Intake leaks

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Aug 24, 2002 | 11:24 PM

mchild

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Intake leaks

I have an `85 460 that has had a rough idle. I checked the intake manifold for leaks by spraying carb cleaner along the top edge of the manifold where it meets the head. Each time I sprayed the engine vacuum went from 17 to 20 inches for a moment, the rpm’s would increase, and the motor would also smooth out.

So I tighten the intake manifold bolts (finding all a little loose) and the motor ran smoother and the vacuum went up to 18 inches. But, since the vacuum went to 20 inches when I sprayed the carb cleaner before I tightened the bolts, I tried it again afterwards. Once again it went up to 20 inches which I am assuming means I still have a leak but, apparently, not quite as bad.

Is there anything else I can do other then pulling the intake and replacing the gaskets? If not then is there a better gasket to use? What about using an RTV sealant around each intake port?

Thanks,

Mark

Aug 25, 2002 | 12:24 AM

LxMan1

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From: Louisville,Ky.

Intake leaks

Unfortunatly, there is no way to seal it other than removing the intake. Use a good Felpro Valley Pan type gasket. It is the one piece gasket that goes under the whole intake.
Only use RTV sealer on the water ports, not the intake ports. Using a little RTV around the outer water ports will help keep them sealed and will also help keep the gasket in place. Be sure to properly torque the maifold correctly so that it doesn't get warped.

Another tip, if you have an aluminum intake, Use a 3/8" bead of RTV on the ends instead of using the supplied gaskets. This is what Edelbrock recommends for their's anyway.

And be sure to drain the radiator before you remove the intake or you will get alot of antifreeze in your oil, and be sure to remove all of the old gasket material from the heads and intake.

Sep 18, 2002 | 08:34 PM

Willie

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From: Oklahoma

Intake leaks

Even though a new gasket will seal in most cases. It is always advisable to check the straightness and flatness of the intake gasket surfaces. It is also a very good idea to have the intake manifold vated to clean out all of the carbon and slug. It should go without saying but be sure to pay attention to the torque sequence.

Sep 19, 2002 | 08:48 AM

laptopgeek

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From: texarkana, tx

Intake leaks

Mchild - don't forget to remove the acorn nuts, too!! The squirrels love to get up ontop of my manifold when the engine is warm and sit there and eat nuts!! Make sure you blow all that garbage away so it doesn't fall down into the ports. I don't think acorn shells are combustible...

Sep 29, 2002 | 07:04 PM

78bigunns

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From: Culpeper, Virginia

Intake leaks

[updated:LAST EDITED ON 29-Sep-02 AT 08:05 PM (EST)]I was working on my intake today, first time ever taking one off. I noticed you said something about using RTV around the water ports LX. I didn't put any RTv at all on mine today, except where the end seals meet the main gaskets on the heads. Is this going to be a major problem? Should I have put a light coating of RTV blue around the ports? I have the intake back on and torqued up. But I haven't gotten the rest all back together yet, didn't have the right carb mount gasket at the store, I have the carb off now. Any thoughts? Thanks Blair

Sep 29, 2002 | 10:27 PM

LxMan1

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From: Louisville,Ky.

Intake leaks

[updated:LAST EDITED ON 29-Sep-02 AT 11:28 PM (EST)] If you used a quality gasket, you may be ok. It may leak later on down the road, but there are no guarantees whether it will or not. Did you use the big valley pan gasket? If so, it should be ok.
Jimmy

Sep 30, 2002 | 07:10 PM

78bigunns

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From: Culpeper, Virginia

Intake leaks

[updated:LAST EDITED ON 30-Sep-02 AT 08:12 PM (EST)]Jimmy, I just got a "regular" Felpro intake reseal set, two end seals, two side gaskets. I tacked the side gaskets in just too hold them, not really for sealant measures. The end seals, I coated on the underside, and once in place, I put it at the joint where it was specified. The old gasket had remnants of blue silicone on it I believe. You think it will leak on the sides? I torqued it up, but would rather hassel with it now, than later after carb is back on, and the coolant is refilled. I now have a engine lift at my disposal, wish I had it the first time. Thanks, Blair