Ok so i recently built a Iron 408 stroker as my first build. So when i took it in to get it tuned my tuner said that my intake manifold wasnt sitting flush on the heads and that i needed to fix that ASAP. So along with other little things that i had to add or redo i though i would try to address the intake issue today.

I pulled my intake today to replace my old LS1 valley cover with a new LS6 valley cover. After i swapped out the valley cover i decided to see if my stock LS1 coolant crossover was causing my intake to not sit flush. So i put the intake on without the coolant crossover to see if it truely was my coolant crossover that was not allowing my intake to sit flush on the heads. To my surprise it didnt sit flush. It sat just like how it did with the coolant crossover on. So i pulled the intake off again and set it upside down on a old rug and put my old LS1 valley cover on it also upside down. To my surprise the bolts lined up with the fin gaps on the bottom for the bolts on my LS3 intake and it sat just like it was supposed to.

So now im all like WTF why isnt it sitting flush on the motor when everything looks perfect off the motor. As i stood there and thought about it i noticed that the intake was wider than the valley cover area on the motor is. So my question is, Is my LS3 intake actually wider than where it sits on the motor?

My 408 is a iron 6.0L block that i think is a gen 3 cause it looks just like a slightly bigger LS1 block. Im running LSA heads and a LS3 intake for a top end. So does this mean that i have to swap my heads back to cathedral port so everything fits like its supposed to?

I really need your guy's advice on this because i dont know where else to turn to and i was told u can run LSA heads and a LS3 intake on this block.

If u guys need more info just ask and ill answer it to the best of my abilities. I tried to research this issue and came up with nothing. Sorry for the long post.

 

You don't have to swap heads, you just need to shave (mill) the manifold to get things to line up. Whether you shave (mill) the bottom or the sides depends on what it takes to get to line up.

 

Were the heads angle milled or the block decked? Either of these can cause intake fitment problems which require extra effort for intake fitment. If a head is ever angle milled, extra precautions have to be taken into consideration that require the intake runner side to be milled to the proper angle again, and in extreme cases, pushrod geometry will need correction as well.

If the heads were not angle milled then that does not become a problem at all. Sometimes you need simple milling to get things to sit properly.

 

Ok so im pretty sure that the heads arent milled because they were cores straight from gm and as far as the block i dont know what machining has been done to it because i bought the short block from Thompsan Motorsports a sponsor on here. Now could i mill off all the fins on the bottom of the intake? And whats the best way to mill the sides of the intake because thats where my problem lies. Thanks for the good news guys because i really didn't want to have to do a head swap.

 

Unless ordered otherwise the only thing TMS should have done was zero decking, but even that is an up charge and not done unless needed.

If the heads aren't milled then I don't know your answer.

 

Pictures???

 

Ill post some pics up today when it gets light. Could the valley cover bolts be the issue? But as far as i know the heads arent milled?

 

Depending on what you are using, the bolts could be hitting. Can you post some pics? It should be a lot easier to get help if you could post some.

 

Im using the stock bolts that came on my new LS6 valley cover. I have pics but i can't figure out how to post em from my phone. So today i ground the honey comb fins on the bottom of my ls3 intake down significantly but i still left a little bit on. That almost did the trick but i feel it could still fit a little better. So i remember reading on here a while back that u had to use special valley cover bolts when u put a FAST intake on so i was wondering if anyone new what ones i should get. I want the lowest possible profile that will work. Also does anyone know why GM put the funny honey comb fins on the LS3 intake? I don't know why/what they are for so i didn't take them all the way off but i greatly reduced there height.

So as i speak now the intake is almost perfectly flush but i would like it to get a little better fitment. Next question, should i run a rubber hose under or over the intake to tie my rear coolant crossover to the front? Again thanks for your guys advice and sorry for the lack of pics i can however text em to someone if they can post em.

 

http://compare.ebay.com/like/170988496712?var=lv&ltyp=AllFixedPriceItemTypes&var=sbar Low Profile Bolts

I would run the coolant hose over the manifold. If you go to the website of Kurt Urban Performance, he sells a coolant hose setup - it is pricey but might serve as model for something you could build cheaper.

 

Thanks for the info hopefully this will be the end of my fitment problems ill keep u guys posted as i go.

 

Local hardware store will have stainless button allen heads that you need for the valley.. Shouldn't be more than 4-5$.

 

Ok so i was searching for those fast bolts and came across a thread over on a corvette forum and they were saying u could grind the heads down a 1/8" on the stock bolts and it would be the same height. Any one think thats a bad idea?

 

What size would i need?

 

Bringing this yr old thread back up because I'm having the same problem.
But it appears to me, the ls6 supplied valley cover bolts fit up inside the honeycomb shapes on the bottom of the LS3 intake.
Was yours a FAST intake or stock GM?
What was the final outcome?
Did you happen to measure the gap you had between heads & intake?

my setup is LQ4, L92 heads only milled .005" that I know of, LS9 hg, new takeoff LS3 intake.

Thanks