Vacuum leak around intake bolt holes

[Dieselman966]

I got my 352 up and running now.  And after cam break in I set the timing and was checking for vacuum leaks.  I have 12" at idle and 21" at 2400 rpm.  When I spray brake clean around the intake bolt holes the idle drops off.   Where is it pulling vacuum from by the bolt holes?  Is it just leaking around the holes and running up the pcv?

[67428GT500]

The bolts don't pass through the ports.  It has to be leaking at the intake gaskets.

[Joe-JDC]

Are you referring to the carb bolt holes, or the bolts that hold the intake to the heads?  Two different problems.  Joe-JDC

[Dieselman966]

Are you referring to the carb bolt holes, or the bolts that hold the intake to the heads?  Two different problems.  Joe-JDC

The bolts that hold the intake to the head. I have no leaks around the carb base.

[C8OZ]

You can just block off the PCV temporarily and see if it responds differently to rule out that it's getting a whiff through the crankcase.

[Dieselman966]

You can just block off the PCV temporarily and see if it responds differently to rule out that it's getting a whiff through the crankcase.

I tried that this morning. I had the same result. I'm susprized it's not using any oil if the intake gasket is leaking.

[Dieselman966]

Are you guys putting any sealant around the intake ports. I did around the coolant passage but not the intake ports.  I usually just do it around the coolant passages.

[jayb]

I've gotten to the point where I always put sealer around the intake ports.  Have had small leaks too often there.  Use a good sealer, like Ford TA-31, or the Right Stuff (if you never want to take it apart again LOL!).

[Posi67]

I've gotten to the point where I always put sealer around the intake ports.  Have had small leaks too often there.  Use a good sealer, like Ford TA-31, or the Right Stuff (if you never want to take it apart again LOL!).

The 428 in my car is sucking oil from somewhere and I do use the "Right Stuff" on the intake ports after a previous bad experience. Gaskets are doubled up which didn't cause a problem the last time I used this setup. Oddly, the car runs quicker with no other changes. It comes apart easily if you use the proper persuasion. I suppose the OP's intake could possibly have a vacuum leak at one of the bolt locations but would think other issues would be more obvious first. 

[blykins]

Are you guys putting any sealant around the intake ports. I did around the coolant passage but not the intake ports.  I usually just do it around the coolant passages.

Always.  I do it on every engine, even non-FE's. 

[Stangman]

X3

[Falcon67]

I'm fixing to start doping up every port after fighting leaks on the 302 with the tunnel ram and even the go-to air gap.  I tried Right Stuff at one time, was not real pleased with the results. 

[Dieselman966]

Sounds like I have a plan then. Remove intake and apply sealant this time. Well see how this works out.  How much vacuum do you guys think this is costing me?  I took it for a drive yesterday and it wouldn't shift on it from 1st to 2nd until higher rpm. I'm thinking that I dont have enough vacuum for the modulator now. 

[Dieselman966]

Well I'm back to the drawing board now. New intake gaskets with sealant around all ports and it still pulling vacuum around the intake bolt holes.  Is there a better gasket on the market than the fel pro blue ones?  I dry fit the intake before I put the gaskets and sealant on. The intake looks to be seating nice before hand.

[GerryP]

Stock intake and heads?  Let us know if otherwise.  Are you using the cork or rubber end seals?  When you dry fit the intake, did you use the end gaskets?  When you dry fit the intake, did you use the dry intake gaskets?  How did you verify the intake to head fit?  By sight or feeler gauges?  What did the intake imprint look like on the old gaskets?  Any apparent alignment concerns, like could you see where the intake was impressing on the gasket and did it look uniform?

A longer shot, but did you carefully inspect the intake for cracks or voids?