Intake sealing and blocking the heat crossover

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kiss

kiss

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I did some forum searches and read several threads but I still have a few specific questions about intake sealing and blocking the heat crossover. The engine is a stock rebuild 360 and I'm putting on an Edelbrock performer intake. For several reasons including how I live in a warm climate I want to block the heat crossover.

From what I gathered sometimes, or often, the gaskets that block it off burn through. Several people on here say they cut a piece of shim stock to assist the gasket blocking the port. I have a few questions about that.

1. Will the thickness of the sheet metal interfere with the intake sealing?? Will it crack the intake if bolted down? Do you guys cut or modify the gaskets to compensate for the extra thickness of the added block off piece?
2. I have .008" stainless steel shim stock, is that thick enough? Or should I order some thicker?
3. How big of a piece should I cut to block the port? Any pics/advice appreciated. I want it to stay in place and not fall in or shift.

Also, which gaskets are you guys using for a build like this? Iron heads and aluminum intake. I read the Felpro printoseal gaskets seem to be popular? Is there a better option for my application? I also read there's Mopar gasket set that come with block off plates but I was unable to find that, and I also want to know if that's a good option. I definitely want gaskets that seal well and are reliable.

Lastly I noticed several people saying to discard the end gaskets and just use a bead of high temp RTV. What's the reason for this? Why not just use the end gaskets and coat both sides in RTV? Are they too thick or something?
 
the felpro gaskets with the blue border around the port openings are good. I use Permatex 99MA the thin red spray in the can and 2 dabs of superglue the size of your pinkie finger to hold the gasket in place on each side maybe about 1/3 and 2/3 along the length just not real close to the port openings. You want to block the round heat riser hole in the center of each head intake face but not the U shaped passage as that is a barrier to keep the heat from the crossover from adversely affecting the adjacent ex ports which are hot enough as is & you need them open for air to circulate out of there. I would epoxy a flat piece of metal into each center hole & there are other ways but I dont remember what some guys have posted regarding this. For your Q .008" ain't thick enough & you wouldn't want any added thickness on the side gaskets which could keep it from sealing. A person could cut the gasket in that center area & add some metal shim there, you just dont want the final thickness to be greater than what the compressed gasket thickness will be. the end supplied gaskets are too high (thick) for alot of apps & that depends on block height/head milling/gasket thickness etc & it ends up letting the front cooling ports leak over time as the intake appears to be tightened down but it is being held up an imperceptable amt by the too thick of end gaskets. EDIT I want the spray all around the port openings but not the super glue
 
Felpro for sure. I epoxied .5 mm Stainless plate into the cavities on my 383's. No vacuum leaks, great exhaust note as bonus!

Ters.
 

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Ters said:
Felpro for sure. I epoxied .5 mm Stainless plate into the cavities on my 383's. No vacuum leaks, great exhaust note as bonus!

Ters.
Click to expand...
So you actually cut the stainless plate to fit down inside the heat crossover hole, and epoxied it into place?

What happens when the epoxy burns off? Wouldn't the stainless plate fall down into the head? Or am I missing something?

EDIT: also how thick of stainless plate?
 
kiss said:
So you actually cut the stainless plate to fit down inside the heat crossover hole, and epoxied it into place?

What happens when the epoxy burns off? Wouldn't the stainless plate fall down into the head? Or am I missing something?

EDIT: also how thick of stainless plate?
Click to expand...

Stock port on cast head is fractionally smaller than cutout in pan gasket. Effectively intake manifold keeps it in place by pressing it onto head. I cut it butt fit into cavity, then epoxied with Pratley epoxy.


Ters.
 
It looks like this is the Mopar gasket set that comes with the block off plates. Has anyone used it? Are these good quality gaskets? Might be the way to go for me if so:
http://www.summitracing.com/parts/dcc-4286569/overview/make/dodge

Here's the Fel-Pro printoseal gasket set and it's steel core. If I just add a thin stainless steel shim stock to this gasket I assume the steel core + the added piece of shim stock would do very well to hold up to keeping the port blocked?
http://www.summitracing.com/parts/fel-1213s3/overview/make/dodge

Any additional input is appreciated. I really only want to do this once.


Ters said:
Stock port on cast head is fractionally smaller than cutout in pan gasket. Effectively intake manifold keeps it in place by pressing it onto head. I cut it butt fit into cavity, then epoxied with Pratley epoxy.


Ters.
Click to expand...
That just sounds risky to me. If that epoxy ever burns off that block off plate you made will fall in. I don't want to risk that.
 
In the past when I wanted to block off the heat riser, I cut up an International Foods Mocha can. Layed a square over the port on the head, put the gasket down over that, put the intake on. Never had one blow out. Easy-peeazy.
 
I solved the problem, by buying an intake that did not have a heated plenum under it. Course the Eddies don't have that passage anyway.
If you do have a heated plenum, it would be a very good thing in CA to eliminate it as it also messes with header scavenging; as the pulses pass under the carb instead of stopping at the back of the valve.
 
kiss said:
That just sounds risky to me. If that epoxy ever burns off that block off plate you made will fall in. I don't want to risk that.
Click to expand...

I understand your concerns sir. Best option would be to buy the valley pan with manufactured blocked of channels then. Other option is of course to have intake channels welded shut....

Ters.
 
A valley pan is not applicable to any normal small block Mopar. They are used on big blocks. It's a combination intake gasket and cover for the lifter valley on the big blocks.
 
The Edelbrock Air-gap effectively acts as a valley pan. Oh...and Mopar has had air-gaps since the 50's V-8's, nothing new.

On my 318 with Weiand manifold I just cut some stainless sheet a little bigger than the opening and installed the manifold with gasket. That was maybe 8 years ago. As far as I know it's still working ok. My car is a little rough when cold and the blocked port may be a big part of that. Once the engine has warmed a little it's fine. Of course I don't drive it in the winter.
 
I guess i'm having a hard time visualizing things. If I used a .020" piece of SS shim stock, or got the Mopar gasket set with the supplied shims that you trim to fit, how can I be sure that's reliable? It would have to be slightly larger than the heat crossover opening on the head to cover it, and then there would need to be enough gasket material to seal around it. I just can't visualize that sealing well in my head, plus the additional .020" thickness possibly causing port seal issues on the whole manifold.

Is it not a big deal if the shim stock isn't surrounded by gasket? Will it flex enough to seal and not allow an exhaust leak?
 
kiss said:
It looks like this is the Mopar gasket set that comes with the block off plates. Has anyone used it? Are these good quality gaskets? Might be the way to go for me if so:
http://www.summitracing.com/parts/dcc-4286569/overview/make/dodge
Click to expand...

So I just bought this gasket set for my 318 with the later 302 heads and a Performer RPM intake. Came with 2 metal plates that I RTV'd to the head, then put the gasket on. Seemed to fit pretty well and once it was bolted up appeared to seal great in that area. HOWEVER, apparently the coolant passages in the gasket are far too big because coolant pours out of the back left side of the intake and head. Probably should have checked the fit before I started sealing stuff in place. Just wanted to share my experience, which may or may not be relevant to your application.
 
Any idea how thick the shims were? I was going to order some stainless steel shims to cut-to-fit and block mine off. Wondering how thick most people buy? .020"? Would .015" work?
 
if your running a heat riser it will burn through , I have removed many intakes that were blocked off the only ones that lasted had headers or heat riser removed.
 
I guess my car decided it didn't want the heat-risers either.....
 

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kiss said:
Any idea how thick the shims were?/QUOTE]

Shoot I literally just installed them under a new gasket so I can't measure. But would estimate looking at my thickness gauges that they're around 25 thousandths
Click to expand...
 
I've argued this point to no avail, but I will again say this. If it is a street car, you need to leave the exhaust passage open.

For gasoline to burn, it must be a vapor. For proper atomization into a vapor, heat is required. This is the whole purpose behind the heat cross over. Better cold weather operation is simply a by product.

With the cross over blocked, engine efficiency will go down on a street car. It's no secret. Google is your friend.

Now argue away.
 
No heat crossover needed in Yuma, AZ. Argue away.

When I blocked mine, I took it up a notch, literally. On my 318 A, I milled a step in the intake manifold crossover port the circumference of the crossover. I then milled a 3/8" steel plug with a corresponding step in the outer edge. Secured it in the manifold with high temp silicone. It sits barely above flush and is held tightly with the fiber gasket. No burn through here.
 
Thanks. I actually found some .020 stainless steel shim stock (annealed). I am going to use that. I don't have the heat flapper thing in the exhaust manifold so I'm hoping it will be OK.
 
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