what do i need to know about intake corssover ?

D

dave silva

New member
Oct 2, 2009
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It's been a long an winding road to diagnose my power problem but the best guess is cracked intake as that fits all the symptoms.

Also, I am told it is very likely the crack will be on the crossover and will be resolved if i block it off.

Assuming that's the case, is there any reason i can't just fab the block plates from some stainless?

--
Dave & Ellen Silva
Hertford, NC

76 Birchaven, 1-ton and other stuff

Currently planning the Great american Road Trip Summer 2021

It's gonna take a lot of Adderall to get this thing right.
 
That depends upon where the crack(s) is(are): The crack(s) is(are) not
only between the crossover and the crankcase or it would not affect your
fuel/air mixture. If the crack's only between the crossover and the intake
manifold, perfect sealing with block-off plates should cure the problem.
BUT, if BOTH conditions exist, the plates won't do the job because there
will still be a leakage path from the crankcase, into the crossover, and
then into the intake manifold.

In that worst case, your only 3 choices, IMHO, are:

1. Weld the crack(s). Which might work, after installing the blockoffs to
keep most of the heat away. But in general, welding manifolds has not
seemed to hold up for long.

2. Seal the crossover completely. I did one 14+ years ago by pouring it
full of "Mondello Metal", a zinc alloy available then from now-departed Joe
Mondello. I've no idea whether it's still available from "Mondello
Performance Products". I've read reports of others melting aluminum
pistons and pouring those into the crossover. I've never seen the
results. Here's my project:
http://www.gmcmhphotos.com/photos/g3115-plugging-intake-manifold-exhaust-crossover.html

3. Replace the manifold.

Good luck!

Ken H.

> It's been a long an winding road to diagnose my power problem but the best
> guess is cracked intake as that fits all the symptoms.
>
> Also, I am told it is very likely the crack will be on the crossover and
> will be resolved if i block it off.
>
> Assuming that's the case, is there any reason i can't just fab the block
> plates from some stainless?
>
>
>
>
>
>
>
>
> --
> Dave & Ellen Silva
> Hertford, NC
>
> 76 Birchaven, 1-ton and other stuff
>
> Currently planning the Great american Road Trip Summer 2021
>
> It's gonna take a lot of Adderall to get this thing right.
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
 
> It's been a long an winding road to diagnose my power problem but the best guess is cracked intake as that fits all the symptoms.
>
> Also, I am told it is very likely the crack will be on the crossover and will be resolved if i block it off.
>
> Assuming that's the case, is there any reason i can't just fab the block plates from some stainless?

Assuming that your intake really is cracked, maybe instead of blocking the crossover, take it to a aluminum foundry and have them pour the crossover.
See this:

http://www.gmcmhphotos.com/photos/g4571-pouring-the-455-crossover.html

Just another option for yo to consider....
--
Larry
78 Royale w/500 Caddy
Menomonie, WI.
 
After installing a couple different intakes.

Please trust me and you simply want dick paterson’s intake block off plates and gaskets.

I dont know where he gets his gaskets(i think he has them custom made). They just fit. There is just not much room for error. The intake is
not as simple as it should be as far as getting the gasket, heads and intake ports to all line up. But the couple patterson gakets i have installed
vs the coop supplied mr gasket 404 and modello plates were night and day difference.

As far as the job, you want good handles on intake to raise and lower and make an alinement bolt(bolt with head cut off and used to guide.

Also most are so full of sledge underneath, that you need to buy a cheap shop vac and sacrifice it to the job of cleaning out all the crud.

I am surprised jim bounds did not block that crossover during the original restoration of the coach. He used to talk about doing that way back then.

--
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
 
There is only 2 kinds of cast iron. The kind that is already cracked, and
the kind that hasn't cracked yet. So where does that leave us? Looking for
an uncracked intake manifold, or figuring out a way to mitigate an already
cracked one. If it is not cracked into the intake passage under the
Carburetor, there are a few ways to mitigate it. Welding is one way,
sometimes successful, sometimes not. I won't go into details here. Another
way is blocking off the crossover passages. Another is to pour aluminum in
the crossover.
I personally prefer to find an uncracked manifold, and blocking off
the crossover using Dick Paterson's stainless steel plates and his special
gaskets. Some manifolds have enough room at the ends to use the neoprene
dams at each end. If the heads have been cut, or the deck surface machined,
then there may not be room for the dams. In that case, "The Right Stuff"
silicone sealer will work on the ends.
I hate the turkey tray intake gasket. Really difficult to install.
Jim Hupy
Salem, Oregon

> After installing a couple different intakes.
>
> Please trust me and you simply want dick paterson’s intake block off
> plates and gaskets.
>
> I dont know where he gets his gaskets(i think he has them custom made).
> They just fit. There is just not much room for error. The intake is
> not as simple as it should be as far as getting the gasket, heads and
> intake ports to all line up. But the couple patterson gakets i have
> installed
> vs the coop supplied mr gasket 404 and modello plates were night and day
> difference.
>
>
> As far as the job, you want good handles on intake to raise and lower and
> make an alinement bolt(bolt with head cut off and used to guide.
>
> Also most are so full of sledge underneath, that you need to buy a cheap
> shop vac and sacrifice it to the job of cleaning out all the crud.
>
> I am surprised jim bounds did not block that crossover during the original
> restoration of the coach. He used to talk about doing that way back then.
>
> --
> Jon Roche
> 75 palm beach
> EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
> St. Cloud, MN
> http://lqqkatjon.blogspot.com/
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
 
I have seen too many filled in intakes that never stayed in place.
The SS block of plate and gasket by Dick Patterson has been a dependable
set up we sell .

> There is only 2 kinds of cast iron. The kind that is already cracked, and
> the kind that hasn't cracked yet. So where does that leave us? Looking for
> an uncracked intake manifold, or figuring out a way to mitigate an already
> cracked one. If it is not cracked into the intake passage under the
> Carburetor, there are a few ways to mitigate it. Welding is one way,
> sometimes successful, sometimes not. I won't go into details here. Another
> way is blocking off the crossover passages. Another is to pour aluminum in
> the crossover.
> I personally prefer to find an uncracked manifold, and blocking off
> the crossover using Dick Paterson's stainless steel plates and his special
> gaskets. Some manifolds have enough room at the ends to use the neoprene
> dams at each end. If the heads have been cut, or the deck surface machined,
> then there may not be room for the dams. In that case, "The Right Stuff"
> silicone sealer will work on the ends.
> I hate the turkey tray intake gasket. Really difficult to install.
> Jim Hupy
> Salem, Oregon
>

>
> > After installing a couple different intakes.
> >
> > Please trust me and you simply want dick paterson’s intake block off
> > plates and gaskets.
> >
> > I dont know where he gets his gaskets(i think he has them custom made).
> > They just fit. There is just not much room for error. The intake
> is
> > not as simple as it should be as far as getting the gasket, heads and
> > intake ports to all line up. But the couple patterson gakets i have
> > installed
> > vs the coop supplied mr gasket 404 and modello plates were night and day
> > difference.
> >
> >
> > As far as the job, you want good handles on intake to raise and lower
> and
> > make an alinement bolt(bolt with head cut off and used to guide.
> >
> > Also most are so full of sledge underneath, that you need to buy a cheap
> > shop vac and sacrifice it to the job of cleaning out all the crud.
> >
> > I am surprised jim bounds did not block that crossover during the
> original
> > restoration of the coach. He used to talk about doing that way back
> then.
> >
> > --
> > Jon Roche
> > 75 palm beach
> > EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
> > St. Cloud, MN
> > http://lqqkatjon.blogspot.com/
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>

--
Jim Kanomata ASE
Applied/GMC, Newark,CA
jimk
http://www.gmcrvparts.com
1-800-752-7502
 
When puts the kits together he uses a thinner gasket that is close to the OEM thickness of the turkey tray which you will not be reinstalling. Then
he uses a stainless plate thickness that is matched to expected crush thickness of the gasket. Get Dicks kit either from him or JImk.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
Thank you for all the great information.

What was the purpose of the turkey tray?

--
Dave & Ellen Silva
Hertford, NC

76 Birchaven, 1-ton and other stuff

Currently planning the Great american Road Trip Summer 2021

It's gonna take a lot of Adderall to get this thing right.
 
If you have to go to Ken's option 3, I have a good 455 intake manifold.

> Thank you for all the great information.
>
> What was the purpose of the turkey tray?
>
>
> --
> Dave & Ellen Silva
> Hertford, NC
>
> 76 Birchaven, 1-ton and other stuff
>
> Currently planning the Great american Road Trip Summer 2021
>
> It's gonna take a lot of Adderall to get this thing right.
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
 
The turkey tray prevented oil from splashing onto the bottom of the hot
intake manifold and " cooking" into hard crusty carbon that eventually
flaked off and sludged up the engine. Modern oils are better at resisting
this. Especially if you block the crossover.
Jim Hupy
Salem,Oregon

> If you have to go to Ken's option 3, I have a good 455 intake manifold.
>

>
> > Thank you for all the great information.
> >
> > What was the purpose of the turkey tray?
> >
> >
> > --
> > Dave & Ellen Silva
> > Hertford, NC
> >
> > 76 Birchaven, 1-ton and other stuff
> >
> > Currently planning the Great american Road Trip Summer 2021
> >
> > It's gonna take a lot of Adderall to get this thing right.
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
 
well the turkey tray really only reduced the oil coking from the crossover heat. A quick look at the photosite shows a LOT of coke in the valley when the tray is lifted
________________________________
From: James Hupy
Sent: Monday, November 22, 2021 8:44 AM
To: gmclist
Subject: [GMCnet] Re: what do i need to know about intake corssover ?

The turkey tray prevented oil from splashing onto the bottom of the hot
intake manifold and " cooking" into hard crusty carbon that eventually
flaked off and sludged up the engine. Modern oils are better at resisting
this. Especially if you block the crossover.
Jim Hupy
Salem,Oregon

> If you have to go to Ken's option 3, I have a good 455 intake manifold.
>

>
> > Thank you for all the great information.
> >
> > What was the purpose of the turkey tray?
> >
> >
> > --
> > Dave & Ellen Silva
> > Hertford, NC
> >
> > 76 Birchaven, 1-ton and other stuff
> >
> > Currently planning the Great american Road Trip Summer 2021
> >
> > It's gonna take a lot of Adderall to get this thing right.
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
 
Yep, they solved one problem, only to create another.
Jim Hupy
Salem, Oregon

> well the turkey tray really only reduced the oil coking from the crossover
> heat. A quick look at the photosite shows a LOT of coke in the valley when
> the tray is lifted
> ________________________________
> From: James Hupy
> Sent: Monday, November 22, 2021 8:44 AM
> To: gmclist
> Subject: [GMCnet] Re: what do i need to know about intake corssover ?
>
> The turkey tray prevented oil from splashing onto the bottom of the hot
> intake manifold and " cooking" into hard crusty carbon that eventually
> flaked off and sludged up the engine. Modern oils are better at resisting
> this. Especially if you block the crossover.
> Jim Hupy
> Salem,Oregon
>

>
> > If you have to go to Ken's option 3, I have a good 455 intake manifold.
> >

> >
> > > Thank you for all the great information.
> > >
> > > What was the purpose of the turkey tray?
> > >
> > >
> > > --
> > > Dave & Ellen Silva
> > > Hertford, NC
> > >
> > > 76 Birchaven, 1-ton and other stuff
> > >
> > > Currently planning the Great american Road Trip Summer 2021
> > >
> > > It's gonna take a lot of Adderall to get this thing right.
> > >
> > > _______________________________________________
> > > GMCnet mailing list
> > > Unsubscribe or Change List Options:
> > >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
 
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