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lazyade 01-12-2013 12:05 PM

350 MCX, water leaking around intake manifold
Anyone had problems with water leaks around the intake manifold before (and fixed it)?!

After installing our new engine we've got a water leak, seemingly coming from the top of the intake manifold (right above the cylinder intake on #2 cylinder, by the rocker cover). We've had the intake of twice now to check the gasket was seated correctly but it still leaks (only when running).

One thought, we're using a reusable intake gasket (which seems quite thick). Anyone else use these, or do you guys stick with paper gaskets?

Any ideas? Keen to sort this out.



snork 01-12-2013 12:57 PM

does the intake and block fit well without the gasket?, could be a flawed intake

Rossterman 01-12-2013 02:02 PM

Also could be the heads and/or block were milled causing the base of the manifold to prevent the gasket on the intake port to not have enough compression. Back in the old days, they made different thickness gaskets (thicker on the intake port pieces) to alleviate this. You may want to remove the intake and put it back together with the gaskets at the front and back removed. Tighten it down slightly and see if the gap between the manifold and block is too small- that will tell you whether the heads and/ or block were milled. If so, i would look for thicker gaskets for the intake ports to allow better sealing or possibly milling the bottom of the manifold.

See this better explained here:

lazyade 01-13-2013 02:50 PM

Thanks for comments. Re-looking at it today the gasket I thought were reusable probably aren't. They've got a small rubber bead that runs round each port. But holding the gasket flat none of the rubber seal appears to be proud of the service, therefore I can't see how it can seal. I expect they were compressed on the first use.

Also the gasket has inserted metal spaces where the bolts go through, therefore there is no way the gasket can compress.

Having done some more research on intake gaskets it looks like there are Vortec and non-Vortec ones, I'm wondering if we've got the wrong one (ours is a Vortec model). If we can get a paper gasket I expect this will compress better around the ports, will do some research tomorrow.

Nothing is ever simple !

PureInboards 01-14-2013 02:55 PM

Vortec ones have different bolt pattern than traditional heads so you can't interchange them. Also those plastic/rubber combos may look reusable but just don't even go there get new ones every time or else you will always have issues sealing unless you get real lucky

lazyade 01-15-2013 02:40 PM

2 Attachment(s)
We've tried again to re-fit the intake manifold, but it's leaking again. I've put a couple of photos below. We think there are two problems: 1) we ordered a Mercruiser Vortec gasket (for a Chevy small block), but this has pure rectangular ports (see the 2nd photo below), the water ports on the Indmar intake have an extra cut out (you can see the imprint of the correct gasket on photo #2); and 2) we had to fill our intake as it wasn't flush, but the filler seems to have not set with a flat surface (even though it was rated for engines).

Can anyone offer any tips on how to repair intake manifolds? It looks like the previous owner hadn't flushed through the intake properly, hence the corrosion.

I guess one good thing, I'm becoming an expert at setting the timing up!

Rossterman 01-21-2013 09:49 PM

You are going to need a good surface on the manifold to seal to. Looks like some corrosion damaged the surface and was repaired with some type of epoxy? If so, you may want to use something stronger like JB weld, build up above surface level, and then file flush. I'd also use some hard setting permatex around the gasket and let set overnight before putting into service as an extra precaution. You could try to have it tig welded but it may become warped with the heat and ruin it rather fit it if the welder isn't highly experienced. I went the welding route once and worked fine but the welder had 40 year experience as a welding instructor and had done a bunch of these before.

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