Chevy big block heads - 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> Hotrodding Basics
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 05-05-2009, 07:47 PM
Registered User
 
Join Date: Apr 2009
Location: Fremont,CA
Posts: 22
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Chevy big block heads

Im curious what heads are better for performance 781"s or 290" thank you

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 05-05-2009, 10:27 PM
DaSouthWon's Avatar
I put up the tools against$300
 
Last photo:
Join Date: Apr 2006
Location: Memphis,Tennessee
Age: 35
Posts: 683
Wiki Edits: 0

Thanks: 0
Thanked 3 Times in 3 Posts
781's are open chamber and flow better.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 05-06-2009, 07:52 AM
Registered User
 
Join Date: Apr 2009
Location: Fremont,CA
Posts: 22
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Heads

Thank you I will go the 781"s
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 05-06-2009, 03:44 PM
Member
 
Last photo:
Join Date: Dec 2004
Location: San Antonio, Texas
Age: 50
Posts: 4,021
Wiki Edits: 0

Thanks: 0
Thanked 23 Times in 23 Posts
781's would be my choice for a street or street/strip build.

but they have big chambers (120cc) and takes a fairly big dome to get the compression up on a 454. Pay close attention to the piston volume and the desired compression ratio.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 05-06-2009, 05:38 PM
Registered User
 
Join Date: Apr 2009
Location: Fremont,CA
Posts: 22
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Heads

Will do thanks im installing these heads in a 21 foot Ultra custom jet boat ,installing Hydralic flat tappet cam .550 lift,with the recommened springs of course,new Comp Cam double roller timing set,Comp roller rockers, new comp pushrods,lifters ,Holley performance fuel pump 80 Gph,Edelbroke Torker manifold,850 Holley double pump.Boat was stock with peanut port heads etc.Only about 300Hp The Berkley jet was done last yr with A impellar + jetovator Im hoping to get alot more out of it with this upgrade
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 05-06-2009, 07:00 PM
DaSouthWon's Avatar
I put up the tools against$300
 
Last photo:
Join Date: Apr 2006
Location: Memphis,Tennessee
Age: 35
Posts: 683
Wiki Edits: 0

Thanks: 0
Thanked 3 Times in 3 Posts
you need to make sure that the compression ratio will be high enough for the cam. I'm not sure what the chamber size of the peanut ports is. If you have flat tops that sit .02" in the hole your going to have a ballpark 8:1 CR.
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 05-06-2009, 07:38 PM
Registered User
 
Join Date: Apr 2009
Location: Fremont,CA
Posts: 22
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Im knew to this is that good compression,i think my stock was 10:1 NOT REALLY SURE
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 05-06-2009, 07:44 PM
Registered User
 
Join Date: Apr 2009
Location: Fremont,CA
Posts: 22
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Thise is the description of the heads im installing 454 HEADS THESE ARE VERY CLEAN JUST REBUILT THE VALVES ARE STAINLESS STEEL 2.190/1.880 THE SPRINGS WILL TAKE .550 LIFT.I did replace these springs to match cam THESE ALSO HAVE A REAL NICE 3 ANGLE VALVE JOB MILLED SURFACES THE THROATS AND BOWLS WERE BLENDED TO MATCH THE NEW VALVES NEW VALVE GUIDES HIGH TEMP SEALS PRO BUILD AT PERFORMANCE SHOP THEY ARE READY
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 05-06-2009, 07:53 PM
Registered User
 
Join Date: Apr 2009
Location: Fremont,CA
Posts: 22
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Sorry all i do have flat top pistons
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 05-06-2009, 08:12 PM
DaSouthWon's Avatar
I put up the tools against$300
 
Last photo:
Join Date: Apr 2006
Location: Memphis,Tennessee
Age: 35
Posts: 683
Wiki Edits: 0

Thanks: 0
Thanked 3 Times in 3 Posts
From what I can find, I believe the peanut ports have around a 120cc chamber. This is good since the 781's are around 118cc, pretty much the same size. So basically the change in your compression ratio is minimal. a 10:1 ratio is pretty decent for a street car. Do you happen to know the brand and part number for the pistons you are using and whether or not the block has been decked. If you know these 2 things we can figure out for sure instead of just assuming. This is important, you know what we get when we "*** ume". It's better to find out on the front end then trying to figure out why your new combo runs like crap after it's reassembled and back in it's living quarters.
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 05-06-2009, 08:25 PM
Registered User
 
Join Date: Apr 2009
Location: Fremont,CA
Posts: 22
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
The block is stock 454 not sure the brand piston installed the only numbers i can see on the piston is the # 8 and 9 on every other piston ,Thank you .I will try to find out more info tomorrow .The block has never been decked ,dont know if this matters on the bottom block it is stamped Hi perf
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 05-06-2009, 09:33 PM
DaSouthWon's Avatar
I put up the tools against$300
 
Last photo:
Join Date: Apr 2006
Location: Memphis,Tennessee
Age: 35
Posts: 683
Wiki Edits: 0

Thanks: 0
Thanked 3 Times in 3 Posts
Just about all BBC's have the "High Perf" cast somewhere in the block, usually behind the timing chain cover. Whats the casting number on the rear of the block, drivers side, top corner where the bellhousing face meets the block. If the block has never been decked, and its a short deck block it has a 9.8" deck height, which is the distance fom the center line of the crank mains to the surface of the deck. The standard compression hight, or distance between the center of the piston pin to the top of the piston, is 1.460". Standard bore is 4.25, and stroke is 4.00. With that bore and stroke, using a .020 piston to deck height, a 4.03 head gasket bore diameter, a .020 compressed head gasket thickness, and 118cc's for the combustion chamber I come up with 8.43:1 compression ratio using this calculator: Compression Ratio Calculator . To get to 10:1, by changing the piston dome alone, you need a piston with a 23.5cc dome. You should measure the combustion chamber size to make sure you actually have 118cc. The production tolerances were rather loose and a better figure to use is 115cc-120cc. Measuring them is the only sure way to know their true size.
Reply With Quote Quick reply to this message
  #13 (permalink)  
Old 05-07-2009, 07:57 AM
Member
 
Last photo:
Join Date: Dec 2004
Location: San Antonio, Texas
Age: 50
Posts: 4,021
Wiki Edits: 0

Thanks: 0
Thanked 23 Times in 23 Posts
If you have flat tops then I would use a set of closed chamber heads and a 0.025" head gasket. You might get the compression up to 9.25:1.

781's with flat tops will make a dog with a big cam. You really need to change the pistons to make power. a 270 degree cam with a bbc needs about 9.0:1 cr, a 280 degrees cam needs around 9.5:1 cr, and a 290 degree cams needs around 10:1.
Reply With Quote Quick reply to this message
  #14 (permalink)  
Old 05-07-2009, 11:16 AM
Registered User
 
Join Date: Apr 2009
Location: Fremont,CA
Posts: 22
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Im Gonna have my mechanic check the piston size etc,i have no idea how to do this ,the number on block is 14015445,was told it is a 4 bolt ,these 781 heads are already at the shop having the comp springs installed plus the valves Hardend seat,sure hope i didn"t screw this up
Reply With Quote Quick reply to this message
  #15 (permalink)  
Old 05-07-2009, 01:23 PM
Member
 
Last photo:
Join Date: Dec 2004
Location: San Antonio, Texas
Age: 50
Posts: 4,021
Wiki Edits: 0

Thanks: 0
Thanked 23 Times in 23 Posts
take a picture of the piston tops and post.

or just measure the dome height and measure the area of the dome to estimate the volume of the dome.
Reply With Quote Quick reply to this message

Recent Hotrodding Basics 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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Chevy 366 Big Block WIZARD221 Engine 57 05-05-2012 03:19 PM
Factory Mopar Big Block Heads A Cork? charger528 Engine 4 11-03-2007 07:39 AM
Building A 302 Chevy Scorpio Shaping Flow Hotrodding Basics 6 01-16-2007 05:55 AM
Big block setup for my 57 Chevy kevink Engine 1 08-24-2003 06:42 PM
Big Block chevy cam help deuce_454 Engine 4 05-20-2002 12:15 PM


All times are GMT -6. The time now is 08:21 AM.


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.