TheAMCForum.com Homepage
Forum Home Forum Home > The Garage > AMC V8 Engine Repair and Modifications
  New Posts New Posts RSS Feed - Intake Manifold Vacuum Leak(s)
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Click for TheAMCForum Rules / Click for PDF version of Forum Rules
Your donations help keep this valuable resource free and growing. Thank you.

Intake Manifold Vacuum Leak(s)

 Post Reply Post Reply Page  <123>
Author
Message
Red20 View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Jan/29/2013
Location: Oceanside CA
Status: Offline
Points: 1556
Post Options Post Options   Thanks (0) Thanks(0)   Quote Red20 Quote  Post ReplyReply Direct Link To This Post Posted: Jan/14/2019 at 12:51pm
Yeah it definitely is acting like it’s reacting to intake pulses.  Regardless, there’s a leak because I can get the idle down and the throttle blades are closed as well as the IAC valve.  Once I get that sorted, I’ll know how much of an issue the dual plane is going to be.  I am running a spacer under the TB.  

As for issues with EFI and dual plane, for sure a single plane is better, but not all EFI TBs will be the same.  The Terminator is particularly difficult because the MAP sensor is on the bottom surface and to the side, so with a plenum divider, it’s only seeing signal from one bank.  Other systems, QFI for example, have the MAP sensor in the ECU and you run a vacuum source to it. 
1969 Javelin SST "Screamin' Banana" - Totaled Feb 2018
1973 Hornet Sportabout X "yellajack" - 360/727/TracLoc DAILY DRIVER
Back to Top
Mopar_guy View Drop Down
Supporter of TheAMCForum
Supporter of TheAMCForum
Avatar

Joined: Jun/07/2009
Location: Ohio
Status: Offline
Points: 4805
Post Options Post Options   Thanks (0) Thanks(0)   Quote Mopar_guy Quote  Post ReplyReply Direct Link To This Post Posted: Jan/14/2019 at 3:52pm
One quick check before you start pulling things apart is to pull the pcv valve and plug it and see how the system reacts to that. I've run into wrong, or bad pcv's that flow to much causing the same issue.

"Hemilina" My 1973, 5.7 Hemi swapped Javelin
Back to Top
Trader View Drop Down
AMC Addicted
AMC Addicted


Joined: May/15/2018
Location: Ontario
Status: Offline
Points: 6761
Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Jan/14/2019 at 4:28pm
An old, DANGEROUS, trick was to use ether and give short mist's around the intake and carburetor and wait for the RPM to jump and find a leak.
Dad used to do this all the time. It worked and he never did fry a vehicle, lucky???
I use carburetor cleaner, much less volatile - no engines catching fire! Do this outside and always have a fire extinguisher handy. Just short bursts - NOT a steady spray!
The RPM will jump at a leak point. Repeat at the same RPM jump point to confirm.

 
Back to Top
Red20 View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Jan/29/2013
Location: Oceanside CA
Status: Offline
Points: 1556
Post Options Post Options   Thanks (0) Thanks(0)   Quote Red20 Quote  Post ReplyReply Direct Link To This Post Posted: Jan/16/2019 at 1:41am
I datalogged hot idle with and without the PCV connected and it ran smoother without it, so that’s an issue.  It’s the right one and it isn’t very old.  I may have a bad one?  I’m considering switching to an orifice type.  

I haven’t sprayed ether looking for a leak, but I sprayed brake cleaner.  Didn’t find anything.  I’m at Disneyland with the wife and kids, so I’ll pull the intake, maybe machine the plenum spacer down a little, and reseal it when I get back. 
1969 Javelin SST "Screamin' Banana" - Totaled Feb 2018
1973 Hornet Sportabout X "yellajack" - 360/727/TracLoc DAILY DRIVER
Back to Top
White70JavelinSST View Drop Down
Supporter of TheAMCForum
Supporter of TheAMCForum
Avatar

Joined: Aug/08/2012
Location: Minnesota
Status: Offline
Points: 4867
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
Back to Top
Red20 View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Jan/29/2013
Location: Oceanside CA
Status: Offline
Points: 1556
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
Back to Top
Red20 View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Jan/29/2013
Location: Oceanside CA
Status: Offline
Points: 1556
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
Back to Top
Red20 View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Jan/29/2013
Location: Oceanside CA
Status: Offline
Points: 1556
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
Back to Top
Trader View Drop Down
AMC Addicted
AMC Addicted


Joined: May/15/2018
Location: Ontario
Status: Offline
Points: 6761
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.  
Back to Top
Red20 View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Jan/29/2013
Location: Oceanside CA
Status: Offline
Points: 1556
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
Back to Top
 Post Reply Post Reply Page  <123>
  Share Topic   

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.03
Copyright ©2001-2019 Web Wiz Ltd.

This page was generated in 0.141 seconds.
All content of this site Copyright © 2018 TheAMCForum unless otherwise noted, all rights reserved.
PROBLEMS LOGGING IN or REGISTERING:
If you have problems logging in or registering, then please contact a Moderator or