Home » Public Forums » GMCnet » replacing driver's side head on a 455 (Jumping into unknown waters and any help appreciated)
| replacing driver's side head on a 455 [message #362723] |
Mon, 08 March 2021 14:46  |
rgogan
Messages: 82
Registered: February 2004
Location: Milwaukee, WI
Karma: 0
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Blew out a water pump last summer and overheated the engine trying to pull over. New water pump installed, but engine is running hot despite a tested good thermostat and good radiator especially on long uphill grades. Pressurized coolant system and found a leak down without any external antifreeze leaks.
Did cylinder compression tests:
All cylinders 150-160 psi on my rebuilt 455 engine with 55,000 miles on it EXCEPT cylinder #5 which is reading 55-60 psi.
Figure I've got one or more of the following:
1) overheated cracked head at cyl #5,
2) overheated warped head and blown head gasket at cyl #5
3) burned valves or seats at cyl #5 or
4) piston ring failure at cyl #5.
Don't think it's a cracked block. Had that before and oil and antifreeze leaking out was pretty evident.
Starting the disassembly process to replace the J head on the driver's side:
After removing the driver's side exhaust header (just installed two years ago) found that the nice thick gasket that Jim K sold me was broken up in the web area between the exhaust ports. No external leaks yet.
Same thing happened on the passenger side last year, but the outside of the gasket broke down it that area and it leaked.
The original heads were designed for manifolds and it was not necessary for the dividing web in the central exhaust to press against the gasket web onto the exhaust header. Talked to my head rebuilder about this and he was willing to put a bead of weld onto the head web to build it up to engage the web portion of the gasket. However, he suggested that I just cut the web out of the gasket to prevent the exhaust pressure from tearing it up and ripping out the more important peripheral gasket.
This is, for sure, the first of many questions that I will have during this rebuild process:
Should I build up the exhaust port web with a weld and machine it to engage the web portion of the gasket or should I just cut out the web part of the gasket so it doesn't tear out the important peripheral sealing portion of the gasket?
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| Re: [GMCnet] replacing driver's side head on a 455 [message #362725 is a reply to message #362723] |
Mon, 08 March 2021 14:55  |
stu@97381.com, Emery
Messages: 232
Registered: June 2020
Karma: 2
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Senior Member |
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I had an overheating problem about 2 years ago on a fairly recently rebuilt 455 engine.
It turned out when the engine overheated two of the center pistons swelled and rubbed on the cylinder walls generating a lot of heat which ruined the engine.
I haven’t made a trip with the latest engine yet due to Covid. Hopefully this summer or fall we’ll take a trip.
Emery Stora
77 Kingsley
Frederick CO
> On Mar 8, 2021, at 1:48 PM, Robert J. Gogan via Gmclist wrote:
>
> Blew out a water pump last summer and overheated the engine trying to pull over. New water pump installed, but engine is running hot despite a tested
> good thermostat and good radiator especially on long uphill grades. Pressurized coolant system and found a leak down without any external antifreeze
> leaks.
>
> Did cylinder compression tests:
>
> All cylinders 150-160 psi on my rebuilt 455 engine with 55,000 miles on it EXCEPT cylinder #5 which is reading 55-60 psi.
>
> Figure I've got one or more of the following:
> 1) overheated cracked head at cyl #5,
> 2) overheated warped head and blown head gasket at cyl #5
> 3) burned valves or seats at cyl #5 or
> 4) piston ring failure at cyl #5.
> Don't think it's a cracked block. Had that before and oil and antifreeze leaking out was pretty evident.
>
> Starting the disassembly process to replace the J head on the driver's side:
>
> After removing the driver's side exhaust header (just installed two years ago) found that the nice thick gasket that Jim K sold me was broken up in
> the web area between the exhaust ports. No external leaks yet.
>
> Same thing happened on the passenger side last year, but the outside of the gasket broke down it that area and it leaked.
>
> The original heads were designed for manifolds and it was not necessary for the dividing web in the central exhaust to press against the gasket web
> onto the exhaust header. Talked to my head rebuilder about this and he was willing to put a bead of weld onto the head web to build it up to engage
> the web portion of the gasket. However, he suggested that I just cut the web out of the gasket to prevent the exhaust pressure from tearing it up and
> ripping out the more important peripheral gasket.
>
> This is, for sure, the first of many questions that I will have during this rebuild process:
>
> Should I build up the exhaust port web with a weld and machine it to engage the web portion of the gasket or should I just cut out the web part of the
> gasket so it doesn't tear out the important peripheral sealing portion of the gasket?
>
>
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| Re: replacing driver's side head on a 455 [message #362734 is a reply to message #362723] |
Mon, 08 March 2021 17:51 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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If you throw out this “warped head” theory and go with just a bad head gasket you have a win. Now sell the headers (proven no gains) and bolt on 2 manifolds and done.
I had a similar “brain logic diagnosis” just a couple weeks ago. Follow me here. My XJ with 300K miles was weekly low on coolant in the overflow. Kept adding 50/50. It would also start in the morning with 1 dead cylinder more and more often. Reving it would clear it and it would not miss all day at any speed. Finally it started with the miss and would not clear. Cyl 2 missfire. Pulled plug expecting the worst. Head gasket. Hoped for carbon in gap, but no, LOOKED fine. Got the METER and Ohmed center to side. Had some value not open circuit. Also metered center to tip and that was 100k too high. So the plug was arcing internally and not visibly bad. 6 new correct plugs and under $20.
Aa for coolant loss, removed cap (fairly new) and cleaned plastic neck with cloth and rinsed cap off. Put a light film of grease under the cap hold down tabs. This earless type cap was now way easier to palm and turn. Turned back and forth several times to get a better seal on plastic neck. No more high speed coolant loss past outer gasket.
Moto is everything pointed to head gasket and it was totally two other issues and an easy fix. Don’t throw out baby with bath water.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: replacing driver's side head on a 455 [message #362855 is a reply to message #362831] |
Tue, 16 March 2021 03:39 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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I would install the stainless blocking plates to keep the hot exhaust from getting to the gasket. The Dick Paterson blocking plate kit has the correct thickness plate and matching gasket thickness to provide a correct seal. Many intake gaskets sold are too thick. Call Dick at Springfield Ignition.
http://www.springfield-ignition.com/
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: replacing driver's side head on a 455 [message #362857 is a reply to message #362723] |
Tue, 16 March 2021 08:55 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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Yep the common 3-5 and 4-6 ports don’t create a clear pulse drive in those header tubes, which then causes poor scavenging in 1, 7, 2, and 8.
John Lebetski
Woodstock, IL
77 Eleganza II
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| [GMCnet] Re: replacing driver's side head on a 455 [message #362859 is a reply to message #362857] |
Tue, 16 March 2021 11:28 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Yep, you would probably notice a loss in torque and horsepower around 5500
- 6000 rpm or so. 1800 to 3600? Bet you not much difference.
Jim Hupy
Salem, Oregon
On Tue, Mar 16, 2021, 6:57 AM John R. Lebetski
wrote:
> Yep the common 3-5 and 4-6 ports don’t create a clear pulse drive in those
> header tubes, which then causes poor scavenging in 1, 7, 2, and 8.
> --
> John Lebetski
> Woodstock, IL
> 77 Eleganza II
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| [GMCnet] Re: replacing driver's side head on a 455 [message #362860 is a reply to message #362859] |
Tue, 16 March 2021 11:40 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Sorta like my answer to the frequent question, "Did you notice any power
loss when you went back to OEM from the Edelbrock Performer intake
manifold": "Not below 4000 rpm."
Ken H.
On Tue, Mar 16, 2021 at 12:28 PM James Hupy wrote:
> Yep, you would probably notice a loss in torque and horsepower around 5500
> - 6000 rpm or so. 1800 to 3600? Bet you not much difference.
> Jim Hupy
> Salem, Oregon
>
> On Tue, Mar 16, 2021, 6:57 AM John R. Lebetski
> wrote:
>
>> Yep the common 3-5 and 4-6 ports don’t create a clear pulse drive in
> those
>> header tubes, which then causes poor scavenging in 1, 7, 2, and 8.
>> --
>> John Lebetski
>> Woodstock, IL
>> 77 Eleganza II
>> _______________________________________________
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>>
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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: replacing driver's side head on a 455 [message #362952 is a reply to message #362723] |
Mon, 22 March 2021 11:03 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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If you choose to follow JohnLs suggestion and revert to exhaust manifolds, Make sure you have both manifolds in hand, with smooth surfaces and no cracks. One side is made of unobtainium, common only to the GMC motorhome fitted with a 455 engine.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| [GMCnet] Re: replacing driver's side head on a 455 [message #362961 is a reply to message #362723] |
Mon, 22 March 2021 21:25 |
stu@97381.com, Emery
Messages: 232
Registered: June 2020
Karma: 2
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Senior Member |
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I put a thin bead of Permatex Ultra Copper sealant on both sides of my Remflex gasket and it has never blown out. You might try it. Your manifold might have a slight distortion or pitting that could cause the gasket to fail. Two failures and anticipating a third one isn’t normal.
Emery Stora
77 Kingsley
> On Mar 22, 2021, at 8:16 PM, Emery Stora wrote:
>
> Do you really lift the engine cover and invite people in for people at a gas station?
>
> That’s a lot more than I do.
>
> Emery Stora
>
>> On Mar 22, 2021, at 5:30 PM, Robert J. Gogan wrote:
>> Still waiting to paint the aluminum intake manifold before I take the cast iron one off. Advance auto had to order the Duplicolor high temp engine
>> paint that should be for an Olds 455. Have to keep things authentic. I get stopped so often at gas stations with inquisitive people wanting to see
>> my vintage coach, I'd be embarrassed if I didn't have the authentic Olds blue paint on the engine.
>> BTY, Head is still on. Will announce the cause of the low compression as soon as it is discovered. The replacement head is at the Head rebuilder for
>> the second time. This time the head is getting the divider (web) between the inside exhaust ports welded up to the gasket surface. Hopefully, this
>> will help the header pipes produce even exhaust back pressure and cooling and keep my Remflex gasket from blowing out a third time.
>> _______________________________________________
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>> Unsubscribe or Change List Options:
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| [GMCnet] Re: replacing driver's side head on a 455 [message #364949 is a reply to message #364947] |
Thu, 24 June 2021 10:38 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Senior Member |
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Robert,
Most of us that know engines see no advantage to coat the Al. intake.
Yes Al. Oxidizes more than steel, but you should be more concerned about
sealing the intake to the head as that is where lot of problems develop.
On Thu, Jun 24, 2021 at 8:05 AM Robert J. Gogan
wrote:
> Compression loss was from head gasket web failure between cylinders #5 and
> #7. I believe this was from inadequate torque on the head bolt at that
> location. Found that all the head bolt bores in the block were the same
> depth but on chasing the threads found that the threads did not extend deep
> enough on the bore in the block on the outboard side between #5 and #7.
> Confirmed this by looking down the bore. Dealt with it by putting a Grade
> #8
> thick washer under that head bolt. I could have cut the bolt shorter or
> tapped the hole deeper with an end tap, but this was the simplest solution.
> All the bolts torqued down as expected.
> Now I am dealing with the aluminum intake manifold which is turning out to
> be less than perfect. New post to follow.
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--
Jim Kanomata ASE
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.gmcrvparts.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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