What psi radiator cap - Page 2 - Yellow Bullet Forums
;

Go Back   Yellow Bullet Forums > Technical Section > Tech Questions - Monson Racing

Tech Questions - Monson Racing

Reply
 
Thread Tools Display Modes
Old 09-24-2019, 10:31 PM   #16
dakster1a
Member
Pullin gears
 
Join Date: Sep 2010
Posts: 895
Default Re: What psi radiator cap

Quote:
Originally Posted by Randy Wilson View Post
We may have been taking a chance, but I literally ran zero pressure on the cap, when I was running wildly ported iron heads that all leaked under pressure, and never watered the track down. But I went to the line as cool as possible to start, but I never overflowed the catch can.
Understood Randy. Not sure if my theory has any merit, just made sense to me.
dakster1a is online now   Reply With Quote
Sponsored Links
Advertisement
 
Old 09-24-2019, 10:33 PM   #17
Randy Wilson
Senior Member
Smoked Another SBC
 
Join Date: Dec 2008
Posts: 23,230
Default Re: What psi radiator cap

Quote:
Originally Posted by dakster1a View Post
Understood Randy. Not sure if my theory has any merit, just made sense to me.
Well, you are right to be concerned. Id never want someone to try it, and spill water on the track. I was very careful, and had no real problems. And, I might add, I wasnt the only class racer to do this. Do what you are comfortable with, and good luck.
Randy Wilson is offline   Reply With Quote
Old 09-25-2019, 03:43 AM   #18
Topfun99
Senior Member
Smoked Another SBC
 
Topfun99's Avatar
 
Join Date: Mar 2009
Location: Temporarily Away, Check Back Later For Updates
Posts: 16,153
Default Re: What psi radiator cap

A radiator system with a 16lb cap will NOT cause or allow anymore water to go to the reservoir then a 26lb cap. That is dependent on the system temperature.

Water is basically in-compressible at those pressures. It will expand exactly the same percentage based on temperature at both pressures.
__________________
Try not to take everything so literally. Just because someone suggests it's time to deal with the Elephant in the room doesn't mean you should break out the peanuts.

Thanks to:

HALTECH (Elite 2500 plus REM)
TRZ MOTORSPORTS
REAL STREET PERFORMANCE
FB PERFORMANCE
PTC
M/T Tires
Kris Starnes Racing

EMAIL - [email protected]
Topfun99 is offline   Reply With Quote
Old 09-25-2019, 07:42 PM   #19
Drag Mouse
Member
Pullin gears
 
Drag Mouse's Avatar
 
Join Date: Oct 2008
Location: Woodstock Ill.
Posts: 804
Default Re: What psi radiator cap

Quote:
Originally Posted by Topfun99 View Post
Of course higher pressure raises the boiling point. The water in direct contact with the hot engine surfaces will start to boil and turn to steam at the metal/water interface. This is what you see at the bottom of a pot of water that is just starting to boil and is referred to as Nucleate boiling. This nucleac boiling can lower coefficient of heat transfer so it can't remove as much heat.

https://en.wikipedia.org/wiki/Nucleate_boiling

I think it's more important to have a higher pressure cap on an electric water pump application than a mechanical (centrifugal) water pump. That's because at higher rpm the mechanical pump's output pressure goes up which raises the system pressure. On my car with a 16 lb cap I see the cooling system pressure downstream of the pump go from 16 to 30 lbs at the higher rpms during a run.

An electric pump's pressure will stay the same during a run so it doesn't "automatically" compensate for the increased surface heat in the heads/block.
I run an electric water pump,so what would you recommend for psi?
Drag Mouse is offline   Reply With Quote
Old 09-25-2019, 08:31 PM   #20
bigblockmark
Senior Member
Smoked another BBC
 
bigblockmark's Avatar
 
Join Date: Dec 2013
Location: Paris Illinois
Posts: 3,846
Default Re: What psi radiator cap

Mine works fine with 10 PSI cap. BBC, Mezeri? 35 GPM electric water pump, dual pass 1" tube aluminum radiator, OEM G body plastic recovery tank. Pump and electric fan on. Pull into the water box at 140, leave the line at 160, 180 back at the trailer. Cools down to 140 in 15 minutes with water pump and fan on. Pump gas 582.
bigblockmark is offline   Reply With Quote
Old 09-25-2019, 11:25 PM   #21
dakster1a
Member
Pullin gears
 
Join Date: Sep 2010
Posts: 895
Default Re: What psi radiator cap

Quote:
Originally Posted by Topfun99 View Post
A radiator system with a 16lb cap will NOT cause or allow anymore water to go to the reservoir then a 26lb cap. That is dependent on the system temperature.

Water is basically in-compressible at those pressures. It will expand exactly the same percentage based on temperature at both pressures.
Well, it seems like the hotter the engine is, the harder the radiator hose is, which seems like more pressure. I would think the 16lb cap would release and start filling the overflow bottle sooner than the 25 lb.
dakster1a is online now   Reply With Quote
Old 09-26-2019, 03:01 AM   #22
Topfun99
Senior Member
Smoked Another SBC
 
Topfun99's Avatar
 
Join Date: Mar 2009
Location: Temporarily Away, Check Back Later For Updates
Posts: 16,153
Default Re: What psi radiator cap

Quote:
Originally Posted by Drag Mouse View Post
I run an electric water pump,so what would you recommend for psi?
For a NA car, 16-24 is fine. A power adder car with more heat and an electric pump I would recommend the higher pressure.
__________________
Try not to take everything so literally. Just because someone suggests it's time to deal with the Elephant in the room doesn't mean you should break out the peanuts.

Thanks to:

HALTECH (Elite 2500 plus REM)
TRZ MOTORSPORTS
REAL STREET PERFORMANCE
FB PERFORMANCE
PTC
M/T Tires
Kris Starnes Racing

EMAIL - [email protected]
Topfun99 is offline   Reply With Quote
Old 09-26-2019, 03:38 AM   #23
Topfun99
Senior Member
Smoked Another SBC
 
Topfun99's Avatar
 
Join Date: Mar 2009
Location: Temporarily Away, Check Back Later For Updates
Posts: 16,153
Default Re: What psi radiator cap

Quote:
Originally Posted by dakster1a View Post
Well, it seems like the hotter the engine is, the harder the radiator hose is, which seems like more pressure. I would think the 16lb cap would release and start filling the overflow bottle sooner than the 25 lb.
As soon as the water starts to heat up it also starts to expand and increase the system pressure. This volume change initially affects the hoses, radiator and other non-rigid components that will expand as the pressure increases. At some point the temperature/pressure increases to the point where the expansion is greater than the amount the non-rigid parts can expand and the system pressure will overcome the radiator cap pressure.

So yes, in reality these non-rigid parts will expand slightly more at 25lbs than 16lbs. But the difference in volume absorbed by this expansion would be small compared to the overall expansion of the water itself. I've run both pressure caps and have never seen a significant difference. If someone has large water hoses that are soft and expand like balloons, maybe it will be significant.

What I've left out of this theoretical discussion are the gases that are in the cooling system. As soon as the water/coolant starts to heat up, gases will come out of solution and expand much more than the liquid. Even after we purge all of the excess air out of the cooling system these gases will still be present.
__________________
Try not to take everything so literally. Just because someone suggests it's time to deal with the Elephant in the room doesn't mean you should break out the peanuts.

Thanks to:

HALTECH (Elite 2500 plus REM)
TRZ MOTORSPORTS
REAL STREET PERFORMANCE
FB PERFORMANCE
PTC
M/T Tires
Kris Starnes Racing

EMAIL - [email protected]
Topfun99 is offline   Reply With Quote
Old 09-26-2019, 10:29 AM   #24
TheNovaMan
Senior Member
Smoked Another SBC
 
TheNovaMan's Avatar
 
Join Date: Jul 2008
Location: Southwest Michigan
Posts: 7,693
Default Re: What psi radiator cap

One thing to keep in mind when considering what pressure cap to run is whether or not you have the stock heater core. Put too much pressure to one and it can blow.
__________________
~Pete
I know enough to know that I don't know enough.

Quote:
Originally Posted by ten5nova View Post
I know you're the Cragar king
You got that right!

Quote:
Originally Posted by Chris Uratchko View Post
there is nothing in an LS that will support more hp per CID than a Gen 1... absolutely zero.
TheNovaMan is offline   Reply With Quote
Old 09-26-2019, 01:09 PM   #25
dakster1a
Member
Pullin gears
 
Join Date: Sep 2010
Posts: 895
Default Re: What psi radiator cap

Thanks for the info!
dakster1a is online now   Reply With Quote
Old 09-26-2019, 07:00 PM   #26
1leg
Member
Pullin gears
 
1leg's Avatar
 
Join Date: Jul 2011
Location: Escondido
Posts: 700
Garage
Default Re: What psi radiator cap

Basic rule for a track only car, 16lbs for standard head gaskets and 7lbs if your running copper gaskets. It would be a very rare case that you would need a higher them 16lbs cap on a drag race only car.

Water boils around 212 and each pound on the cap adds 3 degrees to that so a 7lbs cap should be good tell around 233 degrees before the coolant boils.
1leg is offline   Reply With Quote
Old 09-27-2019, 08:00 PM   #27
Kane
Member
Pullin gears
 
Join Date: Jun 2008
Posts: 904
Default Re: What psi radiator cap

Why the lower pressure for copper gaskets??
Kane is offline   Reply With Quote
Old 09-28-2019, 02:34 AM   #28
Topfun99
Senior Member
Smoked Another SBC
 
Topfun99's Avatar
 
Join Date: Mar 2009
Location: Temporarily Away, Check Back Later For Updates
Posts: 16,153
Default Re: What psi radiator cap

Quote:
Originally Posted by Kane View Post
Why the lower pressure for copper gaskets??
Copper gaskets are great for cylinder sealing but don't seal well at the water passages.
__________________
Try not to take everything so literally. Just because someone suggests it's time to deal with the Elephant in the room doesn't mean you should break out the peanuts.

Thanks to:

HALTECH (Elite 2500 plus REM)
TRZ MOTORSPORTS
REAL STREET PERFORMANCE
FB PERFORMANCE
PTC
M/T Tires
Kris Starnes Racing

EMAIL - [email protected]
Topfun99 is offline   Reply With Quote
Old 09-28-2019, 11:09 AM   #29
Coloradoracer
Senior Member
Smoked another BBC
 
Coloradoracer's Avatar
 
Join Date: Oct 2009
Location: Lehigh Acres, Florida
Posts: 3,529
Default Re: What psi radiator cap

Quote:
Originally Posted by Topfun99 View Post
Copper gaskets are great for cylinder sealing but don't seal well at the water passages.
I run a 16 lb cap and zero issues with copper gaskets. Have yet to have one leak...
__________________
Mark Goulette
Owner and driver, Livin' the Dream Racing Dragster
Speed kills but it's better than going slow!
www.livinthedreamracing.com
Authorized Amsoil Dealer
Coloradoracer is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 09-28-2019, 12:26 PM   #30
boostedbowtie
Senior Member
Smoked Another SBC
 
boostedbowtie's Avatar
 
Join Date: Dec 2009
Location: Florida
Posts: 22,736
Default Re: What psi radiator cap

Is it normal to still have pressure in the system , even after sitting for 5 days or so ?

Started noticing this after putting a new cap on .

Its a 16lb lever style cap like this

boostedbowtie is offline   Reply With Quote
Reply

Thread Tools
Display Modes

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 Off



All times are GMT -4. The time now is 07:09 PM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 0%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Yellow Bullet LLC
 

Garage Plus vBulletin Plugins by Drive Thru Online, Inc.