Need to modify intake manifold to mate with decked heads + block

[VAEeng]

Hi guys, I have a bored .040" over 408 with the J head and air gap intake, ~10.25:1 compression. Just got the engine running about 2 weeks ago.

The engine runs absolutely perfectly, however I have been having smoke on deceleration out of the drivers side (right bank) cylinders. Engine compression is perfect in all bores. I replaced the valve seals, that didn't help. I have now deduced the problem to be the intake manifold not seated. As many of you know (and now I do too,) when you deck the block and heads, you need to either modify the head or the intake so they mate up.

My issue is, I don't know how much material to deck off the intake.

The engine block and heads are my dads and I don't have the information of how they were processed. I can tell you the block is decked to the point that the cylinder is about .001" off the deck. I am not sure how much that means the factory block has been decked. Also, I can tell you the "J" head is at 62cc, and at factory specs they were more like 68-72cc.

I'm hoping someone can tell me how much material has been decked?

Ie: (in order to have the cylinder on the deck, you need to remove "X") + (in order to have the J head at 62cc, you need to remove "Y"). X+Y = total amount decked.

Last but not least, I'm wondering if it's legal to just drill out the holes on the intake bigger so it can mate up with the heads. That would be easiest and cheapest, but I would prefer to do it right. I would prefer to not remove the heads if possible, I would like to race the car in a week and I think removing the heads and having them reworked would pretty much end the possibility of that happening.

Thanks in advance for any feedback!

 

[challenger6pak]

Even if you drill the bolt holes, you will still have the problem of trying to wedge the "too large" manifold between the heads. It simply won't work.

Another solution would be thick head gaskets.

 

[VAEeng]

Even if you drill the bolt holes, you will still have the problem of trying to wedge the "too large" manifold between the heads. It simply won't work.

Another solution would be thick head gaskets.

Thanks. Yeah didn't think of head gasket. That would pretty much be a last resort option.

 

[aussiemark]

Maybe send the engine to the machine shop with the manifold then they can mill the manifold in stages and trial fit it as they go. I think the formula calls for more to come off the ends then the sides of the manifold but you could use a bead of sealant and put it on without the end gaskets.

 

[cudabob496]

remove intake gasket, lay intake between heads, and measure with a feeler gauge what your clearances are around the intake on each head. Or in areas where you can't get a feeler gauge, put something like playdough or a crush gauge to see how much it compresses? Then will know how much metal to remove and where, if you need to at all. May just need a thicker gasket. I did, and I also had to make the bolt holes on the intake slightly larger.