340 Intake Crack take two!

Islandkent · Feb 12, 2021

Good morning gang.
Was bored the other day and decided to spruce up my old 4 barrel intake so I thought I'd give it the big clean/blast and paint.
Removed the heat shield plate on the bottom to see how carboned up it was. Zero carbon, a little soot. While I was cleaning the soot seen the crack right on the heat crossover tube/port. Since I have no plans for it at this time. Really I think it will be for display only purposes. But that being said. If I were to want to use it would you bother to repair it (cast weld / JB weld) or would you let it go? I think it must of been cracked when I had this on my engine 30 years ago and was running it cracked. Would the heat from the engine warm that crack up enough to seal as it expanded?? It would have never affected performance back then eh? Just a small oil leak maybe that I never really noticed at the time?? Any opinions?
Here's a few pictures of the 50lb paper weight. lol

HawkRod · Feb 12, 2021

I'm no expert on these things, but I have heard you can fix cracks. Drill each end of the crack (to stop the spread), then cut a good V notch in the crack and fill with weld. I know you are welding on cast material but I believe that can work. If not, I'm sure others will quickly correct me!

Having said the above, in most performance applications you would block off the crossover anyway, so that would render it, and the crack, unimportant. Even if you used the crossover with the crack, the worst you would get is some exhaust into the engine cavity, similar to blow by past the pistons. Unless it is a lot, I don't think it would cause any significant issues.
I'm sure others will chime in too...

Hawk

Islandkent · Feb 12, 2021

Oh no problem to weld cast these days. Use to be a black art at one time, now pretty common. A few years ago I broke a lug of a clutch I was installing while tightening it. Took it to a local welding shop. fixed it right up. Still in the semi.
Yeah Hawk that what I was thinking. Forgot about that old tip about drilling little holes to stop the crack from spreading. Thanks!
Wonder if JB weld would be up to the task? If it could take the hot and cold? If it fell off it would be inside heat plate anyway. Just thinking out loud.

HawkRod · Feb 12, 2021

Islandkent said:
Wonder if JB weld would be up to the task? If it could take the hot and cold? If it fell off it would be inside heat plate anyway. Just thinking out loud.

I can't imagine there would be a lot of stress on the cracked area. There are no rotational or other forces on it other than expansion and contraction due to heat and the pressure from the exhaust. What I don't have a good feel for is how hot it gets. You might want to check JB Weld's ability to be used on exhaust manifolds. If it can handle exhaust manifold heat I would think it would do fine on the crack.

toolmanmike · Feb 12, 2021

Islandkent said:
Good morning gang.
Was bored the other day and decided to spruce up my old 4 barrel intake so I thought I'd give it the big clean/blast and paint.
Removed the heat shield plate on the bottom to see how carboned up it was. Zero carbon, a little soot. While I was cleaning the soot seen the crack right on the heat crossover tube/port. Since I have no plans for it at this time. Really I think it will be for display only purposes. But that being said. If I were to want to use it would you bother to repair it (cast weld / JB weld) or would you let it go? I think it must of been cracked when I had this on my engine 30 years ago and was running it cracked. Would the heat from the engine warm that crack up enough to seal as it expanded?? It would have never affected performance back then eh? Just a small oil leak maybe that I never really noticed at the time?? Any opinions?
Here's a few pictures of the 50lb paper weight. lol

View attachment 1068061 View attachment 1068062 View attachment 1068063

Take 2

I deleted your Take 1 thread. The "crack" had us going though!

toolmanmike · Feb 12, 2021

Islandkent said:
Good morning gang.
Was bored the other day and decided to spruce up my old 4 barrel intake so I thought I'd give it the big clean/blast and paint.
Removed the heat shield plate on the bottom to see how carboned up it was. Zero carbon, a little soot. While I was cleaning the soot seen the crack right on the heat crossover tube/port. Since I have no plans for it at this time. Really I think it will be for display only purposes. But that being said. If I were to want to use it would you bother to repair it (cast weld / JB weld) or would you let it go? I think it must of been cracked when I had this on my engine 30 years ago and was running it cracked. Would the heat from the engine warm that crack up enough to seal as it expanded?? It would have never affected performance back then eh? Just a small oil leak maybe that I never really noticed at the time?? Any opinions?
Here's a few pictures of the 50lb paper weight. lol

View attachment 1068061 View attachment 1068062 View attachment 1068063

If that crack would open up with a little heat it would be a vacuum leak that would be damn hard to find if it was a intake port. :BangHead:

Islandkent · Feb 12, 2021

Thanks Mike! That will be our little secret! lol Cranky's too! Or was it Pops??? Or not. lol

HawkRod · Feb 12, 2021

toolmanmike said:
If that crack would open up with a little heat it would be a vacuum leak that would be damn hard to find.

Since this is the exhaust crossover I think it would be under pressure (exhaust), so no vacuum.

I had an intake manifold gasket with a very small failure between the intake runner and lifter valley on my 340. As you said, it was very difficult to find, and really only the spark plug told the story - it was sucking in oil from the engine and burning it. Of course, I was also wondering if the rings were bad. Funny thing was, my overall vacuum wasn't that bad; I just attributed it to the performance camshaft I had.

toolmanmike · Feb 12, 2021

hsorman said:
Since this is the exhaust crossover I think it would be under pressure (exhaust), so no vacuum.

I had an intake manifold gasket with a very small failure between the intake runner and lifter valley on my 340. As you said, it was very difficult to find, and really only the spark plug told the story - it was sucking in oil from the engine and burning it. Of course, I was also wondering if the rings were bad. Funny thing was, my overall vacuum wasn't that bad; I just attributed it to the performance camshaft I had.

Right you are. I didn't look close at the other photos. :BangHead:

Islandkent · Feb 12, 2021

So If a fella was to use a set of intake gaskets with the built in block off "plate" problem of blow by would be solved yes?? I was checking out google images and it seems all of the aftermarket heads come with out the intake heat ports anyway.
So if I was to drill tiny relief holes at the ends of the crack and maybe toss the plate and rivets altogether then I should have no problems running this intake? The other question would be why I would want too. lol
Thanks for the replies guys.
Thanks again for the delete Mike.

toolmanmike · Feb 12, 2021

Islandkent said:
So If a fella was to use a set of intake gaskets with the built in block off "plate" problem of blow by would be solved yes?? I was checking out google images and it seems all of the aftermarket heads come with out the intake heat ports anyway.
So if I was to drill tiny relief holes at the ends of the crack and maybe toss the plate and rivets altogether then I should have no problems running this intake? The other question would be why I would want too. lol
Thanks for the replies guys.
Thanks again for the delete Mike.

It would probably be fine. I wonder if the heat riser was stuck closed and caused the crack?

Fran Blacker · Feb 12, 2021

If your not going to use it let the next guy find it.

I'd fix it or mark it and put a tag on manifold about the problem.

Islandkent · Feb 12, 2021

Good question? I bought this engine back in 1983. It was on a 68' 340 block. 2.02 heads on all. Crammed it in my 80 Aspen R/T. Man I had a great summer that year. Young and dumb... 10-4 lol And got there fast. double lol
Oh I forgot to add... I had the engine before the car.
No way Fran. I can't let this icon of my youth go. lol

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HawkRod · Feb 12, 2021

Islandkent said:
So If a fella was to use a set of intake gaskets with the built in block off "plate" problem of blow by would be solved yes??

Yup. Then the crossover does nothing other than to take up space!

Islandkent · Feb 12, 2021

Good deal Hawk. Thanks

Cranky · Feb 12, 2021

@Islandkent Yeah, cast aluminum is much easier to weld these days but it's still not real easy being a casting. TIG welding machines just don't like it that much. About the only cast aluminum welding I've done was to fill up some bolt holes for redrilling and tapping and being good and clean is really important and then you have the problem of it being a casting lol. And down where I live it wouldn't be a problem blocking the cross over but up where you are, it might be a problem if you drive in the winter and don't want to wait for a longer warm period. Using a 100 light bulb or something that makes heat would surely help heat up the carb for easier starting....and yeah, I did that back in 89 when we had our last hard freeze and in the early 80's for the one before. Kinda hard to believe we made it over 30 years without having temps in the 20's....

Islandkent · Feb 12, 2021

Yep She's warming up for sure. But I'm going to leave it at that. -22* C here this morning with the wind Cranky. Not to much into driving the old ones in the nasty cold any more but I do let the Roadrunner warm up for a few minutes before I kick it off high idle. The manifold uptop is a cast iron one. If I was to do LA engine I would definetly be doing the aluminum version for sure. Once I get that Charger finished I might turn some well deserved attention to my life long ownership of my '80 Volare Roadrunner. One of those complete top end kit from Holly or Edlebrock. Here is a pic of my 80 RR bought her when I was 17 still have her at 53.

000000000000000000000000000000000000000000000000000000000000000000000000roadrunner.JPG

Daves69 · Feb 12, 2021

Islandkent said:
...Use to be a black art at one time...

Recently I needed a temporary 4 bbl setup for my car. This cracked CH4B manifold that I couldn't give away, came on a running '74 Trailduster that I bought way back. Evidently it had cracked through the crossover on both sides. It had been welded ("black art" days maybe?), and it had cracked again in the welds.
I sealed (red stuff) up the crossover cracks, taped over one side, filled it with water. It held water for a day with no sign of entering any runners.
So I sealed up both ports with stainless shims made from a 2 buck handy box cover. It's on my engine right now. Other than warm up time no issues.

oldkimmer · Feb 12, 2021

I have had good luck brazing cast iron. Heat it with a torch first then braze away. Kim

furyus · Feb 12, 2021

Well, if you want to know what happens with a hole in the crossover, it blows all that carbon all through the engine, destroying bearings, piston skirts, oil pump.
I had an original police interceptor 428. It had a factory aluminum intake, with the heat shield on the bottom. After my engine was ruined, i pulled the heat shield off, and the crossover had corroded through.

340 Intake Crack take two!

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