Go Back   Ford Truck Enthusiasts Forums > Performance, Engines & Troubleshooting > Small Block V8 (221, 260, 289, 5.0/302, 5.8/351W)
Sign in using an external account
Register Forgot Password?


Welcome to Ford-Trucks Forums!
Welcome to Ford-Trucks.com.

You are currently viewing our forums as a guest, which gives you limited access to view most discussions and access our other features. By joining our community you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is fast, simple and absolutely free so please, join the Ford-Trucks Forums community today!





 
Reply
 
LinkBack Thread Tools Search this Thread
  #1 (permalink)  
Old 08-26-2002, 08:36 PM
charleslincoln charleslincoln is offline
New User
 
Join Date: Aug 2002
Location: Cathlamet, WA
Posts: 15
charleslincoln is starting off with a positive reputation.
Vacuum Leak - Intake Manifold?

1984 351W HO with Motorcraft/Holley 4180c in a 1978 E-150 van. Except for the engine & carb, everything is 1978 stock.

Key symptom: Stalls when put in gear. Manifold vacuum, engine at operating temperature, is 18” and behaves ok per the charts. But put in gear and work the throttle to maintain an idle it drops to 5-6.”

I’ve spent many hours trying to resolve what I thought was a carburetor problem. But recently found this forum and a review of previous postings suggest that a vacuum leak could cause my symptoms. AND I FOUND A VACUUM LEAK!

It appears to be above the #1 cylinder. When sprayed on the upper edge of the valve cover, which is also the location of the intake manifold edge, propane or carb cleaner will cause rpm to increase; water will cause a decrease in rpm.

Is this confirmation of an intake manifold leak? Or is there anything else in close proximity that could be the culprit? Will that cause the stalling? Also, would such a leak affect the mixture for all cylinders? Examination of the sparkplugs - #1 does not appear different from the others.

If I remove the intake manifold, is there any other inspection or maintenance that should be done while the manifold is off?

Finally (for this post ), mounted on the intake manifold to the left of the carb is a vacuum operated device. Is this the exhaust heat control valve? There is no vacuum line connected to it, and it doesn’t engage anything anyway. There is a rotating rod sticking into the manifold, but nothing connected to it. Do I just leave it as is or is there something I should get for it?

I might still have carb and other problems, but vacuum leak seems to be the first to fix before tackling. All comments appreciated. TIA.

Charlie Lincoln
Portland, Oregon USA
clincoln@spiritone.com

Reply With Quote
  #2 (permalink)  
Old 09-03-2002, 12:18 AM
charleslincoln charleslincoln is offline
New User
 
Join Date: Aug 2002
Location: Cathlamet, WA
Posts: 15
charleslincoln is starting off with a positive reputation.
Vacuum Leak - Intake Manifold?

I just botched the intake manifold gasket replacement using “regular” gaskets. Even with two people it seems impossible to place the intake manifold squarely on the new gaskets with out displacing the end seals. (This is a van - installing from the inside.)

I now realize that there is a one piece Valley Baffle gasket for vans, instead of the two intake gaskets, which appears to mount on top of the end seals. My 1984 engine doesn’t have this (I don’t know what vehicle it came out of).

What is the purpose of the valley baffle on the 351W vans? Before trying again, I especially wonder if it will help with intake manifold placement? Any other tips, guidance, suggestions?

TIA,
Charlie Lincoln
Portland, Oregon USA
clincoln@spiritone.com

Reply With Quote
  #3 (permalink)  
Old 09-03-2002, 11:37 PM
cajunbronco cajunbronco is offline
Senior User
 
Join Date: Feb 2002
Posts: 402
cajunbronco is starting off with a positive reputation.
Vacuum Leak - Intake Manifold?

Don't use the end seals,just put a good bead of hi temp silicone.It helps to put silicone around the water jackets for insurance and let the silicone set up for a few minutes so the gasket won't move when you set the intake.Just push on it a little, if it moves let it set up a little longer.Then put the silicone on the ends,you don't want this to set up long before you set the intake.I have seen people take some old intake bolts and cut the heads off or use allthread and put it at the 4 corners so you can set the intake.Then replace them with the proper bolts once it sets up.As for the valley gasket's,most later model motors that have the solid valley don't use a valley gasket.

Billy
Reply With Quote
  #4 (permalink)  
Old 09-04-2002, 08:45 PM
charleslincoln charleslincoln is offline
New User
 
Join Date: Aug 2002
Location: Cathlamet, WA
Posts: 15
charleslincoln is starting off with a positive reputation.
Vacuum Leak - Intake Manifold?

Thanks, Billy. Using RTV instead of end seals will certainly make the process easier. Using guides in the corners is a “no-brainer” I should have thought of.

Can you help me visualize this valley terminology - what is meant by solid valley? With the intake manifold off, the “valley” I see is just a gaping area, lifter rods exposed and a few holes in the bottom, for oil drainage I assume. There is no “pan” except for the riveted plate under the carb mounting area. (I don’t know the original source of this 1984 engine - but that’s another story. The rest of the 1978 van is stock - I’m the original owner.)

- Charlie
Reply With Quote
  #5 (permalink)  
Old 09-05-2002, 05:20 AM
Quantrex Quantrex is offline
Senior User
 
Join Date: Jun 2002
Location: Oklahoma
Posts: 423
Quantrex is starting off with a positive reputation.
Vacuum Leak - Intake Manifold?

Reply With Quote
  #6 (permalink)  
Old 09-07-2002, 09:57 AM
cajunbronco cajunbronco is offline
Senior User
 
Join Date: Feb 2002
Posts: 402
cajunbronco is starting off with a positive reputation.
Vacuum Leak - Intake Manifold?

The valley "pan" Is the solid area between the lifters and pushrods.Some older engines have a valley gasket that is part of the intake manifold.Most newer engines have the 2 piece intake gaskets without the valley cover.When you install the gaskets make sure you seal the corners where the intake gasket and the head meet with a bead of silicone.

Billy
Reply With Quote
Old 09-07-2002, 09:57 AM
Reply

Go Back   Ford Truck Enthusiasts Forums > Performance, Engines & Troubleshooting > Small Block V8 (221, 260, 289, 5.0/302, 5.8/351W)

Tags
289, 351w, gasket, install, intake, leak, manifold, v8, vacuum

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not 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 On
Trackbacks are On
Pingbacks are On
Refbacks are On
Forum Jump



All times are GMT -5. The time now is 04:58 PM.


Powered by vBulletin® Version 3.7.5
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Advertising - Terms of Use - Privacy Statement - Jobs
This forum is owned and operated by Internet Brands, Inc., a Delaware corporation. It is not authorized or endorsed by the Ford Motor Company and is not affiliated with the Ford Motor Company or its related companies in any way. Ford® is a registered trademark of the Ford Motor Company.

vbulletin Admin Backup