Intake Manifold doesn't fit

[lnkncontiverto]

So I've installed a new set of heads that I had bought already freshened/ported. I go to bolt on my stock intake manifold yesterday and much to my chagrin, the f-in holes won't line up. I am running the Felpro 9441 HG's, BTW. Clearly the heads were shaved to true them up, which lowered them about 1/8". My question, since this is a relatively common thing to true up a set of heads, Is there anything I can do besides have my intake manifold machined down to fit?

Thanks!

 

[JayC]

The machine shop can cut the intake to fit. The heads have been more than "trued" if the intake wont fit tho.

 

[lnkncontiverto]

My thoughts were exactly "OMFG, are these really milled down ~1/8"??" Then I looked at a picture I had snapped before bolting them down. Looking at the circled feature, they don't seem to have lost that much meat.

 

[JayC]

The heads were probably decked. Its not that big a deal but it does raise the compression.

 

[Mike Licht]

Those heads are more than a "little decked" if you look at the relief above the exhaust valve on the unported head you can see that it is almost gone on the ported one. I would have them CC'ed if it were me. Also if you cut the manifold to fit it will only fit on those heads. Have the intake faces on the heads cut then you can use any intake on the heads and reuse the intake on different heads later.

Mike

 

[lnkncontiverto]

Those heads are more than a "little decked" if you look at the relief above the exhaust valve on the unported head you can see that it is almost gone on the ported one. I would have them CC'ed if it were me. Also if you cut the manifold to fit it will only fit on those heads. Have the intake faces on the heads cut then you can use any intake on the heads and reuse the intake on different heads later.

Mike

That is a good idea on cutting the intake faces. By CC you mean flow checked? With the compression raised, what issues would that cause? I understand that forced-air engines work well with low compression, but when compression goes up, I assume that lowers the point at which the engine would begin to knock?

Please pardon my ignorance by the way.

 

[Mike Licht]

no check the size of the combustion chanmber so you can get an idea of where the compression will end up. It is done with a graduated cylinder and filling the chamber with fluid usually alky
Mike

 

[earlbrown]

The Felpro gasket is thicker than the metal GM gasket so that will push the manifold higher up.

I went through this exact same thing on my engine build a few months ago...

A day in the life of Earl.... - TurboBuicks.com
Shortly after I drew this picture to help others decide how much needs to be milled.

 

[Nasty Wendy]

Did you use a high-tech CAD program to draw that up Earl? You kill me with crap like that. True as can be but looks like a third grade caveman drew it. LOL.

 

[SNOWBIRD]

I fixed a similiar problam by purchasing a set of thinner intake gaskets from TA PERFORMANCE.

 

[Scott Atk]

I dealt with this in the past. I had my intake machined too much and ended up breaking the corner off when I torqued it down. The 9441PT gaskets are .060" thick, Cometics can be made in any thickness you want, if it was me I'd get a set of Cometics around .080"

 

[lnkncontiverto]

The Felpro gasket is thicker than the metal GM gasket so that will push the manifold higher up.

I went through this exact same thing on my engine build a few months ago...

A day in the life of Earl.... - TurboBuicks.com
Shortly after I drew this picture to help others decide how much needs to be milled.

Earl, thanks, I'm still cleaning up drool from those build pics.

Scott, do you know about how much was shaved off for the flange to break like that?

 

[Scott Atk]

No, but you're not there yet. The recess that you have circled was gone on my heads.

 

[lnkncontiverto]

A little update for those curious, I found a decent/cheap lower manifold and took it into a machine shop down the street. They milled .060" off both surfaces and now it fits like it should. There is plenty of meat left on that flange that I'm not afraid of cracking once it gets torqued down.

Problem = pretty much solved. Thanks to all for their input.

 

[earlbrown]

didn't mean to bump this... My mouse just happened to accidentally do some sort of speed reply in one click

 

[turbodave231]

The angle between the intake face and deck surface on the Buick V6 is 90 degrees. So you don't need Earl's formula to figure out how much to cut off the intake face. If .125 was taken off the head deck surface (WOW that is a ton!) then, .125 off the intake surface of the head should correct the problem.

 

[earlbrown]

It says A=B on my technical drawing!

 

[278cikiller]

A little update for those curious, I found a decent/cheap lower manifold and took it into a machine shop down the street. They milled .060" off both surfaces and now it fits like it should. There is plenty of meat left on that flange that I'm not afraid of cracking once it gets torqued down.

Problem = pretty much solved. Thanks to all for their input.

I have a stage II 153 block with GN-1 heads and a stock manifold with .060 thousand off the sides and .084 off the bottom to make it fit, it fits great but i used only 30 pounds to torqued it down and crack two corners on it, just watch if you think you have a lot meat there it don't take much to crack them, then you won't find out untill you fill the water up in the rad trust me, now i tighten them bi hand.

 

[Jay J]

Does anyone know of a shop that can repair broken lower intakes? With the core prices going higher, seems like there is a need for this service.