2k rpm. We don't run at 5.2k rpm, so realistically, that hp number is not accurate for our usage.

I'm not saying don't do it, just giving you some info.

Earlier you mentioned doing all the work.

Why not build your own 5.7L where you have control over the internal component selections?

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[Guest]

I would love to do that but I need two things;

1st budget of no more than 3K (I am also planning on buying a new outdrive)

2nd Someone to tell me what to buy and where to buy everything , and advice on assembly

If you can help me in these areas I can start immediately and would be happy to post my progress for anyone else that might be interested in doing the same. But I am not looking to go crazy; 325 horsepower will be fine, I am looking for reliability good gas mileage and the engine will be raw water cooled (salt water)????

[2850Bounty]

I've been looking at your user name, and trying to figure out what your first name is.

Is it Rick, as in Mr. Rick B, or something else?

mrrickb wrote:
I would love to do that but I need two things;

1st budget of no more than 3K (I am also planning on buying a new outdrive)

2nd Someone to tell me what to buy and where to buy everything , and advice on assembly

If you can help me in these areas I can start immediately and would be happy to post my progress for anyone else that might be interested in doing the same. But I am not looking to go crazy; 325 horsepower will be fine, I am looking for reliability good gas mileage and the engine will be raw water cooled (salt water)????

If you purchase your own parts and do your own assembly, you can bring this in within a decent budget. (not sure about including a drive in the budget)

This piston type is not all that much more expensive unless you were to go nuts with high dollar forged pistons, etc.

A good Hypereutectic piston works just fine.

There's nothing out of the ordinary that your machine shop needs to know or do.

However, it would be good to stay in communication with them, so they know just what type of build you are wanting to achieve.

CAUTION: some machine shops are so prone to doing the common and ordinary full dished piston build, that they may try to convince you from doing a Q/E build.

This suggests to me that they have limited knowledge regarding the SBC Marine Engines.

Don't let the Nah-Sayers get to you!

This subject has come up more often over the last few years, so I've ear marked a few threads.

Apexaro1 started this thread March 20th.

http://www.baylinerownersclub.org/forum/showthread.php?69478-5-7-mercruiser-rebuild/page2

Then Andrew1 started this thread shortly after.

http://www.baylinerownersclub.org/forum/showthread.php?69504-5-7-volvo-rebuilt-or

Our member Giddy-Up also started a thread which turned to this same topic.

http://www.baylinerownersclub.org/forum/showthread.php?68232-Where-to-buy-SBC-Marine-pistons

All three may be good for you to read.

I have not followed up to see if they actually did this build, but we could steer you to those who have.

Jeff H being one, Dave M. in Spokane, Mike Emm another, and myself many times over.

MichiganMotors is also willing to do this build on a custom order basis.

The quench effect or squish zone is nothing new, and it can apply to any engine that has a wedge portion to the combustion chamber.

The Chrysler Wedge Head boys have been savvy to this for years.

The original 265 cu in SBC incorporated this very same principle back in 1955, and it pretty remained until the 70's when emission controls became mandated.

In came longer runners, smaller combustion chambers, and the full dished pistons! Unfortunately these remained! :thumb

https://"http://www.baylinerownerscl...his thread</b> and read the paragraph "A note of particular importance".

When we give these engines a Quench dimension, we can also give them more ignition lead with less potential for detonation.

Static C/R can also be bumped up a bit, whereas with the full dished we don't dare.

The video and LPCP explanation may help you understand why this works well to develop more hp and torque.

Have fun!

BTW, I sure hate to see you do this do all of this, and then return it to being RWC'd. :sorrow:

Nothing topic for another day!

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[Guest]

The name is Rick. Thanks you for the links. When I said I wanted to do it myself, I would do all the work / assembly . I am very well equipped and have much experience rebuilding (disassembly / assembly) of Porsche 911 engines (air cooled). I have no experience with boats and understand the importance of where your power band of usable power is available. That is why I said if I had someone to tell me / sell me the right combination of parts to get 325 horsepower and keep me at under 3K I am ready to go for it, Once I decide on an engine I will make a decision on the outdrive.

[2850Bounty]

The machine work and assemby will be very much the same as if this was an auto engine. There will be a few differences in parts selections (pistons, camshaft, dual plane intake manifold, etc.)

If you plan to RWC this, you'll need the Marine head gasket set. I don't know if there is a quench style gasket in the marine version. It make require some searching.

The bronze casting core plugs are easy to find.

Once you select bore/stroke, cylinder head and chamber volume, decide upon a static C/R, then you simply plug numbers into one of the on-line static C/R calculators.

You'll play with the numbers (bore/stroke, deck height, compressed head gasket thickness), and can then make a dish volume determination based on you desired C/R.

From there, you decide upon a quench style piston.

The rest is pretty straight foward.

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