Big Block By-Pass - 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 05-10-2007, 12:50 PM
Registered User
 
Join Date: May 2006
Location: Tulsa, Ok
Posts: 22
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Big Block By-Pass

I'm in the middle of changing the water pump on my 454 BB Chevy. Is it nessesary to run the by-pass hose? I would like to leave it off. It's ugly and a pain to put on. Would this cause any problems and why is there in the first place. The new pump is a long style aluminum pump. I do not run a heater. What can I do to make this work? The car, a 65 Shelby Cobra, is only for cruising and good looks. Need help fast. This is an Edelbrock pump. Wayne

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 05-10-2007, 01:51 PM
Registered User
 
Last photo:
Join Date: Apr 2007
Location: Seattle, Wa
Posts: 6,827
Wiki Edits: 0

Thanks: 4
Thanked 451 Times in 386 Posts
The bypass prevents pump cavitation when the thermostat is closed and it allows water circulation inside the cooling passages preventing steam pocket formation before the thermostat opens.

Eliminating this hose risks pump life as cavitation shakes the daylights out of the impeller, shaft and bearing. Steam pocket formation allows local overheating, mostly of and around the exhaust valves with heat stress cracking of the castings, possible loss of hard seat inserts if the heads are aluminum, and reduced valve life because of overheating being some outcomes.

It may be small, it may be ugly, but it is important.

Bogie
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 05-10-2007, 07:23 PM
Registered User
 
Join Date: May 2006
Location: Tulsa, Ok
Posts: 22
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Oldbogie, This is not good news. If remove the thermostat that will only cause other problems! I read someplace that you can drill small 1/8" holes in the thermostat housing to help this by-pass problem. Is this true or just an "old wives tale"? Thanks for the fast reply Oldbogie.
Wayne
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 05-10-2007, 07:42 PM
Classix_Lover's Avatar
Music soothes the soul
 

Last journal entry: Wiring finished finally
Last photo:
Join Date: Jul 2005
Location: League City, TX
Age: 26
Posts: 584
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Quote:
Originally Posted by waykoe
Oldbogie, This is not good news. If remove the thermostat that will only cause other problems! I read someplace that you can drill small 1/8" holes in the thermostat housing to help this by-pass problem. Is this true or just an "old wives tale"? Thanks for the fast reply Oldbogie.
Wayne
I heard that was mainly for helping to bleed any unecessary air from the system.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 05-10-2007, 07:47 PM
Bryan59EC's Avatar
Car? Truck? Who Cares
 

Last journal entry: First week of December
Last photo:
Join Date: Jun 2006
Location: San Antonio, Texas
Age: 54
Posts: 2,367
Wiki Edits: 0

Thanks: 1
Thanked 21 Times in 19 Posts
I have tried with it off, holes drilled in the t-stat, >>>overheat in 10 minutes unless I open the heater valve.>>>>>close valve, car overheats again.

Leave it on

Bryan
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 05-10-2007, 07:47 PM
Member
 
Last wiki edit: Ford axle ratio codes
Last journal entry: Rear Suspension
Last photo:
Join Date: Aug 2005
Location: Prattsville
Posts: 6,388
Wiki Edits: 31

Thanks: 2
Thanked 58 Times in 54 Posts
yep, just lets air out. some stat's are pre drilled with them
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 05-10-2007, 08:20 PM
opinionated old fart
 

Last journal entry: Sheetmetal
Last photo:
Join Date: Jan 2007
Location: Round Rock, Tx
Posts: 65
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I run a 496 with 11 to 1 comp, aluminum pump and no bypass hose with no problems.

Larry
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 05-10-2007, 08:25 PM
Classix_Lover's Avatar
Music soothes the soul
 

Last journal entry: Wiring finished finally
Last photo:
Join Date: Jul 2005
Location: League City, TX
Age: 26
Posts: 584
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Quote:
Originally Posted by CptKaos
I run a 496 with 11 to 1 comp, aluminum pump and no bypass hose with no problems.

Larry
Lucky bastard...
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 05-10-2007, 08:43 PM
opinionated old fart
 

Last journal entry: Sheetmetal
Last photo:
Join Date: Jan 2007
Location: Round Rock, Tx
Posts: 65
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
the bypass hoses job is to let warm water flow to the heater core before the thermostat opens, that is all, no magic, no mystery.

Larry
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 05-11-2007, 06:06 AM
Bryan59EC's Avatar
Car? Truck? Who Cares
 

Last journal entry: First week of December
Last photo:
Join Date: Jun 2006
Location: San Antonio, Texas
Age: 54
Posts: 2,367
Wiki Edits: 0

Thanks: 1
Thanked 21 Times in 19 Posts
That is what I thought too----
My 454 will overheat without it
Another gent on this board (in the same city as me) has a 454 that will run okay without but also has a 396 that has to have it .

When I ran a cooler T-stat with holes drilled----it got hot>>cooled down>>heated up>>>cooled down, several times before settling to an even temp.

With the bypass and a hotter t-stat/no holes---the car will warm up to temp and stay right there----no up and downs.

Bryan
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 05-11-2007, 09:42 AM
Member
 
Last photo:
Join Date: Aug 2005
Location: Virginia
Posts: 875
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
gotta love a guy who puts a big chevy in a Ford!!!!!!!!!!!!!!!
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 05-11-2007, 10:32 AM
Registered User
 
Last photo:
Join Date: Apr 2007
Location: Seattle, Wa
Posts: 6,827
Wiki Edits: 0

Thanks: 4
Thanked 451 Times in 386 Posts
Quote:
Originally Posted by waykoe
Oldbogie, This is not good news. If remove the thermostat that will only cause other problems! I read someplace that you can drill small 1/8" holes in the thermostat housing to help this by-pass problem. Is this true or just an "old wives tale"? Thanks for the fast reply Oldbogie.
Wayne
You can eliminate the hose and provide a by-pass by drilling a couple small holes in the thermostat. This will provide a bleed of coolant which will allow a little circulation. As long as you don't start to wind the revs up before the motor is warmed to the point where the thermostat is opening, this would be OK. The other side effect is the leak past the thermostat to the radiator will increase the time for warm up.

I would think that a couple/three 1/8th holes would do it.

Bogie
Reply With Quote Quick reply to this message
  #13 (permalink)  
Old 05-11-2007, 10:49 AM
Hotrodders.com Moderator
 

Last journal entry: PICTURE TEST
Last photo:
Join Date: Jan 2004
Location: york pa
Age: 52
Posts: 2,795
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
by pass

I also run big blocks with-out the by pass hose and have zero issues with it.. You do need the 1/8" holes in the t-stat..

One big reason for most cars that over heat is incorrect ignition timing... I would bet that the big blocks that have heating issues do not have enough timing on them.

Keith
Reply With Quote Quick reply to this message
  #14 (permalink)  
Old 05-11-2007, 12:09 PM
Registered User
 
Last photo:
Join Date: Apr 2007
Location: Seattle, Wa
Posts: 6,827
Wiki Edits: 0

Thanks: 4
Thanked 451 Times in 386 Posts
Quote:
Originally Posted by k-star
I also run big blocks with-out the by pass hose and have zero issues with it.. You do need the 1/8" holes in the t-stat..

One big reason for most cars that over heat is incorrect ignition timing... I would bet that the big blocks that have heating issues do not have enough timing on them.

Keith
Here's whats going on, or not, inside an engine with out any form of coolant return when the thermostat is closed. Coolant is not circulating! Therefore, the pump is in cavitation which aerates the coolant and causes vibrations of the impeller, it's shaft, bearing and seal that they are not designed for. This increases the potential for failure of these components, which you see as reduced life not so much a catastrophe like the pump blowing off the front of the engine or something exciting like that. More likely the seal suddenly leaks on a holiday weekend when you're a hundred and fifty miles from home. This might me more of an engineers than mechanics issue where engineers worry about things that might be where mechanics worry about things that are. Who knows? If your going to do this you probably should know whether your water pump has a metal or plastic impeller. I'd bet on metal putting up with cavitation for a longer period, but transferring more of the forces to the shaft, bearing and seal. Plastic probably absorbs more punishment without secondary transfer of forces, but won't do it for long. The second big issue with no by-pass during closed thermostat is no coolant flow in the block and heads. This means localized hot spots form around the usual super hot places which is the exhaust valves and seats. This forms steam pockets and steam is not a very good conductor of heat, therefore, the metal in these areas gets very hot and expands. Expansion against colder adjacent metal results in cracked castings for cast iron and will often allow the hard seat insert of an aluminum head to fall out, now that's a real mess. In any casting the valve seats will distort and the valves will leak gasses past these distortions. These results can be a bit expensive to repair.

These aren't just theoretical ramblings this is what's happening. The possibility of damage is a function of how often and how hard you push, all that does is establish when it does damage, nothing for if.

Now the fellow that started this thread stated he had no heater. The heater connection is also a coolant bypass when the thermostat is closed. So normal factory engines really have two bypasses, one being pump to block in the case of the BBC a hose to the manifold, the SBC uses a passage cast into the block and pump under the right side pump horn. The second is the heater core circuit which routes from various places on the engine to various schemes to the intake side of the water pump. This may be to the pump itself or to the cool tank side of the radiator or into a fitting in the coolant pump inlet hose. All of these are used by different years on different models. So if your system includes a heater, you also have a bypass beside the crummy hose between the manifold and the water pump.

Now I've had a few Ford FE engines in my life and owning one of them really makes you insensitive to the whinnings of BBC owners. If you want a bypass that's ugly and is a real pain to repair when it fails, get yourself and FE (332, 352, 361, 390, 391, 406, 410, 427, 428) and find out what real hardship is!

Bogie
Reply With Quote Quick reply to this message
  #15 (permalink)  
Old 05-13-2007, 07:24 PM
Registered User
 
Join Date: May 2006
Location: Tulsa, Ok
Posts: 22
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
k-star, Your right about the timing issue. If I have too much advance it will run hot when I run the engine past 3000 RPM, If I turn the timing back it will overheat in traffic. It took a long time to find out what was the best setup. I understand what Oldbogie is saying. This car is strickly a summertime car. No top, no side glass, a true roadster. Having said that, the car is driven only when the air temp is over 60 so cold starts and long warm-ups are not a problem. The cast iron pump went "south" because the car was not run for all most a year, a heart attack will do that to you. Now I'm ready for the summer. The by-pass hose (the one on my car) is more ugly than it's a pain. This is a hi- dollar pump and I'd like to get the most of the looks dept. or I would of got a stock replacment from Autozone. I have all ready collapsed the upper rad. hose once on warm up with the by-pass connected. I appreciate all the response. It all helps.

BBCMudbogger, If Chevy would not of had the Corvette, the Cobra WOULD of came with a Chevy.

Thanks everybody. Your all good people! Wayne
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
Big Block 82 Pontiac Gran Prix william27103 Engine 3 03-30-2009 12:50 PM
Ford Big block 4 spd bellhousing bigblocktorino Transmission - Rearend 3 10-05-2006 03:56 AM
small block or big block southrncuz1816 Engine 16 03-19-2006 07:40 PM
Small Block Vs. Big Block bfrett123 Engine 3 10-14-2004 05:27 PM
big block or small block ford? stangfiend Engine 3 12-10-2002 09:55 AM


All times are GMT -6. The time now is 05:05 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.