Closed cooling system: Mercruiser manifold and risers with Volvo Y Pipe?

[oregonrafter]

I'm replacing my Volvo 305 with a rebuilt chevy 350, and I want to use a full cooling system (engine coolant circulates through engine and manifolds). As far as I know, there is no Volvo riser and manifold combination that will work for this configuration. The mechanics I have talked-to, say that Volvo does not make a full closed cooling system, and that I will probably have to convert to Mercruiser components if I want to do this. My question is, have any of you done this? If so, what is required for the conversion? I'm concerned about the connection from a Mercruiser riser to a Volvo Y pipe. My concerns are as follows:
1) Is the Mercruiser manifold and riser a similar height to the Volvo manifold and riser? If not, how big of a spacer do you need between the manifold & riser?
2) I understand that the Volvo riser diameter (output end) is approximately 3 3/4" and the Mercruiser is 4". How do you deal with the change in diameter?
3) is the Volvo riser output angle similar to the Mercruiser riser angle? If not, how do you deal with this?

Thanks for your help! -Mike

 

[dypcdiver]

Re: Closed cooling system: Mercruiser manifold and risers with Volvo Y Pipe?

The full closed system on a VP 350 is done with a blanking plate for the water passages between the riser and manifold. Raw water from the heat exchanger is then fed into the riser and out through the exhaust as normal, no need to try and mix VP and Merc parts. However you will need an extra large heat exchanger to keep pace with the heat generated by the manifolds, hence the reason most systems are half systems.
See this post http://forums.iboats.com/volvo-pent...sh-water-cooling-half-full-system-639219.html

 

[Scott Danforth]

Re: Closed cooling system: Mercruiser manifold and risers with Volvo Y Pipe?

you need a larger heat exchanger to to go a full system. while the factory VP manifolds and risers are not machined for the additional ports needed, many of the aftermarket ones from BARR and others are.

not knowing which year volvo you have, can not answer if the mercruiser parts would work. however I know that the angles are not the same between my 1988 AQ271C and any mercruiser.

 

[oregonrafter]

Re: Closed cooling system: Mercruiser manifold and risers with Volvo Y Pipe?

The full closed system on a VP 350 is done with a blanking plate for the water passages between the riser and manifold. Raw water from the heat exchanger is then fed into the riser and out through the exhaust as normal, no need to try and mix VP and Merc parts. However you will need an extra large heat exchanger to keep pace with the heat generated by the manifolds, hence the reason most systems are half systems.
See this post http://forums.iboats.com/volvo-pent...sh-water-cooling-half-full-system-639219.html

The current risers & manifolds I have are center-rise Volvo Penta. The engine I'm using is an early chevy block ('69-'91) 350. I have been told by several manifold suppliers not to try a block-off gasket on the typical center-rise manifold & riser, because they are prone to premature failure. They said it would last for a year or so, but won't last much longer than this. For this reason, they said to go to a Mercruiser setup for longevity. If you search for a block-off plate for these manifolds and risers, you won't find many of them (if any), and supposedly, there is a good reason for this.

I already have a good, large heat exchanger made by San Juan Cooling.

 

[bruceb58]

Re: Closed cooling system: Mercruiser manifold and risers with Volvo Y Pipe?

I already have a good, large heat exchanger made by San Juan Cooling.

Have you called them to confirm this? heat exchanger needs to be almost double the size to do a full system.

 

[oregonrafter]

Re: Closed cooling system: Mercruiser manifold and risers with Volvo Y Pipe?

Have you called them to confirm this? heat exchanger needs to be almost double the size to do a full system.

Thanks for your concern. My question is about which manifolds and risers to use, not about heat exchangers.

 

[dypcdiver]

Re: Closed cooling system: Mercruiser manifold and risers with Volvo Y Pipe?

They said it would last for a year or so, but won't last much longer than this. For this reason, they said to go to a Mercruiser setup for longevity. If you search for a block-off plate for these manifolds and risers, you won't find many of them (if any), and supposedly, there is a good reason for this. .

Then surely these are the people with the knowledge of what will fit from Merc on your Volvo/Chevy.

 

[Scott Danforth]

Re: Closed cooling system: Mercruiser manifold and risers with Volvo Y Pipe?

if you want it to fit the stock volvo Y-pipe, you need volvo EM and risers. if you want it to work with your closed cooling system, they have to be aftermarket to get the extra ports needed, and you need a block-off plate and two gaskets per side.

16 gauge stainless for the block off plate

Barr makes manifolds and risers that have the extra port boss. not all of them are drilled and tapped.

you may have to drill and tap the ports, and most likely you will be making your block off plates.

if your going thru this much trouble, get aluminum manifolds then for the weight, and have custom stainless risers made.