Cylinder Heads - Pontiac GTO Forum
User Tag List

 
LinkBack Thread Tools Display Modes
post #1 of 7 (permalink) Old 07-15-2013, 01:43 PM Thread Starter
 
Join Date: Jul 2013
Location: Gulg Breeze, Florida
Posts: 19
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Cylinder Heads

I purchased a 67 GTO about a year ago and the care does not seem to have the power that I would expect. I put on a new quadrajet, HEI ignition, and Headman Headers. The Heads are stamped 46 and I want to replace them with 670 Heads. I have seen remanufactured 6X heads for sale. I have 2 questions; am I doing the right thing and is there a difference between the 670 and 6X heads?
John
hyfye is offline  
Sponsored Links
Advertisement
 
post #2 of 7 (permalink) Old 07-15-2013, 02:23 PM
64-67 Expert
 
geeteeohguy's Avatar
 
Join Date: Feb 2008
Location: Fresno, California
Posts: 8,543
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 118 Post(s)
670 heads make great power and are original equipment for your car. That said, you can't really use them anymore on a street car. They have too much compression and need too m uch spark advance to be viable. Unless you have an unlimited supply of 100 octane fuel. You want a cylinder head with about an 84-90cc combustion chamber to bring your compression down to around 9--9.5:1. That, and a decent cam will help you in your quest for power. The Wallace Racing site has a list of head casting numbers, and their combustion chamber volume. It's a ballpark list. Some heads vary from others, and the thing to do is to measure the chambers yourself. I use a graduated syringe and ATF, but there are other ways to do it, as well. Also, what are you comparing the power to? These cars, while screamers, are not as fast as some of the new muscle. When I first started driving GTO's in the '70's, I was the king of the street. I'm still driving the same cars, but I'm no longer the top dog....the new supercars simply have more power. Expect a well sorted out streetable 400 Pontiac to be pretty impressive, though, with about 300-400 reliable horsepower readily available.
geeteeohguy is online now  
post #3 of 7 (permalink) Old 07-15-2013, 02:50 PM Thread Starter
 
Join Date: Jul 2013
Location: Gulg Breeze, Florida
Posts: 19
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Thanks for getting back with me. I don"t think that the 400 is original. I even switched the transmission to a 700r4 with 2500 stall and that helped a little. I still can"t even spin the tires. The motor runs smooth, sound great but can't get out of its own way. I had a goat back in the day and could smoke most cars on the road like you said. I did a compression check and each cyclider is measuring about 150. The motor has a cam in it and I think its a mismatch with the heads
hyfye is offline  
 
post #4 of 7 (permalink) Old 07-15-2013, 05:03 PM
 
Instg8ter's Avatar
 
Join Date: Sep 2010
Location: Near Detroit
Posts: 3,931
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 23 Post(s)
What rear end gear are you running, some are as tall as 2:54 and will not be light to light screamers, but will perform well on the highway all the way up past 120 MPH.

Instg8ter is offline  
post #5 of 7 (permalink) Old 07-15-2013, 05:34 PM
64-67 Expert
 
geeteeohguy's Avatar
 
Join Date: Feb 2008
Location: Fresno, California
Posts: 8,543
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 118 Post(s)
My de-tuned (low compression small valve heads) bone stock '67 400 in my ragtop will smoke the tires in the rear (2.56 posi) with no problems at all. I am running the original points distributor, carb, intake, and exhaust manifolds. Something is wrong with your engine set up.....150 psi is about perfect for compression, so it's not the heads. 46 are small valve, but work well on the 400. My suspicion is that the cam is installed incorrectly, probably very retarded. You need to degree the cam to verify that. Pontiacs tend to like an advanced cam. Throw a vacuum gauge on it and see what the manifold vacuum is. Should be 20-21" at idle. Also, snap the throttle in neutral....is it sluggish or does it pick right up? Again, my bet is that it has the wrong cam, or a mis-installed cam. And that will make or break how an engine runs.
geeteeohguy is online now  
post #6 of 7 (permalink) Old 07-16-2013, 02:21 AM
Super Moderator
 
BearGFR's Avatar
 
Join Date: Aug 2008
Location: Springtown, TX
Posts: 5,742
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 122 Post(s)
Garage
It should run better than that even with one cylinder tied behind its back

Start with the basics. Tune-up, ignition timing (total, not initial), carburetor, etc.

Bear

BearGFR
Springtown, TEXAS
BearGFR is offline  
post #7 of 7 (permalink) Old 07-16-2013, 03:08 PM Thread Starter
 
Join Date: Jul 2013
Location: Gulg Breeze, Florida
Posts: 19
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Thanks all of you I think I will take it up and get it dyno'd and see what is in iy
hyfye is offline  
Sponsored Links
Advertisement
 
Reply

  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, Lemans & GTO Complete Engine Compartment Discussion

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Pontiac GTO Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
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:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Similar Threads
Thread Thread Starter Forum Replies Last Post
Advise: cylinder heads 6x8 SPCMarty 1964-1974 Tempest, LeMans & GTO Projects, Barn Finds & Restoration Discussions 2 04-28-2012 06:55 PM
4X Cylinder Heads NEEDLEZ 1964-1974 Tempest, Lemans & GTO Complete Engine Compartment Discussion 0 09-20-2011 04:06 AM
Cylinder Heads JET 1964-1974 Tempest, Lemans & GTO Complete Engine Compartment Discussion 0 06-26-2009 09:19 AM

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

 
For the best viewing experience please update your browser to Google Chrome