Home » Public Forums » GMCnet » Re: [GMCnet] Cracked intake
| Re: [GMCnet] Cracked intake [message #63592] |
Mon, 09 November 2009 14:07  |
chip
Messages: 37
Registered: November 2009
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Rob:
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Are you saying these are the correct gaskets for a 455 ? And they
will be adequate to block off the heat crossover
without filling it in ? Please advise, am new to this and in the
process of pulling my 455 for rebuild ...
Thanks - Chip
1977 Clasco
On Mon 09/11/09 11:56 AM , "Rob Mueller" robmueller@iinet.net.au
sent:
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 [1]
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 [2]
[gmclist-bounces@temp.gmcnet.org [3]] 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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------
[1] http://www.summitracing.com/parts/EDL-7284/?image=large
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| Re: [GMCnet] Cracked intake [message #63620 is a reply to message #63592] |
Mon, 09 November 2009 18:06  |
fred v
Messages: 999
Registered: April 2006
Location: pensacola, fl.
Karma: 0
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| chip wrote on Mon, 09 November 2009 14:07 |
Rob:
Are you saying these are the correct gaskets for a 455 ? And they
will be adequate to block off the heat crossover without filling it in ?
Please advise, am new to this and in the
process of pulling my 455 for rebuild ...
Thanks - Chip
1977 Clasco
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Jim Kanamoto says that there should be no flow in the crossover if the mufflers are both good. if one is partially blocked then you get flow and thus heat in the manifold.
there are two cures for this. go to a single muffler or use the blocking intake manifold gaskets. the other side of the picture is: if your manifold is cracked on the bottom AND under the carb it is possible to suck oil up through these cracks. this has not been proved yet. it is also possible to get exhaust gasses into the carb and a possible reduction of vacuum. if you find cracks you will need to fill the crossover with zinc and use the blocking gaskets.
Fred V
'77 Royale RB 455
P'cola, Fl
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| Re: [GMCnet] Cracked intake [message #63652 is a reply to message #63620] |
Tue, 10 November 2009 06:09 |
Mike Kilroy
Messages: 80
Registered: July 2006
Location: Farmersville, OH (near D...
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as ex of below, my crack allowed air into the fuel mixture going down
intake to pistons - but only after about 20 minutes of driving (guess to
open the crack up when hot. Result was bad backfiring thru carb and
loss of power - at times I had only about 5% power left - could only go
about 15mph max - on flat ground. Kept thinking it was fuel starvation
and so would stop, clean fuel filters, and sure enough, could go again
for another hour or so before it all repeated! Felt sure it was bad
fuel flow so replaced filters, added filters, added ele fuel pump,
replaced fuel pump 2x - all till found it was the crack leaning up the
fuel mixture. So just closing the cross over ends would not have helped
my case. I found a high temp ceramic putty to fill my cross over with -
much easier than molten alum. as well as Dick's block plates.
On 11/9/2009 7:06 PM, fred veenschoten wrote:
>
> Jim Kanamoto says that there should be no flow in the crossover if the mufflers are both good. if one is partially blocked then you get flow and thus heat in the manifold.
>
> there are two cures for this. go to a single muffler or use the blocking intake manifold gaskets. the other side of the picture is: if your manifold is cracked on the bottom AND under the carb it is possible to suck oil up through these cracks. this has not been proved yet. it is also possible to get exhaust gasses into the carb and a possible reduction of vacuum. if you find cracks you will need to fill the crossover with zinc and use the blocking gaskets.
>
>
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Mike (AC8V) & Vickie Kilroy
'73 Canyon Land 26' sidebath
455/ceramic filled crossovers
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| Re: [GMCnet] Cracked intake [message #63655 is a reply to message #63652] |
Tue, 10 November 2009 06:25 |
GMCWiperMan
Messages: 1248
Registered: December 2007
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Procedures have evolved over the past 7-8 years since I posted photos of
pouring Mondello's zinc into the crossover. Since then, people have located
foundries who'll pour aluminum, Mike's found apparently suitable ceramic
putty, etc. But in case anyone still needs to use zinc, here's how I did it
with no previous experience:
http://www.gmcmhphotos.com/photos/showgallery.php?cat=3115&ppuser=
We did others on a couple of occasions using the same equipment and
techniques.
Ken H.
On Tue, Nov 10, 2009 at 7:09 AM, Mike Kilroy <mike@kilroywashere.com> wrote:
> as ex of below, my crack allowed air into the fuel mixture going down
> intake to pistons - but only after about 20 minutes of driving (guess to
> open the crack up when hot. Result was bad backfiring thru carb and
> loss of power - at times I had only about 5% power left - could only go
> about 15mph max - on flat ground. Kept thinking it was fuel starvation
> and so would stop, clean fuel filters, and sure enough, could go again
> for another hour or so before it all repeated! Felt sure it was bad
> fuel flow so replaced filters, added filters, added ele fuel pump,
> replaced fuel pump 2x - all till found it was the crack leaning up the
> fuel mixture. So just closing the cross over ends would not have helped
> my case. I found a high temp ceramic putty to fill my cross over with -
> much easier than molten alum. as well as Dick's block plates.
>
> On 11/9/2009 7:06 PM, fred veenschoten wrote:
> >
> > Jim Kanamoto says that there should be no flow in the crossover if the
> mufflers are both good. if one is partially blocked then you get flow and
> thus heat in the manifold.
> >
> > there are two cures for this. go to a single muffler or use the blocking
> intake manifold gaskets. the other side of the picture is: if your manifold
> is cracked on the bottom AND under the carb it is possible to suck oil up
> through these cracks. this has not been proved yet. it is also possible to
> get exhaust gasses into the carb and a possible reduction of vacuum. if you
> find cracks you will need to fill the crossover with zinc and use the
> blocking gaskets.
> >
> >
>
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
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>
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| Re: [GMCnet] Cracked intake [message #63667 is a reply to message #63620] |
Tue, 10 November 2009 09:32 |
Rick Denney
Messages: 430
Registered: January 2004
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fred veenschoten writes...
> Jim Kanamoto says that there should be no flow in the crossover if
> the mufflers are both good. if one is partially blocked then you get
> flow and thus heat in the manifold.
Jim is a man of few (typewritten) words, so it's easy to extrapolate.
What he said was that the severe problems of having a crossover,
including a cracked intake and a warped carb, are caused by a blocked
muffler forcing flow through the crossover.
He did not say that the crossover won't still get hot enough to, say,
burn off the paint. Even if the air doesn't flow, the heat will. The
blockoff plates are still useful in keeping the carb cool enough to
not boil out when stopped, to keep the fuel/air charge dense, and so
on.
My mufflers were both brand new and I know how hot that crossover got
even so.
> If you find cracks you will need to fill the crossover with zinc and
> use the blocking gaskets.
Or, replace the manifold with a Rockwell aluminum manifold. That is
possible more expensive than filling a manifold, possibly not,
depending on one's ability, desire, and time to handle a pot full of
melted zinc at 1000 degrees plus.
Rick "for whom time is more precious than dollars, but not with an
abundance of either" 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 #63688 is a reply to message #63667] |
Tue, 10 November 2009 10:55 |
Gary Casey
Messages: 448
Registered: September 2009
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Just to add yet another layer on the discussion: Even with perfectly balanced exhaust systems there will be significant flow through the crossover. Reason is that the two center exhaust valves almost point right at the crossover passage, so when those valves open the blow-down jet of hot exhaust is just as likely to go into the crossover as out the exhaust manifold. So there is a lot of pulse flow back and forth and thats what burns off the paint. Recently was the first time I had the opportunity to look closely at the head design and I was mystified as to why the crossover passage in the head was so large. It could have been half that size, I think, and still function just fine. Way, way too much heat in that area, and it all has to be taken away by the cooling system. Just my observation.
I'm anxious to get mine back together with new valves and Dick's crossover plates - and with my uncracked intake manifold...at least I can't find any cracks.
Gary
________________________________
> Jim Kanamoto says that there should be no flow in the crossover if
> the mufflers are both good. if one is partially blocked then you get
> flow and thus heat in the manifold.
Jim is a man of few (typewritten) words, so it's easy to extrapolate.
What he said was that the severe problems of having a crossover,
including a cracked intake and a warped carb, are caused by a blocked
muffler forcing flow through the crossover.
He did not say that the crossover won't still get hot enough to, say,
burn off the paint. Even if the air doesn't flow, the heat will. The
blockoff plates are still useful in keeping the carb cool enough to
not boil out when stopped, to keep the fuel/air charge dense, and so
on.
Rick "for whom time is more precious than dollars, but not with an
abundance of either" Denney
'73 230 Ex-Glacier "Jaws"
Northern Virginia
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| Re: [GMCnet] Cracked intake [message #63711 is a reply to message #63688] |
Tue, 10 November 2009 13:52 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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""Just to add yet another layer on the discussion: Even with perfectly balanced exhaust systems there will be significant flow through the crossover. Reason is that the two center exhaust valves almost point right at the crossover passage, so when those valves open the blow-down jet of hot exhaust is just as likely to go into the crossover as out the exhaust manifold. So there is a lot of pulse flow back and forth and thats what burns off the paint. Recently was the first time I had the opportunity to look closely at the head design and I was mystified as to why the crossover passage in the head was so large. It could have been half that size, I think, and still function just fine. Way, way too much heat in that area, and it all has to be taken away by the cooling system. Just my observation.
I'm anxious to get mine back together with new valves and Dick's crossover plates - and with my uncracked intake manifold...at least I can't find any cracks.
Gary""
Keep in mind that the same manifold in car applications had to transfer all of the exhaust from one bank to the other when the heat riser valve was closed during cold start-ups. The GMC didn't use a heat riser, but used the same manifold.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Cracked intake [message #63736 is a reply to message #63711] |
Tue, 10 November 2009 17:46 |
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mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
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| Bob de Kruyff wrote on Tue, 10 November 2009 11:52 |
Keep in mind that the same manifold in car applications had to transfer all of the exhaust from one bank to the other when the heat riser valve was closed during cold start-ups. The GMC didn't use a heat riser, but used the same manifold.
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I always wondered how that thing on one exhaust manifold helped it heat up... now it is "like Duh!"
Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo'
http://m000035.blogspot.com
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| Re: [GMCnet] Cracked intake [message #63762 is a reply to message #63752] |
Tue, 10 November 2009 20:28 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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""A smaller passage would have worked nearly as well in getting the manifold heated quickly, but would have reduced the magnitude of the overheating that we have seen. It's all history now.
Gary""
Well yes and no. All of our designs comprehended failure mode analyses which in many cases would require a system to handle a failure mode without catastrophic results. Heat riser valves being as crude as they were, failed in many positions. Our designs had to handle things like broken engine mounts, broken throttle cables and springs, and so on. By today's standards, that all seems so ancient now, but at the time you had to design in a lot of redudancy. The cross-over passage was well thought out and remarkably standard practice at the time in almost any domestic V engine.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Cracked intake [message #64788 is a reply to message #63762] |
Wed, 18 November 2009 14:24 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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Well I figured out this weekend that my manifold is not cracked. The 403 has a dual plane intake meaning that the passenger side chamber floor is roughly 1 1/2 inches lower than the driver's side. The driver side passages were nice and clean with no buildup, while the passenger side had a lot of carbon and gooey deposits in it. I cleaned all that up and found that what looked like a crack was just the edge of a thick carbon layer. After doing some digging and talking with my engine buds at GM, I learned that the build-up on the passenger side is normal due to the dual plane design and different temperatures on the intake floor side to side. Given all that, I guess it's time to put the carb back on and get on with it. Sure am getting the bug to take it out again. Between work and moving into a new house, it's been a good couple of months!
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Cracked intake [message #64832 is a reply to message #63592] |
Wed, 18 November 2009 19:30 |
Gail Marks Cruiser
Messages: 125
Registered: August 2009
Location: Gold Coast, Australia
Karma: 0
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G'day,
Yep, I blocked of our Edelbrock manifold with one of Dick Pattersons excellent gasket kits. We got 2hrs down the road on our next trip and had started to notice a loss of power, by the time we stopped for the night I was getting concerned. The give away was the hot floor, bingo, blocked muffler, Nearly had a Terri and Dan style escape hatch.
It had buckled the floor insulation on the right hand muffler untill it was laying on it, but the block off plates held! This could also explain the cracks in the original cast manifold.
Now our GMC is fitted with free flowing mufflers.
Mark Bennett
Gail & Mark's Cruiser
Gold Coast, Australia.
Motorhoming Lifestyle.com
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