Intake Vacuum leaks? - Chevelle Tech
Troubleshooting Diagnosing problems done here.

 6Likes
Reply
 
LinkBack Thread Tools Search this Thread Display Modes
post #1 of 17 (permalink) Old Aug 12th, 19, 10:38 AM Thread Starter
Team Member
Curtis
 
Join Date: Apr 2019
Location: Paradise, Ca
Posts: 49
Garage
Intake Vacuum leaks?

while tuning up my electric choke i noticed a sucking noise on the intake manifold. Its coming from four holes. Put you finger on them and its sucking, all four hole. Quick google and these are the four bolt holes on a edelbrock performer RPM 2 intake #7562. These four bolts are specified in manual as hand tighten only.

Mine have no bolts and you can see the gasket covering the holes between block and manifold. Never was a bolt in any of these four holes.

The question is this, is there any reason this would have been done intentionally? The car runs great, its dyno'd at 638 hp 652 torque. When i plug all four holes the idle drops way down and car barely wants to keep idling.
Attached Thumbnails
Click image for larger version

Name:	Capture.jpg
Views:	43
Size:	111.2 KB
ID:	600362  

Last edited by Curtis Chamberlain; Aug 12th, 19 at 10:55 AM.
Curtis Chamberlain is offline  
Sponsored Links
Advertisement
 
post #2 of 17 (permalink) Old Aug 12th, 19, 12:22 PM Thread Starter
Team Member
Curtis
 
Join Date: Apr 2019
Location: Paradise, Ca
Posts: 49
Garage
Re: Intake Vacuum leaks?

Anyone know of a good BBC forum or tech support type site? Im really concerned about this vacuum, leak issue
Curtis Chamberlain is offline  
post #3 of 17 (permalink) Old Aug 12th, 19, 1:17 PM
Gold Member
Gene
 
Join Date: Sep 2000
Location: Buffalo NY
Posts: 14,271
Re: Intake Vacuum leaks?

Ya, put bolts in them holes! Unless those are some special race heads I am not familiar with , you are missing the four over port bolts. my lack of race head knowledge or not, clearly they are sucking unfiltered air, either from atmosphere or from the galley, so MUST BE squared away.

We dont know crap about BBCs here.
71350SS likes this.

Gene
ACES 3112/Team Chevelle Gold #62
Be big, be a 'builder'!
427L88 is offline  
 
post #4 of 17 (permalink) Old Aug 12th, 19, 1:24 PM
Tech Team
Bill
 
Join Date: Jan 2016
Location: In the Garage
Posts: 863
Garage
Re: Intake Vacuum leaks?

Just doing a quick search, it looks like some heads use them and some don't. My stock heads do. If your heads do not have holes, I bet the intake port shape doesn't match either. Pull the intake and match the gasket to the intake and head ports to see what is not right. Maybe your head has the holes and it's just the wrong gasket.

1969 Sport Coupe SS Tribute Cortez Silver 454 400TH
69SS454 is offline  
post #5 of 17 (permalink) Old Aug 12th, 19, 1:32 PM Thread Starter
Team Member
Curtis
 
Join Date: Apr 2019
Location: Paradise, Ca
Posts: 49
Garage
Re: Intake Vacuum leaks?

They are Patriot 320 CC heads with rectangular ports. Thats all i know about them. This engine came from the builder, Ross Automotive Machine Lapeer Michigan built in 2010 and has been this was since. Made me think it had to be intentional. Maybe the gasket without a hole for those bolts was sufficient to stop leak for a time and its slowed gained the leak? Very strange however as it runs amazing, has tons of power none of the typical vacuum leak issues you would expect.

I ordered some bolts for it. Just hope I don't need to change the gaskets all together and remove the intake.
Curtis Chamberlain is offline  
post #6 of 17 (permalink) Old Aug 12th, 19, 1:36 PM Thread Starter
Team Member
Curtis
 
Join Date: Apr 2019
Location: Paradise, Ca
Posts: 49
Garage
Re: Intake Vacuum leaks?

Quote:
Originally Posted by 69SS454 View Post
Just doing a quick search, it looks like some heads use them and some don't. My stock heads do. If your heads do not have holes, I bet the intake port shape doesn't match either. Pull the intake and match the gasket to the intake and head ports to see what is not right. Maybe your head has the holes and it's just the wrong gasket.
The heads and intake both have rectangular ports per specs. i guess i could poke through the hole and see if the block has bolt holes there.
Curtis Chamberlain is offline  
post #7 of 17 (permalink) Old Aug 12th, 19, 2:31 PM
Tech Team
Bill
 
Join Date: Jan 2016
Location: In the Garage
Posts: 863
Garage
Re: Intake Vacuum leaks?

Even if they are the right gaskets and the ports match, they are leaking and need replaced. Pull the intake, get a new gasket set, and coat them with Gasgacinch Gasket Sealer.
69SS454 is offline  
post #8 of 17 (permalink) Old Aug 12th, 19, 3:08 PM Thread Starter
Team Member
Curtis
 
Join Date: Apr 2019
Location: Paradise, Ca
Posts: 49
Garage
Re: Intake Vacuum leaks?

If i fix these leaks what are the adjustments that will need to be made to offset the adjustments made to counter the leaks? Just add more air at carb?
Curtis Chamberlain is offline  
post #9 of 17 (permalink) Old Aug 12th, 19, 3:35 PM
Tech Team
Bill
 
Join Date: Jan 2016
Location: In the Garage
Posts: 863
Garage
Re: Intake Vacuum leaks?

Hopefully just open the throttle a little more. May need to go with smaller jets. Is this a recent problem or have you made air jet or other adjustments to fix it long ago?

1969 Sport Coupe SS Tribute Cortez Silver 454 400TH
69SS454 is offline  
post #10 of 17 (permalink) Old Sep 7th, 19, 1:00 PM
Tech Team
Steve
 
Join Date: Dec 2012
Location: Oakdale, Ca.
Posts: 243
Re: Intake Vacuum leaks?

Curtis, did you ever get this problem resolved?

67 Chevelle SS:
original paint, M20, & 3:31 posi.
Unrestored, but dreaming of doing so
To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
guitargeak99 is offline  
post #11 of 17 (permalink) Old Sep 7th, 19, 3:04 PM Thread Starter
Team Member
Curtis
 
Join Date: Apr 2019
Location: Paradise, Ca
Posts: 49
Garage
I have not. I got a new gasket just haven’t tackled reliving it yet. Hard to do all that work when it runs soo good lil
LeoP and guitargeak99 like this.

67 Malibu Sport Coupe
496 Stroker, 320CC Heads, 10:1, Demon 850 carb, HEI 65k, 16 Degrees base, 38 final, 638 [email protected], 696 [email protected]
Dakota Digita HDX, GPS, Fan Control
DSE stage 3 susp front and rear
Wilwood 6 piston brakes, DSE master cylinder/booster
DSE PS Gear, quick ratio, Ididit column
Bonspeed 20x10/19x8 with Michelin pilot sport 4s
Curtis Chamberlain is offline  
post #12 of 17 (permalink) Old Sep 8th, 19, 12:06 PM
Senior Tech Team
 
Join Date: Apr 2012
Location: Yerington, Nevada
Posts: 1,719
Re: Intake Vacuum leaks?

Yup, not one of us know anything about fat block Chevy engines, all I ever did with them was fix them after the experts made them work worse, work directly with Duntov at Chevrolet Skunk Works on engine development, and drag race a blown, injected nitro 605 inch one in an AA/Fuel Altered. Makes me dumb as a box of rocks about fat block Chevy engines.

Why not simply put the 4 bolts into the holes and tighten them up, that usually cures leaks at those 4 points. Worth a try, and no pulling the manifold back off if it works.

BTW, best way to find an air leak is to flow a low volume of UNLIT propane around a suspect leak. Engine will perk up a touch, exhaust will smell different, and NO residue on engine parts.
LeoP and blue_69_malibu like this.
Dave Ray is offline  
post #13 of 17 (permalink) Old Sep 8th, 19, 8:21 PM Thread Starter
Team Member
Curtis
 
Join Date: Apr 2019
Location: Paradise, Ca
Posts: 49
Garage
There’s a gasket under the bolt holes, that’s how I know the wrong one was used. I could just drill out the holes I supposed but the fact it is the way it is I would feel better just removing it and making sure it’s right anyways.

I wasn’t implying anywhere didn’t know anything about bbc, I was just looking for another site I could search around on.

67 Malibu Sport Coupe
496 Stroker, 320CC Heads, 10:1, Demon 850 carb, HEI 65k, 16 Degrees base, 38 final, 638 [email protected], 696 [email protected]
Dakota Digita HDX, GPS, Fan Control
DSE stage 3 susp front and rear
Wilwood 6 piston brakes, DSE master cylinder/booster
DSE PS Gear, quick ratio, Ididit column
Bonspeed 20x10/19x8 with Michelin pilot sport 4s
Curtis Chamberlain is offline  
post #14 of 17 (permalink) Old Sep 9th, 19, 2:07 PM
Senior Tech Team
 
Join Date: Apr 2012
Location: Yerington, Nevada
Posts: 1,719
Re: Intake Vacuum leaks?

Actually, to do it RIGHT, pulling the heads to drill the two holes per is the way to go, heads mounted on a milling machine (ONLY if you wanted to do it the right way).

Do you know if it is just the gaskets covering threaded bolt holes, or, are there no holes in the first place???

If ignorance is bliss, why aren't more people totally happy?
Dave Ray is offline  
post #15 of 17 (permalink) Old Sep 9th, 19, 2:11 PM Thread Starter
Team Member
Curtis
 
Join Date: Apr 2019
Location: Paradise, Ca
Posts: 49
Garage
There’s holes just gasket covering them. I picked through it with a pick to confirm

67 Malibu Sport Coupe
496 Stroker, 320CC Heads, 10:1, Demon 850 carb, HEI 65k, 16 Degrees base, 38 final, 638 [email protected], 696 [email protected]
Dakota Digita HDX, GPS, Fan Control
DSE stage 3 susp front and rear
Wilwood 6 piston brakes, DSE master cylinder/booster
DSE PS Gear, quick ratio, Ididit column
Bonspeed 20x10/19x8 with Michelin pilot sport 4s
Curtis Chamberlain is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Chevelle Tech forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address. Note, you will be sent a confirmation request to this address.

Email Address:
OR

Log-in










Thread Tools Search this Thread
Show Printable Version Show Printable Version
Email this Page Email this Page
Search this Thread:

Advanced Search
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome