Moparchat - Home of MOPAR enthusiasts worldwide!



Go Back   Moparchat - Home of MOPAR enthusiasts worldwide! > Technical Forums > Performance Talk

Click here to search for Mopar cars and parts for sale.


Reply
 
Thread Tools Display Modes
  #1  
Old 07-16-2003, 08:40 PM
d.friction's Avatar
d.friction d.friction is offline
Inactive User
 
Join Date: Jun 2003
Location: Austin/Texas
Posts: 281
Default A Head CC Question?

How many thousandths do you need to remove from a head to gain 1. comp point or much needs to be removed to get to a certain cc value?
What is the math?
Reply With Quote
  #2  
Old 07-16-2003, 08:52 PM
rumblefish360's Avatar
rumblefish360 rumblefish360 is offline
Moparchat Bronze member
 
Join Date: May 2000
Location: C
Age: 57
Posts: 11,120
Default

Depends on head. Big block or small block. What head do you have?
Reply With Quote
  #3  
Old 07-16-2003, 09:01 PM
d.friction's Avatar
d.friction d.friction is offline
Inactive User
 
Join Date: Jun 2003
Location: Austin/Texas
Posts: 281
Default

Sorry, Its a big block head 74cc uncut Aluminum
Reply With Quote
  #4  
Old 07-16-2003, 09:27 PM
rumblefish360's Avatar
rumblefish360 rumblefish360 is offline
Moparchat Bronze member
 
Join Date: May 2000
Location: C
Age: 57
Posts: 11,120
Default

Is it a MoPar head or Edel. or Indy or...

Sorry, I do not have specs for the B-RB heads.
Reply With Quote
  #5  
Old 07-16-2003, 09:50 PM
d.friction's Avatar
d.friction d.friction is offline
Inactive User
 
Join Date: Jun 2003
Location: Austin/Texas
Posts: 281
Default

It is none of the above
Reply With Quote
  #6  
Old 07-16-2003, 10:50 PM
23T's Avatar
23T 23T is offline
Inactive User
 
Join Date: Oct 2002
Location: Lubbock, Texas
Age: 77
Posts: 973
Default

There is a way to ball park a # but need more info bore, stroke, head type, head gasket thickness, how far down in the hole are the pistons and what C/R are you looking for etc the more info the closer the number. You may be better off changing pistons to get there, that will keep the valve geomerty? correct
Reply With Quote
  #7  
Old 07-16-2003, 11:26 PM
rumblefish360's Avatar
rumblefish360 rumblefish360 is offline
Moparchat Bronze member
 
Join Date: May 2000
Location: C
Age: 57
Posts: 11,120
Default

Well, I'm not Joe Pro here, but, I'd say give up some info on the head or everthing else. It can't be that top secret.
If it's none of the above, what are we dealing with here?
Reply With Quote
  #8  
Old 07-16-2003, 11:59 PM
d.friction's Avatar
d.friction d.friction is offline
Inactive User
 
Join Date: Jun 2003
Location: Austin/Texas
Posts: 281
Default

Not trying to be top secret. They are a new big block heads from Hughes haven't got them yet so can't help but they seem to have the best of both worlds out of the box a meld of 440-1 and Eddies. The pisons are trw 2295 dome with .150. Other than that stock deck, and stroke.
Reply With Quote
  #9  
Old 07-17-2003, 12:10 AM
dave571's Avatar
dave571 dave571 is offline
Inactive User
 
Join Date: Feb 2001
Location: carstairs,alberta,canada
Posts: 2,809
Default

Engine info is essential to calculate anything.

My question is , why?

A 74 cc chamber with a flat top piston, with .015 deck clearance, and a .040 gasket, on a standard bore 440, is already 11.3 to one.

Even if your building a full race motor then I'd assume your not using flat tops, and your comp will be higher than the 11.3. If you're building a street motor the comp is too high.

If you have more deck clearance than my example, and your trying to boost the comp with the small head, I don't think you could take enough off to get a full point out of it. 74cc is really small already, for a bb. By the time you cut enough off, the valve to piston clearance would be a big issue, and so would making an intake fit, pushrod length, ect..

Not critisizing or flaming, just curious what your objective is.
Reply With Quote
  #10  
Old 07-17-2003, 12:15 AM
d.friction's Avatar
d.friction d.friction is offline
Inactive User
 
Join Date: Jun 2003
Location: Austin/Texas
Posts: 281
Default

Hey no toes stepped on, It is for race only and the piston (by the chart say I will only see 11.4 to one with 74cc) Iwould like to get it up to around 12.5. Maybe my lit was wrong this comp. issue has been a problem sence my 906's
Reply With Quote
  #11  
Old 07-17-2003, 12:24 AM
dave571's Avatar
dave571 dave571 is offline
Inactive User
 
Join Date: Feb 2001
Location: carstairs,alberta,canada
Posts: 2,809
Default

There's a really cool calculator, at www.kb-silvolite.com That's what I used for my example.

Punch in your numbers, and see. If your piston is domed, and the head really is only 74 cc, then I think you're already 12.5 or better.

74 cc's seems really small(I don't know anything about the heads you have) Eddy's are 84, open iron(906) 88-90, closed iron (915-516) 78cc.
Reply With Quote
  #12  
Old 07-17-2003, 12:35 AM
d.friction's Avatar
d.friction d.friction is offline
Inactive User
 
Join Date: Jun 2003
Location: Austin/Texas
Posts: 281
Default

With out all the specs on the heads yet it would be hard to calculate I will keep the link in mind. I got my numbers off flatlanderracing.com . If this is not accurate let me know this is all I have found thus far.
Reply With Quote
  #13  
Old 07-17-2003, 12:40 PM
drag-n-cuda's Avatar
drag-n-cuda drag-n-cuda is offline
Inactive User
 
Join Date: Apr 2003
Location: Tully, NY
Age: 57
Posts: 240
Default

Ask Hughes for the cut vs. cc loss. This new head probably has a new combustion chamber geometric shape that will not will work with cut .010" from yields -1cc. This is an example, not an exact figure. Someone could probably give those numbers from the MP bible.

drag-n
Reply With Quote
  #14  
Old 07-17-2003, 08:37 PM
23T's Avatar
23T 23T is offline
Inactive User
 
Join Date: Oct 2002
Location: Lubbock, Texas
Age: 77
Posts: 973
Default

Per Ma Mopar " For the 73.5cc chamber heads, remove .0062" from the head surface per 1cc of chamber volume. For 79.5, 82.0 and 83.1 chamber heads, remave .0042" from head surface per 1cc of chamber volume. For each .010" removed from the head, .0123 must be removed from the intake face of the head." Hope this gives you a starting spot
Reply With Quote
  #15  
Old 07-17-2003, 09:31 PM
6 packin's Avatar
6 packin 6 packin is offline
This account disabled due to bad email address!
 
Join Date: Apr 2002
Location: Under my car!
Age: 48
Posts: 1,551
Default

Its hard to say, it depends on the head, it will make a big diff when cutting a closed chambered head compared to an open chamber head. I tell ya this, if I was paing $2200 for a set of heads, I woudnt be milling the $hit out of them to gain a extra point in compression, there is other ways, like custon head gasket thickness, and the correct piston. Decking the heads for that purpose only hurts you in the long run, Yes I did have a set of 516 closed heads decked .080 to get 65 CC chambers, talk about small, but there no $2200 heads too.
__________________
68 Coronet
69 Super Bee......new 500 cid comin soon!
73 Duster witha missing 440/727
Reply With Quote
  #16  
Old 07-17-2003, 10:02 PM
d.friction's Avatar
d.friction d.friction is offline
Inactive User
 
Join Date: Jun 2003
Location: Austin/Texas
Posts: 281
Default

6 packin- I just wanted to know. I was just brain storming if it would even be worth the milling. I understand the long run. Yes the pistons suck for what I whant now but to change them isn't cheep, neither is decking.
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
bb head question bulldog426 Performance Talk 5 05-19-2012 06:11 PM
New head question Dave Baker Circle Track Chat 7 01-31-2010 12:24 PM
516 head question BigBlockDude Performance Talk 1 05-06-2008 09:37 PM
Head question jimmycarter Performance Talk 3 10-05-2002 08:05 PM
J head question Rex Jr Performance Talk 4 11-24-2000 03:56 AM




All times are GMT -4. The time now is 05:47 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
. . . . .