If the manifold faces were 90 degrees to the heads tha would be 100% correct. On a Y block they're not. You're dealing with a compound angle because the port face is angled. I'm not sure what that angle is. Ted or John can give you the actual number, but I'd start with .030" on the manifold also.    

           I meant to add, if you take off .030 from the heads take 020 off the intake faces or half of the .042" you calculated. I'm sure you knew that but reminders dont hurt.

       I have had pretty good like with the ARP's Mummert sells. You can also buy them seperately at you local speed shop, if they have one out there.

       Since you already took 028 off the block the total is now .060 (.056) so the 040 works great. What for gaskets?  

       John and I thrashed this out off line. Seems to me the right answer is whatever you take off the face of the head is what you take off the port face. Only make sure that the head gasket is the same thickness as what you started with. .030 = .030 per head

     He's closer to right than I am. Also, are you sure the heads haven't been milled before? 

     All the theory in the world won't replace the fact that John's answer works. I based the first answer on the port faces being 90 degrees to the deck, They're not. They are at 15 degrees.

      When you mill a head with 90 degree ports, the distance between the heads or any point on the port face closes up at the rate of 1.42 x what is milled. Since there's two faces you'd take off half from each side. When you throw the extra 15 degrees in to the mix you have remove the height of that triangle into the numbers. Sit down with a piece of paper and trace how things move, and it'll start to make sense. I'm supposed to be an engineer and it took me about an hour to understand what happened. Your answer will work, John's answer will work a little better. Remember he's built about a 100 of these things, so he knows what works.

        For 90 degree faces, you have a right triangle, the distance between the heads being the Hypotenuse. C is the hypot, a and b are the other sides. When you mill the heads or the deck you reduce the adjacent sides. Formula is C= Square root of  A squared plus B squared.

There are several engineering papers around that show how mechanical "creep" effects are combated when establishing fastener preloads. The one that caught my eye came from the guys who make the "Superbolt" fasteners for our giant mining machines. It suggested that new fasteners be torqued/tensioned to full load - and then fully released to give the thread roots one full "load and release" cycle before going to the assembled torque we desire. This was said to eliminate future creep - and we have tried this a couple of times now (with big Grade 8, 1-1/2 -6 UNC fasteners) and it seems to have worked. It will take years before we know the whole truth however.  

To prevent bottoming torqued fasteners - in blind holes in big gearboxes, we usually put the fasteners in "hand tight" (this is a relative term here when those big 1-1/2's are being turned in) and measure the remaining "grip" standing out of the case to compare against the thickness of the main caps and cover flanges. I once found a huge bolting flange that wasn't tapped deep enough for full grip of the (30) 1-1/4-7UNC Socket Head capscrews we were about to fit (and torque) - and I had to have the field machinists come and rework the crawler right in place. Its a lasting experience.......

I am a little confused as to how they came up with these figures, for one surface "B" is not at a 10* angle to surface "A". it may be at 80* which would be 10* from a right angle of 90*

I agree the angle has to be ratioed out. for example: a dial indicator at a 45* angle is reading twice the actual reading. so at a 45* angle the ratio would be 2 to 1 (head milling being the 1 and intake milling being the 2)

I am missing something here about how they are coming up with these formulas based on their angles?

Not trying to be a smart a*@ or nothing but I think you meant the intake face is 75 degrees from from the head deck face, not 15 degrees.

With the block decks being 90 degrees from each other and the Head to intake face 90 degrees, this would be a perfect 1 to 1 ratio. If the intake was 45* to the head deck, this would be a 2 to 1 ratio (whatever you take off the head or deck you would need to double it at the intake.) If the intake surface was at 22.5* from a 90* which would actually be 67.5* to the deck of the head, this would be a 1.5 to 1 ratio. (whatever at the head or deck and 1.5 times that at the intake.) again divided in half to assume the intake is at 11.25* from 90* gives us 78.75*, this would be a 1.25 to 1 ratio.

So if the Y block intake is at 75* to the deck it would be around a 1.3 to 1 ratio assuming the block decks are a 90* V8, if the block decks are not 90* apart from each other then it changes the whole scenario.

The compressed gasket thickness was .044 with a mic.

Quite a few of the intake valves were a mess.  They looked worse than the exhausts on their flutes, like combustion gases were leaking back into the head intake ports.  Heads only had 2000 miles since rebuild.  Maybe the unknown NOS 270 cam required different than stock valve clearances.   Even if so it has been replaced.  

.028 have been taken off the deck and also .028 milled from the head's deck surface.  How would you make sure the bolts arent bottoming out?

The bolts are from one of the later model truck engines and have markings that look as if they are grade 8.

Mike

Mike

I would like to report that the intake fits perfect, but cant.  It does fit OK.  No problem threading bolts.  It is a little low, with center of threaded head holes a little above center of the intake holes after compressing gasket.  It will make another cut on the heads easily done at some future time.  At least most all of the interference between the Blue thunder and the DS rear of the valve cover is gone.  The milling took all of the top intake flange of the heads off, even a very little from the skirt forming the base of the valve cover.  .045 may be getting close to max.

At maximum lobe lift the valve/piston clearance was way more than adequate. 

Chuck, you talk about a chore removing heads:  the C2AE motor I tore down this summer, had both heads STUCK.  I barely suspended the longblock from an unbolted head, and still had to take a long bar inserted into the center crossover, put one foot on the opposite side and pull with a lot of effort.  Both sides needed the same treatment.

Regarding the combustion gases apparently blowing past the intakes.  Could this be from inadequate spring pressure and the 270 degree .460 lift cam that was being used, causing the valves to maybe bounce? 

I have been thinking more on this too.  All of the head milling has been done on my watch.  They had .025 taken off two years ago.  When I started the post my plan was to take .003 more, and then like I said, when I was at the shop decided to take .005 which would have equaled a total of .030.  Gary's warning on valve interference has sunk in, and I am going to call the shop Mon. can tell them not to take any further off the deck side of head, so it will stay at .025.

However, I am not sure the block deck hasnt been milled by a previous owner.

So, as I understand you and John's thinking, there is .053 milled (.025 head and .028 deck), .020 extra gasket thickness, net loss of .033, and .033 to be taken from intake side of head?

Mike

Mike

As you can tell from all the foregoing posts, I am no expert here by a long shot.  This is how I figured the angle vs. the related calculation of head milling vs. intake milling.  I put a head on a horizontal, level surface, and placed and angle gauge up against the intake flange.  The anlge gauge said 75 degrees, so I took that to mean 15 degrees in relation to the heads as stated in the diagram, thus 1.4.  My trig. left a long time ago so cant go too much further on the angles and ratios.

Given all the experience presented in this thread, against the Hastings info., my current plan is to split the difference between the calculation and John and Frank's recommendation.  .033 vs. .046 comes out to .040.

Mike 

FYI, since questions regarding cost of machine work often arise.  The charge for intake mill, and chem dip is $70 here, with bare heads arriving at the shop.

Way back in the '50s Hot Rod Magazine had a chart for manifold milling.  1.4 was the number for the Y Block.  I personally mill the manifold side of the head instead of the manifold, that way I can switch manifolds and not have to mill each one.  The heads can be swapped from engine to engine without manifold milling also.

John in Selma, IN

.042 off each head is correct.  Also, the original Y head bolts have 4 marks, which makes them grade 6.  Why bolt manufacturers didn't make the number of marks match the grade is beyond me.  Anyway, the originals do stretch, no matter the grade they are.

John in Selma, IN

John in Selma, IN

I believe Chuck is alluding to pulling the heads with the head studs in place while in the vehicle.  Typically, the heads will not clear the master cylinder or the heater box with the studs in place thereby requiring removal of the studs before attempting to pull the heads.  But if the heads are stuck hard to the gasket, then head removal chances are logrithmically compounded with the studs in place.

If you are planning on pulling the heads a multitude of times, then studs are good in that the threads in the block are not being worn out as fast but the correct bolts are more than up to the job in most instances.

Although most Y’s came through with head bolts having four hash marks (of which I’ll go along with John and call them grade six as they are not listed in my bolt manual either),  I do on rare occaision come across a factory installed set with six hash marks making these grade eights.  Even in these cases, I will replace the bolts with a new set simply because the original bolts are roughly a half a century old and fatigue becomes a factor.  And never torque the bolts with the threads being dry as insufficient torque is typically being applied due to the additional friction that's occuring within the bolt threads.