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Discussion Starter · #1 ·
I need to know how much to remove or machine from the situation explained below.
I have a intake port that is .250 mismatch with the head port on the floor and roof when viewed through the intake runner. The intake port is too high for the heads as far as port alignment. In other words the intake needs to be machined on each of the 45 degree surfaces that mates to the head surface.
I have done my math and I come up with (depending on how you set it up) .177 per side or .125 per side. This is with the intake mounted on a 90 degree angle plate from the lifter valley pan being parallel to the angle plate and the head on the bridgeport mill on a 45 degree angle. If you move the knee of the mill up you will need to remove .177 or if you leave the knee alone you will need to remove .125 with a straight quill or spindle move.
Then you will need to remove the .250 from the valley pan or gasket base seal area of the bottom of the intake because it is to drop it .250.
I have questioned 3 different machine shops and they all gave different answers ranging form double the .250 down to they don't know they just cut until enough is removed.
Hope I have not confused everyone but if you have had experence with this your help will be greatful. I don't want to screw this nice intake up.
Well, we will have some conversation here or want we?
 

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I ran the math for you and assuming you are correct on the mating surface being at a perfect 45 degree angle I get ~0.17677. I'm sure you don't want me to give you anymore decimal places than that.
 

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I dont think i would want to guess and take the max amount right out of the box. Just never seems to work out that way. I setup and cut mine twice to get it right. Wound up taking 130 per intake face but leaving the bottom close as to only take a small amount of sylicone to seal that. About .04 clearance there i like it better that way no gasket there now. I did mine on a cnc vertical mill with a 4th axes.
 

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I mill the intake flange the amount needed to fit and then trial fit it with gaskets or shims taped to the heads to set the intake about where it will sit. If the block portion of the intake hits I just measure the gap and cut an additional .040-.060 off the intake and it always works. I know you want exact math, but that rarely seems to work in reality...
 

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Discussion Starter · #5 ·
OK, We have a little response here.
McCarthy 4, You get the .177 that I did. This would be by moving the knee of the mill up .177 right? Or it will also be .125 by moving the spindle, which is on a 45 deg. straight into the 45 deg. surface of the intake. Is this correct with your thoughts?

Coolfalcon, you stated that you removed .130 Which direction of measure did you use? If you removed .130 what was the mismatch?

ou812, Exact math would be great, but would only be as accurate as the measurement. Off the top of your head, if you had a mismatch of .100 how much would you mill? .100 or less? Which axis would you use? Do you turn your mill head on a 45 degree, and have the intake valley mounted to the 90 deg. surface plate perpendicular to the table.

Thanks for everyones effort.
 

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I have some machining experience, but am not a machinist by trade. I did the math and geometry. I'm an engineer and like to lay out everything on paper first before I start wasting material. The number I figured was straight into the flat mating surface of the intake to the head. To be safe, I would still probably do only .1 or so to start and take it down in increments as suggested by other, but the math I did pointed to the .177 coming off each side of the intake. Still, always better to be on the safe side and err in favor of caution. You can always take more material away, it is hard to put it back.
 

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I apolagise. I looked at where I did my calculations again and the .177 was not straight into the surface like i stated previously. It should have been that amount by raising the spindle. The .125 figure you stated earlier should be about right going straight into teh surface.

Sorry for getting my numbers mixed up on you.
 

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Did you account for the thickness of the COMPRESSED intake gasket thickness........?

FE
 

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Discussion Starter · #10 ·
McCarthy4,
I have calculated this several times on paper. I almost went for the .177 but when I thought about how I was to set the intake up for milling I noticed that I may be wrong.
I wanted a second opinion to see if I could get any clear answers on what the amount would be. Seems like when working with triangles with two 45 deg. angles, seems to be the most confusing.
I have had a couple engine builders who said you need to remove about the same as you measure, this would resemble the .707 of .250 which will be the .177 amount, and if you added the gasket thickness to the equation like FALCONAROUND said it would be about .250.
This does not relate to the .125 number which I was hopping for.
Thanks for your time.
Anyone else have any comments or experience with this?
Thanks
 

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Discussion Starter · #11 ·
McCarthy4,
Think about it from scratch again and see if you get the same answer. Also think about how you would set it up for milling.
Thanks
 

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Pinto, I redid the math from scratch and yes I'm coming up with .250 straight into the surface. I still get .177 for the amount the manifold needs to drop straight down, but I had one my calculations inversed before. Assuming that the .250 the the port are off is with a compressed gasket in place when you measure.
 

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Honestly, if you have a good machinist do the work you should be able to trust their measurements. Even if you know what the math says, you should only machine part of that at a time and recheck a few times, just in case of mistakes or an inaccurate measurement. Just fo avoid some of the confusion, it would be a lot easier if I had a diagram of all your measurements and how you made them and if I had an easy way to send my calculations back to you as a diagram with measurements labeled.

When I say the intake needs to drop .177 straight down, that is as it would be assembled on the engine. My figured says that means milling .250 striaght into the mating surface between the haed and the intake.
 

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The only true way to do it is to have the mock right in front of you as you do it. It is a trial and error job. You can figure all you want but you won’t know tell all is said and done and it’s bolted to the heads and block. It best to cut a couple of times and get it right rather then trig it out and mill too much trying to get it done in one shot. . Then you’re screwed. We use to drag the mock up right to the machine. Mill it check it then mill it and check it.
 

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Discussion Starter · #15 ·
coolfalcon,
You are correct, a little at a time. I was only concerned because I have a very expensive intake at this time. If I calculate it to only need .125 removed and machine it to .125 a little at a time and in reality it really needs .300 I am in trouble and have just trashed an expensive intake that is worth nothing after trying to remove .300
 

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I was wondering the same thing. On some intakes the mounting flange would be pretty thin if .250 was taken off.

Which heads and which intake? Just curios.
 

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Discussion Starter · #19 ·
On 2006-06-08 09:31, chipmechanic wrote:
Why such the port mismatch in the first place if you don't mind my asking?
Ok, good question,
I am using the older A3 heads on a 9.2 cleveland block and the intake is a Edelbrock 351Y 2991 which is also for the 9.2 block but it is for the RAISED PORT C3 heads. The A3 is not a raised port head and this is where the mismatch comes from.
I purchased this from a Nascar engine builder. I went to his shop with one of my heads and bolted the intake to the head and it was a perfect match, however when the heads are bolted to the block the distance from the deck to the top of the intake port is about .250 difference between the two heads.
This intake has been ported by Roush and it is a super job well done. I hate to miscalculate the amount thats needs to be removed because I think I can use this intake and heads on a 9.5 windsor block and the problem will not exist beacuse there is a .300 difference between the two blocks. May need to run a thicker gasket though.
Just trying to make it work on the 9.2 cleveland. Hope this helps.
 

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Ahhh. That explains it.

Sounds like a cool combo.

Eric
 
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