Plugging heat riser
 

I wished I would have looked at this closer earlier. I want to block the HR and asked Butler about it more than once. Their tech guy says the gasket will do it.
It has no steel insert that I can see.

I suggested to him they should offer a option to plug it with a thin pipe plug.

The Edelbrock heads are mounted. the angled hole is barely bigger than a penny. I thinking of using the high temp JB Weld and epoxying a couple of pennys in the heat riser hole.

Looking for some feedback on this.
I have received great advice on here and it’s great for a novice like me.

Thanks!


I’ll try to post some pics of my engine build when I’m through.

I would pack the hole with a wadded up paper towel and tap it for a pipe plug, probably 3/4 NPT. Get out your calipers and see what size hole you have and maybe the tap will work with the hole that’s there already.

Vacuum the chips out and remove the paper towel or cloth or whatever. Some grease to catch the chips would be helpful too.

No way would I depend on JB Weld or just the gasket that’s going to burn through in nothing flat.

There are steel cup plugs that will fit that hole .

The hole is at an angle and is not deep enough for a normal pipe plug. I guess I could try to shorten the pipe plug. But I’m not sure how to do that. Not much to hold on to to grind.

I’ll look and see if they make a very thin pipe plug

I bet you would be lucky to stack 3 pennies in there. The pennies almost fill the hole they just barely lean. I don’t know if there enough clearance to use a piece of beer can as a shim and hammer it in.

People have used a thin stainless steel putty knife blade to fashion a block off to sandwich between the gasket and the intake with success.

Thanks guys!!!
Great ideas.

P. S. That's not the "heat riser", that's the exhaust crossover passage. The heat riser valve (later name = "Early Fuel Evaporation" (EFE) valve) is what forces exhaust gas across the crossover passage to the other side of the engine.

If you want to do it once and do it right then take a measurement and then buy the two needed Allen set pipe plugs ( aluminum ones are fine ) and the needed drill bit and tap.

Take your time and drill and tap deep enough to get the plug .050” deep off the intake flange of the head.

In the Aluminum type you can even find shallow ones so you do not have to tap as deep.

All the stainless steel block-offs always burn thru, not sure how a plug would fair. It would be better, last longer, but how much longer is the question.

There is a slight performance aspect to the crossover, tho not sure how much of a benefit there is. I suspect 'conventional' methods to provide the same benefits would be just as effective, possibly more so.

I used to block them off but gave up. It's just not a priority IMO.


EDIT: My understanding is that the best way to block the crossover on OE heads is to fill them, then grind them smooth and to shape.

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I put a steel cup plug in to block that off. A little tricky since it was drilled at a angle.

Thanks for the help!

P.S. I also installed the water pump. What contraption that thing is.

I made block off plates out of stainless to fit the felpro gaskets. Laser cut to drop right into the intake gasket. Have extras if anyone is interested. Also EGR block off plates.

With my 62 casting number heads, many years ago, I used a pair of galvanized steel pieces (thicker than shim stock, but not so thick as to upset the intake manifold seal) to block off the exhaust crossover. It probably had 40k street miles after these were installed. When I took the engine apart for the current refresh, both of the galvanized plates looked almost pristine. The cylinder head side had some exhaust soot on it, but there was no discernible wear, and the galvazing was still noticeable on both sides of the metal when I cleaned them up. Certainly, the best way to block them off with factory cast heads is to fill the ports with molten aluminum and hand blend the bowl area. I had not paid attention to the best way to plug the crossover for either the Edelbrock or Kauffman D port heads since the ProFlo4 intake I have for my current build does not have an exhaust crossover at all. I would imagine that if it were necessary to plug that (relatively) small hole, a threaded pipe plug (of a similar aluminum alloy) might work ok as long as you are careful to ensure it is tapped and installed so that the plug can not drop down into the port.

1911a1, I would suggest that your idea about the penny(s) and JB weld is a potential failure point. While JB Weld is very good stuff, it is not intended to withstand the heat of direct exposure to the hot exhaust, especially the intense heat you get at that shared center port. Buy some stainless steel shim stock that would allow a good seal with the gasket, maybe use a little copper RTV there too, and call it done. The best "easy" option would have been to tap the holes in the Edelbrock heads and carefully install the thin aluminum pipe plugs before you installed the heads. Based on my experience with using galvanized mild steel sheet, I did not have any leaks, but I did not have aluminum heads on that engine in the past

This has been an interesting thread to read. Back in the 70s and 80s I always just used the factory Pontiac block off intake gaskets PN 9777526 and never had any problem with them burning through with the factory iron heads. Now I am curious to see what Pontiac used for the metal plates. I will have to see if I have any left and check to see if they were stainless and how thick they were. Maybe someone else knows the answer?

I’ve had the block off plates burn through. When I had sd performance port my iron heads he filled them with aluminum and shaped them inside. He said he melted down old pistons.

This thread is very timely. I'm having my 421 tripower rebuilt and I'm looking for a way to prevent engine paint from burning off the exhaust crossover part of the intake manifold. It seems one way to do that Is to block off the exhaust crossover port, which I presume also means removing the heat riser valve from he exhaust manifold?

But is there another way? For example, has anyone had success using specialized paint, like the high temp version of POR-15 (https://por15.com/products/high-temp) perhaps as a primer, and then covering this base coat with regular engine paint? The high temp POR-15 is supposed to tolerate up to 1200 F. Anyone know how hot the exhaust crossover gets?

Brad

Yup, the heat riser has to be disabled if you block the exhaust crossover through the intake manifold.

Therefore, at best you'll need choke adjustment to make-up for the lack of heat on the bimetallic coil.

I'd be surprised if 1200 degree paint will be sufficient under heavy throttle without blocking the crossover.