Thermostat bypass on Vortec conversion - 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 07-10-2009, 09:32 PM
Registered User
 
Last photo:
Join Date: Feb 2006
Location: Chattanooga, TN
Posts: 114
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Thermostat bypass on Vortec conversion

Reading the installation instructions for a Vortec manifold I purchased I see a note stating that I need to install a thermostat bypass since the 96+ blocks do not have the bypass in the block like the older generation.

Well, I'm wondering if my application will be OK as is. I'm installing this 98 Vortec truck engine in a 76 Nova. The 98 block indeed does not have the bypass hole in the block that mates with the water pump. But I will be using the old style water pump and v belt. The Nova application has one heater hose routed to the manifold water crossover and the other hose routes to the waterpump.

Wouldn't this routing work well enough to serve as the bypass? And is there a chance the open lower hole in the old style pump might push fluid out when mounted to the flat surface of the 98 block?

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 07-11-2009, 03:24 AM
DoubleVision's Avatar
Not Considered a Senior Member
 
Last photo:
Join Date: Oct 2002
Location: Heart Of Dixie
Age: 40
Posts: 10,655
Wiki Edits: 0

Thanks: 15
Thanked 59 Times in 56 Posts
Drill one 3/16 hole in the outer paremeter of the thermostat, instant bypass.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 07-11-2009, 04:23 PM
Registered User
 
Last photo:
Join Date: Feb 2006
Location: Chattanooga, TN
Posts: 114
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Yea, but if the routing I described does works as a bypass them I might be doubling the bypass flow.
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 07-12-2009, 04:56 AM
NorthStar's Avatar
Member
 
Last photo:
Join Date: Feb 2003
Location: Minnesota
Age: 50
Posts: 847
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Th heater hose is also acting as a bypass but having a small hole in thermostat guarantees there wont be any trapped air pockets forming and will always be some water flow when thermostat is closed.
You could tap the hole in water pump for 1/8" pipe plug.

But just do what DoubleVision said its good advice.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 08-10-2012, 10:42 AM
Registered User
 
Join Date: Jul 2012
Posts: 15
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
year one crate engine vortec cooling

I have been searching the forums trying to figure whats best for my application here. I have a year one crate engine with the iron vortec heads and the late 90's style block without the therm. bypass in the block. This is in a 56 chev truck. I have one heater hose hooked to the nipple on the top of the water pump and the other plumbed into the top front of the intake. I understand this completes the bypass they say is necessary,but is there enough flow through the heater core to be adequate? Also, what about when the heater control valve closes stopping the coolant flow? Is there a better way I can do this to accomplish the bypass no matter what position the heater control valve is in? thanks
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 08-10-2012, 02:52 PM
Registered User
 
Last photo:
Join Date: Apr 2007
Location: Seattle, Wa
Posts: 6,770
Wiki Edits: 0

Thanks: 4
Thanked 429 Times in 368 Posts
Quote:
Originally Posted by TNshadetree View Post
Reading the installation instructions for a Vortec manifold I purchased I see a note stating that I need to install a thermostat bypass since the 96+ blocks do not have the bypass in the block like the older generation.

Well, I'm wondering if my application will be OK as is. I'm installing this 98 Vortec truck engine in a 76 Nova. The 98 block indeed does not have the bypass hole in the block that mates with the water pump. But I will be using the old style water pump and v belt. The Nova application has one heater hose routed to the manifold water crossover and the other hose routes to the waterpump.

Wouldn't this routing work well enough to serve as the bypass? And is there a chance the open lower hole in the old style pump might push fluid out when mounted to the flat surface of the 98 block?
Actually the hole between the right head and block isn't a bypass it was intended to balance the flow between the left and right banks as the V-belt driven pump favors a greater output to the right side of the engine. The Serpentine belt drives the pump in the reverse direction to the Belt pump so the bypass on the right side became useless for flow balance purposes plus it never did a sufficient job in this regard anyway which is probably why GM never bothered with moving it. The heavy duty racers used to block almost half the block inlet from pump discharge before the flows would get close to even left to right, so what chance did that small hole ever really have of being close to effective.

The normal thermostat bypass is the 5/8ths and 3/4 hose arrangement from the intake ahead of the thermostat to the heater and return to somewhere on the pump inlet side. The purpose is to circulate a lot of coolant when the engine is cold to prevent super hot spots from forming in the critical zones around the exhaust valve seats, especially the paired ones, and the spark plugs. The intent of this is to prevent very hot concentrations from forming in the otherwise surrounding cold iron as this causes cracking in the valve seats and port walls, and around the spark plugs as well as preventing the plugs from overheating and becoming a place for pre-ignition to happen. That itty-bitty bypass hole on the right head in no way can supply enough coolant to prevent these most unpleasant events. To a lesser important extent, in my mind at least, is that the external bypass also prevents the pump from cavitating which will beat the air in the coolant out of solution causing bubbles that will become trapped in the upper areas of the engine usually over the rear combustion chambers of the each head, in the 400 these can shut off the coolant flow through the vents that bypass the siamesed cylinders again resulting in the all too familiar cracking of the castings.

So while the external bypass isn't all that pretty it serves an important purpose.

Venting holes in the thermostat will not allow sufficient coolant to flow as a bypass and even though they are small will increase warm up time which is very undesirable from a wear standpoint. I regularly do this to help with venting the block when filling it with coolant, but I appreciate the issues that come with it and don't push on the motor till its warmed up including the oil temp.

The Vortec often bypasses into the heater circuit from the backside of the intake. I actually like this a lot especially if you arrange it to bypass off both sides then Tee them together to either pass to through the heater or straight back to the pump's suction side. Over the years and with different models the return can be back to the fitting on the top of the pump, or back to the cold pump side of the radiator tank, or to a Tee fitting in the lower hose to the pump. An important function that appears when bypassing at the back of the heads is that steam and cavitation gases have an escape route from getting trapped over the rear combustion chambers. (Funny how Smokey complaines of this in his books but never seems to hit on venting the back of the head as the solution... one wonders if this is an oversight on his part or if he's keeping a secret about the solution.) One of the reasons the rear vented LT1 and LT4 heads worked so well? This arrangement also supplies early heat to the heater/defroster for those of us living in cold climates and not having air-conditioning to do the defrosting.

Bogie
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 08-11-2012, 05:26 AM
Registered User
 
Join Date: Jul 2012
Posts: 15
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Thanks

Thanks for the response. I looked into this because the car does run on the hot side. (seeing 215 occasionally) I just dropped down to a 160* thermostat that I drilled 4 3/16 holes in. I was originally thinking that would be sufficient for the bypass function. However, after thinking some more and reading more posts, I think I will also do the external bypass. I think I will bring a 5/8 line from the driver side rear coolant port of the intake to the 5/8 nipple on the suction side of the water pump. I also need to hook up the return side heater hose here. Would it be acceptable to use a 5/8 tee just off the nipple on the top of the pump with one line obviously going to the pump, one line going to the heater core, and one line going to the coolant port at the rear drivers side of the intake? This car does not have any ports on the radiator.
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 08-11-2012, 11:47 AM
Registered User
 
Last photo:
Join Date: Apr 2007
Location: Seattle, Wa
Posts: 6,770
Wiki Edits: 0

Thanks: 4
Thanked 429 Times in 368 Posts
Quote:
Originally Posted by Dmgarage View Post
Thanks for the response. I looked into this because the car does run on the hot side. (seeing 215 occasionally) I just dropped down to a 160* thermostat that I drilled 4 3/16 holes in. I was originally thinking that would be sufficient for the bypass function. However, after thinking some more and reading more posts, I think I will also do the external bypass. I think I will bring a 5/8 line from the driver side rear coolant port of the intake to the 5/8 nipple on the suction side of the water pump. I also need to hook up the return side heater hose here. Would it be acceptable to use a 5/8 tee just off the nipple on the top of the pump with one line obviously going to the pump, one line going to the heater core, and one line going to the coolant port at the rear drivers side of the intake? This car does not have any ports on the radiator.
This sounds acceptable, what about the 160 thermostat and the 215 temperatures, is this together or some other situation/combination of things?

Unless you did modifications to the EFI computer, a 160 degree thermostat and running at that temp will keep the fuel injection in cold start mode (choke function on a carburetor if you will) which will keep the mixture too rich. This is hard on the catalytic converter running 'em hot and, also, hard on the pistons, rings, and cylinder walls as the excess unburnt fuel in the blow by washes the top end lube off the cylinder walls. Anytime the engine is under about 175 degrees the cold start function kicks in, so you don't want to use a thermostat lower than 180. All this of course depends on the real running temp of the engine, if it runs 215 with a 160 thermostat the fueling is correct but you've got problems elsewhere perhaps with flow rate through the radiator which may need replacement because the core tubes are plugging up, or something like that.

Bogie
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 08-11-2012, 01:49 PM
Registered User
 
Join Date: Jul 2012
Posts: 15
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
This is an old school hot rod. 56 Chevy truck with a carb in front of a turbo 350. It has a large aluminum radiator & only a 16" electric fan. If there is any problem it is that the fan is not doing a good enough job. I was hoping doing the bypass might help. I would put a stronger, better shrouded fan on, but I am limited by the space between the rad & the water pump (about 3 1/2"). I may end up putting a mechanical fan on with a custom made shroud.
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 08-11-2012, 01:51 PM
Registered User
 
Join Date: Jul 2012
Posts: 15
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Also, the one time it did reach 215, I had a 180* stat with no bypass holes in it. It was also the first drive w the new engine
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 08-11-2012, 03:05 PM
Registered User
 
Last photo:
Join Date: Apr 2007
Location: Seattle, Wa
Posts: 6,770
Wiki Edits: 0

Thanks: 4
Thanked 429 Times in 368 Posts
Quote:
Originally Posted by Dmgarage View Post
This is an old school hot rod. 56 Chevy truck with a carb in front of a turbo 350. It has a large aluminum radiator & only a 16" electric fan. If there is any problem it is that the fan is not doing a good enough job. I was hoping doing the bypass might help. I would put a stronger, better shrouded fan on, but I am limited by the space between the rad & the water pump (about 3 1/2"). I may end up putting a mechanical fan on with a custom made shroud.
So does it get hot when standing/idling or when cruising?

Typically when idling it's an air flow issue through the core.

When it happens at cruise either the radiator is too small or the flow through the tubes is restricted because of dirt and corrosion becoming lodged in the tubes.

Usually lowering the thermostat opening temp only delays the overheat situation but doesn't change the end result if the engine is operated long enough. If you get a sustained difference it probably tells you the original thermostat is defective.

The bypass has little effect on temperatures whether it's there or not, all it does is recycle coolant when the thermostat is closed so hot spots can't form in otherwise cold castings. When a local area is hot enough to boil coolant to steam then local cooling of that place stops and the area super heats very quickly unless there is enough coolant circulation to keep these hot spots around exhaust valve seats and spark plugs wet. Keep in mind that when the engine is cold, pressure has not built up in the cooling system, therefore local boiling will happen at a much lower temperature than when the system is hot and pressurized.

A fan whether electric or pump driven off the engine needs a shroud that fits around the perimeter of the core, usually the tanks and radiator's frame, at one end and over the fan blades (about half deep of blade width). This lets the fan lower the air pressure inside the shroud so that air flows in over all the surface area of the core. This has a massive improvement in cooling capability compared to any other configuration of fan or fans. Certainly a larger more streamlined enclosure is more efficient, but even a couple, three inches deep is a significant improvement in fan/cooling performance.

Bogie
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 08-11-2012, 04:02 PM
Registered User
 
Join Date: Jul 2012
Posts: 15
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I agree with you, the lower temp thermostat is only delaying the inevitable. It will get the temp up just idling in the shop with the fan running. The core is not dirty or clogged at all. The fan is a typical 16" that is attached right to the core with the nylon mounts. the only shroud is the one the fan provides for that 16" diameter. Im fairly certain this is probably the problem. I really would like to get a shroud to mount the electric fan in. Jegs does sell an aluminum one that accomodates the fan, I just am not sure I have the clearance between the rad and pump. I am trying to avoid remounting the rad. I can only move it forward about 3/4 of an inch anyway.The core size of the the rad is roughly 16x19 and it is a thick aluminum one so that should be sufficient. The air conditioning condenser is mounted a couple inches in front of the radiator too. Im not sure how much that affects things.
OK on the bypass purpose, I completly understand.
Reply With Quote Quick reply to this message
  #13 (permalink)  
Old 08-12-2012, 07:30 AM
Registered User
 
Join Date: Jul 2012
Posts: 15
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I decided I am doing this right. As I already said, I will do the bypass. Im also going to move the radiator forward 3/4 of an inch. that will allow me to use a flex a lite "black magic" fan I already have that is fully shrouded covering almost the whole radiator core and pulls 2800 cfm. It has a thermostat to control it which I will set at 185-190*. I will also go back to using an engine thermostat of 180* with a couple bypass holes drilled in it. This should do it and do it the right way. What do you think. Thanks again for the advice.
Reply With Quote Quick reply to this message
  #14 (permalink)  
Old 09-03-2012, 08:35 AM
Registered User
 
Join Date: Jul 2012
Posts: 15
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
update

Well, I did all of the things I had previously listed plus put a new Edelbrock water pump and 180* high flow thermostat. I also added Redline water wetter to the coolant mix. It does run cooler, but simply not as cool as it should. Cruises around town at about 205. I took it on the highway for a few miles and it got up to 215 and I believe it would of kept climbing. The rad is aluminum and and measures 22" wide (with the tanks) and 19" high. Is this too small? Engine is a 355 that made just over 400 hp.
Reply With Quote Quick reply to this message
  #15 (permalink)  
Old 09-04-2012, 10:09 AM
Registered User
 
Last photo:
Join Date: Apr 2007
Location: Seattle, Wa
Posts: 6,770
Wiki Edits: 0

Thanks: 4
Thanked 429 Times in 368 Posts
Quote:
Originally Posted by Dmgarage View Post
Well, I did all of the things I had previously listed plus put a new Edelbrock water pump and 180* high flow thermostat. I also added Redline water wetter to the coolant mix. It does run cooler, but simply not as cool as it should. Cruises around town at about 205. I took it on the highway for a few miles and it got up to 215 and I believe it would of kept climbing. The rad is aluminum and and measures 22" wide (with the tanks) and 19" high. Is this too small? Engine is a 355 that made just over 400 hp.
The radiator is too small for this engine. A crossflow of 30x19 inches with 2 rows of 1 inch tubes would be the minimum. With a 180 thermostat (opening temp) this combination should show 190-195 all the time. The 30x19 is a production size radiator for the 350s for machines such as the Monte-Carlo, Malibu, etc. These cars came originally with with a copper-brass radiator of these same external dimensions but they used 3 and sometimes 4 tubes of about .5 inch wide.

A vertical flow radiator would need to be the same area dimensions as the crossflow with the same tube count and size just stood on end.

Bogie
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
Vortec head conversion - EGR chevy_c10 Engine 10 03-29-2009 11:20 AM
carb/fuel injected intake to vortec tb conversion plate 383silverado Engine 5 09-09-2007 10:36 AM
Water pump bypass, vortec heads blndweasel Engine 2 06-17-2005 05:10 PM
NEW GMPP VORTEC heads !! terror385 Engine 1 07-11-2004 09:48 AM
Hotrodders Knowledge Cluster: Disc Brake Conversions Jon Suspension - Brakes - Steering 0 08-29-2003 03:34 PM


All times are GMT -6. The time now is 02:34 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.