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Apr 26th, 2026 | | AD Chevy Trucks  Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
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| | | | Joined: Mar 2011 Posts: 58 New Guy | | New Guy Joined: Mar 2011 Posts: 58 | Question came up when I had the original radiator re-cored.... do I want high or low pressure system??? What is the advantage? I am going from stock 228 to 302 street rod/push truck. | | | | | Joined: May 2001 Posts: 7,438 Extreme Gabster | | Extreme Gabster Joined: May 2001 Posts: 7,438 | The 228 used a 4 lb. cap. Modern V8s use 15 lb. or more. The higher the pressure, the higher the boiling point of water.
I don't know what pressure the 302 originally used so I can't make a recommendation.
| | | | | Joined: Apr 2005 Posts: 1,107 'Bolter | | 'Bolter Joined: Apr 2005 Posts: 1,107 | i have a 4 lb cap on my 270 thats in the ashton and 235 thats in the 6100. the rad on the 40 is atmospheric so it doesnt matter what cap you put on it it aint gonna blow nor raise the boiling point. a five psi cap will allow it to reach 224 degrees. since i dont have my steam tables in front of me i cant tell you what 4 psi is. a seven pound cap will put you to 235 degrees. | | | | | Joined: Dec 2001 Posts: 14,522 Moderator: Welcome Centre, Southern Bolters, Legion Hall | | Moderator: Welcome Centre, Southern Bolters, Legion Hall Joined: Dec 2001 Posts: 14,522 | From memory I think for each pound of radiator cap you raise the boiling point 3 degrees. Thus a 15 lb cap will raise the boiling point to 257 degrees.....if my memory is right. | | | | | Joined: Mar 2011 Posts: 58 New Guy | | New Guy Joined: Mar 2011 Posts: 58 | Thanks guys,
I'm running a five jug Howard intake and may need the extra heat. What do you think? | | | | | Joined: Jan 2001 Posts: 5,337 'Bolter | | 'Bolter Joined: Jan 2001 Posts: 5,337 | If you are running an original heater you do not want to run much pressure or you could cause the core to leak.
See the USA in your vintage Chevrolet! My Blog | | | | | Joined: Dec 2008 Posts: 1,922 'Bolter | | 'Bolter Joined: Dec 2008 Posts: 1,922 | X2 - the limit is the oldest and weakest bit that sees pressure.
may need the extra heat
???? | | | | | Joined: Aug 2005 Posts: 6,377 Ex Hall Monitor | | Ex Hall Monitor Joined: Aug 2005 Posts: 6,377 | Excellent input Dave, I hadn't even considered the heater core.
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