250 6 cylinder exhaust manifold leak

[Conroe trucker]

Hello Guys,

I have a rebuilt 250 6 cylinder engine and am having hell getting the exhaust manifold to seal after the first cylinder at the bottom.

I am also curious if the exhaust preheat valve could be sticking and causing additional back preasure.
It is not sticking, but what if I wired it open?
Picture on the left is at rest while warm.
Picture at the right is under some tension to old in that position.
Can anyone tell me which off these is the open position?

I have a really quiet muffler on it, so I expect I have some back preasure anyway.

I put the second gasket on and it did not seal at all, looking for ideas.

I thought I read that you must put the intake and exhaust on together but not bolted up, tighten everything, then tighten the preheat cavity.

Also looking for a tuning schematic for the 1BBL carbs if you might know where to find one.

Mike
CUSTOMAL@FLASH.NET

[Wood Booger]

I have not put my engine together yet, but I I just met a guy that built some pretty sweet sixes and he told me to coat the gasket with some high temp rtv and then let it dry before installing it. He also told me to get some good studs and use brass nuts. My preheat vaulve also has another little spring type thing between the manifold and the the spring that puts tention on the vaulve. I don't know if it limits the throw on the vaulve, or what, but it doesn't look like yours has that piece. I hope this helps I'll find out if it works when I put my engine together. Good luck.

[chevybuldr]

So did you have this surfaced? If not I would suggest it. Loosed the bottom bolts and put your manifold on and tighten it up. Then tighten up the bottom bolts. As for the gasket, Silicon is not good for high heat. Believe it or not use a thin layer grease. The grease will actually carbon and create a seal. On exhaust manfolds that we surface we always say no gaskets just a thin layer of grease. It works I know cause been like that for the last 10 years on my 'burb. Cause yours is a int/exh you cant do that but use some grease.

[Conroe trucker]

First, thanks to everyone for the ideas.

I have been told to also use copper gasket sealer.

I am going to try that, and if it fails, gease will be next.

Also I was told to remove the alignment studs and put bolts in there also. That really makes sense, but I will try the easy way out and use the copper gasket sealer first.

If all else fails I will have the manifold resurfaced.

Keep those ideas coming!

Mike