milling cylinder heads for compression question

[Beagle]

I've got this out at the 460 board and wanted to check input here as well...

Hello all,

I have a set of D3's that I followed Scotty's directions on (tried to anyway) and I'm wanting to get a few CC's back since I laid the intake wall back just a bit on the combustion chamber. I had a couple of questions and thought I might toss them out here for feedback. The end goal is a 5000-5200 hp peak torque focused 466. With the chambers in at 98cc or so now, I'm coming up with 8.7:1 with zero deck and 16cc dish.

I don't think this engine was ever apart before so I'm fairly sure the heads have never been cut. I'd like to cut enough to get it down to about 92cc but I don't think I can get there with any normal cut. Here's my questions -

the stuff I find says .0065 inch per cc roughly, and I'm considering a .050 cut, is that too much? Is that estimate close for these heads? I thought that number might be okay for a 350 sized head but these have a larger chambers diameter. Is there a better estimate number?

At .050, that's roughly 7.7 cc if my math is right. Is .050 too much for these heads?

Would angle milling be a better choice? I'm guessing the manifold will need trimming too either way. I did the math at 3.85 stroke, 4.39 bore, .041 thick x 4.5 diameter gasket, zero deck with 16cc dish.

I ran it through a buddy's simulator with a WG1167 Wolverine cam (214/224 @ .050, 112 LSA, 107 ICL) and it looked like the roughly half a point was worth 13 cranking PSI (167 v 180).

Am I overthinking this for a .5 point difference? The heads will get cut either way, I just figured I'd try to get an extra few ponies and "crispier" response from it while I was already there.

Open to suggestions, math corrections, etc. Thanks folks!

[JeffMcKC]

.5 diff wont mean much you will pick up more comp by advancing the cam 2*

[anotheridiot]

we raced with a set of angle milled heads, intake gaskets were always a problem. Then of course you are stuck with that intake system unless you or anybody else that runs them machine any other deal you might want to change to at a later time, some actually need to be built up with weld to keep the ports lined properly. Once all that is done you probably could have bought two sets of pistons to get more squeeze. Either way, clay the chamber to see how much space you have now. You need to be a minimum of .060 valve clearance. Just suggesting you are gonna be pretty stuck once you decide to angle mill, so you will have limits of changing cams or intake systems at a later date. That head is holding it all together, milling that much sure seems like you are putting them a their limit.

[milner351]

I would not angle mill - as stated - you're building custom pieces at that point that can't be interchanged.

It's a shame thin head gaskets are not more common - and leak proof, most I've seen require an o-ring machined into the head - by the time you do that - you could have gotten them milled, and probably cheaper.

[BBR]

Do a search for "milling" on 460ford. There are a ton of threads about milling. Some as much as 0.110"! If you do mill, mill the head's deck and intake side. Do not mill the intake manifold itself. That way you only have 1 modified part instead of 2.

[JeffMcKC]

Losing .50 comp means very little, think Nascar 9to1 comp. they gain the cylinder pressure back with the camshaft. Your not going to use a huge duration one and if your running pump gas your going to be limted there also.

[Beagle]

Thanks guys -

Jeff, agreed... it's a really small cam already, maybe a bit too much intake for the compression it has and way not enough for the other set of heads I have.

BBR - there's something goofy with that forum. When I was looking through the posts it only showed one page, but when I searched I got a ton back. Since I didn't see anything just viewing it, I posted it up. It was early, I don't know why seeing it that way kept me from searching. Thanks for the suggestion, I'll go reading. A .100 cut would definitely get it where I want it. The valve reliefs in the pistons I have are pretty deep already. The intake side cut makes total sense - I've read that before and forgot about it. Stupid early morning posts, that's what I get for typing with no BAC.

ai, good points. BBR's cut the intake side too would keep me out of a lot of trouble!

John, The .039-.041 gaskets commonly available are pretty much what I want as well with zero deck... makes quench the same as the head gasket size which is what I think I want.

[A/Fuel]

Are your valves dished, do they make flat ones for your engine?

[Beagle]

^^ yes and probably ... I'm so bumming. I just checked CL for grins and somebody just sold a 521" shortblock for 450.00 , plan Z was "stroker.. stroker...stroker" since we know stroke adds S.C.R.