pontiac engines - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum

Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine
User Name
lost password?   |   register now

LinkBack Thread Tools
  #1 (permalink)  
Old 01-23-2012, 07:43 PM
Registered User
Join Date: Jan 2012
Posts: 1
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
pontiac engines

Bought a Pontiac motor, I'm pretty sure it has a 350 block with #46 heads. I believe this head castings are from a 69 400/428, is this correct? If correct these heads should be 72 cc with 1.96" intake and 1.66" exhaust. I would like to put these heads on a 400. Is this a good combination? Can the bigger valves be machined into these heads (2.11"intake and 1.77"exhaust) ? Is it worth rebuilding these heads?

Reply With Quote Quick reply to this message
Sponsored Links
  #2 (permalink)  
Old 01-23-2012, 07:53 PM
LATECH's Avatar
Hotrodders.com Moderator

Last journal entry: GTO Reproduction Hood
Last photo:
Join Date: Jul 2010
Location: Northeast Pennsylvania
Posts: 7,003
Wiki Edits: 0

Thanks: 438
Thanked 632 Times in 549 Posts
Number 46 heads were used in 73. They also used the same number to designate the earlier 428 heads.Check the date codes on them.That will be the determining factor. If the block is a 350, most likely it is a 73 and the heads will be too. Check the date codes to be sure.
I just ran across the same thing at a salvage yard when looking at a poncho motor that had been around for a long time. I got excited at first, then I checked the date codes......
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 01-24-2012, 06:47 AM
Registered User
Join Date: Nov 2011
Location: Virginia
Posts: 877
Wiki Edits: 0

Thanks: 2
Thanked 133 Times in 116 Posts
Correct. The "early" 46 was used on 428 360 HP "grocery-getters". Joe Roberts' '69 Catalina wagon is so-equipped. Decent mileage, good low-end and mid-range power. Usually around 76-80 CC chambers.

The '74 46 was the head used on GTO 350s. One can easily spot the difference by looking for "screw-in" studs (the early one had pressed studs) and the "cavity" above the exhaust crossover for post-'71 "EGR" heads. Usually 92-96 CC chambers.

The early head is a paper weight unless you're restoring a car with them "original". The late head is a decent performance head on larger displacement engines. As it has "small" valves (1.96 in. and 1.66 ex), it is an excellent candidate for "large" valves (2.11/1.77). The ports are cast virtually the same in all the "d-port" heads. By opening the seats up for larger valves, one can take advantage of the situation and use modern cutters to re-profile the seat to flow MUCH better than the original Pontiac approach. We've learned a LOT about flow and valve jobs since the 1960s!

Once porting begins, d-ports are all pretty much the same.


Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 01-24-2012, 08:34 AM
cobalt327's Avatar
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Posts: 5,031
Wiki Edits: 1616

Thanks: 128
Thanked 616 Times in 565 Posts
The intake seat would stay 30 degrees, wouldn't it? What angles above and below the seat do you recommend for a street/strip Pontiac?
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 01-24-2012, 11:38 AM
Registered User
Join Date: Nov 2011
Location: Virginia
Posts: 877
Wiki Edits: 0

Thanks: 2
Thanked 133 Times in 116 Posts
The intake seat will have a 30 deg angle, yes. This should only be changed if high-lift flow is called for. Low- and mid-lift flow are far better with the shallower angle. There is no "top" angle, as the 30 deg. seat will make the transition to the chamber better, the "further" the seat goes "out". The throat angle is 70 deg. There's a slight 45 in between.

The exhaust side is the "key" to Pontiac performance. The intake port is very efficient and flows quite well for the cross-section. The exhaust has an horrendous 135 deg. "turn" in the port, seriously confusing the sound wave. By enlarging to the 1.77" valve, that is helped (not "cured"). A very thin 15 deg. top angle, 45 deg. seat and 70 deg. throat all "help". We use a profiled "radius" cutter to rough "in" the exhaust, then after grinding the seat to size, some mild "blending" is done.

These changes work well on their own, but offer a dramatically better "starting point" for a good port job. Our d-ports tend to flow as well as others at high lift (over .500), but generally dwarf the theirs regarding low- and mid-lift flow. Contrary to what advertisers want you to think, "peak numbers" aren't nearly as significant to overall power production as the "average" of flow. More low-lift tends to increase torque production across the RPM range. We've actually changed "lift rule" small blocks to 30 deg. intake seat in circle track engines where the modification is legal under the rules. If it can't open the valve more than .410", who cares what the heads flow at .500...

Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Please select your insurance company (Optional)


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools

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

Similar Threads
Thread Thread Starter Forum Replies Last Post
pontiac engines hippy70 Engine 4 11-12-2011 04:40 PM
the big pontiac engines Jared Engine 33 10-27-2009 10:11 AM
what's up with pontiac engines (or BOPs) bullheimer Engine 15 09-11-2009 09:57 PM
Pontiac Engines at Rolex 24 Gabbyp Engine 11 03-17-2006 08:45 PM
Pontiac engines? voodoosurfer Engine 5 09-08-2004 07:08 AM

All times are GMT -6. The time now is 03:11 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.