Slant *        6        Forum
Home Home Home
The Place to Go for Slant Six Info!
Click here to help support the Slant Six Forum!
It is currently Wed Jan 08, 2025 7:24 am

All times are UTC-08:00




Post new topic  Reply to topic  [ 8 posts ] 
Author Message
 Post subject: head milling choices
PostPosted: Wed Mar 03, 2004 8:50 pm 
Offline
Board Sponsor & SL6 Racer
User avatar

Joined: Fri Nov 08, 2002 4:48 pm
Posts: 5835
Location: Burton BC canada
Car Model:
I got my 69 head back from the machine shop. For the price of a standard valve grind and guides I got my SBC valve seat work done ,new guides , spring seats machined for SBC springs. He also enlarged the throats below the valve seats. $300 US
I need to blend in the bowls and do a little port matching.
My questions revolve around deck heights and where to mill.

Dart 270 angle milled the head to achieve compression resulting in a more closed chamber with more quench.

Long rod engines use the raised piston to achieve compression rather than milling. This creates a more open chamber and less quench.

On a torque oriented engine at a target ratio of 9.0 to 1 is the closed chamber with more quench going to be more efficient?
Is angle milling for quench worth the trouble?

3000 lb 65 Valiant
225 super six
5 speed 3.23 gears
4500 rpm max
TBI to follow

http://www.arrowtipi.com/My%20Webs/index%20Valiant.htm


Top
   
 Post subject:
PostPosted: Wed Mar 03, 2004 11:18 pm 
Offline
Guru
User avatar

Joined: Sat Oct 12, 2002 11:22 am
Posts: 3740
Location: Sonoma, Calif.
Car Model: Many Darts and a Dacuda
The truth is that you will not be able to get quench with a 9 to 1 SL6 unless you get a set of custom made pistons. Quench chamber Slants run around 12 to 1 compression minimum.

For your application you should take some measurments and mill the block and head the amount needed to get your target 9 to 1 compression ratio.
DD


Top
   
 Post subject: head milling choices
PostPosted: Thu Mar 04, 2004 8:35 am 
Offline
Board Sponsor & SL6 Racer
User avatar

Joined: Fri Nov 08, 2002 4:48 pm
Posts: 5835
Location: Burton BC canada
Car Model:
My buddy has a machine shop where I have full priviledges. We plan to mill both the block and head to get 9-1. By the time I clean out the chambers and relieve a little around the valves my chamber volume will be greater than stock. I can take meat off both the head and the block. Is there an advantage to milling one more than the other? Is there a "target" chamber volume? Do bigger Valves and ports mandate a larger chamber volume? Am I being overly fussy about where to remove for compression?


Top
   
 Post subject: Re: head milling choices
PostPosted: Fri Mar 12, 2004 7:16 pm 
Offline
EFI Slant 6

Joined: Wed Sep 10, 2003 7:15 am
Posts: 285
Location: N. California
Car Model:
Quote:
is the closed chamber with more quench going to be more efficient?
Yes. And that does seem to be the direction that cylinder head design has been going, in the past few decades.

I'm guessing what you're looking for in efficiency is the "squish" action. This rather sudden turbulence at the end of the stroke does a great job of spreading the flame front quickly. (Increased turbulence is also the underlying reason for so-called swirl induction created by appropriately placed intake valves.)

I was told years ago that milling the block was better than milling the head because it increased the squish action and therefore the efficiency. That would seem to make sense, as long as we're considering the closed chamber head design.
Quote:
The truth is that you will not be able to get quench with a 9 to 1 SL6 unless you get a set of custom made pistons. Quench chamber Slants run around 12 to 1 compression minimum.
That is very believable, given the -.140 deck height of a 225. What about the zero deck height of the 170? Wouldn't "squish" be much easier to obtain?

- Erik

_________________
Lots of early Valiants and Barracudas have crossed my path.
Also a handful of other toys for variety now and then.


Top
   
 Post subject:
PostPosted: Fri Mar 12, 2004 8:19 pm 
Offline
Board Sponsor & SL6 Racer
User avatar

Joined: Fri Nov 08, 2002 4:48 pm
Posts: 5835
Location: Burton BC canada
Car Model:
Would the head not be a better place to remove material to increase squish?

Image


Top
   
 Post subject:
PostPosted: Sat Mar 13, 2004 6:29 am 
Offline
Board Sponsor & Moderator
User avatar

Joined: Mon Oct 21, 2002 11:08 am
Posts: 16810
Location: Blacksburg, VA
Car Model:
That would be my thought, Sandy. You will decrease the chamber area presented to the bore by milling the head. Basically, all Slant heads are open chamber unless you mill them at least 0.100", and more like 0.150".

Lou

_________________
Home of Slant6-powered fun machines since 1988


Top
   
 Post subject:
PostPosted: Sat Mar 13, 2004 7:43 am 
Offline
Board Sponsor & SL6 Racer
User avatar

Joined: Fri Nov 08, 2002 4:48 pm
Posts: 5835
Location: Burton BC canada
Car Model:
I am thinking of "bore notching" or relieving the block a little for better flow around my larger valves as well as sweeping the chamber. Both those operations increase volume. If I mill everything from the head to get my 9:1 ratio I might approach .100. Time to have a closer look at the Docs "smiley chambers"

_________________
Yeah....Im the one who destroyed this rare, vintage automobile.....

Image


Top
   
 Post subject:
PostPosted: Sat Mar 13, 2004 8:11 am 
Offline
Board Sponsor & Moderator
User avatar

Joined: Mon Oct 21, 2002 11:08 am
Posts: 16810
Location: Blacksburg, VA
Car Model:
0.100" is no problem at all for a Slant head. I've done a 0.080"/0.180" angle mill (0.120" net for flat mill) head and a 0.100"/0.200" mill (0.140" net) head and no worries after 40k+ on each. The latter is 30-33ccs if I remember right.

Don't ask if the angle milling makes a difference. I just did it on a recommendation from Meril Bruner and they have worked well for me, but I have no direct comparisons to flat milled heads. The chamber may get a little smaller area with the angle mill, esp on a pre-68 head.

Lou

_________________
Home of Slant6-powered fun machines since 1988


Top
   
Display posts from previous:  Sort by  
Post new topic  Reply to topic  [ 8 posts ] 

All times are UTC-08:00


Who is online

Users browsing this forum: Google [Bot] and 5 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Limited