Angle Milling the Slant Head

-
Garrett Ellison

Garrett Ellison

Up in the holler…
FABO Gold Member
Joined
Jan 1, 2018
Messages
6,357
Reaction score
6,317
Location
Southwest VA
Would it work? We’ll have to sacrifice a slant head to find out. But, looking at it, angle milling towards the plug like in a small block Chevy looks like it would help flow by rotating the valve bore towards the centerline of the cylinder. It’s probably thick enough to take a .180 cut off with an angle cut. Of course, looking at correcting rocker geometry, too. And then redrilling and spot facing bolt holes. But probably get a heckuva compression boost at the least. The manifold face would need corrected, well if you wanted to keep it under hood, at least. What say ye, slant fans and builders?

att.ExwigFDg2G2mgGF7MntDdVNTBBK28RDWyqOFrlL1Grw.jpeg
 
Last edited:
thought about this with an AMC 258 or 4.0. same issues: redrilling head bolts and spot facing bolt holes, will the pushrods rub on the head and is there enough meat to grind for clearance, maybe shorter pushrods also. at the carb end, you would need an angle plate to keep the carb level, unless you went with EFI. also wondering if anybody has done this.
 
It's an interesting thought. I have LOTS of slant heads, too. I scanned this article and it seems to say a change of a degree or two doesn't require bolt hole mods or dowel pin mods. So I reckon the question becomes, "how much" can be gained (if any) from a one or two degree change? I'm not very familiar with angle milling other than knowing what it is. I don't think a one or two degree change would cause interference with the hood, lol, but I do think it would be something you'd want to correct. As for the rocker geometry, we got Mike @B3RE B3 Racing Engines to help with "ALL THAT". But I'm willing to get one cut just to see what it would look like, although I don't have a working project to put it on......I GUESS I COULD yank the head back off Cheap & Nasty and have it angle milled. lol Here's the Hot Rod article on it.

www.hotrod.com

Angle-Milling Cylinder Heads - Play All The Angles

Angle-Milling your cylinder heads is a great way to make some power gains from your race engine without adding any new equipment - Circle Track Magazine
www.hotrod.com www.hotrod.com
 
I didn't think about valve angle increasing HP, I was looking more at the ram effect the angle would have on the air/fuel. in that case, what about angle milling the intake so it's at an angle?
 
abdywgn said:
I didn't think about valve angle increasing HP, I was looking more at the ram effect the angle would have on the air/fuel. in that case, what about angle milling the intake so it's at an angle?
Click to expand...
The flow improvement is gained from changing the relationship of the valve angle to the cylinder bore. Much like aftermarket SBC heads that have 21 or 18 degree valve angles. LS engines have a 15 degree valve angle.
 
Garrett Ellison said:
The flow improvement is gained from changing the relationship of the valve angle to the cylinder bore. Much like aftermarket SBC heads that have 21 or 18 degree valve angles. LS engines have a 15 degree valve angle.
Click to expand...
I'm not arguing, I'm just throwing this out there, because this is how my mind sees it. And I'm sure it's WRONG. LMAO But what I see when I look at that diagram above is, it appears if you mill the spark plug side of the head, you are making the curve into the cylinder from the intake port more "sharp", while milling from the intake side would "soften" the curve and make it easier for the air to enter the cylinder. ...am I just stupid?
 
Garrett Ellison said:
The flow improvement is gained from changing the relationship of the valve angle to the cylinder bore. Much like aftermarket SBC heads that have 21 or 18 degree valve angles. LS engines have a 15 degree valve angle.
Click to expand...
Slanty valves are, unlike SBC/BBM, on bore center.....and the angle doesn't create nearly as much chamber shrouding...not to mention the angle is better that both of those. If You don't mind losing all of Your hood clearance, getting the ports up in relation to the bore could reap a reward, but everything You just suggested to 'fix' the hood clearance is the exact opposite of what You'd want to do to take advantage of that.
 
RustyRatRod said:
I'm not arguing, I'm just throwing this out there, because this is how my mind sees it. And I'm sure it's WRONG. LMAO But what I see when I look at that diagram above is, it appears if you mill the spark plug side of the head, you are making the curve into the cylinder from the intake port more "sharp", while milling from the intake side would "soften" the curve and make it easier for the air to enter the cylinder. ...am I just stupid?
Click to expand...
This is the way I see it as well. In essence, raise the intake plenum, raise the runners. Straighten everything out so it's a straight shot with one turn at the short side. Get rid of that gradual curving floor.
 
It would not hurt the Colt with the Webers.
I did not have much clearance with the single four.
But the Colt is not like any of the A Bodies.
IMG_0071.JPG
IMG_0073.JPG

These 2 pictures show the effect of the LONGER intake.
On the 62 Lancer with the Hyper Pak intake on a 170 (remember 1 inch lower deck) I had issues.
I ended up lowering the crossmember to keep the off set Max Wedge aircleaner off the inner hood.
Snip Engine.JPG


But with most 67-76 A Bodies with stock intake or Offy/Clifford I would think you would have room.

I will ask around the /6 racers about doing an angle mill, seems like it has been done,
 
Slant-6 heads have been angle-milled. Doug Dutra has done it, if I'm not mistaken (which stands to reason; he's done just about every possible thing to just about every possible version and variant of every possible Slant-6 engine and component over the decades).
 
slantsixdan said:
Slant-6 heads have been angle-milled. Doug Dutra has done it, if I'm not mistaken (which stands to reason; he's done just about every possible thing to just about every possible version and variant of every possible Slant-6 engine and component over the decades).
Click to expand...
I'm SURE he has. I'm also sure if there was any real benefit, he'd shared it all over the internet. He's good about that kinda thing.
 
He certainly was for a lot of years. His shop and the majority of his cars, tools, parts, literature, aluminum-head blueprints, etc burned up in the Camp wildfire some years back, and since then he's been just about silent online.

As I recall, the finding was that there is a benefit – which makes sense, given the geometry and valve shrouding we're starting out with on the \6. I don't recall the particulars, but Here's a good place to start looking into it.
 
slantsixdan said:
He certainly was for a lot of years. His shop and the majority of his cars, tools, parts, literature, aluminum-head blueprints, etc burned up in the Camp wildfire some years back, and since then he's been just about silent online.

As I recall, the finding was that there is a benefit – which makes sense, given the geometry and valve shrouding we're starting out with on the \6. I don't recall the particulars, but Here's a good place to start looking into it.
Click to expand...
I remember when that happened. It was a complete catastrophe. Thanks for the link, but I have to create an account and login. Already a member of too much I don't use.
 

I was just reading alot of posts on that subject just today mostly from the other /6 site.
Lou over there ("Dart270") mostly.
And RRR, in one of them, your one of a kind /6 head came up as did your excessive milled head, in another. I know you have a different screen name there
 
It looks to me as if there advantages to milling each side, so maybe the best thing to do is to just mill it conventionally flat. That way you get both sides.
 
Slanty valve angle- 12° that's Brodix/Dart/Buick/Pontiac NAPCAR head territory, valve angles need no correction.
Slanty chamber shrouding, not a problem, a 1.81" intake valve installed with an as-cast chamber checked at;
LIFT. CLEARANCE. IDEAL. MARGIN +/-
.450" .360" .362" -.002"
.500" .390" .400" -.010"
.550" .425" .440" -.015"
.600" .455" .480" -.025"
As is obvious, the .190" oversize valve would need very little grinding to achieve the needed clearance. It is the
bore-to-valve proximity that is the issue shrouding-wise.
Stock 1.62" Intake valve to chamber at bore wall is .135".
Stock chambers on tube & peanut plug heads are;
3.435" lateral (plug-side to port-side), &
3.475" longitudinal, inline with valves/guides.
Re-establishing the same bore-side shrouding will take the large 3.66" bore Endurotec gasket, & a good size relief in the bore for the 1.81". Moving the guide towards the center will help, but will need the exh. valve to be moved as well, or reduced in diameter.
The upshot is, angle milling is primarily a chamber volume/burn-speed modification, which itself is a worthwhile goal if one is serious.
 
Killer6 said:
Slanty valve angle- 12° that's Brodix/Dart/Buick/Pontiac NAPCAR head territory, valve angles need no correction.
Slanty chamber shrouding, not a problem, a 1.81" intake valve installed with an as-cast chamber checked at;
LIFT. CLEARANCE. IDEAL. MARGIN +/-
.450" .360" .362" -.002"
.500" .390" .400" -.010"
.550" .425" .440" -.015"
.600" .455" .480" -.025"
As is obvious, the .190" oversize valve would need very little grinding to achieve the needed clearance. It is the
bore-to-valve proximity that is the issue shrouding-wise.
Stock 1.62" Intake valve to chamber at bore wall is .135".
Stock chambers on tube & peanut plug heads are;
3.435" lateral (plug-side to port-side), &
3.475" longitudinal, inline with valves/guides.
Re-establishing the same bore-side shrouding will take the large 3.66" bore Endurotec gasket, & a good size relief in the bore for the 1.81". Moving the guide towards the center will help, but will need the exh. valve to be moved as well, or reduced in diameter.
The upshot is, angle milling is primarily a chamber volume/burn-speed modification, which itself is a worthwhile goal if one is serious.
Click to expand...
That's good stuff! Thanks for that!
 
For the chamber shrouding, I dug this cutaway out & snapped these;
.450" lift:
20251110_172844.jpg

.500":
20251110_173031.jpg

.550":
20251110_173730.jpg

.600":
20251110_175013.jpg

You can easily open the chamber to take a 1.92" valve, but the throat & bore makes that a racer-only magic act.
 
Mopars always had better valve to bore relationships. That's why MP didn't offer different valve angle heads (that I recall) but Chevy did.

When running large valves in the 273, MP talked about clearance in the block to aid airflow. I always wondered about that if I was to run Magnum heads on a 273. The slant might want the same trick.

Remember, if you shift the head, you're also shifting the intake and exhaust manifold hardware. Start angle milling the intake face and those bolts start going goofy relative to the manifold.
 
jos51700 said:
Mopars always had better valve to bore relationships. That's why MP didn't offer different valve angle heads (that I recall) but Chevy did.

Remember, if you shift the head, you're also shifting the intake and exhaust manifold hardware. Start angle milling the intake face and those bolts start going goofy relative to the manifold.
Click to expand...
BBM heads are 15°, but the valves are horribly positioned past bore center, & open even further away from it....like SBC's, that's why the funky notches in the head gaskets.
 
Killer6 said:
BBM heads are 15°, but the valves are horribly positioned past bore center, & open even further away from it....like SBC's, that's why the funky notches in the head gaskets.
Click to expand...
There appears to more than a little sbc that got copied into the bbm cylinder heads. Eric Weingartner says that the ports behave and respond to changes nearly identically.
 
You must log in or register to reply here.
-
Back
Top Bottom