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aluminum intake manifold install on 455 [message #364952]

Thu, 24 June 2021 12:20

rgogan

Messages: 82
Registered: February 2004
Location: Milwaukee, WI

Karma: 0

Member

Finally installed my aluminum intake manifold after sitting on the shelf for 6-10 years. Purchased from Jim Bounds. Casting labeled "RPM'.
#1 casting is about .25 inches thicker (higher) than the original steel casting.
#2 as a consequence, the passenger side venturi bracket would not fit without grinding it down
#3 also, the AC compressor bracket does not line up with the bored and tapped hole for it in the aluminum manifold because of the increased height. No solution for this yet. The outer part of the AC bracket attached well to the head bolt fixture for it and that seems a solid enough mount for it now.
#4 the vacuum port behind the carburetor was moved forward for unknown reasons and it interferes with the fit of the accelerator mounting bar on the back of the carb. Had to grind that mounting bar down too.

The fit to the heads seemed excellent. My head thickness after machining was 1.986" at the short head bolt area. With the head gasket compressed to 0.037 this kept the fit perfect using Jim Patterson's intake manifold gasket and block off plates with ultrablack RTV. (used entire tube). Still have not fired up the engine to check for leaks. Did have a leak at the thermostat housing. Seems like the recess for the thermostat was not machined deeply enough in the intake manifold. The high flow thermostat prevented the gasket from sealing. Will redo using two gaskets. More progress reports to follow.

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Re: aluminum intake manifold install on 455 [message #364964 is a reply to message #364952]

Thu, 24 June 2021 18:10

Carl S.

Messages: 4186
Registered: January 2009
Location: Tucson, AZ.

Karma: 13

Senior Member

I ground a notch in the accelerator cable bracket to accommodate the vacuum port. You may need to enlarge the hole in the AC compressor bracket to fit te bolt into the manifold.

http://www.gmcmhphotos.com/photos/gary-rockwell-aluminum-intake-manifold-installation/p44399-throttle-cable-bracket.html

Carl Stouffer '75 ex Palm Beach Tucson, AZ. Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member

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Re: aluminum intake manifold install on 455 [message #364979 is a reply to message #364964]

Fri, 25 June 2021 09:33

rgogan

Messages: 82
Registered: February 2004
Location: Milwaukee, WI

Karma: 0

Member

Thanks to the reference to your pictures. Wish I had been aware of them before I started my project.

#1 I liked your idea of tapping, plugging and drilling the heater outlet at the rear of the aluminum intake manifold which didn't take the larger fitting from the steel intake manifold. I filled mine with JB weld and drill out it out to the flow limiter size. This apparently keeps the noise down of coolant flowing through the heater core

#2 I haven't enlarged the AC bracket hole to engage the tapped bore on the Aluminum intake manifold. I am hoping the bracket is secure enough that this attachment point will not be needed

#3 I had to grind down the right venturi bracket so it would clear the higher intake manifold

#4 I dealt with the accelerator bracket interference with the vacuum port in an identical way to your solution. Others have changed the vacuum port to a different fitting so it clears the bracket.

#5 I am going to wrap .25 inch copper tubing around my exhaust header connected to the choke to keep the original thermal choke working without going to an electric choke conversion. Trying to figure out how to route it though. If anyone has done this and has some pics, it would be appreciated

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Re: aluminum intake manifold install on 455 [message #364994 is a reply to message #364979]

Fri, 25 June 2021 13:46

Carl S.

Messages: 4186
Registered: January 2009
Location: Tucson, AZ.

Karma: 13

Senior Member

I'm Happy my photo album helped. I just went with an electric choke. It had it's drawbacks, mostly it pulls off too soon, but overall it is a good and easy solution.

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Re: aluminum intake manifold install on 455 [message #364998 is a reply to message #364994]

Fri, 25 June 2021 19:55

Matt Colie

Messages: 8547
Registered: March 2007
Location: S.E. Michigan

Karma: 7

Senior Member

Carl S. wrote on Fri, 25 June 2021 14:46

I'm Happy my photo album helped. I just went with an electric choke. It had it's drawbacks, mostly it pulls off too soon, but overall it is a good and easy solution.

Carl, If the electric choke pull open too soon, you have some ways to correct this. This is a mod I have done more than once, some took extra tries.

I am going to guess that you set it to just close at room temperature like it was before. Just a little tighter won't hurt, but more than that will make it bogg just as you come off idle. That won't last long, but it is annoying.

First, if you are activating it with the ignition, you can't do a pre-crank light check. If you choose to do that, flip the ignition on, look at the lights and instruments and turn it back off. Give the heater a chance to cool down.

Second, if you have still have an isolator, put it on the center terminal. That works real well, but you can't do that on a street car. If that is still too fast, add a single 5amp diode to its lead. Mine was a little early, but this made it great.

The electric choke on Chaumière works as well for me as any of the manual chokes I have had.

Matt

Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit

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Re: aluminum intake manifold install on 455 [message #365383 is a reply to message #364952]

Mon, 12 July 2021 16:01

rgogan

Messages: 82
Registered: February 2004
Location: Milwaukee, WI

Karma: 0

Member

Had to pull aluminum intake manifold off and refit it. Had oil leak at the front and rear. Didn't follow Patterson's advice on putting that thick 3/8" bead of RTV on the front and rear of the block because I was running short with only one tube of RTV. Two tubes of RTV are definitely needed for this job. Cost me having to redo the whole thing. Also found that the recess for the thermostat was machined too small and the thermostat was sitting too proud for even 3 stacked gaskets to seal. Had to chamfer out the opening with a Dremmel tool and now the thermostat fits flat.

Also, probably because of different machining on one rebuilt head versus the other, the aluminum intake manifold did not fit level and the gap between it and the front and rear of the block was greater on the passenger side than on the driver's side. Using RTV rather than the OEM rubber gasket allowed compensation for that difference, but it took a lot of RTV. BTW, I used ultrablack Permatex.

Will be another day or two before everything gets put back together to know for sure my oil leak is solved, but now I know to use an inspection mirror to check that adequate squeeze out of the RTV has occurred at the front and rear block to intake manifold gap. BTW, I am doing this in the coach not on an engine stand.

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[GMCnet] Re: aluminum intake manifold install on 455 [message #365385 is a reply to message #365383]

Mon, 12 July 2021 16:34

James Hupy

Messages: 6806
Registered: May 2010

Karma: -62

Senior Member

I have put 3 of those Aluminum intake manifolds on 455's. None fit without
some kind of an issue. I attributed the poor fit to 40 year old engines and
cylinder heads matched from different engines. And machine shops "decking"
the blocks, etc. But, if you don't pay extremely close attention to the
intersection where the intake manifold, cylinder head, and block all meet
up, you will have oil leaks. I Gur-an-tee it. Look for about 1/16" to 1/8"
space between the ends of the intake manifold and the block dams. More than
that, it is very difficult to achieve a long lasting seal.
Jim K. assures me that later manifolds had better quality control in
the fit department, than the first production run.
All I know about that.
Be ultra careful and make all surfaces "squeaky" clean. A hint here.
The black Goo that I have had great success with is a Permarex product
known as "the right stuff" I use the quick skinning version, but you might
want a bit more time than that. Just what I do.
Jim Hupy
Salem, Oregon

On Mon, Jul 12, 2021, 2:01 PM Robert J. Gogan wrote:

> Had to pull aluminum intake manifold off and refit it. Had oil leak at
> the front and rear. Didn't follow Patterson's advice on putting that thick
> 3/8" bead of RTV on the front and rear of the block because I was running
> short with only one tube of RTV. Two tubes of RTV are definitely needed for
> this job. Cost me having to redo the whole thing. Also found that the
> recess for the thermostat was machined too small and the thermostat was
> sitting
> too proud for even 3 stacked gaskets to seal. Had to chamfer out the
> opening with a Dremmel tool and now the thermostat fits flat.
>
> Also, probably because of different machining on one rebuilt head versus
> the other, the aluminum intake manifold did not fit level and the gap
> between
> it and the front and rear of the block was greater on the passenger side
> than on the driver's side. Using RTV rather than the OEM rubber gasket
> allowed compensation for that difference, but it took a lot of RTV. BTW,
> I used ultrablack Permatex.
>
> Will be another day or two before everything gets put back together to
> know for sure my oil leak is solved, but now I know to use an inspection
> mirror
> to check that adequate squeeze out of the RTV has occurred at the front
> and rear block to intake manifold gap. BTW, I am doing this in the coach not
> on an engine stand.
> _______________________________________________
> GMCnet mailing list
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Re: aluminum intake manifold install on 455 [message #365388 is a reply to message #365383]

Mon, 12 July 2021 17:37

Larry

Messages: 2875
Registered: January 2004
Location: Menomonie, WI

Karma: 10

Senior Member

rgogan wrote on Mon, 12 July 2021 16:01

Had to pull aluminum intake manifold off and refit it. Had oil leak at the front and rear. Didn't follow Patterson's advice on putting that thick 3/8" bead of RTV on the front and rear of the block because I was running short with only one tube of RTV. Two tubes of RTV are definitely needed for this job. Cost me having to redo the whole thing. Also found that the recess for the thermostat was machined too small and the thermostat was sitting too proud for even 3 stacked gaskets to seal. Had to chamfer out the opening with a Dremmel tool and now the thermostat fits flat.

Also, probably because of different machining on one rebuilt head versus the other, the aluminum intake manifold did not fit level and the gap between it and the front and rear of the block was greater on the passenger side than on the driver's side. Using RTV rather than the OEM rubber gasket allowed compensation for that difference, but it took a lot of RTV. BTW, I used ultrablack Permatex.

Will be another day or two before everything gets put back together to know for sure my oil leak is solved, but now I know to use an inspection mirror to check that adequate squeeze out of the RTV has occurred at the front and rear block to intake manifold gap. BTW, I am doing this in the coach not on an engine stand.

I had the leak experience early in my Intake manifold swaps. One thing I finally did was to take a nail punch and punch a bunch of divots in the front and rear intake manifold machined surfaces and on the block front and rear surfaces so the RTV had something to hold on to. When you do this, spread a 3/8"bead, carefully lower the intake in place and push down on intake by hand, Put the intake bolts in and finger tighten them. Allow to cure overnight. The next day, torque to spec. That then makes the bead of RTV act like a "O" ring. Just the way I do it.

Larry

78 Royale w/500 Caddy
Menomonie, WI.

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Re: aluminum intake manifold install on 455 [message #365430 is a reply to message #364952]

Wed, 14 July 2021 14:39

rgogan

Messages: 82
Registered: February 2004
Location: Milwaukee, WI

Karma: 0

Member

I have had the unfortunate experience of having to pull off my aluminum intake manifold 500 mi after I installed it. Didn't have enough RTV on the front and rear gaps to the block and it leaked oil in both areas. Was amazed to find how clean the valley was compared to the appearance with the old cast iron manifold with the cross over. The bottom of the crossover had cracked and was probably pressurizing the valley and sump in addition to frying the oil.

My wife also does not miss the boiling gas smell when we would shut the coach down and the hot cross over would boil the carb. I wish I had installed this aluminum intake manifold years ago, but apart from my wife's complaining, didn't have much incentive to do it.

With all the installation advice now posted, I would urge everyone to do it. Just the look of the fried oil under the exhaust crossover and dropping into the turkey pan is enough to think you are driving on a time bomb with this type of setup.

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Re: aluminum intake manifold install on 455 [message #365431 is a reply to message #365430]

Wed, 14 July 2021 16:37

Bill Van Vlack

Messages: 419
Registered: September 2015
Location: Guemes Island, Washington

Karma: 14

Senior Member

I used an electric choke that came with a heat sensor that mounts under a manifold bolt and wires in series with the bi-metal strip in the carb choke. IGN voltage is split between the choke and the sensor so the choke is held back by the sensor, which decreases in resistance as the manifold heats until full voltage is across the bimetal coil.

Bill Van Vlack '76 Royale; Guemes Island, Washington; Twin bed, full (DS) side bath, Brazilian Redwood counter and settee tops,455, 6KW generator; new owner a/o mid November 2015.

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