My heads were milled several times by the time they found their place on my motor... 4-5 I believe. They are Lloyd Elliot heads so I believe he goes .010" each time over the mill. I never did have any problems lining up the bolt holes on the intake and everything seemed to go together fine but Ive been reading sources saying I need to mill the dame intake now or it may suck oil from the inside. The heads have been on for close to a year now and I may just be getting used to the power but it seems a tad slower than it was when I first intalled the heads last December.

Am I in trouble here or am I just paranoid my LT1 isnt running its best? The only thing is Im down 1/2 quart of oil in 3k miles or so and it has never burned a drop... but then again I also switched to 0w40 M1 at the same time.

 

I suppose any time you mill the heads you need to mill the intake.

Lloyd milled my heads .020" and i couldnt get my bolts for the intake to line up. I ended up just drilling the holes out bigger.

There is a formula for how much you need to mill off the intake depending on how much was taken off the heads/block. I dont know it off the top of my head, but I can look it up for you if you want.

 

Thats really weird b/c I know for a fact my heads were milled several times well over .020" and the bolts went in just fine. I cant believe Lloyd didnt suggest that I mill the intake with the number of passes those heads took.

Story goes 1 of the heads was ported by him and the guy dropped a bolt down the cylinder so that head was .010 miled already plus it had to be fixed and milled some more.. maybe .020"? Then he got his heads back and didnt torque them down properly so they had to be milled AGAIN which is when I got them. So there has to be at the very least .040" taken off them.

I guess I should say I am running stock short block with stock gaskets.

 

I'd like to know too as my heads were milled .010 and i had my block decked i think another .01, but my intake is untouched.

 

Get a set of paper gasket's.Glue them on with 3M trim cement. Grease the intake and very carefully install and torque. Remove and check the port alignment.Bolts don't matter ya can fix the holes to line up.
Before I glue the gasket on I would set the intake on and put a 3/8"(about .060) flat washer under all 4 corners. With a feeler guage check the top and bottom of the surface where the gasket goes. If over .020 then I would have it corrected.

 

my heads are milled .010 and my block has been decked. my intake bolts were a toughy to get lined up. one of the intake bolts actually striped itself too. never did fix that...

 

Here is something that might help you guys.

"Whenever you remove material from the combustin deck surface of the heads, you obviously shorten the head, which can affect the sealing surface angles between the intak manifold and the cylinder head. If the resurfacing process removes up to a max. of about .019" you will likely be ok. If you remove .020" or more from the combustion decks, corrective material removal from the intake port deck and intake-to-block rails will be nesessary. Here's a handy reference to use if you need to match the intake angles.

Consider the amount removed from the combustion deck and multiply this by a factor of 1.2 in order to obtain the amount that must be removed from either the intake manifold mating surface of the head orfrom the intake port deck of the intake manifold. So, if .010" is removed from the combustion deck, you need to remove .012" from either the intake side of the head, or from the intake port deck of the manifold.

You also need to remove material from the front and rear rail surfaces of the intak manifold, where they contact the block (since now the intake will sit to high to allow proper sealing at the port decks). Based on the amount of material you removed from the cylinder head combustion decks, multiply this by a factor of 1.7 to abtain the amount of removal needed at the intake manifolds front and rear rails. If you milled .010" from the heads combustion decks, you would need to remove .017" from the intake manifolds front and rear surfaces.

Combustion deck removal amount X 1.2 = Material to remove from intake port side.

Combustion deck removal amoutn X 1.7 = material to remove from intake manifold front and rear rails."

Wow, that was a lot of typing but should solve your problems though. I took this info from a book.

"How to Rebuild Small-Block Chevy LT-1/LT-4 Engines" by Mike Mavrigian

 

I personally have Intake milled, when i get heads milled.

But im a perfectionist on some things, might not be neccasary.

 

You want to explain to me how the angles relating to the intake manifold head mounting surface change if you flat mill the deck of the heads OR mill the block?

I've personally had blocks milled .040" and heads milled .020" in the same combination and if there is area along the china rail for some silicone then I'm happy as a clam...... how knows if I'm a perfectionist or not? I just spent today lapping valve guides in to get my valve to guide clearance perfect on a set of heads. A couple of .0001 here and there can cause issues, but it's rare to find the china rail surface to tight but YOU DO have to slot the bolt holes. Sometimes you do find the mounting flanges on the heads and intake too tight but that's really rare..... they only change angles IF you angle mill something, but then you should correct the heads for this not the intake.

Bret

 

I dont know if that was directed at me or not, but my post didnt mention anything about angles.

Im not an expert at all and never claimed to me. My post above is a quote from a book, but it makes sense that if your bolt holes arent lined up anymore, then neither are your ports.

 

I know you quoted Mike there.... I'm just encouraging you to think a little harder about what people wright and question them.

Your ports can be lined up... but it's best to check everything on the block.

Bret

 

Bret,

I am aware the angles do not change if you flat mill a head. But what does change however, and I cant believe you could overlook this, is gap between the heads and the intake. When you flat mill a head it will pull alway from the intake creating a possible leak and of course the ports may become slightly misaligned.

Next when you bolt the intake down there is more force applied to the top of the intake flange because of the bolt hole orientation on the intake. This is where I can see potential problem arising because the intake flange gets warped or pulled closer to the head at the roof than at the floor... that could cause a small leak sucking oil from inside the lifter valley.

I respect your opinion and value your expertise on this board but I believe you have overlooked something here.

 

My block was decked to zero and my heads milled just enough to clean them up. My intake bolt holes on the drivers side lined up okay except for the 2 back ones. The 2nd furthest back went in hard, but went in till tight, the last last one went in but, only halfway before I gave up. Everything seems sealed up just fine and the car runs like a raped ape.

These heads are going out to be ported in the next 6 months, they can fix the holes then.

 

Think about what you said.....

Now how is milling material OFF of the intake face of the intake going to HELP that? You are now INCREASING the gap between the intake and the head... when the intake was getting CLOSER to the head before.

I'll get back to this post tomorrow.

Bret

 

The intake sits higher on the heads. Milling a little bit off the intake will lower it down and make it sit properly aligning the ports and the bolt holes. And since the intake will be sitting lower, you have to take some material off of the front and rear rails too.