Remflex vs copper exhaust gaskets

RF_Burns

RF_Burns

Super Moderator
Staff member
Sep 7, 2008
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Ontario Canada
My driver's side exhaust manifold has a large crack so I am replacing it with a used but good condition cast iron manifold. It has a few small pit
clusters that are not deep and appears to have been plained but never used after that.

Two questions:
I have a new set of DaveL copper gaskets and a new set of Remflex gaskets. I'm wondering which would be the best. I know if it did not have any pits
I would use the copper gaskets, but I'm leery because of the pits. How much pitting can copper withstand? I would be installing them with some
Permatex high temperature copper sealant for exhaust manifolds. My worry about the Remflex is the higher temperature the manifolds run at due to the
poorer heat transfer compared to copper.

Second thing is the top center bolt for the manifold broke while trying to remove it. I read where some do not bother to install this bolt as it is
recommended not to torque it. So do I just leave the broken stud there as a installation guild, or do I need to remove it and re-install a new one.
They had been installed with never-seize, likely zinc based. I'll be using copper based this time.

Thoughts, ideas, experiences...?

--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
 
Sir, my thoughts is if there is enough of the broken bolt to clamp solid a pair of vice grips, soak it and soak it and soak it @nd try to get it out.
I have had luck center welding a nut on the broken part to remove with a wrench. I know a lot recommend not even using the center bolt but it was put
there by GM.

> My driver's side exhaust manifold has a large crack so I am replacing it with a used but good condition cast iron manifold. It has a few small pit
> clusters that are not deep and appears to have been plained but never used after that.
>
> Two questions:
> I have a new set of DaveL copper gaskets and a new set of Remflex gaskets. I'm wondering which would be the best. I know if it did not have any
> pits I would use the copper gaskets, but I'm leery because of the pits. How much pitting can copper withstand? I would be installing them with some
> Permatex high temperature copper sealant for exhaust manifolds. My worry about the Remflex is the higher temperature the manifolds run at due to
> the poorer heat transfer compared to copper.
>
> Second thing is the top center bolt for the manifold broke while trying to remove it. I read where some do not bother to install this bolt as it
> is recommended not to torque it. So do I just leave the broken stud there as a installation guild, or do I need to remove it and re-install a new
> one. They had been installed with never-seize, likely zinc based. I'll be using copper based this time.
>
> Thoughts, ideas, experiences...?

--
C. Boyd
76 Crestmont
East Tennessee
 
On the driver’s side, you get good access to the cylinder head surface if
you remove the inner fender well. There is room for a drill.

I had the same broken-bolt problem when I installed headers years ago. I
used a sharp 1/8” left-turning drill, which was part of an extraction kit,
and drilled all the way through the bolt. Going all the way through is
important. The center hole is open at the back, as I recall, so you can
also attack it with Kroil from the back side. Kroil also makes an
acceptable cutting fluid—also important. I enlarged the hole, and
eventually the left-turning bit pulled all the remains out.

I think the top bolt is needed to keep the manifold from rocking up and
down, but I may be the only one who thinks so.

As to the pitting, it depends on whether the pits create a tunnel around
the crush ridge on the copper gasket. You should be able to tell that by
inspection. If it might, then either plane it down more or use the Remflex
gasket. The carbon composite used by Remflex is a pretty good thermal
conductor. But copper is, of course, better. You can plane the manifold
with aluminum-oxide sandpaper laid down on a hard, flat surface, like a saw
table or even a smooth concrete floor.

Rick “whose manifolds were cracked, welded, and cracked again, making
headers an easy decision” Denney

On Sat, Sep 21, 2019 at 11:04 AM Bruce Hislop via Gmclist <

> My driver's side exhaust manifold has a large crack so I am replacing it
> with a used but good condition cast iron manifold. It has a few small pit
> clusters that are not deep and appears to have been plained but never used
> after that.
>
> Two questions:
> I have a new set of DaveL copper gaskets and a new set of Remflex
> gaskets. I'm wondering which would be the best. I know if it did not have
> any pits
> I would use the copper gaskets, but I'm leery because of the pits. How
> much pitting can copper withstand? I would be installing them with some
> Permatex high temperature copper sealant for exhaust manifolds. My worry
> about the Remflex is the higher temperature the manifolds run at due to the
> poorer heat transfer compared to copper.
>
> Second thing is the top center bolt for the manifold broke while trying to
> remove it. I read where some do not bother to install this bolt as it is
> recommended not to torque it. So do I just leave the broken stud there as
> a installation guild, or do I need to remove it and re-install a new one.
> They had been installed with never-seize, likely zinc based. I'll be
> using copper based this time.
>
> Thoughts, ideas, experiences...?
>
> --
> Bruce Hislop
> ON Canada
> 77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
> http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
> My Staff says I never listen to them, or something like that
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
'73 X-Glacier 230 "Jaws"
Northern Virginia
Offlist email: rick at rickdenney dot com
 
> My driver's side exhaust manifold has a large crack so I am replacing it with a used but good condition cast iron manifold. It has a few small pit
> clusters that are not deep and appears to have been plained but never used after that.
>
> Two questions:
> I have a new set of DaveL copper gaskets and a new set of Remflex gaskets. I'm wondering which would be the best. I know if it did not have any
> pits I would use the copper gaskets, but I'm leery because of the pits. How much pitting can copper withstand? I would be installing them with some
> Permatex high temperature copper sealant for exhaust manifolds. My worry about the Remflex is the higher temperature the manifolds run at due to
> the poorer heat transfer compared to copper.
>
> Second thing is the top center bolt for the manifold broke while trying to remove it. I read where some do not bother to install this bolt as it
> is recommended not to torque it. So do I just leave the broken stud there as a installation guild, or do I need to remove it and re-install a new
> one. They had been installed with never-seize, likely zinc based. I'll be using copper based this time.
>
> Thoughts, ideas, experiences...?

Bruce,

Two things...
If the pitting is not deep, the copper gaskets will probably do just fine. They will require multiple re-torques before they settle in. The Remflex
should not. Reflex are a clad graphite gasket and will have more compliance than the copper and should not gain much from a re-torque. At 7 #ft, how
would you know?

A word of caution...
The good copper anti-seize all contain lead as well. This can foul an O2 sensor and make it either slow or dead. This is not true of the nickel
based anti-seize. In fact that lead is why there is nickel based anti-seize.

A short lesson I have learned along this road....
If you get done working on an exhaust system and you do not have anti-seize all over you, then you did not use enough.......

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
Bruce,

Purely opinion, but I'd use the Remflex, leave the broken stud in place,
and use NO sealant.

Remflex because of its ability to conform to your still-pitted manifold.
Stud 'cause it ain't hurtin' nuthin'.
No sealant because Remflex doesn't need it and it would probably be the
weak link.

Ken H.

On Sat, Sep 21, 2019 at 11:04 AM Bruce Hislop via Gmclist <

> My driver's side exhaust manifold has a large crack so I am replacing it
> with a used but good condition cast iron manifold. It has a few small pit
> clusters that are not deep and appears to have been plained but never used
> after that.
>
> Two questions:
> I have a new set of DaveL copper gaskets and a new set of Remflex
> gaskets. I'm wondering which would be the best. I know if it did not have
> any pits
> I would use the copper gaskets, but I'm leery because of the pits. How
> much pitting can copper withstand? I would be installing them with some
> Permatex high temperature copper sealant for exhaust manifolds. My worry
> about the Remflex is the higher temperature the manifolds run at due to the
> poorer heat transfer compared to copper.
>
> Second thing is the top center bolt for the manifold broke while trying to
> remove it. I read where some do not bother to install this bolt as it is
> recommended not to torque it. So do I just leave the broken stud there as
> a installation guild, or do I need to remove it and re-install a new one.
> They had been installed with never-seize, likely zinc based. I'll be
> using copper based this time.
>
> Thoughts, ideas, experiences...?
>
> --
> Bruce Hislop
> ON Canada
> 77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
> http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
> My Staff says I never listen to them, or something like that
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
Well, checking the replacement manifold over after finding DaveL's instruction.. I found its not perfectly flat. Using a straight edge its out by
0.015" and looking at my micrometer the pits are upwards of that depth too. There is one area of pits that I'm thinking the copper will not seal
well.

I had these manifolds planed when I had the engine rebuilt. I swear the guy running the planer went for lunch break in the middle of the job because
he took so much off I had to flatten the dipstick tube to get it to fit in between. So I don't want to go down that road again.

Rick mentioned the Remflex had good heat transfer, so I think I'll go that way.

The broken bolt was a grade 8 with about 1/8" sticking out. I'm thinking that will be a hard drill-out. All the bolts are open at the back, except
this one. I have a small electric MIG welder, but I haven't welded much in a long time. I'm likely to do more damage with spater flying all over!

Without the center bolt, I worry that the weight of the front of the mufflers hanging from the manifold may put a twisting torque on it and cause the
Remflex's to open at the top.

I worry too much while others go ahead with blind abandonment and it all works out well for them! :roll:
--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
 
Bruce if you have an 1/8" of that bolt sticking out its going to be near impossible to drill as is....let alone grade 8. To get it out you have 2
choices: grind it flat to the head so you can center drill everything properly or weld a nut onto the end....i would choose #2 personally if i wanted
it gone.

So if it was me i would leave it alone....my opinion is the bolt was a production thing...a way to assemble the manifolds on the assembly line without
the need of guide pins etc to put it together....it really does very little to clamp anything properly in tjis setup.

As for gaskets....im fighting the exact same thing....front right cylinder blew out gasket so i put a nice copper one in with copper rtv spray to seal
up the pits.... i took a chance but it didnt work and honestly in my mechanics gut i knew it wouldnt...so i ordered a set of Reflexs and i should have
done that from the start.

Im actually starring at the gaskets right now but because i just got in from a business flight and go back to the airport tomorrow morning for another
the gaskets are going to have to wait another weeks.
--
Rich Mondor,

Brockville, ON

77 Hughes 2600
 
As for the exhaust hanging on the manifold....you should have the spring bolts in there which allows all that to move and not nuts/studs....i think
that is how all this gets messed up in the first place.
--
Rich Mondor,

Brockville, ON

77 Hughes 2600
 
0.015" is a lot! It's going to put a lot of stress on that manifold if you try to clamp that down that way. Time to get it milled (if it were
mine). I did one of mine on a Bridgeport one time for a 6.5L diesel.
--
Todd Snyder, Buffalo NY
1976 Eleganza II
 
> Well, checking the replacement manifold over after finding DaveL's instruction.. I found its not perfectly flat. Using a straight edge its out by
> 0.015" and looking at my micrometer the pits are upwards of that depth too. There is one area of pits that I'm thinking the copper will not seal
> well.
>
> I had these manifolds planed when I had the engine rebuilt. I swear the guy running the planer went for lunch break in the middle of the job
> because he took so much off I had to flatten the dipstick tube to get it to fit in between. So I don't want to go down that road again.
>
> Rick mentioned the Remflex had good heat transfer, so I think I'll go that way.
>
> The broken bolt was a grade 8 with about 1/8" sticking out. I'm thinking that will be a hard drill-out. All the bolts are open at the back,
> except this one. I have a small electric MIG welder, but I haven't welded much in a long time. I'm likely to do more damage with spater flying all
> over!
>
> Without the center bolt, I worry that the weight of the front of the mufflers hanging from the manifold may put a twisting torque on it and cause
> the Remflex's to open at the top.
>
> I worry too much while others go ahead with blind abandonment and it all works out well for them! :roll:

Bruce,

Now where to start....
I agree that 0.015 is probably more than Dave's gaskets will like.

Remflex are metal clad flexible graphite and are not very good at heat transfer. (I used to make gaskets like this all the time at McCord.)
It will accommodate the non-flat much better than the copper.

Grade 8 should not be used in exhaust for lots of reasons that I will not go into right now. Do not worry about drilling it as it is not Gr.8 now.
If you want to try the weld a nut on, get a piece of aluminum flashing about 8" square and cut a 1" hole in it. Hang it on the valve gear cover with
tape so it stays out of the way. If spatter does get through the hole, a chisel should knock it right off.

If you haven't used this box in a while I suggest that you find something to practice on as you will be in a bad location and off-hand. Please have
someone else on hand with an extinguisher. (Just about every time I weld on an assemble vehicle, I set something I can't see on fire.) (Not DC... A
squirt bottle will do.)

When you weld, don't give it time to cool, have some ATF or PS fluid there in a pump oil can and cool it with that. (Be aware the any local First
Peoples may respond to this signal.) The reasoning (and proven) is that the hot joint will suck the lubricant in and the ATF is because it does not
like to burn or coke so it will stay liquid longer than most things.

The heating and cooling trick does work because on heating, the fastener expands and crushes the scale in the joint. Then the addition of any
lubricant sucked into the joint has a much better chance. Before I did the work on my own engine, I had four other 455 heads to get manifolds off.
Many broke, but I only had to play dentist with one in the final count.

Best of luck.

Are you hoping to make Mansfield??

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
The top center bolt just holds the manifold in place so you can attach the other four bolts. Do not torque this bolt down, as it can pull the top
surface in and resulting in the bottom not sealing tight against the block. I did use and would use the Remflex. Follow their instructions carefully.
If there is enough of the top bolt protruding, I would consider leaving it alone and just hang from it.
Tom
--
2012 Phoenix Cruiser model 2552
KA4CSG
 
I'm just going to leave the broken top bolt alone. There is enough of it left to use for gasket alignment.

I had a set of Remflex on before the engine rebuild... about 3k miles I'm guessing and they worked well. Just hope the higher manifold temps don't do
in my cast iron manifolds.

Thanks for the help guys.

Matt, What should I be using for manifold bolts? These were installed by the fleet garage that R&R my engine back about 10 years ago.
--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
 
>
>
> Thanks for the help guys.
>
> Matt, What should I be using for manifold bolts? These were installed by the fleet garage that R&R my engine back about 10 years ago.

Bruce,

Grade 2 is just fine. As I recall, Remflex calls for a final torque of 7.5
That is just fine with grade 2. Try to find them unplated.

And Again, if you do not finish the job covered in anti-seize, you didn't use enough.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
> >
> >
> > Thanks for the help guys.
> >
> > Matt, What should I be using for manifold bolts? These were installed by the fleet garage that R&R my engine back about 10 years ago.
>
> Bruce,
>
> Grade 2 is just fine. As I recall, Remflex calls for a final torque of 7.5
> That is just fine with grade 2. Try to find them unplated.
>
> And Again, if you do not finish the job covered in anti-seize, you didn't use enough.
>
> Matt

The Remflex 11-001 i have for my 403 say 20ftlbs on the sticker.

--
Rich Mondor,

Brockville, ON

77 Hughes 2600
 
My recent Remflex gaskets stated: "Suggested Torque 20 LB FT".

Rob
Victoria, BC
76 Royale - Rear Twins/Dry Bath

>
> Bruce,
>
> Grade 2 is just fine. As I recall, Remflex calls for a final torque of 7.5
> That is just fine with grade 2. Try to find them unplated.
>
> And Again, if you do not finish the job covered in anti-seize, you didn't use enough.
>
> Matt
> --
> Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
> Electronically Controlled Quiet Engine Cooling Fan
> OE Rear Drum Brakes with Applied Control Arms
> SE Michigan - Twixt A2 and Detroit
 
> My recent Remflex gaskets stated: "Suggested Torque 20 LB FT".
>
> Rob
> Victoria, BC
> 76 Royale - Rear Twins/Dry Bath

Good on both of you, I don't know where I remembered the 7-1/5 from, but it is way below Dave's 25 and many retorques.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
The sticker on my Remflex package says 14-18ft-lbs, but I've had them for a few years.

Matt, is there any issue with using the grade 8 bolts? I have them re-installed, but only finger tight. I have some plated 3/8" bolts.. with the 3
bars on top so they are grade 5 I believe.. TSC stores up here have switched to black phosphate bolts in their bins.

We are registered for Mansfield. I have a Chemo treatment on Tuesday so hopefully I'll be bright-eyed and bushy-tailed in about a week after that.

--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
 
Bruce,

The last set of Remflex I used (for the Cad 500, not an Olds) had original
14-18 ft-lb with sticker saying 20 ft-lb. I think they had a change of
heart.

Ken H.

On Sat, Sep 21, 2019 at 7:23 PM Bruce Hislop via Gmclist <

> The sticker on my Remflex package says 14-18ft-lbs, but I've had them for
> a few years.
>
> Matt, is there any issue with using the grade 8 bolts? I have them
> re-installed, but only finger tight. I have some plated 3/8" bolts.. with
> the 3
> bars on top so they are grade 5 I believe.. TSC stores up here have
> switched to black phosphate bolts in their bins.
>
> We are registered for Mansfield. I have a Chemo treatment on Tuesday so
> hopefully I'll be bright-eyed and bushy-tailed in about a week after that.
>
> --
> Bruce Hislop
> ON Canada
> 77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
> http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
> My Staff says I never listen to them, or something like that
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
Bruce,
IIRC, Remflex makes two different gaskets for the 455 - one for manifolds, and one for headers. I didn't know that when I put ours on about 10 years
ago. I think we have the ones for headers, but we have manifolds. So I don't think it matters much...
--
John Shotwell
Ridgeville Corners, OH
78 Royale Center Kitchen
 
Ken, That's good to hear because my 3/8" torque wrench is rated for specs between 20 and 150ft-lbs... so I'm good with that.

John, would the one for headers have the center piece for the dual port center position? Mine is open there.

--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
 
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