Questions about Cast Iron Intake and heads

[71CHEVYSHORTBED402]

Working on a 71 402 with cast iron heads and intake. I did not rebuild the engine, only swapped out the pump and chain. It's still on the last rebuild, ran like a top, and hopefully still does.


By some measure this is a duplicate thread. I started one elsewhere, there weren't many responses, but more than that this has grown into something more. That's what happens when you're new at all this

Near as I can tell there's only one intake manifold gasket option for this application, which is a Fel-Pro 90240. They say NO to sealant anywhere but the four corners, because it can break the gasket never mind ruin the intent. They say you must level out the pitting however, either with metal epoxy or you're off to a machine shop. So yeah, I have some pitting around the water ports. Has anyone dealt with this and how did you remedy? At this point I'm leaning to using JB Weld.

Also, any thoughts on the hole on back of the intake? See pictures, all input appreciated, thank you.

[geezer#99]

Contrary to what they say I use a light film of form a gasket around all the ports on the head side.
Don’t use the end gaskets. Run a 1/4 inch deep bead of silicone instead.
Don’t use jb weld. Hard to make it level again.
Those pins are what were used to hold the oil splash shield onto the bottom of the intake.
The shield keeps your intake plenum from getting too hot. Yours was removed.

Also to answer a question in your other thread about the rear ports closed on the intake.
It’s because of coolant flow. You don’t want the coolant to be diverted from flowing thru the heads.
The heads are open because the heads are designed to be put on either side of the motor.

[71CHEVYSHORTBED402]

Originally Posted by geezer#99

Contrary to what they say I use a light film of form a gasket around all the ports on the head side.
Don’t use the end gaskets. Run a 1/4 inch deep bead of silicone instead.
Don’t use jb weld. Hard to make it level again.
Those pins are what were used to hold the oil splash shield onto the bottom of the intake.
The shield keeps your intake plenum from getting too hot. Yours was removed.

Also to answer a question in your other thread about the rear ports closed on the intake.
It’s because of coolant flow. You don’t want the coolant to be diverted from flowing thru the heads.
The heads are open because the heads are designed to be put on either side of the motor.

Awesome response and more, thank you. I was talked into the 1/4" bead front and back, nice to have confirmation.

So you seal all ports. I see some guys just hit the water ports, but I like it. Is that enough to keep the gaskets from slipping? What seal(s) do you recommend? I have a ton of Permatex ultra black, don't ask

And SHUCKS I'm missing a oil splash. They wouldn't have removed it for clearance after machining the heads right? From what I read they get gummed up. Perhaps it was damaged when Mickey rebuilt the engine, or he wasn't a fan. He was real good, but not sure what to think on the oil splash less installing another. Seems they're available.


Other than that there's this replacement intake I have my eye on for (gulp!) $220, and I'd have to spend another 5 hours painting, three coats with a brush. I do stuff backwards sometimes, thought this was clean so painted it. The surfaces weren't that close to clean after all, and of course no oil splash

[geezer#99]

I’ve used ultra black. Or form a gasket. A super thin smear is all you need.
If your motor was running fine without a shield you might want to leave it alone. Attaching one can be a pain. You need to be absolutely sure whatever you attach it with does not ever come loose. There are deflector trays you can use as a shield.
Like this.

https://www.summitracing.com/int/par...5320/overview/

[71CHEVYSHORTBED402]

Originally Posted by geezer#99

I’ve used ultra black. Or form a gasket. A super thin smear is all you need.
If your motor was running fine without a shield you might want to leave it alone. Attaching one can be a pain. You need to be absolutely sure whatever you attach it with does not ever come loose. There are deflector trays you can use as a shield.
Like this.

https://www.summitracing.com/int/par...5320/overview/

Best advise I've heard all day, I'll install as is. Ran like a Swiss watch beforehand, no overheating and that, oil always clear and I never added a drop. Then again, I didn't really drive it much

I'll mark off the gaskets to get a clear picture where to seal her up and install this already. Waiting for my son who's currently on a crab boat, these are real heavy. I make new things difficult, he makes stuff easy and he's a strong buck too, so we make a good pair. He's getting a nice truck someday, so is the plan.

Thanks a bunch Geezer.


Wow, interesting. Looks easier than gaskets. I'm assuming you'd still want to seal up the ports. https://www.youtube.com/watch?v=fhWgSGGxVN8

[Mike C]

I use the aviation form-a-gasket that comes in a bottle with a brush top for the flat sides of pretty much everything but head gaskets. I also second the bead of sealer on the ends of the heads.

[geezer#99]

When you lay the 1/4 inch bead on the end rails, wait for it to surface dry for 15 minutes.
That way the bead will stay in place and not squish off the rail when you put that heavy intake in place.

[71CHEVYSHORTBED402]

Originally Posted by geezer#99

When you lay the 1/4 inch bead on the end rails, wait for it to surface dry for 15 minutes.
That way the bead will stay in place and not squish off the rail when you put that heavy intake in place.

[weq92f]

.
To do it by yourself... get two slightly longer bolts ( same thread as the intake hold down bolts ) and grind off the head. Pick one side and install these now headless studs into a head along the top rail. Now you can install the heavy-@ss intake all by yourself and get perfect alignment the first time! Simply line up the intake on those two studs and slowly lower it into place! The studs should come out real easy with fingers or needle-nose.

I use Gasgacinch to hold the gaskets in place! YMMV.

-klb

[71CHEVYSHORTBED402]

Originally Posted by weq92f

.
To do it by yourself... get two slightly longer bolts ( same thread as the intake hold down bolts ) and grind off the head. Pick one side and install these now headless studs into a head along the top rail. Now you can install the heavy-@ss intake all by yourself and get perfect alignment the first time! Simply line up the intake on those two studs and slowly lower it into place! The studs should come out real easy with fingers or needle-nose.

I use Gasgacinch to hold the gaskets in place! YMMV.

-klb

I'm a firm believer using studs, but didn't figure they'd line up because of the angle. Didn't think to do one side, great idea.

[71CHEVYSHORTBED402]

For whatever it's worth, I read that contrary to belief an oil splash is intended to protect a manifold, it's for preventing oil from burning on the crossover. I suppose it could accomplish both.

I looked it up in the parts book. The BBC oil splash is part 3919853, though you have to search for "oil splash" to find it. They show a splash for 70-71 BBC truck, but not for a 72. Probably an error, because the same splash shows for a 72 402 in a Chevelle.

I'm still on-board going without, worked before. Maybe I'll change my oil more often