# problem aligning the intake manifold with the heads



## 1625Goat (Feb 25, 2011)

I replaced the 6x heads on my 73 455 with 4x heads. Now I find the intake mounting holes won't line up with the 4x heads. Some are aligned but other are not!! When I look at the hole I can see only half of the hole?? The 73 455 should have come with 4x heads and I believe the intake is the same. I could really use some help!!


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## Mr. P-Body (Jan 20, 2011)

Is the hole "high" or "low"? If the hole in the intake is too high to line up with the holes in the heads, the heads and/or block have been "milled" a significant amount. Milling the intake's flanges is the "fix". 

If the holes in the manifold are "too low", the intake has been milled significantly.

There is no difference between 4X and 6X as far as the flange pattern and "positioning" are concerned. It has "been done" to "slot" the holes to allow the bolts to go. Not optimum, but not uncommon.

Hope this is helpful.

Jim


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## ALKYGTO (Mar 29, 2010)

:agree Better check cc. of chambers on these heads, you could be in for a major compression ratio change.


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## 1625Goat (Feb 25, 2011)

Jim, actually all the holes are at the same level but a couple of the holes are off a bit front to back. I don't believe the intake was milled as it is stock with stock 6x heads. 
You confirmed what I thought about the positioning of 4x vs 6x heads; I thought they would be the same. As I thought the stock intake would also be the same. Jim I appreiciate you response.

Byron


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## 1625Goat (Feb 25, 2011)

ALKYGTO said:


> :agree Better check cc. of chambers on these heads, you could be in for a major compression ratio change.


Why do you think their might be a compression change? The 73 motor came with the 4x heads but someone had switched them to 6x and put the 4x heads in the trunk.


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## BearGFR (Aug 25, 2008)

1625Goat said:


> Why do you think their might be a compression change? The 73 motor came with the 4x heads but someone had switched them to 6x and put the 4x heads in the trunk.


If the heads have been milled, then the chambers will be smaller --- that will make the compression ratio higher. 

I read your other post that said the alignment problem isn't "top to bottom", but is "front to rear" --- is that right? Have you installed and tightened the bolt from the top of the timing/cover to the front of the manifold yet? If so, loosen that, then start the bolts from manifold to the heads - barely snug them but don't tighten, then tighten up that front bolt, then torque the manifold bolts.

Bear


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## 1625Goat (Feb 25, 2011)

BearGFR said:


> If the heads have been milled, then the chambers will be smaller --- that will make the compression ratio higher.
> 
> I read your other post that said the alignment problem isn't "top to bottom", but is "front to rear" --- is that right? Have you installed and tightened the bolt from the top of the timing/cover to the front of the manifold yet? If so, loosen that, then start the bolts from manifold to the heads - barely snug them but don't tighten, then tighten up that front bolt, then torque the manifold bolts.
> 
> Bear


Oh thanks for the explaining Bear. I don't believe I did yet but I did torque down the head bolts, do you think that could have caused the change? I tried to put in the bolts in loosely and some would align but others wouldn't. It really has me stumped; I've never faced this before.


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## BearGFR (Aug 25, 2008)

1625Goat said:


> Oh thanks for the explaining Bear. I don't believe I did yet but I did torque down the head bolts, do you think that could have caused the change? I tried to put in the bolts in loosely and some would align but others wouldn't. It really has me stumped; I've never faced this before.


Oops - I hope I didn't mislead you -- yes, the head bolts, the ones that hold the heads onto the block, should be torqued already. I meant the bolts that secure the manifold to the heads. If you've got the small bolt that pulls the water crossover at the front of the manifold up to the back of the front cover loose, and still can't wiggle the manifold around enough to start all the intake bolts with your fingers, then something's wrong. I'm stumped about what would cause them to be out of alignment front to back though...:confused

Bear


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## 1625Goat (Feb 25, 2011)

BearGFR said:


> Oops - I hope I didn't mislead you -- yes, the head bolts, the ones that hold the heads onto the block, should be torqued already. I meant the bolts that secure the manifold to the heads. If you've got the small bolt that pulls the water crossover at the front of the manifold up to the back of the front cover loose, and still can't wiggle the manifold around enough to start all the intake bolts with your fingers, then something's wrong. I'm stumped about what would cause them to be out of alignment front to back though...:confused
> 
> Bear


That's what I thought you meant, you didn't mislead me. I've done this job before on a few cars but never swapped out different heads. I'm going to play around with it again tomorrow and post my outcome. It's really kicking my butt though! Thanks for the response Bear. I've seen your responses to other posts and can see you are very knowledgeable.


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## 1625Goat (Feb 25, 2011)

BearGFR said:


> If the heads have been milled, then the chambers will be smaller --- that will make the compression ratio higher.
> 
> I read your other post that said the alignment problem isn't "top to bottom", but is "front to rear" --- is that right? Have you installed and tightened the bolt from the top of the timing/cover to the front of the manifold yet? If so, loosen that, then start the bolts from manifold to the heads - barely snug them but don't tighten, then tighten up that front bolt, then torque the manifold bolts.
> 
> Bear


I checked the intake again this afternoon and the holes are off top to bottom; you guys were right on with your assessment. So I guess that means the heads were probably decked. Is their anything I can do to get them to align properly??


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