Hitman's Pontiac Trans Am Forum

Trans Am Information => Trans Am Tech => DriveTrain => Topic started by: 1973Formula on December 13, 2008, 06:08:14 PM

Title: '68 Intake on 6X-4 Heads, Rear coolant port troubles? Help.
Post by: 1973Formula on December 13, 2008, 06:08:14 PM
I am in the process of reassembling my 455 engine.  I am using a '71 455 block with '78 6X-4 heads and a '68 iron intake.  I just realized a problem.  What do I do with the rear coolant ports on the 6x heads?  Below is a picture.  Both rear ports are completely open with the intake in place.  Suggestions?  I would rather not change components. 

Thanks,

(http://forums.performanceyears.com/forums/attachment.php?attachmentid=151376&stc=1&d=1229209331)
(http://forums.performanceyears.com/forums/attachment.php?attachmentid=151377&stc=1&d=1229209331)
(http://forums.performanceyears.com/forums/attachment.php?attachmentid=151378&stc=1&d=1229209331)
Title: Re: '68 Intake on 6X-4 Heads, Rear coolant port troubles? Help.
Post by: turbota400 on December 13, 2008, 07:46:34 PM
On mine, I know one of the ports has a "nipple" pressed into it that hooks to one of the heater hoses and IIRC the other has a freeze plug pressed into it.  I would go look but it is blizzarding outside and I don't want to go uncover it in this weather.
Title: Re: '68 Intake on 6X-4 Heads, Rear coolant port troubles? Help.
Post by: Rick on December 13, 2008, 11:54:03 PM
Driver's side gets a freeze plug, passenger side gets the nipple Shawn describes, and it is an interference fit like the freeze plug.  There is a heater hose that goes from the nipple to the heater core to provide the source of heat, and it circulates all the time whether or not the heater control is "ON" or "OFF".  The other side of the heater core, of course, goes back to the water pump on the small nipple just about the lower radiator hose connection.
Title: Re: '68 Intake on 6X-4 Heads, Rear coolant port troubles? Help.
Post by: milly on December 14, 2008, 01:51:54 AM
Like I said over at TAC, my '76 6X-8 heads have heater nipples on both heads. There is a Pontiac guy in the area that has both heads connected to a tee junction before going to the heater core. He claims it keeps both heads the same temp. Not sure if it adds any performance or not. When I put mine back together, the left and right heads will be connected by the hearter nipples. I have bypassed the heater core, so the coolant will flow through both heads.
Title: Re: '68 Intake on 6X-4 Heads, Rear coolant port troubles? Help.
Post by: Eagle 1 on December 17, 2008, 12:42:41 PM
I recently went through this with my engine.   The freeze plug I used on the drivers side I believe was a 30mm that I got from O'Reillys auto parts. 
It was a tight fit to start, so I ever so lightly ground off the edge of the freeze plug to get it started, and then of course used rtv.
As mentioned, the hole on the passenger side is for a heater core nipple if you plan on hooking up the heater core.
BTW, pick up two freeze plugs.  If your luckier than I am you will only need one and still have a spare.   ;)
Title: Re: '68 Intake on 6X-4 Heads, Rear coolant port troubles? Help.
Post by: eroc022 on December 17, 2008, 09:39:05 PM
should be an american sized freeze plug not the metric.....i know most auto parts stores carry them in stock...
Title: Re: '68 Intake on 6X-4 Heads, Rear coolant port troubles? Help.
Post by: 1973Formula on December 17, 2008, 10:11:01 PM
30mm will fit, or whatever the closest English size approx. 1-11/64".  I ended up using two heater hose nipples.
Title: Re: '68 Intake on 6X-4 Heads, Rear coolant port troubles? Help.
Post by: Mr. P-Body on December 18, 2008, 09:03:41 AM

   The "correct" size of the plug is 1 13/64". Pioneer part no. EPC-134 or EPC-134-B (brass). Dorman lists it as a 1 3/16" plug, but we've found that to be a bit small and not as secure a seal.

   The heater hose nipple is available from Ames Performance or Performance Years, about $29.

   The question of "balancing the temperature" from one head to the other is "on going". Chevy boys have been doing it for many years. We tried it on a few Pontiacs, but have no specific data to defend or oppose it. Couldn't hurt!

Jim
Title: Re: '68 Intake on 6X-4 Heads, Rear coolant port troubles? Help.
Post by: Eagle 1 on December 18, 2008, 10:23:46 AM
should be an american sized freeze plug not the metric.....i know most auto parts stores carry them in stock...
Yea I know it should be a 1 13/64 but most auto parts stores around here didnt carry that size.
The 30 mm is a good tight fit though.
Title: Re: '68 Intake on 6X-4 Heads, Rear coolant port troubles? Help.
Post by: LeighP on December 21, 2008, 07:22:45 AM
Like I said over at TAC, my '76 6X-8 heads have heater nipples on both heads. There is a Pontiac guy in the area that has both heads connected to a tee junction before going to the heater core. He claims it keeps both heads the same temp. Not sure if it adds any performance or not. When I put mine back together, the left and right heads will be connected by the hearter nipples. I have bypassed the heater core, so the coolant will flow through both heads.

John....when you connect them up, run a T fitting and run it forward to the water pump heater hose input, so theres a positive draw of coolant from the back of the heads back into the pump. I currently run my single outlet that way (to bypass heater)....will change to dual like you when I do my next engine.
Title: Re: '68 Intake on 6X-4 Heads, Rear coolant port troubles? Help.
Post by: scubaanddreams on November 12, 2014, 10:23:13 PM
Sorry to revive this thread, I am curious if I want to keep the "nipple" on the head but I am not running a heater at the moment, can I just attach a small hose and cap it off so I don't have to put in a freeze plug and then reinstall the nipple later on?