I ordered the wrong intake gaskets as I need the upper bolt holes for a 502 Mag. Fel Pro offers 17342 which is like the stock gaskets, with the rear water passage closed and a notch for the lifter valley pan tabs. But it will take much longer to get here. I see they also offer 1211 that doesn't have the rear water passage closed. Is it okay to use the 1211 as I can get that one tomorrow? I am in fresh water only.

I have read many posts that state they used the 1211 gasket but wanted to make sure.

The bottom gasket pictures looks like what was on my 502 MPIs but the openings for the water didn’t cover the bronze very well (similar gaskets didn’t cover the bronze at all on my Merlin intakes).

It may be better to order the factory replacement from Merc.

Not sure what you consider a lot longer but Summit has the 17342's in stock. You would probably have them Monday if you order them today.

I saw that Summit and Jegs had them Right now I am way behind and finally have some time this weekend so I wanted them yesterday. LOL

Local napa hub can’t get one to your local naoa store for tomorrow ?

No but they can get the FelPro 1211S-3, which is a heavy duty gasket as well. Just doesn't have the closed rear water passage.

if the head and intake are blocked off ?? it doesn't matter

Stock 502 MAG EFI intake so blocked off. I am am 99% sure I ran open rear gaskets on my last 502. I can't see how it would matter, but I don't like to assume things. I could see in salt it could eat away at the aluminum manifold.

Saltwater (even freshwater over time) will eat away at the intake even if the gaskets are closed. The closed section of the gasket stays wet and swells allowing water to get behind the gasket. You end up with with a nasty aluminum sludge.

I thread seal all intake bolts, yrs ago on a 502 mpi had one that would weep oil and a small puddle by the distributor over night.