SBC with no PCV - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 05-25-2006, 05:36 AM
Registered User
 

Last journal entry: Better late than never
Last photo:
Join Date: Feb 2006
Location: Palm Beach, FL
Posts: 237
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
SBC with no PCV

Just rebuilt my SBC and was very happy until I noticed some oil apearing on the floor under it after the first 50 mile outing.

I noticed oil along the intake manifold where it mates to the valve covers and thought it was the valve cover gaskets but now I think it is being forced out from under the intake manifold.

Checking on the site here I suspect my crankcase ventilation system is not up to scratch, see picture.



As you can see my only breathing is through the front mounted vent tube. When I remove the cap with the engine idling I see a noticable amount of fumes coming out. My local and seemingly knowledgable NAPA guy says it will reduce in time as the rings seal and quite normal?

I dont see any way to install a PCV on these covers which is a crying shame as I love them.

So, will having run this for a hundred or so miles in this configuration done any harm or weakened the rear seal or even worse any damage to the engine? Replacing the intake gasket isnt a problem, replacing the rear seal is!

Am I able to get near identical covers that allow a PCV?

This is a real disappointment after the many weeks getting it back together.

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 05-25-2006, 05:52 AM
Registered User
 
Last photo:
Join Date: Nov 2004
Location: Cali
Posts: 994
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I noticed oil along the intake manifold where it mates to the valve covers...
This is a little confusing as the intake manifold doesn't mate to the valve covers. Is the oil coming out from under the valve covers? Possibly the end of the intake?
Is this a later block without the draft tube hole in the rear behind the distributor?
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 05-25-2006, 06:05 AM
302 Z28's Avatar  
Last photo:
Join Date: May 2003
Location: North Texas
Posts: 10,837
Wiki Edits: 0

Thanks: 1
Thanked 86 Times in 73 Posts
The front breather tube should be enough to prevent positive pressure in the crank case. If it were mine I would do away with that front breather tube and install a traditional PCV system. I know it would defeat the nostalgia look, but it is a much better system.

Is that the fuel hose i see draped over the header .

Vince
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 05-25-2006, 06:17 AM
Registered User
 

Last journal entry: Better late than never
Last photo:
Join Date: Feb 2006
Location: Palm Beach, FL
Posts: 237
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
thanks guys,

onovakind67, my intake certainly does run alongside the valve cover. It may not technically 'mate' to it but I think you know what I mean. They come within a 1/4" of each other for the length of the engine etc. This ia an early 80's 305 block and does not have the vent tube at the rea of the block. I removed the oil and restarted the engine. The oil started to reappear from under the manifold.

302/Z28 dont worry that was the old PCV hose from the previous set of covers. I hadnt gotten around to removing it as of that photo. The engine had not been run at that point and in fact took another week of installing the front end/rad etc.

Lying under the car a few minutes ago I am now conerned that I have some oil seepage around the rear seal too.

It would appear excessive pressure may be the problem then?
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 05-25-2006, 06:52 AM
Redman Racing
 
Last photo:
Join Date: Sep 2003
Location: Philadelphia
Age: 33
Posts: 235
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Hi there, Just gonna jump in and ask if the motor was bored and honed or did you just put some new rings on. basically I am asking, How was the motor prepped?
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 05-25-2006, 07:01 AM
Registered User
 

Last journal entry: Better late than never
Last photo:
Join Date: Feb 2006
Location: Palm Beach, FL
Posts: 237
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Thanks, the bores were fine and so just honed and new rings put in.
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 05-25-2006, 07:06 AM
Frisco's Avatar
Glad To Be Here
 
Last photo:
Join Date: Nov 2002
Location: Canton, North Carolina
Age: 72
Posts: 2,244
Wiki Edits: 0

Thanks: 0
Thanked 8 Times in 8 Posts
A PCV valve can be installed in the intake manifold. Remove the intake. Find an area in the top of the intake towards the rear where you can drill & tap thru the intake into the block valley area. Do not drill into any of the runners. The tap size will be for a screw-in PVC valve. Install a flat plate to the underside of the intake covering the area where you drilled & tapped the hole. Space the plate away a very small amount (1/16-1/8"). This plate is to prevent oil from being sucked into the PCV valve. Connect a hose from the other end of the PCV to the appropriate fitting at the base of the carb.

The oil leak around the intake could be from the end gaskets. I do NOT suggest using the rubber end gaskets. Use a generous amount of clear RTV both front and rear. Depending on the gap between the bottom of the intake and the block; you may put a 3/8-1/2 high bead in this area. Let the RTV "skim" over for about ten minutes before installing the intake. When installing the intake place it straight down with no sideways movement (or as little as possible). Install the intake bolts by hand and then tighten starting from the center most bolts alternating from one side to the other. Do not over-tighten. Most torque wrenches will not fit in this area so just hand tighten as evenly as you can. The excess RTV will push out and can be trimmed with a razor blade after it dries. I also put a small amount of the clear RTV around the water ports in the intake gaskets. Use quality gaskets. I like Fel-Pro 375-1204. You may also want to put some RTV on the intake bolt threaded areas where the bolt holes are thru holes. Oil can weep up and out along the threads. If you have your oil pressure sending unit installed next to the distributor, check to see if the fitting there is weeping oil as well. For the thick aluminum valve covers I like the thick Fel-Pro 375-1604 gaskets. I glue them to the valve covers with the same clear RTV and don't use anything on the head surface area.

EDIT: The tapped hole should be sized by whatever threads are on the PCV valve you get. I believe the early '60's Corvette PCV valves were threaded on one end.
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 05-25-2006, 07:13 AM
Registered User
 

Last journal entry: Better late than never
Last photo:
Join Date: Feb 2006
Location: Palm Beach, FL
Posts: 237
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Frisco, great solution!

So this way I can run a proper PCV AND keep the covers.

I will call my local speed shop this morning and see if they stock the screw-in PCV valve.

FYI I did install the intake with sealant at the ends instead of the rubber gaskets. I was worried it wouldnt seal as well but wouldn't you know it that is one place there appears to be no oil leaking!!

I will monitor the siutation and see whether the engine has to come out. The rear seal is worrying me.

Just a thought...coudlnt I fit a PCV in the existing hole in the intake instead of the front breather tube?
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 05-25-2006, 07:20 AM
Redman Racing
 
Last photo:
Join Date: Sep 2003
Location: Philadelphia
Age: 33
Posts: 235
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
How many miles were on the motor when you did this? Reused the stock pistons? The reason I am asking this is that it the cylinders might have have been a little out of round, and if that maybe the one of the causes for the excessive pressure but I cant see you messing up the rear main seal with that front breather.
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 05-25-2006, 07:33 AM
Frisco's Avatar
Glad To Be Here
 
Last photo:
Join Date: Nov 2002
Location: Canton, North Carolina
Age: 72
Posts: 2,244
Wiki Edits: 0

Thanks: 0
Thanked 8 Times in 8 Posts
Quote:
Originally Posted by pcoghlan
I will monitor the siutation and see whether the engine has to come out. The rear seal is worrying me.

Just a thought...coudlnt I fit a PCV in the existing hole in the intake instead of the front breather tube?
You need the tube in the front of the intake. It is the oil fill tube as well as the breather. With a PCV valve you need a breather to enable fresh air in.

Wait on pulling the engine until after you get the PCV valve installed. Once you have eliminated the pressure build up in the bottom end, the "leak" you see at the rear seal should go away. One note though. Without the PVC and a breather; excess pressure can build and "blow out" the seals. Back in the early '60's when PCV valves were being forced on residents in California for older vehicles, the road draft tube (crankcase breather) would get a rubber plug jammed into it and the fill tube cap (also a breather) would be changed to a sealed cap. This caused excessive pressure to build in the crankcase and would blow out rear seals. It was then discovered that the crankcase had to be able to breath.
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 05-25-2006, 07:33 AM
Registered User
 

Last journal entry: Better late than never
Last photo:
Join Date: Feb 2006
Location: Palm Beach, FL
Posts: 237
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
sorry, unknown miles on the motor. I bought it showing 8k miles on the clock but in an old rod that means nothing.

The machine shop said they measured fine and only needed a hone to make 'good to go'.

I did use the existing pistons alright with new rings, bad move? They looked fine and the shop cleaned them up very nice.
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 05-25-2006, 07:35 AM
Registered User
 

Last journal entry: Better late than never
Last photo:
Join Date: Feb 2006
Location: Palm Beach, FL
Posts: 237
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
OK Frisco, I will install a PCV and the see how it goes.

Local shops dont have screw-in PCVs and one said he hadnt heard of them?!

I will hit the usual places (summit, Jegs etc) and see how I get on.
Reply With Quote Quick reply to this message
  #13 (permalink)  
Old 05-25-2006, 07:41 AM
Redman Racing
 
Last photo:
Join Date: Sep 2003
Location: Philadelphia
Age: 33
Posts: 235
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by pcoghlan
sorry, unknown miles on the motor. I bought it showing 8k miles on the clock but in an old rod that means nothing.

The machine shop said they measured fine and only needed a hone to make 'good to go'.

I did use the existing pistons alright with new rings, bad move? They looked fine and the shop cleaned them up very nice.
Not a bad move reusing them. Maybe it will be fine with time and some more miles. PCV valve is a good move.
Reply With Quote Quick reply to this message
  #14 (permalink)  
Old 05-25-2006, 08:01 AM
Frisco's Avatar
Glad To Be Here
 
Last photo:
Join Date: Nov 2002
Location: Canton, North Carolina
Age: 72
Posts: 2,244
Wiki Edits: 0

Thanks: 0
Thanked 8 Times in 8 Posts
Quote:
Originally Posted by pcoghlan
OK Frisco, I will install a PCV and the see how it goes.

Local shops dont have screw-in PCVs and one said he hadnt heard of them?!

I will hit the usual places (summit, Jegs etc) and see how I get on.
I did a search and am fairly certain that the 62-63 Corvette is what you are looking for.

As to the local shops never hearing of screw-in PCV valves; tell them to look up a PCV valve for a 3.0 Mitsubishi engine (Plymouth Voyager almost any year). They are screw-in and may even work for your application. I'm not sure if the flow of the Chrysler unit would be enough for your engine.

I've not seen PCV valves listed at Summit or Jeg's.

Scroll down to where you can see part #13 in picture on the right side of page. Corvette PCV

It shows the screw-in PCV at the rear of the intake with a hose going to the sealed cap filler tube. It also shows a breather hose coming from the valve cover to the air cleaner. In your situation you would run the hose from the PCV to the base of the center carb and use a breather cap on the filler tube. Nothing would be connected to the valve covers.

Last edited by Frisco; 05-25-2006 at 08:11 AM. Reason: added link
Reply With Quote Quick reply to this message
  #15 (permalink)  
Old 05-25-2006, 08:14 AM
Registered User
 

Last journal entry: Better late than never
Last photo:
Join Date: Feb 2006
Location: Palm Beach, FL
Posts: 237
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Got it, thanks!

http://www.zip-products.com/Zip/dept...26929FE894FFD6

http://cgi.ebay.com/ebaymotors/CORVE...QQcmdZViewItem
Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
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 for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

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


Similar Threads
Thread Thread Starter Forum Replies Last Post
SBC 350 superiority rebuttle...was:POWERED BY CHEVY, WRITTEN ON A FORD, (from 'Engine Oldsmolac911 Hotrodders' Lounge 50 01-12-2011 10:00 PM
Why not a 350 sbc? bowtieorbust Engine 29 09-05-2008 09:43 AM
Need help with PCV hose on my sbc 350 Bakdok Engine 1 08-21-2005 03:48 AM
Pcv - Does My Sbc Really Need One? HJCHEVY400 Engine 5 04-13-2004 05:44 PM
PCV Valve - SBC - 50's style valve cover spudone Engine 4 10-03-2003 08:22 PM


All times are GMT -6. The time now is 12:59 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.