Closed Cooling Manifolds or Not?

[SeattleMatt]

So I have a closed cooling system on my 5.7 that does not include the manifolds in the loop, they are raw cooled. I'm confused as to why they would do this and I have seen that most systems include the manifolds and only raw is the risers for output.

Is it possible and smart to convert to this system? I am replacing manifold and engine due to blown corroded manifold.

There are a lot of threaded plugs on both my risers and my manifolds so I assume i could convert fairly easily?

 

[HT32BSX115]

Re: Closed Cooling Manifolds or Not?

Howdy,

You can easily convert your closed (half) system to a "full" system.


You may have to replace your heat exchanger though as it might not be large enough to do both the engine and manifolds. The heat load is quite a bit more doing both.


Talk to San Juan Engineering in Bellingham Wa. They design and sell them.



Regards,


Rick

 

[SeattleMatt]

Re: Closed Cooling Manifolds or Not?

Really? That's not cost conducive, that would mean i'm not doing it.

 

[SeattleMatt]

Re: Closed Cooling Manifolds or Not?

Has anyone tried this without upgrading their HS?

 

[HT32BSX115]

Re: Closed Cooling Manifolds or Not?

I don't think there are many that have tried it.

You can only get a certain maximum amount of heat transfer in a given heat exchanger.

If the heat exchanger won't do the job, ( and while it might work ok at low idle/medium power) the engine will overheat quickly (at higher power settings) if the heat exchanger cannot do the job.


So, I guess you can try it..... The "down-side" will be an overheat.


For example, the infamous 3.7L, 470 Mercruiser engine had overheat problems with the originally installed 3" heat exchanger. Mercruiser finally upgraded newer models with a 4 inch heat exchanger which seemingly solved the over heat problem.

Unless you're a mechanical engineer and can do some fairly complicated heat transfer calculations, it would be better to just call San Juan or other manufacturer and give them your heat exchanger measurements and see if yours is approx big enough to do both the block and manifolds.

The 1/2 system heat exchangers are usually considered not "big" enough to do both....

 

[SeattleMatt]

Re: Closed Cooling Manifolds or Not?

Further investigation shows that I actually have an Orca heat exchanger on my system. I am going to give them a call and see what they say.

 

[fishaman]

Re: Closed Cooling Manifolds or Not?

I'd be very interested in the results... I am converting to a full system from half system now, my half system is also Orca. I believe Merc is not putting full systems on carbed engines for a while now for a number of reasons:
1) Flexibility, with half system you do not need any raw water pump modifications even for Alpha engines;
2) Cost... small exchanger always cheaper.
3) Reliability during the warranty period, less chance of a manifold/riser gasket failure when they are at the same temperature, and no water standing at the seam when not in use. Flip side is that you have to replace both manifold and riser at the same time after 4-5 years.

My old engine has a full system, and I am transferring it to a new half system engine with Orca exchanger. Full system exchanger is 5" diameter vs 4" Orca, and the water is going through it in 4 passes while half system has 2 or 3.

I think it also depends on where you boat, I have read at least one report of successful conversion without exchanger replacement in Puget sound area. It helps to have cooling water at about 53 degrees year round.

 

[SeattleMatt]

Re: Closed Cooling Manifolds or Not?

Yeah, the water temperature is definitely what I would be gambling on if I were to do it. At first glance it looks like it would need:

2 straight hose fittings to the risers for raw water out through risers ($10)
2 90 degree hose fittings for the manifolds for coolant back from manifolds ($10)
2 block off plates for risers ($20)
1 Closed Cooling Thermostat housing 55131A5 ($150!!)

The current HE has only one HOT input, so there would have to be a point where the two manifold outputs are combined for a single HOT hose input to the HE.

It looks like the flow is block > manifolds > HE > water pump > block >>
Hottest flow is back from top of manifolds to HE

One part that confuses me on the full system is that the thermostat housing has no bypass back to the engine.

This is starting to look expensive and difficult actually

Is it possible that the Alpha drive doesn't have enough water flow to do this?

 

[fishaman]

Re: Closed Cooling Manifolds or Not?

From what I know, a full system for 350 engine requires an engine mounted, like Bravo, raw water pump.