Home » Public Forums » GMCnet » [GMCnet] Manifolds vs Headers
| [GMCnet] Manifolds vs Headers [message #355086] |
Sun, 24 May 2020 16:50  |
Mike Kelley
Messages: 467
Registered: February 2017
Karma: -2
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Senior Member |
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Hi fellow GMCers:
Mine is a 76 Eleganza II 455 w/ 3:21 final drive. I have cracked manifolds on my Dick Patterson rebuilt engine (about 80,000 miles in rebuild and 225,000 miles on coach).
Looking for advise as to which way to go. I have access to a set of used manifolds at $400.00. I also have access to a new set of Thorley headers at $250.00. I know I will need add’l exhaust work if I go w/ headers. I am told to plan on insulating them if I go w/ headers due to excess heat in engine bay but have no idea what this may cost. Have also been told ceramic coating may be advisable but am not sure if that would solve the heat problem. I am not a mechanic so will be paying for the installation portion also.
Ok - my GMC friends - advise as to the best way to go and why and approx $ cost.
Thanks,
Mike/The Corvair a holic
Sent from my iPhone
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| Re: [GMCnet] Manifolds vs Headers [message #355089 is a reply to message #355086] |
Sun, 24 May 2020 17:09  |
6cuda6
Messages: 975
Registered: June 2019
Karma: -6
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Senior Member |
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Mike i think it will be a wash either way.....if you go with headers you will need to do something for heat and modify your current exhaust to fit up to the headers.
If you go with the manifolds you might have to get them trued but no exhaust mods needed.
Neither will give you anything performance wise or MPG wise [IMO] and both will blow gaskets eventually (if you use gaskets on your manifolds).
Sorry cant give you prices but i think from a parts perspective you'll be about the same $$$ wise in the end...JMHO.
Rich Mondor,
Brockville, ON
77 Hughes 2600
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| Re: [GMCnet] Manifolds vs Headers [message #355090 is a reply to message #355086] |
Sun, 24 May 2020 17:12 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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Read Rob Muellers in depth dyno lab testing write up. They are neck and neck. Not much gain as cyls 3/5 and 4/6 don’t drive their respective tubes due to shared large rectangular ports
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Manifolds vs Headers [message #355092 is a reply to message #355086] |
Sun, 24 May 2020 17:21 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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I have had Doug Thorley Ceramic Coated Headers on my 403 in my 78 Royale
since at least September, 2008. Mileage then was 89,758. Mileage now, over
140,000 in 2020. So, judge for yourselves if the headers will hold up or
not. I have not replaced the graphite exhaust gaskets, nor do I have any
exhaust leaks. Don't know if his headers are still made of the same
material and the same thickness as mine are or not. They are a quality
product.
I have replaced numerous cast iron exhaust manifolds in that same time
frame on both right and left sides, and on 403 as well as 455 engines, due
to cracked castings. So, I kinda lean towards headers a bit. They will
cause your engine to run a bit lean, due to improved scavenging, although
that effect is minimal below 2500 rpm. A good CO exhaust check is a good
idea after your install. Maybe, a slight rejecting may be necessary, or
install a throttle body fuel injection system like the Howell system which
is infinitely tunable for changes like porting, headers, port matching,
shaved heads, aftermarket cams, pistons, etc.
Jim Hupy
Salem, Oregon
On Sun, May 24, 2020, 2:50 PM Mike Kelley via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Hi fellow GMCers:
> Mine is a 76 Eleganza II 455 w/ 3:21 final drive. I have cracked
> manifolds on my Dick Patterson rebuilt engine (about 80,000 miles in
> rebuild and 225,000 miles on coach).
> Looking for advise as to which way to go. I have access to a set of used
> manifolds at $400.00. I also have access to a new set of Thorley headers
> at $250.00. I know I will need add’l exhaust work if I go w/ headers. I
> am told to plan on insulating them if I go w/ headers due to excess heat in
> engine bay but have no idea what this may cost. Have also been told
> ceramic coating may be advisable but am not sure if that would solve the
> heat problem. I am not a mechanic so will be paying for the installation
> portion also.
> Ok - my GMC friends - advise as to the best way to go and why and approx $
> cost.
> Thanks,
> Mike/The Corvair a holic
>
> Sent from my iPhone
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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| Re: [GMCnet] Manifolds vs Headers [message #355093 is a reply to message #355086] |
Sun, 24 May 2020 17:52 |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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Senior Member |
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Mike- call cinnebar. I would be tempted to buy “new” manifolds. Not much
More then your “used price”.
But that is if you think your head face are in good shape. Use lenzi copper gaskets with the new manifolds.
If you heads are buggered up. Then I would try headers.
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
[Updated on: Sun, 24 May 2020 17:53] Report message to a moderator |
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| Re: [GMCnet] Manifolds vs Headers [message #355094 is a reply to message #355092] |
Sun, 24 May 2020 17:35 |
Mike Kelley
Messages: 467
Registered: February 2017
Karma: -2
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Senior Member |
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Thanks guys (Rich M., John L., and, Jim H.):
I appreciate your responses and your advice!
Now time to do a bit of research to make this difficult decision!
Mike/The Corvair a holic
Sent from my iPhone
> On May 24, 2020, at 5:21 PM, James Hupy via Gmclist wrote:
>
> I have had Doug Thorley Ceramic Coated Headers on my 403 in my 78 Royale
> since at least September, 2008. Mileage then was 89,758. Mileage now, over
> 140,000 in 2020. So, judge for yourselves if the headers will hold up or
> not. I have not replaced the graphite exhaust gaskets, nor do I have any
> exhaust leaks. Don't know if his headers are still made of the same
> material and the same thickness as mine are or not. They are a quality
> product.
> I have replaced numerous cast iron exhaust manifolds in that same time
> frame on both right and left sides, and on 403 as well as 455 engines, due
> to cracked castings. So, I kinda lean towards headers a bit. They will
> cause your engine to run a bit lean, due to improved scavenging, although
> that effect is minimal below 2500 rpm. A good CO exhaust check is a good
> idea after your install. Maybe, a slight rejecting may be necessary, or
> install a throttle body fuel injection system like the Howell system which
> is infinitely tunable for changes like porting, headers, port matching,
> shaved heads, aftermarket cams, pistons, etc.
> Jim Hupy
> Salem, Oregon
>
> On Sun, May 24, 2020, 2:50 PM Mike Kelley via Gmclist gmclist@list.gmcnet.org> wrote:
>
>> Hi fellow GMCers:
>> Mine is a 76 Eleganza II 455 w/ 3:21 final drive. I have cracked
>> manifolds on my Dick Patterson rebuilt engine (about 80,000 miles in
>> rebuild and 225,000 miles on coach).
>> Looking for advise as to which way to go. I have access to a set of used
>> manifolds at $400.00. I also have access to a new set of Thorley headers
>> at $250.00. I know I will need add’l exhaust work if I go w/ headers. I
>> am told to plan on insulating them if I go w/ headers due to excess heat in
>> engine bay but have no idea what this may cost. Have also been told
>> ceramic coating may be advisable but am not sure if that would solve the
>> heat problem. I am not a mechanic so will be paying for the installation
>> portion also.
>> Ok - my GMC friends - advise as to the best way to go and why and approx $
>> cost.
>> Thanks,
>> Mike/The Corvair a holic
>>
>> Sent from my iPhone
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
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| Re: [GMCnet] Manifolds vs Headers [message #355095 is a reply to message #355094] |
Sun, 24 May 2020 18:00 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Mike,
If you decide to go with the headers (as I would), do NOT try to control
heat from them by wrapping them -- that will almost inevitably cause them
to rust thorough pretty soon. If you get them ceramic coated, that would
delay the rust, but I still would not wrap them. Nor will ceramic coating
help much with the heat (still worth doing for longevity). The best
solution for the heat is to cut away the inner 1/3 of the wheel well liners
(especially on the right side) to let it escaped. If your engine hatch
cover is well sealed and insulated, you probably won't notice additional
heat; but, you'll probably find them a little nosier than the manifold was
before it cracked.
JMHO,
Ken H.
On Sun, May 24, 2020 at 6:36 PM Mike Kelley via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Thanks guys (Rich M., John L., and, Jim H.):
> I appreciate your responses and your advice!
> Now time to do a bit of research to make this difficult decision!
> Mike/The Corvair a holic
>
> Sent from my iPhone
>
>> On May 24, 2020, at 5:21 PM, James Hupy via Gmclist gmclist@list.gmcnet.org> wrote:
>>
>> I have had Doug Thorley Ceramic Coated Headers on my 403 in my 78 Royale
>> since at least September, 2008. Mileage then was 89,758. Mileage now,
> over
>> 140,000 in 2020. So, judge for yourselves if the headers will hold up or
>> not. I have not replaced the graphite exhaust gaskets, nor do I have any
>> exhaust leaks. Don't know if his headers are still made of the same
>> material and the same thickness as mine are or not. They are a quality
>> product.
>> I have replaced numerous cast iron exhaust manifolds in that same time
>> frame on both right and left sides, and on 403 as well as 455 engines,
> due
>> to cracked castings. So, I kinda lean towards headers a bit. They will
>> cause your engine to run a bit lean, due to improved scavenging,
> although
>> that effect is minimal below 2500 rpm. A good CO exhaust check is a good
>> idea after your install. Maybe, a slight rejecting may be necessary, or
>> install a throttle body fuel injection system like the Howell system
> which
>> is infinitely tunable for changes like porting, headers, port matching,
>> shaved heads, aftermarket cams, pistons, etc.
>> Jim Hupy
>> Salem, Oregon
>>
>> On Sun, May 24, 2020, 2:50 PM Mike Kelley via Gmclist > gmclist@list.gmcnet.org> wrote:
>>
>>> Hi fellow GMCers:
>>> Mine is a 76 Eleganza II 455 w/ 3:21 final drive. I have cracked
>>> manifolds on my Dick Patterson rebuilt engine (about 80,000 miles in
>>> rebuild and 225,000 miles on coach).
>>> Looking for advise as to which way to go. I have access to a set of used
>>> manifolds at $400.00. I also have access to a new set of Thorley
> headers
>>> at $250.00. I know I will need add’l exhaust work if I go w/ headers.
> I
>>> am told to plan on insulating them if I go w/ headers due to excess
> heat in
>>> engine bay but have no idea what this may cost. Have also been told
>>> ceramic coating may be advisable but am not sure if that would solve the
>>> heat problem. I am not a mechanic so will be paying for the
> installation
>>> portion also.
>>> Ok - my GMC friends - advise as to the best way to go and why and
> approx $
>>> cost.
>>> Thanks,
>>> Mike/The Corvair a holic
>>>
>>> Sent from my iPhone
>>> _______________________________________________
>>> GMCnet mailing list
>>> Unsubscribe or Change List Options:
>>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] Manifolds vs Headers [message #355121 is a reply to message #355086] |
Mon, 25 May 2020 21:26 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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If you get headers, which I recommend, Do NOT not wrap them. From aviation experience if you do not heat the up every day to dry them out, and do not park inside in a dry area, moisture will collect in the I believe he welds up the separation between cylinders 4 and 6 also 3 and 5. I know the one we did he had us tell the machine shop doing the heads to weld them up that way.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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