How does this happen?

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Posted

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I was rippin' today and the engine was getting a little warm. So I pulled into my shop and greased the steering rack.

Now it ran extremely well when I shut it off. I went to start it up again and it refused to idle and throttle made it idle very rough. It sounded like the choke was stuck open, like a pulsing sucking noise:bathfun:. I pulled my manual choke apart and it seemed okay. Try it again, still won't idle. Then I take notice the petcock vacuum line fell off. No cigar so I must have bumped that line when I was fumbling with the choke. Next I go to loosen up the carb boots and I notice this burnt hole in the intake next to the left stud. "Well thur's yur problem."

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Posted

Well at least it looks like you found the problem ,good thing it was probable running a bit lean.

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Posted

that is a very odd placement -- from the looks of it (makes no sense btw) it looks like something arc'd from *inside* the manifold to the tip of the nut. SMH.

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Posted (edited)

That is just a Hollow Post for a Wire to go thru On the Plastic Cooling Shroud needed or not, yup it goes right thru so Fan Forced Air is coming out, the Top has been busted off thats all. there is No Problem there, that little escaping air will have nothing to do with any running condition. 

They are all like that. this is mine. the wire running thru mine is for my inductive Tach. other than that it wasn't used in this application.

Put a Glob of Black Silicone on it and the other hole to keep that fan forced air inside and Boom yer done.

Ya got other problems..

 

 

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Edited by pistonguy

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Posted

That is just a Hollow Post for a Wire to go thru On the Plastic Cooling Shroud needed or not, yup it goes right thru so Fan Forced Air is coming out, the Top has been busted off thats all. there is No Problem there, that little escaping air will have nothing to do with any running condition. 

They are all like that. this is mine. the wire running thru mine is for my inductive Tach. other than that it wasn't used in this application.

Put a Glob of Black Silicone on it and the other hole to keep that fan forced air inside and Boom yer done.

he's talking about "burnt hole in the intake next to the left stud" not the "hollow post" you mention, which is what I was pontificating about.

M

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Posted

Ah I see the blem. its a blem bubble in the manifold, it goes to nowhere.

Here is the OE from mi, darn near same blem

That rubber is like a .250 thick molded over top the aluminum it would really have to come un-bonded in a big way to cause a leak

 

 

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Posted

Ah I see the blem. its a blem bubble in the manifold, it goes to nowhere.

Here is the OE from mi, darn near same blem

That rubber is like a .250 thick molded over top the aluminum it would really have to come un-bonded in a big way to cause a leak

 

 

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I was wondering how the aluminum under the rubber could crack but your pictures explain it very well:thanks:.  It must have cracked all the way through because I put some RTV on the crack and cranked it to suck it in.

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Posted

Actually taking a second look at mine the blemish goes all the way thru to the Aluminum. I can see it but can't get a good picture of it..

 

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Posted

Actually taking a second look at mine the blemish goes all the way thru to the Aluminum. I can see it but can't get a good picture of it..

 

so what on earth causes such a blemish? Seems unlikely given the small mass involved.

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Posted

so what on earth causes such a blemish? Seems unlikely given the small mass involved.

It looks like that was a hole drilled in the aluminum to locate it in the manufacturing process. The only way I'd think this could happen the way it did for me is if the engine backfired through the carb. It NEVER backfires but who knows? That would explain the burn though.

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Posted

Ah I see the blem. its a blem bubble in the manifold, it goes to nowhere.

Here is the OE from mi, darn near same blem

That rubber is like a .250 thick molded over top the aluminum it would really have to come un-bonded in a big way to cause a leak

 

 

IMG_1629.jpg

IMG_1645.jpg

IMG_1630.jpg

Nah the Aluminum under the Rubber is Not cracked, its very solid one piece Aluminum under the Rubber.

I couldn't crack it even if I hit it with a hammer on the bench. Even a Nitrous explosion will only blow the carb back off the spigot its claimed to

There is nothing internal or external to "burn" a hole thru it. its solid behind it.

Probably your Socket grabbed that little blem and ripped a little piece off thats all

That hole you see is the vacuum port in from of the stud.

Best I can figure is that part of the manifold the rubber is thin, in and around that stud hole, don't really need a whole bunch of rubber there.

If its a concern just dob a glob of RTV on it

 

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Posted

And that's exactly what I did. It's holding up for now but if for some reason it happens again I have Dan on speed-dial.

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Posted

Nah the Aluminum under the Rubber is Not cracked, its very solid one piece Aluminum under the Rubber.

I couldn't crack it even if I hit it with a hammer on the bench. Even a Nitrous explosion will only blow the carb back off the spigot its claimed to

There is nothing internal or external to "burn" a hole thru it. its solid behind it.

Probably your Socket grabbed that little blem and ripped a little piece off thats all

That hole you see is the vacuum port in from of the stud.

Best I can figure is that part of the manifold the rubber is thin, in and around that stud hole, don't really need a whole bunch of rubber there.

If its a concern just dob a glob of RTV on it

 

That's the first thing I thought of also. Does someone like to reach for the impact driver whenever they are spinning hardware off and on?

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Posted

That's the first thing I thought of also. Does someone like to reach for the impact driver whenever they are spinning hardware off and on?

Honestly I don't use impact drivers. I like to feel how much I'm torquing the nut.

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Posted

Well the RTV lasted for a day but now it seems the rubber wants to rip around the part. I can't even get it started without putting my finger on the hole. I'll send a request to Dan the Man.

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