I'm looking at angle milling my heads for more compression.
I know that the intake manifold interface and the head bolt holes will need to be changed to accommodate the change in the angle of the head surface.
Are there other considerations due to the angularity change, like pushrod or rocker geometry (other than pushrod length), exhaust manifold face etc?
Anyone done this themselves and found what all it affected?

 

No expert here, but when I had .060 removed from my heads several shops recommended against angle.

My guess is flat is just easier.

Then they just had to take a little material off the intake China walls and use a thinner intake gasket and it all lined up.

 

Sell those heads and get a set with smaller combustion chambers . A world of easy going that way ..

 

I couldn't remove .060 if I wanted to. Max flat milling is .030 then you encounter the intake valve.

Actually these would be new heads not the SHP's I have currently. I would like around 56cc's (least I could get is 55 cc's) in the heads for a 10.5 CR with the current pistons.
Not a deal breaker or anything I could flat mill it to 60 cc's which would give me 10.0 CR. Just exploring some different options.

Any good suggestions for heads that could be flat milled to 56cc's would be good as well as long as it's aluminum (IE, no vortec's) and heads have decent flow out of the box.

 

By the time you have ALL of the machining done to correct the angle differences in the heads and intake manifold you'd be much better off either changing the heads or pistons. Many years ago some drag racers angle-milled heads to improve the angle of the intake valve for better breathing at high rpm but for a street driven engine it wouldn't be advisable.

 

I have a BBC and Edelbrock said no issue removing that much.

If you are buying new see what they say about how much can be removed.

 

My 210 AFR's are angle milled. They needed a surfacing, so I went with angle as per AFR instructions doing the minimum for future millings. It was popular to get to less valve angle than the 23 degree for some valve unshrouding and piston to valve clearance. Like my over .700 lobe profiles. Small amounts of angle milling you can just use a thicker intake gasket. Large cuts require intake milling and possibly mill head bolt holes. Mine is jut really tight on a couple of head studs

I don't believe minor changes in C/R make lots of difference. You can go from a .039 compressed head gasket to a .015 and change a few cc's like on the angle milling charts.

Small cc chambers are more thermally efficient. Your 10 - 14 degree race heads are often only 40 some cc's

 

If I thought you had any idea what you are talking about I might consider what you said. I don't and I won't.

It's .030 for flat milling. SBC not BBC.

It will make a difference here. This for an altitude build. Every bit I can get will have an effect. right now I can run 85 octane with 9.9 CR. That's telling me I'm not very close to the CR I should have.
Not wanting to change the pistons as that represents more time and money vs angle milling.
I'm already using .015 head gasket. Piston .025 in the hole.

I don't believe the angle is even 1* and the manufacturer recommends a .120 intake gasket if I get it angle milled. So it must be a relatively minor angle change. Right now it's holiday season and everyone is off so a phone or e-mail conversation is not possible with the manufacturer.
Thanks for your input Gkull.

 

I looked up my heads on the AFR site.

Milling flat mill .006 = one cc So to go from stock 65 cc to 60 cc would be a .030 total cut and that is the recommended max

Angle milling is .009 = one cc So to go from stock 65 to 60 cc would be a cut of .045 and the recommended max is to get down to 55 cc which would be a .090 cut.

I couldn't find the formula for the manifold cut but logic tells me it must be about the the same amount of the bottom edge

 

Ok yeah I see how I could plug that into a formula and get the angle of cut. That's a .090 tapering to a 0 cut maybe? Or they could be cutting on the intake side still to minimize the angle change and the required modifications due to the angle change. In which case the .030 on the intake valve side is the limitation.

I found this formula:
C=.0175 x W x A

C= cut
W= width of head (7.6" or so)
A= angle

So if I solve for C and I assume a 1* angle i get .133" of cut.

C= .0175 x 7.6 x 1
C= .133"

Since your example is .090" of cut that is 68% of a 1* cut. Which means the cut would be .68*, less than one degree to get down to 55cc's.

The variable I don't know for sure is the width of the head.
Thanks again.

 

Trick Flow has alum sbc heads with 56cc chambers but they are all small 1.94" vlv heads and i dont know what would be max vlv size for those heads (if u bought bare). Trick flow has some 62cc alum heads also BTW.

GM no longer sells the Bowtie "phase" heads with tight chambers. All the GMPP full race kind of heads are the huge runner stuff. GMPP still sells the legacy L98 heads in 58cc chambers (again small vlvs) along w/iron Vortec & Vortec Bowtie series w/64/66cc chambers (small vlvs to). Ooops u said "no" Vortecs - sorry. Oh and the Fast Burn sbc heads w/62cc chambers.

I think your finding there is no market for heads w/your specs even though the LT1/LT4 heads had 54cc chambers and were the final evolution of the sbc heads. Let me eblaborate here and say u can convert the LT1 heads - though maybe somewhat costly - and install at least the 2.00"/1.55" vlvs. I only say this as mostl LT1 owners of stock LT1 heads are ready to give them away to get rid of them. I think if u paid $300 for a pair u paid too much. Maybe some fuel for someone's OCD i dont know. But if u want a good flow head w/tight chambers to experiment on there u go. Oh u have to mod your intake to fit an LT1 also.

Good luck head hunting Reel'r.

 

Talk to race car shops they do this quiet often although the mostly burn alcohol

 

Decided to pull the trigger on a pair of AFR 180's. Getting them angle milled to 56cc's.
$225 over cost of heads.
That includes milling the intake face and spot facing the bolt holes. Not too bad as flat milling is $100 here locally and angle milling is not available.

Will give me the needed CR bump and smaller intake tracts that I need for some velocity increase. Also much better flowing heads than the Darts I've been using.

Looking forward to the results.

 

When angle milling the deck, they should correct the angle on the intake flange of the heads not the intake manifold. Also you have to drill and then spot face the head bolt holes.
Will

 

My advice is to get bigger heads because HP is addictive.

 

Lol, I'm not sending my intake to AFR. Maybe I wasn't clear. All those things are included.

 

You're right, it is. I'll save feeding that addiction with a 406.

 

This correct and you're doing it right with AFR. You always want to mill the intake face of the heads...NEVER the manifold. Folks who cut manifolds just married the heads and manifold to be a set and eliminated easy swaps to other parts later.

My BBC heads have been angled milled like crazy! And any intake I use bolts on with no drama.

Pay attention to valve clearance in the pockets. Not sure about your pistons/cam..but be sure the different angle doesn't run things into each other.

Angle milling also reduces intake flow somewhat most of the time..so a little work to get it back in line is in order. But you never know unless the heads are on a bench.

But I'd have bought some heads to work with that 406!!

JIM

 

Just a quick question for those that know in real experience.....

If you angle mill the heads, does that change the head bolt/stud alignment? In other words, do you have to modify the original headbolt hole in the head to line up?

Just curious...

Txs
Bman

 

yes at some point of angle milling the head bolt holes would cause interference. Generally you are talking less than .060 cut and that is so trivial as to the angular change of a 23 degree head