Intake manifold not fitting flush

[78SierraGrandeTX]

Hello All,

I am having an issue where I have a “gap” between the intake and the rear China wall. This gap is just below the distributor. It is wide enough where I can fit the distributor gasket underneath the intake.

I have tried 2 different intakes and still have the same issue. It fits flush everywhere else and all bolt holes lineup. At this point I’m just gonna assume the previous owner just build up that area with gasket maker to fill it.

Does anyone have any insight on this? I have search into this and haven’t seen anyone else having this problem.

 

[Dmack]

Most engine builds I have seen they use a large bead of rtv on both the front and rear China rails. Much better chance of not having leaks than the factory gaskets.

 

[dvdswan]

Some gasket kits for SB engines have gaskets for the china walls.

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[shiftpro]

That's normal. As Dave said above, use rtv... the black ****... The Right Stuff. I like to measure the gap and get an idea how much there is to fill. Then on the perfectly clean china wall, I'll lay a bead and let it set up. I'll 'fill' in the edges to thicken it. I'll shoot for building it up almost to close the gap and after it's well set, I'll apply more and then actually set the intake on it to torque down. Good luck. If done correctly it will never leak.

 

[shiftpro]

Some gasket kits for SB engines have gaskets for the china walls.

You must be registered for see images attach

Many of us have found better luck just using the RTV and tossing the rubber china fillers.

 

[Raider L]

Yeah, unfortunately those rubber gaskets pieces don't seal very well and will leak after awhile. You'd think they would have made something better to put at the back of the block. These things were used on the early blocks with smaller heads that allowed the intake to sit lower and tighter. So the little gaskets worked and at first they do work and the engineers felt they were sufficient for the 350's and 400's. The design changes went into the head gasket sides and they just didn't bother with the ones for the front and rear.

If you bother with actually read the instructions it does say apply some rtv in those corners, the edge of those little rubber gaskets and the side gaskets. The trick would have been to make a one piece gasket with a blue or red bead down the middle like the side gaskets have, for the end parts of the block, for the one piece gasket.

Yeah, just put a healthy bead of either red or black RTV on the front and rear block.

 

[Raider L]

I thought I had a pic of what the RTV bead looked like on my engine. I'll post it but you may have to look hard to see it.

You must be registered for see images attach

 

[Rusty Nail]

Everything else is the same? I have never once used the supplied gasket there - always ran silicone instead and yeah - it's a big gap. Same distributor you took out and everything huh?

 

[ali_c20]

I never used the gasket. Just a fat bead of RTV. Never failed.

 

[dvdswan]

Many of us have found better luck just using the RTV and tossing the rubber china fillers.

I agree. I does work a lot better without the rubber pieces. I was just pointing out he could fill his gap with one if it was big enough.

 

[78SierraGrandeTX]

Thank you all for the information! I appreciate it. I will be using RTV to close the gap.

 

[shiftpro]

I agree. I does work a lot better without the rubber pieces. I was just pointing out he could fill his gap with one if it was big enough.

When I first heard that, chuck the china gasket, I just couldn't believe it. Buddy of mine who was an engine builder also told me and he gave me the tip of building up a ridge first and then hit ti again and install the intake.

I've also successfully repaired leaks over the rear china wall without pulling the intake. Lots of brake cleaner in there, and dry with paper towels. Compressed air and then push Right Stuff into it.

I think that building up a ridge first really is the safest way too, as too much sealant all at once might squeeze a blob out that ends up in the oil pump's screen.

 

[Michael Benardo]

Yeah, unfortunately those rubber gaskets pieces don't seal very well and will leak after awhile. You'd think they would have made something better to put at the back of the block. These things were used on the early blocks with smaller heads that allowed the intake to sit lower and tighter. So the little gaskets worked and at first they do work and the engineers felt they were sufficient for the 350's and 400's. The design changes went into the head gasket sides and they just didn't bother with the ones for the front and rear.

If you bother with actually read the instructions it does say apply some rtv in those corners, the edge of those little rubber gaskets and the side gaskets. The trick would have been to make a one piece gasket with a blue or red bead down the middle like the side gaskets have, for the end parts of the block, for the one piece gasket.

Yeah, just put a healthy bead of either red or black RTV on the front and rear block.

Double up on those gaskets, then you will have no problem, and I use soft-setting gasket cement rather than RTV.