1968 GT S Code 390 Coupe Overheating problem ???

Mustang Australia

Author Topic: 1968 GT S Code 390 Coupe Overheating problem ???  (Read 717 times)

Offline 69 SCJ

  • Stallion
  • **
  • Posts: 93
1968 GT S Code 390 Coupe Overheating problem ???
« on: November 28, 2019, 10:46:08 AM »
Hi guys
Thanks for your comments ( Reason for checking all this is getting my coolant is running out of overflow every time I take it out.
Or when the engine heats up.
I Have checked the following
The Timing is spot on
The Points are checked and fine.
The coil is a Accel 8140 seems fine.
The spark plugs are Autolite 45 ( Do I need to replace these ) not sure how old they are??
Radiator has been checked out its fine.
Bleed air out of Radiator
Installed a radiator shroud.
Your comments would be greatly appreciated.
Thanks in advance.
Steve
« Last Edit: December 01, 2019, 01:44:38 PM by 69 SCJ »

Offline barnett468

  • Shelby
  • *********
  • Posts: 6984
Re: 1968 GT S Code 390 Coupe spark plug gap size PLEASE
« Reply #1 on: November 28, 2019, 12:38:16 PM »
The gap size depends some on the type of ignition you have, so if you post the type of coil, and if if has electronic ignition like a pertronix or a high volt ignition box etc, it will help.

Offline GLENN 70

  • GT 500
  • *********
  • Posts: 8435
  • Location: Gold Coast .
Re: 1968 GT S Code 390 Coupe spark plug gap size PLEASE
« Reply #2 on: November 28, 2019, 04:34:58 PM »
I think they are the small plug ? The ones they take a 5/8 plug socket ? . NGK -BP 6 FS , 35 tho gap . 

Offline 69 SCJ

  • Stallion
  • **
  • Posts: 93

Hi guys
Thanks for your comments ( Reason for checking all this is getting my coolant is running out of overflow every time I take it out.
Or when the engine heats up.
I Have checked the following
The Timing is spot on
The Points are checked and fine.
The coil is a Accel 8140 seems fine.
The spark plugs are Autolite 45 ( Do I need to replace these ) not sure how old they are??
Radiator has been checked out its fine.
Bleed air out of Radiator
Installed a radiator shroud.
Your comments would be greatly appreciated.
Thanks in advance.
Steve

Offline 289 vert

  • Thoroughbred
  • **
  • Posts: 164
  • Location: Brisbane
Re: 1968 GT S Code 390 Coupe Overheating problem ???
« Reply #4 on: December 01, 2019, 01:57:10 PM »
If you fill the radiator to the top, it will overflow. Cover the core by 1/2-3/4"

Offline 69 SCJ

  • Stallion
  • **
  • Posts: 93
Re: 1968 GT S Code 390 Coupe Overheating problem ???
« Reply #5 on: December 01, 2019, 02:03:18 PM »
Hi Mate
Thanks for your reply
So you are saying leave don't fill to top of radiator leave 1/2 to 3/4 inch from top..
Is this correct.
Thanks Steve  :cheers:

Online sms777

  • Worked
  • ***
  • Posts: 505
Re: 1968 GT S Code 390 Coupe Overheating problem ???
« Reply #6 on: December 01, 2019, 02:05:16 PM »
Make sure you are using the correct radiator cap with the correct pressure rating. There are recovery type which requires an overflow bottle fitted or the non-recovery type which runs a piece of hose pointing to the ground. The correct pressure for a 390 is around 15psi unless you have an alloy radiator which requires around 20-24 psi cap. It's a cheap item so get a new one. 
Click Banner


Offline 69 SCJ

  • Stallion
  • **
  • Posts: 93
Re: 1968 GT S Code 390 Coupe Overheating problem ???
« Reply #7 on: December 01, 2019, 02:12:51 PM »
Thanks I don't have a overflow bottle may have to fit one.
Also just replaced cap with number 13 for the 390.
I will back off filling radiator to full and leave 1/2 to 3/4 from top.
Hopefully this fixes it.
Thanks for your great comments
Cheers Steve

Offline 69 SCJ

  • Stallion
  • **
  • Posts: 93
Re: 1968 GT S Code 390 Coupe Overheating problem ???
« Reply #8 on: December 01, 2019, 02:14:44 PM »
Sorry last question
Also would you leave these Autolight 45 spark plugs in or replace with ??
Thanks Steve

Offline GLENN 70

  • GT 500
  • *********
  • Posts: 8435
  • Location: Gold Coast .
Re: 1968 GT S Code 390 Coupe Overheating problem ???
« Reply #9 on: December 01, 2019, 03:00:06 PM »
NGK -AP 5 FS for a stock engine city driving  NGK -AP6 FS if you like to give it a bit . NGK plugs are the go and at 35 tho .  Some times changing the plug near the brake booster ,can be easier to take the valve cover off 1ST ,see how you go .

Offline jack67fb

  • Pony
  • **
  • Posts: 23
  • I'm new here
  • Location: WA
  • Car: 1967 GT S code fastback
Re: 1968 GT S Code 390 Coupe Overheating problem ???
« Reply #10 on: December 01, 2019, 03:09:18 PM »
I have a 67 s code, original radiator.If i fill it all the way to the top it will overflow
.I just leave a little space as suggested above and problem solved.
67 gt fastback s code
16 gt fastback

Offline 289 vert

  • Thoroughbred
  • **
  • Posts: 164
  • Location: Brisbane
Re: 1968 GT S Code 390 Coupe Overheating problem ???
« Reply #11 on: December 01, 2019, 06:25:47 PM »
Assuming a functioning cooling system with no leaks.
The level it stops overflowing at, is the maximum fill level. The space above is what's needed for expansion.
I usually fill to around 1/4" below maximum level.
« Last Edit: December 01, 2019, 06:53:44 PM by 289 vert »

Offline 69 SCJ

  • Stallion
  • **
  • Posts: 93
Re: 1968 GT S Code 390 Coupe Overheating problem ???
« Reply #12 on: December 02, 2019, 08:00:56 AM »
Hi guys
Thanks for your comments ( Reason for checking all this is getting my coolant is running out of overflow every time I take it out.
Or when the engine heats up.
I Have checked the following
The Timing is spot on
The Points are checked and fine.
The coil is a Accel 8140 seems fine.
The spark plugs are Autolite 45 ( Do I need to replace these ) not sure how old they are??
Radiator has been checked out its fine.
Bleed air out of Radiator
Installed a radiator shroud.
Your comments would be greatly appreciated.
Thanks in advance.
Steve

THANKS GUYS YOU ALL HAVE BEEN A GREAT HELP  :cheers:

Offline barnett468

  • Shelby
  • *********
  • Posts: 6984
Re: 1968 GT S Code 390 Coupe Overheating problem ???
« Reply #13 on: December 02, 2019, 12:29:26 PM »
Also would you leave these Autolight 45 spark plugs in or replace with ??

those are the correct plugs, so if they are not bad, there is no need to change them.

Offline barnett468

  • Shelby
  • *********
  • Posts: 6984
Re: 1968 GT S Code 390 Coupe Overheating problem ???
« Reply #14 on: December 02, 2019, 12:32:47 PM »
coolant is running out of overflow every time I take it out. Or when the engine heats up.

The Timing is spot on

Radiator has been checked out its fine.

1. How hot does it get?

2. How did you determine that?

3. Although it may not have rust in it, it may be too small for your particular app.

 

Visit Custom Mustangs

Visit Custom Mustangs