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intake manifold leak

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socalrider
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intake manifold leak

#1

Post by socalrider » Sun Jun 13, 2010 6:22 pm

i know this subject has been covered extensively but with all that i've read , i still can't find a solution to my leak. i've tried new o-rings, oem clamps ,2 piece clamps, stainless steel aircraft clamps, all to no avail. its the front head only and occurs on the same spot,from about 12 to 2 o'clock. i rotated the manifold while under pressure to see if the leak location moves with the rotation but it did not . the rear head seals up perfectly with a minimal amount of clamp pressure. i looked at the gap between the manifold and front head intake port with the rear clamp and o-ring installed. it appeared tight and inline. i also looked at the gap internally with both clamps and o-rings installed , the gap on both sides appears equal and tight.i loosed the front head and rotated it clockwise about 2* to get a better alinement between the 2 intake ports,hoping this would tighten the gap (i did this on my shovel and it solved the problem) this did not help either. the motor is a 65 all original including the intake manifold. the intake manifold was chromed by the former owner, so im thinking that might be the problem. but if that were the case , would'nt the leak move when i rotate the manifold?will the james viton o-rings help? what about having the chrome removed from the intake manifold? all help GREATLY appreciated!
gracias,
arnulfo



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Re: intake manifold leak

#2

Post by Bigincher » Sun Jun 13, 2010 11:38 pm

At the risk of being ridiculed, I will say that I've used red RTV silicon sealant-- sparingly-- on the manifold where the O-ring seats, to help seal the O-ring when it is too stubborn to seal on it's own.

Robert Luland
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Re: intake manifold leak

#3

Post by Robert Luland » Mon Jun 14, 2010 12:43 am

Bigincher wrote:At the risk of being ridiculed, I will say that I've used red RTV silicon sealant-- sparingly-- on the manifold where the O-ring seats, to help seal the O-ring when it is too stubborn to seal on it's own.

Tom, Why would anybody ridicule you for trying to make something work. I used as you mentioned, Silicone, Teflon tape and electrical tape over the years and everything in between. Face it, It was a suck as design to save the MC money. You do what you got to do to get the job done. I’m sure it worked half ass right out of the factory. Now you got people fifty years later slapping things together. One head might have been decked were the other wasn’t. Chips on the inlet nipples, inlet nipples out of round and dented. Just think of what these poor parts have been put though and you get your answer. Bob L

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Re: intake manifold leak

#4

Post by Cotten » Mon Jun 14, 2010 1:47 am

Bigincher.

Do you really really think that RTV survives modern fuels?

Worse than setting yourself up for ridicule, you lead others to folly.

And Robert.

If you haven't had electrical tape turn to snot, and teflon tape let the clamps slide crooked, then you really never tried them. Either is a band-aid destined for failure. Just hope you are close to home when it happens.

Arnulfo!

Chrome where it is not supposed to be is always evil, but it may not be the culprit.
If you can find a #9 rubber stopper at a wine-and-beer-making supply, you will be able to poke a hole through it for use like your testplate.
This will allow testing of your port without the clamp and o-ring in the way. You may possibly find an invisible hairline crack, or perhaps even a casting porosity.
Two more stoppers held into your manifold spigots with a vise or C-clamp will let you test the manifold separately if need be.

Viton o-rings are best for the long run, but even a common clean and dry o-ring should pass a bubbletest.
And by all means, stick with the OEM design of clamps.

Let us know how it goes,

....Cotten

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Re: intake manifold leak

#5

Post by Robert Luland » Mon Jun 14, 2010 2:09 am

Stoppers! Did ya mention stoppers? Widgetco.com

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Re: intake manifold leak

#6

Post by socalrider » Thu Jun 17, 2010 4:54 am

Got the rubber stopper, it worked like a charm.unfortunately there is a hairline crack on the intake spigot of the head, just as cotten suspected,about 3/4" long.i guess it has to go to headhog for repair. Thanks for the help to everyone.
Arnulfo

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Re: intake manifold leak

#7

Post by Bigincher » Thu Jun 17, 2010 3:05 pm

No, Mr. Cotten, I don't know what will actually survive modern fuels today. My manifold has some slight pitting on the O-ring surface (side, not the end), and it occured to me that a thin coating of RTV may help to seal those pits. When tested with my block-off plate and 7-10 lbs air pressure applied, it did not leak, so perhaps the pits were not an issue, or perhaps the sealant temporarily worked. May not ever know-- at least in the short term.
As for misleading posts, I believe that the readers are intelligent enough to judge for themselves, and I have seen other posts throughout the internet that must be read with due interpretation. If everyone stopped posting for fear of misleading, the internet would become a very quiet place.
I was merely offering my own admittedly limited experience (only 35 years), but if you'd like me to refrain from comment, please advise. I mean no ill will towards anyone.

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Re: intake manifold leak

#8

Post by Cotten » Thu Jun 17, 2010 4:33 pm

Bigincher wrote:but if you'd like me to refrain from comment, please advise. I mean no ill will towards anyone.
I would never abridge anyone's Freedom of Speech, even if he maliciously denied mine, and signed his name as well.

....Cotten

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Re: intake manifold leak

#9

Post by Hog54 » Fri Sep 24, 2010 4:50 pm

I have a rule of thumb since I worked in a shop 25 years ago.I never chrome anything that has to seal air,oil,or water.When they chrome something at the chrome shop they have to polish it first and you dont know if the guy polishing the part is polishing it out of round or polishing the gasket surface uneven.Plus the smooth surface of chrome will never seal right unless you use sealant.

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