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Copper head gasket leaking compression


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#1 kev

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Posted 30 September 2019 - 02:51 PM

When I was cruising down the highway at about 70mph for several minutes, I noticed a large puff of smoke out the tailpipe as soon as I let off the gas.   Also, after increasing boost, I started to pop the dipstick and purge oil all over the engine bay.   My initial focus was with my crankcase evaporation system but the problem stayed consistent regardless of what I did on that end.    Obviously, I was seeing an extensive amount of blow-by.

Next performed a compression check; 135psi consistent across all four when warm.   Then went to a leak-down test.   I was seeing 4% leak-down on all four at 90 psi pressure; pretty consistent as well and not bad numbers.  But while on cylinders 3 and 4, I heard a faint gargle in the coolant system.   I popped on the pressure gauge from my radiator pressure tester and saw the pressure rising slowly while the leak-down test was being performed.  

My thoughts went right to the head gasket, which was indeed correct after tear down (see photos below).  As I pulled apart the upper engine, I noticed carbon deposits on items within the same plane as the  HG on the passenger-side, consistent with the marks shown on the HG and block mating surfaces.  Looking close at the HG, you can see where it leaked into the oil passage of which was causing my crankcase over pressurization and blow by issue.   Surprisingly I had no signs of bubbling in the slop tank or overheating.  

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What I’m trying to figure out is why this happened?  I’m running a SCE 91534 copper head gasket, .048” thick.   My block has been machined for o-ring grooves.  Grooves cut .050” from the cylinder edge and are .040” wide.   I do not have receiver grooves cut in the head.   Block was machined flat prior to the cutting the grooves.  Head is a new AMC marnal casting.

I was using SCE 31542 stainless steel o-rings, .041” diameter.    Prior to installation, I scuffed all mating surfaces of the head gasket with red scotch brite and then applied two coats of copper adhesive.   In addition, I added hydromar sealant around all oil and coolant passages.  
Have ARP studs which were lubricated with ARP moly lube.   Torqued to 85 ft-lbs and retorqued after first heat/cool cycle once running.

After tear-down, I checked the o-ring protrusion in greater detail than what I did during engine assembly.   I have some ups and downs but everything is within spec (.007-.010” protrusion, with .008” as the average).

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I’m baffled.  I always knew that copper head gaskets were known to leak coolant but not compression!





#2 speedyquest

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Posted 30 September 2019 - 07:04 PM

I can only add two bits of information I know through various paths of research and you probably know both but just in case I'll list them here.

1) The general consensus for o-ring block protrusion is they should be half of the crush thickness of your head gasket. And that the ends of your rings should be butted with no gap.

2) That any engine/head combo running a metal head gasket whether it's MLS or not needs to have a mirror finish to properly seal. I don't know specifically that this fully pertains to you.

These are just two things that instantly popped into my mind. Take them with roughly two grains of salt.

I'll re-read this later and think some more and take any replies into account. Good luck, I appreciate that your pushing boundaries.

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#3 croquest87

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Posted 30 September 2019 - 07:17 PM

I do see lots of milling cutter markings printed on that gasket. I work in aerospace machining industry and know for  fact that all sealing surfaces are supposed to be smooth and circular if any lines in any sealing area and not across like that. Like valve seat if you put a deep scratch across it.  There is lots of pressure in there and things will get through them lines. That would have passed w Felpro gasket and such but just to rough for copper in my opinion.  I see leaks flowing under pressure through them grooves when l enlarged the picture.

#4 tsi_tom

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Posted 30 September 2019 - 07:20 PM

When I did my rebuild Indiana told me to have the machine shop use the CBN machine so that the surface is smooth.  This would allow the head and the block to move.  Not sure if that helps but it looks like deep grooves in your deck.
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#5 ucw458

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Posted 30 September 2019 - 09:25 PM

I've always considered a copper HG to be race only.  I've never heard of them lasting on a street car.  They always start leaking.  Maybe some people have had good luck with them but I've never seen it.


My block is also O-ringed with a marnal head.  I run a felpro 8770 HG with zero leaks.  Just something to think about.
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#6 kev

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Posted 01 October 2019 - 08:03 AM

Thanks guys!   Yes, I did see the milled surface marks on the gasket and it it does make sense and is most likely the cause.  Interesting, I'll have to run back through SCE's recommendations.  I didn't see anything in regards to surface finish.  Although it makes sense because I'm seeing no issue on the head mating surface which is very smooth.  

I had this block machined and the oring grooves cut years back when that was the common thing to do.   When I got around to building this engine, I attempted the felpro 8770 HG with the stainless o-rings.   It wouldn't even hold coolant in a static condition.  As soon as I filled the radiator, it came dripping down the side of the block.  The orings pushed up on the fire ring of the gasket and just wouldn't deform enough to allow it to seat.   I pulled the head off and went the route above with the copper gasket...only to find this problem.  

I ordered an AJUSA MLS gasket from EMS yesterday.   What I'm contemplating is to use copper o-rings with an MLS gasket.   This is something I have been reading about on several forums but have yet to have seen it done on a conquest.   But now I'm concerned that it will be too rough of a finish with that gasket as well?

Thanks again!

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#7 kev

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Posted 01 October 2019 - 08:26 AM

Here is a photo taken during engine build that shows the surface finish of the block

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#8 87redcat

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Posted 01 October 2019 - 08:50 AM

Cant seem to find that felpro gasket.  They have a 9116 PT and a 8770 PT.  Was the HG a discontinued one?
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#9 psu_Crash

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Posted 01 October 2019 - 09:01 AM

Kev I ran the Ajusa gakset with SS o-rings for years without any leaking issues. I was also at .007-8" protrusion. I always thought copper o-rings would be the way to go with a less crush friendly gasket, but the SS wire was already installed by the shop. My BIG downfall with all of that was the placement of the o-rings butting together. Directly between cylinders 3-4 they had both rings butted up at the worst possible place. Eventually that's where the gasket blew out.
I know a couple guys who run the SCE gasket on "Street Machines" and it works. That said they probably put 100 non-drag strip miles on them a year. So it is also my opinion those gaskets don't belong on drivers.
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#10 psu_Crash

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Posted 01 October 2019 - 09:02 AM

View Post87redcat, on 01 October 2019 - 08:50 AM, said:

Cant seem to find that felpro gasket.  They have a 9116 PT and a 8770 PT.  Was the HG a discontinued one?

HG = Head Gasket ;)
He is talking about the 8770 PT
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#11 kev

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Posted 01 October 2019 - 09:22 AM

I pulled out my SST wires this weekend.  I ground a small chisel to a nice edge.  I went close the end of the wire and tapped it a bit with a hammer to pop the wires out.   It worked pretty good.  

Yes I meant 8770 PT.  HG was for head gasket.   Again, I had no luck what-so-ever with using that gasket with the stainless o rings.   I thought about using this gasket with copper o rings but figured I'd try the AJUSA MLS.  


This surface finish thing is bothering me.  


Also the engine has only around 300 miles since assembly but I first noticed the smoke issue on my first drive on the highway which was at about 100 miles...so it never sealed even from the start.  

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#12 psu_Crash

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Posted 01 October 2019 - 11:07 AM

View Postkev, on 01 October 2019 - 09:22 AM, said:

This surface finish thing is bothering me.  


Kevin

That would bother me too. The minute someone puts a thought like that in my head, it's all I can think about!
Did you use any sealant on the copper gasket? The spray copper gasket sealer may have made a difference?
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#13 croquest87

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Posted 01 October 2019 - 11:57 AM

View Postpsu_Crash, on 01 October 2019 - 11:07 AM, said:



That would bother me too. The minute someone puts a thought like that in my head, it's all I can think about!
Did you use any sealant on the copper gasket? The spray copper gasket sealer may have made a difference?
Probably would work.  But  l wouldn't put it all back together only to find out it's still leaking if this was my build . Little elbow grease and some good old fashioned quality machining. Should be good for long time after that.

Edited by croquest87, 01 October 2019 - 12:02 PM.


#14 markhansenconquest

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Posted 01 October 2019 - 03:03 PM

Before u put a new gasket on ......Stone the  block with a stone and look at the surface around the bolts and u wlll see how much the bolts have pulled up the flat head  ..........IMO...........

#15 87redcat

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Posted 01 October 2019 - 03:32 PM

HG... Duh
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#16 ucw458

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Posted 01 October 2019 - 05:51 PM

Perhaps your rings protrude too high from the deck.  I torqued my felpro 8770 with stock head bolts to 90-95 ft lbs without issues.  So my head bolts are at minimum 20 lbs tighter than the factory spec.  ARP stud torque spec is 90 ft lbs not 85.  It is recommended to go a little more with an o-ringed block.


Also, don't re-torque a HG.  Every thread about a bad HG starts out with "I re-torqued the HG".  Everyone seems to think you need to but I bet it causes more issues than it cures.  I have never re-torqued a HG and haven't had any HG failures from not doing so.  In fact most HGs nowdays have instructions saying they don't need to be re-torqued.  That's what the PT at the end of a felpro part number means, perma torque, no re-torque needed.
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#17 kev

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Posted 02 October 2019 - 12:48 PM

It's actually 80 ft-lbs per the ARP instructions.  I've always used 85 on my former cars.   I normally never retorque with a conventional gasket.  I only did so because this one was copper and it was explicitly stated in SCE's instructions.   I was trying to do everything correct knowing that these copper gaskets were known to leak coolant.   Guess I just missed the surface finish.  

I'm contemplating hand stoning the block in the car...although not looking forward to it.  Copper orings arived, just waiting on the ajusa gasket.

#18 ucw458

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Posted 02 October 2019 - 05:00 PM

Actually it's 90 per ARPs instructions.

The ARP page listing for G54B head studs
https://arp-bolts.co...p?RecordID=1247

The instructions from the link on that page.
https://cdn2.arp-bol...ns/207-4202.pdf
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#19 Dad

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Posted 02 October 2019 - 05:44 PM

Finish looks a bit rough, but you will have machine marks with  cutters,  Pictures can be deceiving,  Your protrusion variance of .003 concerns me, I would feel better if within .001, however that could be hard to measure if the wire isn't tight down in the bore,  Be sure there are no chatter marks in the groove for the wire, have seen that cause uneven protrusion.  ends need filed flat to remove chisel point from cutters and should be put close to bolt/ stud holes.  when installing wire I use an aluminum flat block and small hammer,  you don't want to flatten the wire at all.  Normal copper with 041 wire should have 1/3   of thickness protruding along  with a receiver groove in the head .060 wide, but for the life of me I can't recall the depth on the receiver groove.

Since the Ajusa isn't a true MLS ( no one makes an MLS for the G54B) gasket you may get away with  a rough finish,  but .007-.010  protrusion will be too much in my opinion.    I would have it about .004 into the fire ring,   You could put copper wire in then file it flush to the deck  to eliminate using wire.  Be sure to look close around bolt hole and water holes for cracks.

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#20 croquest87

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Posted 02 October 2019 - 05:44 PM

View Postucw458, on 02 October 2019 - 05:00 PM, said:

Actually it's 90 per ARPs instructions.

The ARP page listing for G54B head studs
https://arp-bolts.co...p?RecordID=1247

The instructions from the link on that page.
https://cdn2.arp-bol...ns/207-4202.pdf
You are correct they are torqued to 90 w lube that is provided.

Edited by croquest87, 02 October 2019 - 05:59 PM.





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