Engine milling maths
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Another thought comes to mind.........does the surface to volume ratio when machining factory iron heads carry over to Eddy heads, as they do have a different shape and that would have an effect on how much to cut for a given chamber volume.........
nm9stheham
Well-Known Member
The Eddie (or any of the closed chambers) cuts for each cc will be more like the Mopar closed chamber. It ought to be pretty close, but that is why I mentioned that you can just touch the chambers a bit if you over cut a bit. Accuracy requires that you re-measure as you adjust it in.
The deck cuts will be very close to the cc change of the open chambers... which is the .0048" per cc mentioned earlier.
Treat the open chamber and deck cuts as simple changes in cylindrical volume. Divide the diameter by 2 and put that in the 'radius', and the cut will be the 'height'.
The results will be in cubic inches so to convert to cc by multiplying by 16.4.
You can find a cylinder volume calculator here:
Volume Calculator
The deck cuts will be very close to the cc change of the open chambers... which is the .0048" per cc mentioned earlier.
Treat the open chamber and deck cuts as simple changes in cylindrical volume. Divide the diameter by 2 and put that in the 'radius', and the cut will be the 'height'.
The results will be in cubic inches so to convert to cc by multiplying by 16.4.
You can find a cylinder volume calculator here:
Volume Calculator
If you mill one side of the head, I'd always mill the corresponding amount from the intake side. That way you can use the heads on any block. If you are just cleaning up or equalizing the block decks, I doubt you would have to take that into account. If you are milling .060 from the decks, then I'd be into milling the intake. But typically I'd be looking at different pistons, even custom. But if we are honest, there are usually at least 6 different ways to do anything. As for volume, I would assume the formula would be different. Maybe contact Edelbrock?
yellow rose
Overnight Sensation
Sorry my friend, but you are still mistaken. You make the assumption that every intake manifold is the same size, and they are not. Not even close.
One of the few times I’ve machined the heads was a SBC and the customer was adamant about milling the heads, because we were going to the dyno. He had 2 intakes, both brand new, both ordered at the same time. Edelbrock Victors.
He wanted a back to back test on a virgin casting verses his porting, which I thought was a great test. When doing the pre-assembly the intake needed something like .040 off of it. So I called him and told him to bring the ported intake by so I could fit that one and see what it needed and surface it if required.
He read all the books and **** like that and he wanted me to mill the heads instead, so he could drop on any intake he wanted. I told him it doesn’t work that way, but I gave in and gave him what he wanted.
So the engine goes together and we get to the dyno and we flog on the stock unported intake and then we go to change to the ported manifold. Guess what? No fit. Not even close.
Luckily, we had enough intake gaskets to stack 2 .060’s together and tested it. His ported intake did very well. I forget what it picked up, but IIRC it was a 30 HP average.
The best part of the day was the dyno guy asked who the idiot was that milled the head and not the intake. The owner of the engine had to fess up to that.
No 2 intakes are the same measurement. So milling the heads is not going to do you any favors, or make it so you can swap any intake on you want.
Again, I will not kill a head face. It’s just dumb. Unless you are running a class with a port volume requirement and then you have to do it.
Sounds like some idiot already ruined (or made it to only fit one combination) one of the intakes, and your customer didn't know it. For a street engine, with used iron heads, I always mill the heads to get a flat surface.
yellow rose
Overnight Sensation
Can you read? He ordered BOTH at the same time, from the same place and they came together. Both were brand new.
WTF? Do you not understand there is a tolerance for intake manifold width like everything else?
They grab the castings and machine off enough to get a flat, clean surface and it’s done.
You can take 10 intake manifolds exactly a like and you may have 2 or 3 that will fit and 7 that won’t.
It’s no different that when the factory mills a head decks and manifold faces. They have a spec they have to make. If it cleans up on the high side they send it. If it takes milling until it hits the low side, they do it. If it goes under, they set them aside and find a use for them later.
That’s why looking at a blueprint you see the NOMINAL deck height. Whatever it is...say 9.600 but that doesn’t mean that’s what it comes off the mill at. My X block was .040 or so over that. I’ve seen some blocks that were .050 under nominal. It depends on the casting.
Just like heads. The chambers have a nominal volume. Most are way bigger that that, because when the heads come though the mill, they only mill enough off to clean up the castings.
This **** isn’t complicated. It’s just a fact of building engines. I don't know a single machinist who mills the heads. Not one. They all know better.
No it is not complicated unless you make it. .120 off, standard tolerance? Not in a million years.
yellow rose
Overnight Sensation
Do the math. I took .040 off the head. The width of the intake from high to low is at least .060 so that’s .100 right there.
I have no idea if some dick took .020 off the head before my customer for them. Who knows, maybe they already took .040 off for some reason.
Real life isn’t like the comic books.
Do what you want, but it will bite you in the *** someday doing it that way.
Graham is doing my intake. Here is pics with no end rail gaskets. I had to push it down pretty good to get the bolts in. The heads were milled .031 after these pics. Not sure what the spec is for milling the intake. He would not do the head intake face. He said that’s the wrong way to do it. Kim
yellow rose
Overnight Sensation
So are you saying he won’t mill the heads to make the intake fit, or he won’t mill the face of the intake manifold?
I’m just trying to be clear which way he does it.
TIA
He won’t mill the heads. He has the LD340 intake there now. My pics show the Intake on before the heads were milled. Kim
B3422w5
Well-Known Member
agree, its not like your taking 1/2 an inch off or something. I milled my current eddies down to 57cc to get more compression using the stock 360 pistons. Airgap intake fit just fine. Never had an alignment problem worth worrying about.
MOPAROFFICIAL
Oogliboogli
The flat spot in the chamber next to the spark plug is where they base there mill depth. Correcting if it didnt make the margin was done later or they were scrapped. They knew by each chamber cutting to x amount depth would yield x amount of chamber volume. Rough but quick for production.
I mill the head if possible before the intake, incase I wanna use the intake on something else later...Anyone who says that's wrong will never be machining my stuff. Neither is wrong, one is just limiting the future usage.
I mill the head if possible before the intake, incase I wanna use the intake on something else later...Anyone who says that's wrong will never be machining my stuff. Neither is wrong, one is just limiting the future usage.
nm9stheham
Well-Known Member
OK: How you show the bolts is how you want it to be when you loose fit the bolts, with the bolts at the bottom edges of the intake holes. The intake moves straight down as it crushes the gaskets, and the intake holes will move so that they become better centered on the head holes and bolts.
BTW, do you have the thinner intake gaskets on there?
With head milling, the bolts will be harder to line up (tighter to the bottom of the intake holes) and if my wee brain is working the geometry right today, milling the intake face will correct that particular issue of the bolts and bottoms of the intake hole interfering. Milling the head's intake face will also fix it, as the vertical drop in the level of the intake holes gains you clearance. Either way is like putting in a thinner intake gasket. I thought that the intake face angles have been set up by design to allow that to happen once the head is milled on the main face and this particular problem shows up.
What you don't want is for the bolts to line up at the TOP of the intake holes when loose fitted. If so, then the bolts have to bend or tweak the holes in the heads as things get torqued, and face milling on either side will make this worse.... again, if my brain is working the geometry right. The only solution once you get there it to use thicker intake gaskets.
BTW, having flat washers under the bolt heads is important to allow the movement of the intake relative to the bolt heads as things are torqued, especially with an aluminum intake. Hardened SAE (narrow) flat washers are best IMHO.
FWIW, someone here told the story in the past of of having someone else standing on the top of the intake to crush things enough to get the bolts started in a case like this LOL
BTW, do you have the thinner intake gaskets on there?
With head milling, the bolts will be harder to line up (tighter to the bottom of the intake holes) and if my wee brain is working the geometry right today, milling the intake face will correct that particular issue of the bolts and bottoms of the intake hole interfering. Milling the head's intake face will also fix it, as the vertical drop in the level of the intake holes gains you clearance. Either way is like putting in a thinner intake gasket. I thought that the intake face angles have been set up by design to allow that to happen once the head is milled on the main face and this particular problem shows up.
What you don't want is for the bolts to line up at the TOP of the intake holes when loose fitted. If so, then the bolts have to bend or tweak the holes in the heads as things get torqued, and face milling on either side will make this worse.... again, if my brain is working the geometry right. The only solution once you get there it to use thicker intake gaskets.
BTW, having flat washers under the bolt heads is important to allow the movement of the intake relative to the bolt heads as things are torqued, especially with an aluminum intake. Hardened SAE (narrow) flat washers are best IMHO.
FWIW, someone here told the story in the past of of having someone else standing on the top of the intake to crush things enough to get the bolts started in a case like this LOL
MOPAROFFICIAL
Oogliboogli
Those heads will work on any other block.
They're 'corrected' to fit an intake designed around all those other 'stock blocks'... I know you know this. You must just have your mind wrapped around something else.
All those whom agreed with YR need to do their math over again.
You are just widening what you narrowed by milling the heads ...and the intakes and as cast port windows leave plenty of room to massage and align.
MOPAROFFICIAL
Oogliboogli
I'll add that if you use a thicker intake gasket...the cut intake could work on other blocks as well. Thing is if you measure and cut based off the thinner gasket... you will have more room for gasket compensating for the gap...cause it will be less now to start. I'd still rather cut the heads intake face once going beyond about .045
Consider if the motor came with a .020 shim.. then you mill .045...but then add a .046 8553PT... though the compression went up and the chamber got smaller by 8cc... the intake alignment only changed by, what... .021?
I sacrificed a set of head gaskets when I checked the intake alignment. The 8553s. Intake gaskets were the std 340/360 gaskets that come in the kit. I will be using factory bolts with the washer on them when I assamble it next week. Kim
You said one intake worked? Then the other did not? Never had a problem fitting intakes in real life. Not Ford, Not Chevrolet, Not MOPAR. But I can measure and know the numbers. Keep guessing away.
yellow rose
Overnight Sensation
They will work with any other block IF the deck heights are the same. Seriously? WTF?
I’ll give you an example and the numbers are rough because it’s been awhile since I milled my block, but it’s close.
To get the deck of my piston out of the deck .038, to get the CR I wanted I had to mill (again IIRC) .080 off the deck of the block.
So now, I screw up heads by milling the intake face of the head the amount needed to make an intake manifold fit it.
Now, I’m sick of those heads, so I put them for sale on FABO. And you buy them. And your block has only been milled...IDK...let’s say just .010 to clean it up. And you THINK any intake is going to drop right on? If you do, you are bat **** crazy.
That’s why you don’t mill the heads. Intakes manifolds and intake manifold gaskets are much cheaper than heads.
Come on, get real.
yellow rose
Overnight Sensation
LOL. Yeah ok. **** just falls together for you. You are either stupid or lying.
I don’t see you ragging on oldkimmer and his machinist because there is another “idiot” who does it wrong. You have a hard on for me because I call out fools like you who wreck **** for the next guy to fix.
I’ll say it AGAIN because you ain’t getting it. No two manifolds are the same. Not brand new. That’s why one fit, and the other didn’t. Get it yet? Your fantasy of zero tolerance stack up is silly and smacks of gross inexperience.
The other cheap assed fixed I’ve seen done over the decades is slotting the bolt holes. Which is fine if you are a hack and you don’t care if the ports line up. But the intake “fits”.
I have 3 Intakes that were milled to fit other motors that I bought from members on her and other sites. Enough that I could see it by eye They fit good on my engines. I measured them against other intakes I had and they were definitely milled. Idt u can see it in these pics. Kim
MOPAROFFICIAL
Oogliboogli
im
You made up the perfect storm to enforce your approach.. but that's one that's completely unique to your approach. I do agree, mostly, brand to brand and old era vs new..no 2 intakes are the same u less off the same run. Close enough to work at least in that case.
OP isn't, nor I, nor they ...nor them or their cousins buddies uncle... are milling .080 off the block. But hey to play along... i pose a variable to your example... the intake happens to be vintage and cannot be replaced ..so milling it isnt an option....so you're buying pistons, like you probably should have anyways.
That's a very plausible situation....if you're YOU trying to dodge the ball.... lmao WHO IN THE HECK MILLS THE BLOCK DECK .080 TO GET A PISTON WHERE YOU WANT IT?! BUY THE RIGHT/CUSTOM PISTON...SAME MONEY AFTER .080 OFF EACH DECK AND THE CHINA WALL, CAUSE THATS HOW MUCH YOU'RE MILLING AT THAT RATE.
You made up the perfect storm to enforce your approach.. but that's one that's completely unique to your approach. I do agree, mostly, brand to brand and old era vs new..no 2 intakes are the same u less off the same run. Close enough to work at least in that case.
OP isn't, nor I, nor they ...nor them or their cousins buddies uncle... are milling .080 off the block. But hey to play along... i pose a variable to your example... the intake happens to be vintage and cannot be replaced ..so milling it isnt an option....so you're buying pistons, like you probably should have anyways.
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The vintage non replaceable intake I get as I was a little leary of having it milled. LD340. Graham has been doing this for more than 30 years, so I went with what he knows from years of doing this. I only got to know him this year. This is the first work he has done for me. Never heard of him b4. Then a few ppl say: hey I know that guy, he does good work. He balanced the rotating assambly also. He is very good to talk to. Only thing we kinda disagreed on was: he wanted to zero deck the pistons and use the .039 gasket. Most on here said leave the piston the .015 above deck and use the .053 gasket. Which he reluctantly agreed. I actually was thinking that first, but u guys on here seemed to think either way would work. So we left it as us and still milled the heads .031. Compression is 10.2-1 with the thick gasket. I can’t thank u guys enough for all the help with my buddies build. Even after he changed ideas a few times. Kim
PRH
Well-Known Member
For 30 years I’ve been milling the intake surfaces on heads the corresponding amount that goes along with how much the decks have been cut.
I’ll probably just keep doing it that way.
Does that mean an intake manifold doesn’t ever need cutting?
Not by a long shot.
But what it does is reestablish the relationship between the port height and the mounting width back to “normal”.
If you have a set of heads and intake manifold sitting on the engine, and the intake fit is good....... you can mill the decks and intake surfaces, and everything will still fit like it did before the heads were milled.
I’ll probably just keep doing it that way.
Does that mean an intake manifold doesn’t ever need cutting?
Not by a long shot.
But what it does is reestablish the relationship between the port height and the mounting width back to “normal”.
If you have a set of heads and intake manifold sitting on the engine, and the intake fit is good....... you can mill the decks and intake surfaces, and everything will still fit like it did before the heads were milled.
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