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Kirkham Motorsports

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  #1 (permalink)  
Old 11-28-2012, 01:06 PM
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Default Intake Gasket Leak?



Last week I noticed a small pool of oil around the front most bolt above cylinder No. 1 on the intake manifold and another small pool of coolant in the valley of the water pump as noted in the photo, the photo was taken after I cleaned the affected areas. I'm looking for an analysis and most likely a confirmation that I have a leaking intake manifold gasket. I've long suspected there may be a leak as the No. 1 cylinder spark plug has a slightly lighter color than the other plugs but, I have been unable to confirm this using the carb cleaner, propane or WD 40 methods.

I retorqued the intake manifold bolts, but the leaks reappeared after about 200 miles. There are no leaks while the engine is running, they appear overnight. No coolant in the oil and no smoke/steam from the exhaust. The engine runs strong and has acceptable idle for the installed cam.

The intake manifold is a RPM Airgap and heads are Brodix 5.0 STR.

Brodix recommends Felpro 1250 gaskets; are ther better ones available?
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Old 11-28-2012, 01:38 PM
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Make sure it isn't leaking from the thermostat housing, especially if you have a chrome one with o-rings instead of a flat paper gasket. I replaced the o-ring type housing with a factory type with paper gasket and cured my leak. Good luck.
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Old 12-05-2012, 03:31 AM
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Go lookup the port size of the #1250 felpros and replace them with the correct size edelbrock gaskets - Brodix probably wont recommend this as Vic and chisty make heads as well .....!

On antique fords, if I can use an edelbrock intake gasket - I do!
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Old 12-28-2012, 02:09 PM
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Results of my intake manifold gasket leak investigation:


This is the water passage and intake port above cylinder No. 5. There was no leak here, I wanted to show it because I couldn't believe what I had found.


This is the water passage and intake port above cylinder No. 1. Definitely a leak here!

.
This is the corresponding water passage and intake runner on the manifold above cylinder No. 1.

I'm curious as to the cause of this. Is it really the fault of the FelPro 1250 gasket or is it poor preparation and installation technique?
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Old 12-28-2012, 05:44 PM
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Can't see your pics, can you post them some other way?
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Old 12-28-2012, 06:10 PM
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Here ya go.

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Old 12-29-2012, 02:10 AM
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What fills the gap between the base of the inlet manifold and the top of the block, valley area?

Reason being a gasket here may not allow the manifold to seat well against the heads. A bead of silicon works best.

Does the inlet manifold EXACTLY match the cylinder head angles?

The sealant type and application technique is poor quality.
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Old 12-29-2012, 04:04 AM
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Looks like overtightening and squishing the gasket out. The silastic helps in doing this.
JD
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Old 12-29-2012, 09:38 AM
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Looks like over tightening and bad prepping to me as well.
Replace with fel pro 1250S.
The S stands for sandwiched steel core.
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Old 12-29-2012, 01:47 PM
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Thanks for the replies. I already concluded the manifold and cylinder head preparation was less than ideal. I suspect the surfaces had some oil residue remaining prior to the application of an excessive amount of silicone as evidenced in the photos.

After removal of the old gasket material and a thorough cleaning of all surfaces I replaced the gaskets with FelPro 1250 S3 and used "The Right Stuff" on the China Walls and a very thin application of RTV around the water passages on the manifold and cylinder heads.
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