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Riser Gaskets

M

mzimmer

New member
I am not sure how the upper gaskets should be on my exhaust risers.
The bottom gaskets I am sure about, PORT is UN-Restricted, STARBOARD is RESTRICTED.
My question is the top gaskets... I'm pretty sure they should match the bottoms but wanted to ask someone before I torque them down.
Shown here is a picture of what I am talking about.
1999 Maxum 5.0 L V8 2 bbl. Open cooling

gaskets.gif
 
Depends on your cooling system.... If you have a heat exchanger, i.e. "Fresh water cooled" BOTH risers should be per the illustration for "starboard" top and bottom.... If raw water cooled, i.e. no heat exhanger, BOTH should be per the illustration for "port". REGARDLESS of type of cooling system, BOTH port and starboard are to be configured the same way..... gasket wise.
 
sandkicker said:
Depends on your cooling system.... If you have a heat exchanger, i.e. "Fresh water cooled" BOTH risers should be per the illustration for "starboard" top and bottom.... If raw water cooled, i.e. no heat exhanger, BOTH should be per the illustration for "port". REGARDLESS of type of cooling system, BOTH port and starboard are to be configured the same way..... gasket wise.
Click to expand...

It is raw water cooling, so no heat exchanger. Since I have restricter gaskets then I should put a restricter gasket on each side ?
When I took them apart I did not keep track of how the top gaskets where. The bottom gaskets are UN-Restricted on PORT, and Restricted on Starboard.

So on the PORT side I should put UN-RESTRICTED on bottom and RESTRICTED on top
and on STARBOARD I should put RESTRICTED on bottom and UNRESTRICTED on top

Does that sound correct ?
Thanks!
 
That is a miss print,
Instead of saying Port/starbord.
That image should have said cooling design 1 or design 2.

The full flowing as shown on left would be used when only ONE hose from thermostat housing goes to bottom of manifold.

Image on right is used with two hoses from thermostat housing where one goes to elbow and other goes to manifold. (More restrictive gasket)
And yes, use unrestricted on bottom below spacer on both sides and restricted (if cooling hose goes to elbow) between spacer and elbow
 
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kghost said:
Again, depends what cooling hoses go where.
That image would be for two hoses, one to manifold and other to elbow
Click to expand...

both exhaust manifolds get water from the thermostat hosing to the bottom of the manifold, no other hoses on manifold or risers.
lake water also enters the thermostat housing and output from the engine water pump.

So to balance pressure on both sides I should have one restricted and one unrestricted on each side ?
 
1. This is not a question of balancing flow. It is a matter of design. (RAW WATER SYSTEM ONLY)


This is how I see it, in other words, MY OPINION

TWO hoses calls for RESTRICTED gasket to restrict flow to ELBOW

ONE hose to exhaust manifold calls for UNRESTRICTED flow to ELBOW.


Design 1. TWO HOSES

TWO hoses, one to manifold and one to elbow. Cold fresh water flows all the time to ELBOW keeping exhaust cool to keep rubber from melting. Once thermostat fully opens to normal temperature that cold flow reduces to elbow and thermostat controlled water now flows thru manifold and out elbow thru open slots in gasket between manifold and elbow and mixes with COLD water from input hose to elbow. If spacers are used bottom gasket is unrestricted and upper gasket is restricted, Open gasket below spacer keeps spacer cool, if restricted gasket was used between manifold and spacer, spacer would get very hot..

Design 2. ONE HOSE

ONE single hose to bottom of Manifold ONLY. This design should have UNRESTRICTED gaskets to allow maximum water flow all the time through the elbow to cool exhaust rubber. If spacer is used BOTH gaskets should be unrestricted.



Below are two pages from 1998-2001 service manual #24 (see note at bottom in red outline)


cooling123.png

After reviewing two manuals it does not actually specify which gaskets to specifically use, restricted or unrestricted.

It clearly states to make sure you replace with the factory installed gaskets. so if you did not pay attention the final decision is up to you based on the note in the image I attached.

Next time, PAY ATTENTION
 
If as you state you have a raw water cooling system, how would the elbow with a restricted gasket get any cooling water ????

To recap what been said... and KGHost and O2bat sea.... one side of that diagram shows what gaskets on BOTH sides should be for ONE type of system...the other side for that other type of system... one hose (per side) = raw water cooled and NO restrictor gaskets , two hoses = freshwater (heat exchanger) and one restrictor gasket PER SIDE. BOTH SIDES NEED TO BE THE SAME.... if port and stbd on your engine were in fact "different" when you took it apart, then the last mechanic who worked on that engine was a rank amateur (at best!).
 
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Capt Bob,

A closed system will always have two hoses, one to elbow with raw cold water.
The other hose going to manifold bottom will be coolant mix with a return hose to closed system for circulation.
Between manifold and elbow will be a BLOCK OFF gasket.

Some raw water designs have two hoses as I described above.
My boat has two hoses and is raw water.

His boat is also raw water but has ONE hose to bottom of manifold. No second hose to elbow.
 
kghost said:
Capt Bob,

A closed system will always have two hoses, one to elbow with raw cold water.
The other hose going to manifold bottom will be coolant mix with a return hose to closed system for circulation.
Between manifold and elbow will be a BLOCK OFF gasket.

Some raw water designs have two hoses as I described above.
My boat has two hoses and is raw water.

His boat is also raw water but has ONE hose to bottom of manifold. No second hose to elbow.
Click to expand...


KG.... two hose raw water... is that the "warm manifold" setup ???
 
sandkicker said:
KG.... two hose raw water... is that the "warm manifold" setup ???
Click to expand...

Not sure what you mean.

My system has a restricted gasket between manifold and elbow.
I have raw cold water to both elbows.
I also have temperature controllled water to bottom of manifold.

I would think, "warm" manifold would be the one as the OP has.
Single hose to bottom of manifolds only.
 
Jack...

Just checked my notes... If the manifold is in the T stat "loop" ( temperature controlled water) its a " warm" manifold.... if its a one hose ( in manifold out elbow) its... "cold"... Warm manifold setups supposedly reduce condensation in the manifolds.
 
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