Engine building help needed.

[dtanker65]

Anybody willing to share a secret to getting intake manifold gaskets to seal? I have a recurring problem on my old Mustang. I am pretty sure the gasket is failing on one of the back two ports on the left side. I keep oil fouling the back two plugs, sucking oil from the case I am pretty sure. The last time it happened, when I pulled the carb there was an oil trail in both of the problem cylinder intake runners. I tried silicone around the ports on a FelPro gasket but it failed again I think. The motor is a 408W with RHS 225 cfm heads and there is not much meat on the head gasket mating surface around the ports. The engine is all new except for the block.

[Suck fumes]

Ultra grey RTV

[marshall_mosty]

Dennis,
I use Ultra Black RTV on the coolant passage ports and also a dollup between 2/3 and 6/7 to hold the gasket in place. I also ditch the cork gaskets on the front/rear and just lay a really thick bead of RTV down.

[Alien]

When you say new, you mean new heads that haven't been milled? Was the block decked? In some cases if that has been done, the intake would also need to be milled down too.

[dtanker65]

Thanks Marshall,
I have only had this problem once before when I used an aluminum intake off of a blown motor that had overheated and warped the intake. I have always ditched the cork seals in favor of silicone and mostly just used copper coat on both sides of the gasket on the ports and passages. I think I am going to pull the intake and look real closely at the gasket on the 3/4 ports. I suspect the intake is not clamping the gasket enough on the bottom of the ports, if the gasket has failed again I may replace the intake. The gasket is real skinny on the bottom third of the port.

[dtanker65]

Block was decked and bored .030 over, everything else is brand new. The heads are new I assembled them with new valves and seals so I don't think it is a valve seal. I hadn't considered the intake needing to be milled, how would I measure this?

[mach1]

What gaskets are you using, 1262?

[Storm Trooper]

Anybody willing to share a secret to getting intake manifold gaskets to seal? I have a recurring problem on my old Mustang. I am pretty sure the gasket is failing on one of the back two ports on the left side. I keep oil fouling the back two plugs, sucking oil from the case I am pretty sure. The last time it happened, when I pulled the carb there was an oil trail in both of the problem cylinder intake runners. I tried silicone around the ports on a FelPro gasket but it failed again I think. The motor is a 408W with RHS 225 cfm heads and there is not much meat on the head gasket mating surface around the ports. The engine is all new except for the block.

Do you need a whole Lotta Chevy Orange on that motor!!!! :-)

[Pranav]

It is standard SOP in SBC/LT1 land to have the intake milled down to better fit a long block with heads that have also been milled (or the block deck milled).

I know my first two builds suffered from poor intake sealing and extreme difficulty in getting bolt holes to line up. Now that I've had my intake milled on the last two builds, bolt holes line up perfectly and intake gaskets seal/crush well.

I have a couple of "virgin" LT1 intakes sitting in my garage; compared to the milled one on my current motor the flanges are waaay thicker.

[mach1]

What is your intake torque procedure, what torque are you using. I have also had luck with ultra gray on the ends vs cork or rubber. I also spread rtv around the water ports.