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Intake Manifold Vacuum Leak(s)

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Red20 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Red20 Quote  Post ReplyReply Direct Link To This Post Topic: Intake Manifold Vacuum Leak(s)
    Posted: Jan/23/2019 at 3:05am
Looks like I’m getting it all sorted out.  Much better now.  It also turns out that some of my extra air was a result of dirty secondary throttle bores and a sticky shaft not allowing the secondaries to close completely at idle.  This was a used throttle body and I guess I didn’t look it over closely enough.  Some cleaner and working it back and forth for a while worked wonders.  The ECU is maintaining my 750 RPM target idle speed now.  
1969 Javelin SST "Screamin' Banana" - Totaled Feb 2018
1973 Hornet Sportabout X "yellajack" - 360/727/TracLoc DAILY DRIVER
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PHAT69AMX Quote  Post ReplyReply Direct Link To This Post Posted: Jan/22/2019 at 9:17pm
So shouldn't someone be able to use a carpenters square to check the geomtry
of an intake to see if it is machined at 90 ?
On the Block between the heads to check 90 the Carpenters Square won't work though, right?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Red20 Quote  Post ReplyReply Direct Link To This Post Posted: Jan/22/2019 at 6:56pm
Originally posted by Fluffy73 Fluffy73 wrote:

I chased vacuum leaks on my 360 for several years. It wasn't until somebody introduced me to "The Right Stuff"©®™ by Permatex that I solved most of my intake sealing problems.

Yessir, that’s what I use.  Do you use it around the intake runners as well as the water jackets?  I’ve always been under the impression that it could soften and deteriorate exposed to the fuel/air at the intake ports.  
1969 Javelin SST "Screamin' Banana" - Totaled Feb 2018
1973 Hornet Sportabout X "yellajack" - 360/727/TracLoc DAILY DRIVER
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fluffy73 Quote  Post ReplyReply Direct Link To This Post Posted: Jan/22/2019 at 5:53pm
I chased vacuum leaks on my 360 for several years. It wasn't until somebody introduced me to "The Right Stuff"©®™ by Permatex that I solved most of my intake sealing problems.
I am genetically incapable of being Politically Correct.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Red20 Quote  Post ReplyReply Direct Link To This Post Posted: Jan/22/2019 at 4:25pm
I guess I didn’t mention what type of intake.  It is an Air Gap.  Good call on the washers, thanks!

I got everything buttoned up last night.  I just need to put the plugs back in and break in the cam.  After that, I’ll let it settle into an idle and learn for a bit.  Hopefully I’ll be able to get some response from the IAC valve and everything will be solid.  I’m ready to start driving and tuning this thing and get back to enjoying my car.  


Edited by Red20 - Jan/22/2019 at 4:29pm
1969 Javelin SST "Screamin' Banana" - Totaled Feb 2018
1973 Hornet Sportabout X "yellajack" - 360/727/TracLoc DAILY DRIVER
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Jan/22/2019 at 6:51am
Assuming an air gap or other aluminum intake, you may also want to add hardened steel washers under the bolts to provide more even torque and larger clamping area.
A bolt clamping directly on aluminum alloys tends to pick up/deform some softer metal before full clamping force, giving a false torque. Steel on steel will slide and provide a much more even torque/clamping.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Red20 Quote  Post ReplyReply Direct Link To This Post Posted: Jan/22/2019 at 5:49am
With the intake installed dry, the top of the flanges has a .0025” gap.  That’s not what I like to see, but I’m giving it a shot anyway.  I’m using .030” Edelbrock gaskets.  Hopefully with gasket crush and the brush on copper coat I used, I’ll get a good seal.  It looked and felt really good and the bolt holes lined up perfectly.  
1969 Javelin SST "Screamin' Banana" - Totaled Feb 2018
1973 Hornet Sportabout X "yellajack" - 360/727/TracLoc DAILY DRIVER
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Red20 Quote  Post ReplyReply Direct Link To This Post Posted: Jan/21/2019 at 4:45pm
So I just said screw it and jerked the intake off and pulled the performer cam.  I’m going to put this Summit 8600 cam in and carefully mock up everything with this intake to see if there are any issues and ensure I get a good sealing surface.  
1969 Javelin SST "Screamin' Banana" - Totaled Feb 2018
1973 Hornet Sportabout X "yellajack" - 360/727/TracLoc DAILY DRIVER
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Red20 Quote  Post ReplyReply Direct Link To This Post Posted: Jan/18/2019 at 10:29am
That’s scary!  Thanks for the reality check, Armand. 

Well I’m back from Disneyland.  It rained the entire time, lol.  I hope to get time to work on the car this weekend.  I originally wanted to have a LOT more done and be heading to the Zip-Tie Drags in Tucson this evening, but that plan was shot weeks ago. 

At any rate, I’m going to pull the throttle body and spacer and check the gasket imprint for proper sealing and mic the aluminum spacer for trueness.  Then I’m going to seal up all of the ports on the intake and see if I’m getting a significant vacuum at the breather tube, which I’m sure I will be.  I’ll likely be pulling the intake manifold and resealing it.  

In order to not have the intake off again in the near future, I may go ahead and install the Summit 8600 cam I have waiting to go in.  The risk is the EFI not running well enough to break in the cam as well as the general rule of thumb that you should only do one thing at a time.  I’m pretty confident it’ll fire up and run at 2500 RPM for at least 20 minutes for me though.  
1969 Javelin SST "Screamin' Banana" - Totaled Feb 2018
1973 Hornet Sportabout X "yellajack" - 360/727/TracLoc DAILY DRIVER
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Post Options Post Options   Thanks (0) Thanks(0)   Quote White70JavelinSST Quote  Post ReplyReply Direct Link To This Post Posted: Jan/18/2019 at 9:07am
Red20,

Use extreme care with brake cleaner, it's very bad nasty stuff when burned. It really shouldn't be burned at all. The by product of burning brake clean is phosgene gas, lethal as can be. 

Here's a testimonial


Use extreme caution with shop chemicals everyone.
70 Javelin SST, second owner, purchased 1972
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