intake gaskets on 305 Ho

[David A Young]

Ok so I have an intake leak on the gmc. I installed a 305 high output cabureted out of a 87 firebird in my truck. I'm replacing the intake gaskets tomorrow and I'm wondering should I use rtv anywhere other than the China walls? And which way do the nipples go on the China wall gaskets? Thanks. Been a while since I've done any intake gaskets.

[LTZ C20]

Don't bother at all with gaskets for the walls, just use RTV with a bit extra at each end where it meets the heads. Then when you put the intake gaskets on, go in at an angle, about half way between flat against the head and straight up and down. Sink the tabs of the gaskets into the ends of the RTV.and then lay them over onto the heads as they should be installed without pulling them out of the RTV. Then allow the RTV to be come tacky (I think it's about 15 minutes wait time) once it's tacky, then set the intake manifold on and install the bolts finger tight. Then re tighten all the bolts in the correct order. Using 3 passes, tighten them to a low torque value, then a medium torque value and then the final torque value. Take the factory torque spec, divide it into 3rd's and that will be your first, second and final torque numbers. Also I recommend using "The Right Stuff" RTV in your choice if grey or black or General Motors Engine Sealant RTV.

[bd]

To augment LTZ's post, preparation and organization will improve the results.  While it's apart, clean all the bolts and bolt holes.  The intake manifold four center bolt holes on either flange open into the valley.  To prevent oil from seeping up around the intake bolts coat the clean bolt threads and underside of the bolt heads with high quality Teflon paste sealer (e.g., ARP, Loctite, Permatex, etc).  Then thoroughly clean and wipe the gasket surfaces of the China wall, intake and heads with lacquer thinner or naphtha.  Perform these steps before applying silicone to anything.  Also, I recommend smearing silicone on both sides of the intake gaskets at the four corners around the coolant crossover passages.  Then torque the intake bolts in sequence to ~50%, then ~80%, then 100% of final torque.  Wait for 1-2 hours (or more) and retorque the bolts in sequence to 100% of final torque.

[David A Young]

So just rtv the front and back walls and around the water ports? No rtf file around combustion chamber ports? And does it need to be on both sides of the gasket?

[bd]

Smear a sparing coat of silicone sealer on both sides of the gaskets around the coolant ports only.  This will help extend the life of the seal.  As long as you use a quality gasket set, you shouldn't need sealer on any other surfaces of either gasket.

[David A Young]

Fel pro from Napa is what I have for it. The kit comes with a distributor gasket and a larger circular gasket. Anyone know what the bigger one is for? Bigger od and id than the distributor gasket

[bd]

FelPro makes a good product.

[David A Young]

Yep they make good stuff

[bd]

The kit comes with a distributor gasket and a larger circular gasket. Anyone know what the bigger one is for? Bigger od and id than the distributor gasket.

FelPro typically inventories the box contents on their label.  What does the label indicate?

[Rattler12]

Water inlet/Thermostat cover?

[LTZ C20]

To augment LTZ's post, preparation and organization will improve the results.  While it's apart, clean all the bolts and bolt holes.  The intake manifold four center bolt holes on either flange open into the valley.  To prevent oil from seeping up around the intake bolts coat the clean bolt threads and underside of the bolt heads with high quality Teflon paste sealer (e.g., ARP, Loctite, Permatex, etc).  Then thoroughly clean and wipe the gasket surfaces of the China wall, intake and heads with lacquer thinner or naphtha.  Perform these steps before applying silicone to anything.  Also, I recommend smearing silicone on both sides of the intake gaskets at the four corners around the coolant crossover passages.  Then torque the intake bolts in sequence to ~50%, then ~80%, then 100% of final torque.  Wait for 1-2 hours (or more) and retorque the bolts in sequence to 100% of final torque.

Oh yea this too. But to be honest, if you don't have lacquer thinner or naphtha, brake clean works great too. It's fast drying, it evaporates and cleans excellent. Just spray some on a clean rag and wipe the surfaces down.

[LTZ C20]

FelPro makes a good product.

Yep.

[David A Young]

The box says it has two distributor gaskets. The smaller one looks like the one Ive always used on a sbc distributor but the bigger one I don't recall ever using on anything. But much to my dismay I was in the process of changing the gaskets today and the intake is cracked at the bottom of the center port on the drivers side. Which is were it was leaking from in the first place. So ill be searching for an intake. Edelbrock most likely. Seems to be the cheaper choice. Edelbrock 2104 seems to be the right intake. The GM part # is 14101074.