which bbc head to use - 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
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 01-12-2004, 08:35 PM
bigwildgrin's Avatar
Rooster
 
Join Date: Mar 2003
Location: montana
Posts: 176
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
which bbc head to use

ok I am rebuilding a 427 chevy and have a set of oval and rectangle port heads. I was told years ago that oval port heads were used in trucks for torque and the rectangle heads were used in cars and for a hot rod the rectangle heads were the best choice. I just seen a dragster today with a 427 and it had oval port heads and needless to say it was very fast, which now makes me confused as to which heads are best. the oval ones I have are new out of the box, but I would have to rebuild the rectangle heads. it's all going in a very lite weight car with a 4 speed and 4:56 rears, the engine is balanced, if that makes any difference on which heads to use.

I did a search on this topic and found nothing; just to let you know that I've done my homework...
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 01-12-2004, 08:51 PM
Member
 
Join Date: Sep 2003
Location: Ottawa, Ontario
Posts: 35
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
You'll want to use the oval ports. Rectangle ports are overkill for all but larger BBC's, or engines built to operate in a 6000 to 8000 rpm power band. And when you say oval ports, you really mean oval, and not the round port truck heads.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 01-12-2004, 08:52 PM
4 Jaw Chuck's Avatar
Hotrodders.com Moderator
 
Last photo:
Join Date: Mar 2002
Location: Manitoba, Canada
Age: 46
Posts: 4,812
Wiki Edits: 0

Thanks: 0
Thanked 60 Times in 48 Posts
It depends more on the type of cam and rpm range your intending to run BWG, most streeters do just fine with the oval ports and will likely outperform the rect heads in around town driving.
__________________
Outlawed tunes from outlawed pipes
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 01-12-2004, 11:40 PM
Member
 
Join Date: Aug 2003
Location: calgary canada
Posts: 727
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Yup good point redsled make sure that thats it acual over port heads you have and not peanut port (paper wieghts)
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 01-13-2004, 10:28 AM
firestone's Avatar
http://teamrfc.gospelcom.net
 
Last photo:
Join Date: Nov 2003
Location: Fenton MI
Age: 32
Posts: 1,743
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
I would have to agree on the ovals unless you are going to take the motor to 8000 like someone else said. I am building a pump gas 496 being rapped to 6500 rpm, and I am still using a set of polished and ported 781 ovals. You could use rectangular in my case, but I was after the torque.

Good luck
Adam
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 01-13-2004, 10:44 AM
Member
 
Join Date: Sep 2003
Location: Illinois
Age: 40
Posts: 105
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I would also agree with everyone on the ovals even though I have a 396 w/ rectangular ports. Here's a question though, a BBC in a street car has enough torque to typically smoke the tires at will, can you really use more low end torque than what the rect ports will provide? Other than just doing big smoky burnouts
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 01-13-2004, 10:56 AM
firestone's Avatar
http://teamrfc.gospelcom.net
 
Last photo:
Join Date: Nov 2003
Location: Fenton MI
Age: 32
Posts: 1,743
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
I know there is going to be a little torque overkill, but we already had a set of polished and ported 781's, that we were going to use on a 461. Then we found a cheap 496 short block and decided to use that. The motor is going into a tube chassis 1967 Nova, it has a full interior and eveything, and the body is all steel except bumpers and hood, and weighs 2700lbs with a big block, so that is just more reason to not need the torque, but the car should be fun to drive.

Adam
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 02-01-2004, 12:06 PM
Member
 
Join Date: Dec 2001
Location: MN
Posts: 32
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I completly understand your question and you should really weigh in the benifits and disadvantages of each design.
1) Oval ports- Generate very high intake velocities and generally flow well up to 6000RPM. This will give crisp acceleration at amy RPM. Dis-addvantages they are pretty much all done at about 6000RPM. These are very drivable street heads. If you are going stock lock for casting 049, 290, in closed chamber. Port the bowls out and run big valves. 2.19I 1.88E
2) rectangular ports- Do not run all that well below 3000RPM. They are terrible around town. Have a noticible chug ( I think fuel actually condenses in these if you idle araound. Over 4000RPM hold on, there is nothing like them. they will flow great after and keep flowing well above 7000RPM.

I speak from experience as I ran both in my '68 Vette 427 tie-power. Currently I am switching back to the ovals and reserving my rectangulars for a 489 stroker. I personally think the rectangular ports are to big for a street 427, 402, 396. If you design your engine to make power over 6000RPM go rectangular. If not the Ovals will perform better on the street.
Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply
Message:
Options

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:
If you do not want to register, fill this field only and the name will be used as user name for your post.
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:

Log-in

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



All times are GMT -6. The time now is 04:48 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.