mvrotc

iTrader: (4)

Alright so i just built a LM7 for my fbody , Stock bottom end , 224r cam , ported polished 5.3l heads with 2.02/1.57 valves milled .030 to 58cc .

Car runs good but i cannot get the intake manifold to seal to save my life.

I have tried both my FAST 78 , and my stock ls1 intake, BOTH leak bad enough to throw off the idle and sometimes even stall , if i spray the base of either intake with starter fluid the idle goes berserk, and when i remove the intake there is oil underneath the gaskets so its not sealing for sure. I feel like i have tried everything, i have counter sunk the valley cover bolts for flush finish , i tried brand new felpro gaskets, i torqued the bolts to spec and in sequence i just cannot get the damn manifold to seal, i really just wanna enjoy my swap so any help is appreciated

pearsonmx6

When you deck the heads you have to notch the corners of the intake. The heads now sit lower and the intake is isn't .

Burken01

iTrader: (88)

Im not sure but your heads have been milled to 58cc? did they mill the side were the intake sits?

I've never had to do it, but when you mill your heads that much Ive heard of people milling the side where the intake sits because that area gets narrow as you take alot of material off the heads...

mvrotc

iTrader: (4)

pearsonmx6 can you explain what you mean by corners of intake ? a pic would really help

Burken01

iTrader: (88)

heres some threads on this

https://ls1tech.com/forums/generatio...-side-too.html

https://ls1tech.com/forums/generatio...nger-fits.html

mvrotc

iTrader: (4)

i dont think heads are milled that much to where its not fitting properly, after i torque bolts down the ittake appears to sit perfectly flush , just wont seal

Burken01

iTrader: (88)

well if its sitting flush with new intake gaskets and still not sealing then its probably not alligning square over the hole, post some pics?

Burken01

iTrader: (88)

milling to get 58cc is alot for stock GM casting heads...

SMKE EM

iTrader: (2)

I suspect the deck isn't perfectly straight or was milled improperly. The only times I have had intakes not seal correctly with multiple intakes was an uneven surface or warped heads.

PAGregSS

iTrader: (10)

I'm going to ask this not to be a d*ck, but to cover the bases. You did install the o-ring seals around each port on the intake, right?

Another thing to consider is if the heads are sitting much lower due to milling (which I would think would be a lot of milling to have this happen), are the intake bolts too long or are you running out of thread on the bolts and they aren't torqueing down the entire way?

mvrotc

iTrader: (4)

58cc isnt alot when they start at 61.5cc , and does anyone know of a way to make the gaskets thicker? or a set to buy that is thicker?

CouJoe56

iTrader: (4)

you can buy cometic MLS gaskets to your desired thickness, but its going to defeat the whole purpose of decking the heads

CouJoe56

iTrader: (4)

you didnt have a pushrod length problem?

dirtbag

iTrader: (2)

It seems your problem may be one of the following:
1. Your heads are not milled correctly.
A. Intake side is not milled and throwing off the alignment of gaskets on intake chambers on heads.
B. heads are not milled evenly as mentioned above.
2. Gaskets not installed properly. Or gaskets do not protude enough to make a good seal.
3. Intake bolts are not torqued properly.
4. Intake does not clear coolant tubes underneath manifold.
5. Intake is not notched and does not clear heads on corners as mentioned above.
6. Intake is cracked.

Try sorting through the above suggestions, then report back with your findings. Good luck.

mvrotc

iTrader: (4)

ok so the gaskets are alligned with the ports just fine, can someone explain what they mean by notching the intake manifold , or perhaps a few pics?

dailydriver

I believe (correct me if I'm wrong) that he was asking for a way to get thicker individual intake manifold gaskets, NOT head gaskets.