Sealing intake manifold?

[ChuckN]

What do you guys prefer as far as intake RTV?

I had an intake leak at all four corners and maybe in the intake ports as well since I have a miss that I can’t find the cause of.

The water jackets had ultra grey on both sides. I can’t see any interruption in the RTV where it was bolted down, on either side. Yet I was having coolant leak at the corners.

Also, I want to do a better job of sealing the intake ports and I know it will get exposed to gasoline. But it will need to take up space for any imperfections in the angles of the mating surfaces.

Any recommendations? Thanks in advance.

Chad

 

[xm20k]

The bolts on the outer ends by the water passages on some aftermarket heads are not blind and can leak they need sealer as well.

Ultra grey is good anywhere it comes in contact with oil and fuel.

I run a thin film on the water passage ends of the gaskets and carry that into a 1/4"n thick bead over the China walls front and rear and on the 4 corner bolts on mine. Let it sit for about 10-20 min before dropping the intake in place.

 

[ChuckN]

Ok, I’ll try again then. My corner holes are blind, just checked. Even still, I put ARP thread sealant on every bolt and it still leaked. I’m kinda stumped, I’ve never had one fight me like this before. I had ultra grey on both sides of the gasket on the water passages.

 

[xm20k]

Are you sure the bolts are not too long? I've seen that as well they bottom out feel and look like they are correct but just long enough that most of the manifold does not seal. There are a couple lengths for a small block, I've had it happen.

 

[WFarm]

Are you sure the bolts are not too long? I've seen that as well they bottom out feel and look like they are correct but just long enough that most of the manifold does not seal. There are a couple lengths for a small block, I've had it happen.

Yes. I’ve seen multi-million dollar machines fired up after maintenance, only to be shut down due to unexplained leaks. Proper sealants and torques had been used but new fasteners were a bit too long. They installed and torqued fine but provided very little clamping force as you were torquing against the bottom of the bolt hole.

 

[ChuckN]

Are you sure the bolts are not too long? I've seen that as well they bottom out feel and look like they are correct but just long enough that most of the manifold does not seal. There are a couple lengths for a small block, I've had it happen.

I might try some washers under the corner bolts and see if I can get a little more oomph on them. I think you’re onto something.

 

[hogdaddy]

Tell us some more. What heads, intake, gasket?

 

[ChuckN]

@hogdaddy Heads are Brodix IK 200. Performer RPM intake.

Brodix recommends FelPro 1206, but when I fit tested them, they are too thin for the combination and the intake sat so low it wouldn’t seal at the top of the intake ports very well. So I used FelPro 1266 and that much improved the location of the ports.

 

[hogdaddy]

Was the block decked and how much?

 

[ChuckN]

Was the block decked and how much?

Well, I never got a final answer from the shop, because he was aiming for 5 thousandths in the hole. So if stock is 25 , then that would mean .020?

 

[hogdaddy]

Which block?

 

[ChuckN]

1976 350 010 4-bolt. @hogdaddy

 

[Ricko1966]

Did you get your problem solved? If not are you going to have the manifold back off? If so bolt the manifold to one head only with an old gasket. Check the clearance to the other head and to the China wall. Check the manifold to head clearance on the loose side to make sure it is parallel front to back and top to bottom. Those things will tell you what thickness gaskets you need, and whether the manifold needs machining.

 

[ChuckN]

Did you get your problem solved? If not are you going to have the manifold back off? If so bolt the manifold to one head only with an old gasket. Check the clearance to the other head and to the China wall. Check the manifold to had clearance on the loose side to make sure it is parallel front to back and top to bottom. Those things will tell you what thickness gaskets you need, and w whether the manifold needs machining.

Good idea, thanks bud. What I’m picking up is that will show if the china wall is parallel to the end of the manifold on the horizontal plane and then also how much clearance I have on the other side (no gasket).

 

[Ricko1966]

Also it will tell if your gasket mating surface on the manifold is parallel to the head,If the manifold is bottoming out on the China wall.If the top edge of the port is closer to the manifold than the bottom and whether the manifold is parallel end to end(no taper). If everything's not parallel you are going to have a rough time trying to get things to seal.