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Cracked intake [message #63569]

Mon, 09 November 2009 11:16

Bob de Kruyff

Messages: 4260
Registered: January 2004
Location: Chandler, AZ

Karma: 1

Senior Member

Has anyone had a 403 intake manifold crack? I'm pretty sure mine is. About 2 months ago, I had a very bad case of what I thought was fuel starvation even with the electric pump running. That was very unusual for my coach. I discovered the carb was loose and at the time, decided I'd pull it off and rebuild it after almost 20 years. Just before installing it, I gave the manifold a good inspection and it appears to have a crack in the bottom floor, but I really need to clean it up a bit to be sure. I don't recall anyone ever mentioning this on a 403. Luckily small block intakes are readily available. I could go with aluminum but then the next question is what are the issues of blocking the crossover with an aluminum intake.

Bob de Kruyff
78 Eleganza
Chandler, AZ

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Re: [GMCnet] Cracked intake [message #63576 is a reply to message #63569]

Mon, 09 November 2009 11:46

Rick Denney

Messages: 430
Registered: January 2004

Karma: 0

Senior Member

Bob de Kruyff writes...

> I could go with aluminum but then the next question is what are the
> issues of blocking the crossover with an aluminum intake.

My understanding is that there is no issue. I added a layer of safety
(literally) by using Dick Paterson's stainless-steel block-off plates
to keep the surface of the aluminum from eroding. Those blocking
plates seem adequate to the task even for an unfilled iron manifold.

Doesn't the 403 use the same intake gaskets as the 455? I know the
intake itself is narrower.

Rick "belt and suspenders-heh" Denney

'73 230 Ex-Glacier "Jaws"
Northern Virginia

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'73 Glacier 230 "Jaws"

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Re: [GMCnet] Cracked intake [message #63584 is a reply to message #63576]

Mon, 09 November 2009 12:18

Bob de Kruyff

Messages: 4260
Registered: January 2004
Location: Chandler, AZ

Karma: 1

Senior Member

""Doesn't the 403 use the same intake gaskets as the 455? I know the
intake itself is narrower.""

The turkey tray type appears to be different, but that begs the next question--to turkey tray or not? I guess before I get too excited I really need to check out what appears to be a crack and clean it up a bit.

Bob de Kruyff
78 Eleganza
Chandler, AZ

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Re: [GMCnet] Cracked intake [message #63590 is a reply to message #63584]

Mon, 09 November 2009 13:56

Rick Denney

Messages: 430
Registered: January 2004

Karma: 0

Senior Member

Bob de Kruyff writes...

> The turkey tray type appears to be different, but that begs the
> next question--to turkey tray or not? I guess before I get too
> excited I really need to check out what appears to be a crack and clean it up a bit.

I didn't use a turkey tray. Without the hot crossover, I figured there
was no need. Most I've asked agree, but a few didn't.

Rick "you pays yer nickel..." Denney

'73 230 Ex-Glacier "Jaws"
Northern Virginia

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Re: [GMCnet] Cracked intake [message #63591 is a reply to message #63576]

Mon, 09 November 2009 13:56

USAussie

Messages: 15912
Registered: July 2007
Location: Sydney, Australia

Karma: 6

Senior Member

G'day,

Nope! The ports in a 403 are smaller than a 455.

I was shipped a set of Mr. Gasket intake gaskets for a 403 by a supplier by
mistake. I didn't notice it until after I glued them down with Gorilla snot.
I noticed that the valley gaskets were way too short and that prompted me to
examine the installed gaskets. I could see cast iron around the sides and
bottom of the port but not the top. I stuck my finger in the port and could
feel the gasket extending down from the top of the port a bit. I didn't
check how far as I was too busy cursing and ripping them off! Fortunately
the Gorilla snot hadn't set up and I was able to peel them off and scrap the
residue off the heads without too much bother.

I agree with Rick and I don't think it's necessary to use block off plates
but if I were to do it again I would use these gaskets from Edelbrock.

http://www.summitracing.com/parts/EDL-7284/?image=large

Here's the text from the ad:

Brand: Edelbrock
Manufacturer's Part Number: 7284
Part Type: Intake Manifold Gaskets
Product Line: Edelbrock Intake Manifold Gaskets
Summit Racing Part Number: EDL-7284
Port Style: Stock
Port Height (in): 2.440 in.
Port Width (in): 1.440 in.
Gasket Material: Composite
Thickness (in): 0.060 in.
Quantity: Sold as a set.
Notes: Nitrile bead around port openings.

Produce maximum and efficient power with precise sealing.

Properly sealing an engine is paramount to making maximum horsepower.
Edelbrock intake manifold gaskets are designed to give your manifold and
cylinder heads an exact seal with their composite and steel core
construction.

Note the Nitrile bead and steel core!

Regards,
Rob Mueller
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426

-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org
[mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Rick Denney
Sent: Tuesday, 10 November 2009 4:47 AM
To: Bob de Kruyff
Subject: Re: [GMCnet] Cracked intake

Bob de Kruyff writes...

> I could go with aluminum but then the next question is what are the
> issues of blocking the crossover with an aluminum intake.

My understanding is that there is no issue. I added a layer of safety
(literally) by using Dick Paterson's stainless-steel block-off plates
to keep the surface of the aluminum from eroding. Those blocking
plates seem adequate to the task even for an unfilled iron manifold.

Doesn't the 403 use the same intake gaskets as the 455? I know the
intake itself is narrower.

Rick "belt and suspenders-heh" Denney

'73 230 Ex-Glacier "Jaws"
Northern Virginia

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List Information and Subscription Options:
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Regards, Rob M. (USAussie) The Pedantic Mechanic Sydney, Australia '75 Avion - AUS - The Blue Streak TZE365V100428 '75 Avion - USA - Double Trouble TZE365V100426

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Re: Cracked intake [message #63714 is a reply to message #63569]

Tue, 10 November 2009 13:58

Bob de Kruyff

Messages: 4260
Registered: January 2004
Location: Chandler, AZ

Karma: 1

Senior Member

I never did hear whether anyone has ever had a 403 intake crack--does that mean a no Smile

Bob de Kruyff
78 Eleganza
Chandler, AZ

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