Multi Layer Steel Headgasket Cometic or Scheid I want updates!!
09-06-2007, 09:07 PM
#16
Chapter President
It's strange to me that no one from Scheid suggested using the 14's? Not saying it didn't happen, but it was stressed to me that using 14mm studs was important.
John_P asked this question before... Who did you speak with from Scheid and at what shop?
John_P asked this question before... Who did you speak with from Scheid and at what shop?
09-06-2007, 09:28 PM
#17
Administrator
ok i am gion to start over and give the whole story instead of blaming others first. when i ordered my parts i was not told about the 14mm studs just asked if i need to buy studs to. i said no i have just bought arps earlier that day before calling scheids. i had the cyl head surface at the place i work. the finish was basically a mirror finish. i check the block with a straight edge before preping it and afterwards and i could not get a .0005 feeler gauge under it any where. installed everything and torqued the head to 96ft/lbs and ran. put oil in the coolant and found an oil leak on the drivers side above the inspection plate on the side of the block. retorqued to 122ft/lbs still putting oil into coolant and leaking oil. retorqued to 150ft/lbs and no more oil in coolant but still the oil leak. when i called scheids for some help it took three days to get to talk to the right person and was told they would call me, i had to call them. first was told it was because i didnt use the 14mm studs. and then the leak was blamed on coming for every other possible place besides the HG. after basically getting no respect or the possiblity that it could be the HG i told myself oh well lesson learned. i never once asked for my money back or a new gasket, just help. as far as how i found where the leak was coming from i had to spay down the side of the area with brake cleaner star and run the enige for about 10 mins stop and the star removing every thing to get behind the injector lines. with the shape of the head i had use a mirror and light to see the leak. the oil spot was at the top of the of the bottom gasket leaving part of the steel plate oily but the top edge and top gasket were dry. i ran the engine again for a short time and recheck to se where it was coming from just double check and make sure it was between the the steel plate and gasket. i have already bought a stock gasket to install when i have the down time.
Jvenne:
As I read your post I saw something right off that concerned me. You said at the beginning "you torqued the head to 96ft. lbs. and ran." By saying "you ran" I am assuming you started and ran your engine RIGHT AFTER you did the 96 ft. lb. torque of the ARP nuts, is that right?? I have no problem with being corrected on this, but it is my understanding and past experience that ALL three of the torque sequences are to be done first, then after that you start your engine, let it warm up and then perform a second retorque. I do not believe it is proper procedure to run the engine after each torque sequence, but things may have changed from ARP on that. Also, on 12mm studs, it has been my understanding that they are torqued to 75, 96, and then 122, however, I guess you have the high dollar ARP 12mm studs that are in fact taken to 155 ft. lbs.
As far as any blame on the size of the studs (12mm vs. 14mm studs) you have already read what DTR Member Mike D. has said about "how Scheid Diesel had recommended the 14mm studs to him" in conjunction with the MLS gasket he wanted in his truck. You said yourself in your post that "you told Scheid Diesel you already had the 12mm ARP studs." I fail to see how that is Scheid Diesel's fault???
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John_P
09-06-2007, 09:38 PM
#18
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I know Scheid recommends using the 14mm studs with that gasket, torqued to 155 ft. lbs.
I will say one of the advantages of going with the Schied gasket is the lower compression using the Scheid .090 vs .060 from Cometic. My guess it that it probably lowers the compression about a point. I would have to ask those who are stronger suited in the math department to figure it to be sure. Banshee? Hohn?
I will say one of the advantages of going with the Schied gasket is the lower compression using the Scheid .090 vs .060 from Cometic. My guess it that it probably lowers the compression about a point. I would have to ask those who are stronger suited in the math department to figure it to be sure. Banshee? Hohn?
For a 17:1 HO, you're looking at 14.3:1 with the Cometic .060 and 13.3:1 with the Scheid .090 gasket.
The 16.3:1 SO trucks will be lower still, but proportionally not as much of a loss. I frankly don't want to run those numbers right now-- but it would br proportional. Just figure if the 17:1 truck loses "x" percent of ratio, the 16.3:1 truck loses the same percentage.
IMO, that's a pretty drastic drop in either case. I wouldn't go beyond the .020 thicker Cummins gasket.
JMO
09-06-2007, 09:56 PM
#19
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the gaskets would be .060 and .090 overall .070 is stock as far as I know and .090 is the .20 over marine. so they would give no where near the compression drops as sugested by hohn
no one has mentioned the machine surface difference between the cr and the older motors. kta and I just had this discussion tonight.
no one has mentioned the machine surface difference between the cr and the older motors. kta and I just had this discussion tonight.
09-07-2007, 01:06 AM
#21
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Because if a good deal of material is needed to be removed from the head surface then you could have issues with the spray angle of your injectors as well as piston to valve clearance when a aftermarket cam is installed ( my Helix2 for instance), so to keep everything correct you can add the amount removed from the head on to the gasket that you order from Cometic, but seeing how my head was in really good shape I only needed the stock thickness, now mind you im not a machinist so all info as it was explained to me is just 2nd hand, but I can tell you this, my truck runs very very hard and is holding 60 psi no problem
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09-07-2007, 01:08 AM
#22
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09-07-2007, 01:20 AM
#23
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the gaskets would be .060 and .090 overall .070 is stock as far as I know and .090 is the .20 over marine. so they would give no where near the compression drops as sugested by hohn
no one has mentioned the machine surface difference between the cr and the older motors. kta and I just had this discussion tonight.
no one has mentioned the machine surface difference between the cr and the older motors. kta and I just had this discussion tonight.
09-15-2007, 12:52 PM
#24
Registered User
Heres a few things you need to know when using a Cometic MLS gasket.
First the head has to be machined to RA25, this is the roughness average. The smaller the number the smoother it is. Its also best for the block to be done. If the surface is rougher then run diminish the gaskets ability to seal properly. MANY of the machine shops still use a 75-90 RA, this is NOT GOOD. Also, make sure the head and block are clean and dry and that the head sits down evenly when installing, if you ding an embossment, it will weaken the gasket.
Many factories are using MLS gaskets as OEM because they are more durable, most of your competition cars use them as well.
First the head has to be machined to RA25, this is the roughness average. The smaller the number the smoother it is. Its also best for the block to be done. If the surface is rougher then run diminish the gaskets ability to seal properly. MANY of the machine shops still use a 75-90 RA, this is NOT GOOD. Also, make sure the head and block are clean and dry and that the head sits down evenly when installing, if you ding an embossment, it will weaken the gasket.
Many factories are using MLS gaskets as OEM because they are more durable, most of your competition cars use them as well.
09-15-2007, 04:40 PM
#25
Registered User
mopar2ya it needs a 50ra finish the lower the better. and the block only has to be flat, mls told me to use a small amount of ultra copper between the gasket and the block to fill any low spots, also the better the ra rating the better the seal. my head has a crankshaft journal finish around 15ra i could use it as a mirror. i ran into problems with my orings and so far love the mls its seen 80 lbs boost on my truck and holds solidly no leaks. im waiting on a custom gasket from them for my zz fab intake manifold. that is how much i like the gasket.
01-17-2008, 08:22 AM
#26
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finally got the down time and here is your update
[IMG]
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this is the bottom of the steel spacer plate, notice the oil around the push rod holes.
[IMG]
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this is the bottom gasket and you can see the oil on it around the push rod holes
[IMG]
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bottom of the head no oil. so after looking at this pictures it is very clear to me that my oil leak was coming from inbetween the top of the bottom gasket and the bottom of the steel spacer plate.
[IMG]
[/IMG]this is the bottom of the steel spacer plate, notice the oil around the push rod holes.
[IMG]
[/IMG]this is the bottom gasket and you can see the oil on it around the push rod holes
[IMG]
[/IMG]bottom of the head no oil. so after looking at this pictures it is very clear to me that my oil leak was coming from inbetween the top of the bottom gasket and the bottom of the steel spacer plate.
01-17-2008, 10:00 AM
#27
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Using Hohn's numbers I've determined that a .20 over gasket lowers compression by less than one compression point. I came up with .82-.90 compression drop depending on which example's ratio I used *looking for the smiley to poke Hohn with* The math's not perfect, but good enough to answer the question at hand.
01-17-2008, 10:01 AM
#28
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the gaskets would be .060 and .090 overall .070 is stock as far as I know and .090 is the .20 over marine. so they would give no where near the compression drops as sugested by hohn
no one has mentioned the machine surface difference between the cr and the older motors. kta and I just had this discussion tonight.
no one has mentioned the machine surface difference between the cr and the older motors. kta and I just had this discussion tonight.
Spill it 
01-18-2008, 09:18 AM
#29
Registered User
Because if a good deal of material is needed to be removed from the head surface then you could have issues with the spray angle of your injectors as well as piston to valve clearance when a aftermarket cam is installed ( my Helix2 for instance), so to keep everything correct you can add the amount removed from the head on to the gasket that you order from Cometic, but seeing how my head was in really good shape I only needed the stock thickness, now mind you im not a machinist so all info as it was explained to me is just 2nd hand, but I can tell you this, my truck runs very very hard and is holding 60 psi no problem.
.1) I talked to Don about this after the machine shop pulled .028" off my head and he told me that there is actually more piston to valve clearence at TDC with the H2 than the stock cam
2)Injector spray angle is easy to change back with sealing washer thickness.
01-18-2008, 09:22 AM
#30
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