Exhaust Gaskets for Closed Cooling System - 4.3

[big zeke]

My 4.3 was pulled last fall to allow some transom repairs, during the pull, apparently someone loosened the exhaust elbows off (I was told it made disconnecting the Y pipe easier). The engine has been sitting on a stand in my garage and today I pressure tested the cooling loop (it's a Merc closed loop system, just about as easy as pressure testing a car). A small leak where the elbow bolts to the port exh manifold was obvious in seconds. I torqued down the 4 hold-down bolts and the system held 15# for about 30 mins (while I ate supper). I normally don't like to reuse gaskets esp once the have had a leak cross them and when I went online I found several gaskets that fit this spot on a 4.3. It looks like there is an open, a closed and a restricted gasket, my first guess is that the "closed" one is suited for this application as the others would let the antifreese be pumped into the exh manifold and off to the sea. Can anyone confirm which is the correct Merc part number for this application...the choices are:
closed: 27-860231
open: 27-818832
restricted: 27-41813

Thanks in advance for the help...you guys are brilliant

Zeke

 

[achris]

Re: Exhaust Gaskets for Closed Cooling System - 4.3

Engine serial number? Or at least a year that will get us in the ball park.... 4.3 has been around since 1985, and in many variants....

 

[big zeke]

Re: Exhaust Gaskets for Closed Cooling System - 4.3

Ya, we've been down this road before Chris. There is no discernable serial number on this engine. The last time you helped me with this (the missing timing marks from about a month ago) we concluded it was a 93-95 engine Thunderbolt 4, 4bbl, vortec and probably a Gen2. Perhaps I'm wrong here but the closed loop system is the same over many model years, no? Oh ya, 2 piece exhaust manifolds. Does any of this help?

 

[achris]

Re: Exhaust Gaskets for Closed Cooling System - 4.3

ok... That was you...

Your exhaust manifolds and elbows, dry joint or the older wet-joint? If you don't know, post a photo...

If they are dry-joint the gaskets are SERIOUSLY expensive (like about $90 each in Australia), part # 27-864549A02

Wet-joint exhaust system gasket part # 27-41811 (supersedes to 27-8637251)

Chris.......

 

[big zeke]

Re: Exhaust Gaskets for Closed Cooling System - 4.3

Sounds great Chris, the elbow is a wet joint style and the part number you have indicated corresponds to the "closed" gasket. This makes sense as the mechanic that did my rebuild several years ago commented that he mistakenly ordered the open gaskets and if he had put them in I would have pumped the cooling system empty in a about a minute (he was trying to explain a delay in completing the engine).

Thanks a ton
Zeke

 

[Don S]

Re: Exhaust Gaskets for Closed Cooling System - 4.3

This service bulletin may help.

View attachment 99_10 Exhaust Gaskets.pdf

 

[big zeke]

Re: Exhaust Gaskets for Closed Cooling System - 4.3

Ok guys...this just keeps getting weirder. I pulled off one of the elbows and found a solid gasket (the above P/N that indicates closed) adhered to the exhaust manifold, another identical stuck to the mating surface of the elbow and a piece of stainless steel (slightly thicker than tinfoil but really stiff) in between these gaskets. I am comfortable that I need gaskets that block off the antifreeze passages as this is closed loop cooling but I have no idea what to make of this stainless plate gasket of it I can re-use it (it would never have come in contact with any liquid as it is sandwiched between the gaskets). My best gues is that it is used to make sure the paper gaskets never blow out or distort under the cooling system pressure.

Any insights into this configuration? Can I reuse this stainless plate? Does this thing have a part number just in case I want to replace it?

 

[achris]

Re: Exhaust Gaskets for Closed Cooling System - 4.3

I haven't seen one of the new gaskets, but I believe what you are seeing is one of them. It's a stainless plate sandwiched between 2 gaskets, and all adhered together. It's a single part that has come apart.

Chris.....

 

[tazrig]

Re: Exhaust Gaskets for Closed Cooling System - 4.3

I haven't seen one of the new gaskets, but I believe what you are seeing is one of them. It's a stainless plate sandwiched between 2 gaskets, and all adhered together. It's a single part that has come apart.

Chris.....

I saw one of the new style of gaskets just the other day but for a V-8. Chris is correct. It is a thin textured piece of metal in between two gaskets but is meant to be all one piece. If it's come apart you're probably best off not re-using it just to be on the safe side.