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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: OldGray on July 14, 2016, 04:19:17 pm

Title: 305 Intake manifold bolt question - open to oil?
Post by: OldGray on July 14, 2016, 04:19:17 pm

I have read where the middle bolt holes on a 350 intake manifold go all the way through the head.  Does anyone know if they do on a 305?

I had a small oil leak near one once and a dab of RTV on the end of the bolt fixed it, so I am guessing the middle ones go all the way through.

Anybody know?  I am hoping to use it (with a hollow bolt) for a bypass oil filter return.  Here is where I got the info:

http://www.wonders-in-wood.us/images/frantz/86install/frantzinstall.htm

Title: Re: 305 Intake manifold bolt question - open to oil?
Post by: bd on July 14, 2016, 05:09:08 pm

The intake manifold center bolt holes penetrate through the cylinder head flange into the lifter valley.

Title: Re: 305 Intake manifold bolt question - open to oil?
Post by: OldGray on July 14, 2016, 05:56:25 pm

Ok - so I should be good with running a low-pressure oil return there?

Title: Re: 305 Intake manifold bolt question - open to oil?
Post by: bd on July 14, 2016, 07:23:52 pm

Not if that means sacrificing clamping force on the manifold flange.  In addition, the exhaust crossover port is between those two bolts.  There is risk of gradually coking oil in the fitting.

Title: Re: 305 Intake manifold bolt question - open to oil?
Post by: OldGray on July 14, 2016, 07:49:12 pm

There is a hollow bolt made for this specific application (http://www.frantzoil.com/catalog/item/4746217/8845157.htm).  It gets torqued down and the oil return fitting threads into it. 

Thanks!

(http://www.frantzoil.com/i/tn_HollowBolt_2.jpg)