Inlet Manifold Leak

[zrayr]

Are you putting the gasket on dry in the area of the leak ? If so, try some of the permetex thermostat & water pump gasket sealer. It is superior to every other type of RTV. Your idea of a waterless coolant is just a bandaid, and has little chance of success anyway. Your better off with another strategy.

Z.

[Gaz64]

Originally Posted by undy

You need to check the gaps between the intake and the head. You might have a misalignment/uneven gap. No gasket will seal well with that. Place the manifold down without a gasket under it and run a feeler gauge around on both ends and on the china wall. they should be symmetrical. You might have an intake that's been cut wrong.

Originally Posted by zrayr

Are you putting the gasket on dry in the area of the leak ? If so, try some of the permetex thermostat & water pump gasket sealer. It is superior to every other type of RTV. Your idea of a waterless coolant is just a bandaid, and has little chance of success anyway. Your better off with another strategy.

Z.

I agree with both of the boys above.

A gasket never fails on it's own.

It's a uneven clamping issue, intake not machined at same angle as the heads, or the two intake faces aren't parallel end to end.

As stated above, fit the intake to bare heads and the abnormality will show up from a feeler gauge test.

[RICK LAKE]

Fatboy Couple of ideas I have and you need to check first,
1 Was the heads or block milled? Are all these parts new when the motor was built?
2 Need to pull drain the motor and pull the intake bolts out and check the angles of both heads and intake manifold sealing surfaces. Check in here for another thread about limit for sticking a feeler gauge between the 2.
3 4 th set of gaskets, Did you try HigH-tAC SEALER? Spray on a couple of coats and let dry. Spray on a lite coat and install on the heads. Center the holes on the heads. All surfaces must be cleaned. get another person to help center manifold on motor. install studs in the heads on all 4 corners around coolant passages. Rest of holes can be bolts with washers. Go in 5 pound incromints of torqueing down manifold. I think the spec is 35-38 ft pounds. Allow this to cure for 24 hours. Start motor and run for couple of minutes and let cool. Do this a couple of times (3) . Retorque manifold bolts and nuts. Go road test and recheck. If you still have a leak the manifold is porous. need to pressure test and seal or weld area to seal. If this problem happens, you might want to sent the manifold here to Joe Craine and let him works his magic for repairs and porting. Does great work. Good price and the part looks like jewelry.
You already use RTV gasket. Stay with th silver color stuff and give it 24 hours to cure.
What is the material of the heads and block? Aluminum and iron? Aluminum and Aluminum? Iron heads and aluminum block? Here's the thing there are different expandsion ratios of these metals heating up. This may also cause the creeping of the gaskets. Retorque will only work 2-3 times. Rick L.

[FatBoy]

Hi all,

Thank you everyone for the detailed advice.

In response to some of the questions:

The block is an original iron 427 S/O ('67 I think). The heads and intake are aluminium Edelbrock items. The engine was built by Bill Parham at Southern Automotive, who also CNC ported the heads and intake, which were new.

I don't think there is a porosity issue because the leak only manifests after a period of time e.g. 1-2 years.

I used the silver/grey RTV on the head side of the gaskets only (I read somewhere that was the correct thing to do, but not sure why ).

I'll pull the manifold and check all faces for straightness as suggested.

Opinion seems to be split between Cometic and Felpro gaskets. I've used Felpro on two previous occasions, but not the ones with a steel core. I've also tried Mr Gasket.

Thanks again. I'll report back when I've pulled and checked the intake.

Paul

[mrmustang]

Originally Posted by FatBoy

Opinion seems to be split between Cometic and Felpro gaskets. I've used Felpro on two previous occasions, but not the ones with a steel core. I've also tried Mr Gasket.


Paul

Paul,

There were some issues with Edelbrock intakes a few years back, never advertised or brought to light in a public manner, but handled internally at Edelbrock. With that said, you might want to find a new intake that you can check measurements with.







I'll leave it at that





Bill S.

[jhirasak]

Have you checked to make sure that none of the manifold bolts are bottomed out before the gaskets are fully compressed? This can be easily done when the manifold is being test fitted to the engine without gaskets to check manifold gaps. It is just a precaution that could explain the cause of the stated problem.

Cheers,

John

[FatBoy]

Originally Posted by jhirasak

Have you checked to make sure that none of the manifold bolts are bottomed out before the gaskets are fully compressed? This can be easily done when the manifold is being test fitted to the engine without gaskets to check manifold gaps. It is just a precaution that could explain the cause of the stated problem.

Cheers,

John

Good point and worth checking, although I'm pretty confident that they all pull up on the manifold okay.

Thank you,
Paul