Why not to spray MLS headgaskets: Discuss

[Spoolin98]

Doug, thanks for explaining your technique.

And for the record, I have spayed al least 100 mls gaskets with copper spray and have yet to see any failure.

Thats what I like to hear.

 

[Scrymerr]

I did not deck my block or spray my headgasket and it was fine with 25+ psi for many months (as i said earlier) before I blew the rings, but I will spray my next MLS HG.

 

[pneumo]

It seems DCX has changed policy regarding spraying MLS HG. Was this due to some kind of change in the HG itself? I noticed on Cometics website they say their Viton coated MLS HG don't need spray, perhaps DCX has updated their design and won't need spray anymore?

It may be difficult to give out one recomendation since we have so many different HG available. These gaskets will be installed on heads/blocks with varying levels of flatness and surface smoothness, plus various levels of mechanical skill and experience. I'm not sure if it can be said with certainty, 'do this, don't do that'. Well, except for 'follow manufacturers instructions.'

There have been plenty of threads about HG failures in these forums. Most of the time it gets blamed on the HG. Perhaps we should look harder at the method used to install each type of HG? ie. Mitsu composite, Mitsu MLS, Cometic MLS, copper, generic autopartstore, ect. Plus, was it sprayed? Head bolt/stud torque? Torque sequence? Torque cycled? Was the block and head resurfaced, how flat, and how smooth? Was all machine oil residue cleaned off before the HG was installed? Was the sealing surface of the HG handled with oily, dirty fingers?

 

[Doug99RS]

It seems DCX has changed policy regarding spraying MLS HG. Was this due to some kind of change in the HG itself? I noticed on Cometics website they say their Viton coated MLS HG don't need spray, perhaps DCX has updated their design and won't need spray anymore?

It may be difficult to give out one recomendation since we have so many different HG available. These gaskets will be installed on heads/blocks with varying levels of flatness and surface smoothness, plus various levels of mechanical skill and experience. I'm not sure if it can be said with certainty, 'do this, don't do that'. Well, except for 'follow manufacturers instructions.'

There have been plenty of threads about HG failures in these forums. Most of the time it gets blamed on the HG. Perhaps we should look harder at the method used to install each type of HG? ie. Mitsu composite, Mitsu MLS, Cometic MLS, copper, generic autopartstore, ect. Plus, was it sprayed? Head bolt/stud torque? Torque sequence? Torque cycled? Was the block and head resurfaced, how flat, and how smooth? Was all machine oil residue cleaned off before the HG was installed? Was the sealing surface of the HG handled with oily, dirty fingers?

All of that is pretty much why I moved it out of the Tech Articles and in to this Head and Engine Block section. As you pointed out there's just too many discrepancies in the job of replacing the headgasket with the people we have reading these threads.

To the best of my knowledge DCX has NOT changed anything about the headgasket itself as far as a coating. The change in policy was brought to my attention at the Cam in Head class I took earlier this month. The course covered the DCX 2.4L (for all intents and purposes it's the 2gnt/neon motor), the 3.7/4.7L Jeep engine, the 2.7L DOHC Stratus/LH/LX platform engine. The "no-spray" instructions started with these engines and was stressed even more when we learned about the New World Engine (1.8L, 2.0L, 2.4L out of the same block). Tolerances were so tight on the NWE that they said 1. spraying wasn't necessary, and 2. spraying does the heat cycle damage explained in the original post.
Doug

 

[pneumo]

So it seems DCX has designed the HG, block and deck surfaces and installation technique to work together as a system. Perhaps the spray is another uncontrolled variable that they designed to eliminate.

I think we might be able to make some general recomendations for the DSM HG. What do you think of these:

1. Stock unsurfaced head and block- use Mitsu composite HG.
2. Resurfaced block and head with smooth finish- use MLS HG.
3. Resurfaced head/stock block or resurfaced block/stock head- use magic enchantations and voodoo dolls?

Whether to spray it or not is optional. If copper spray is used, do not spray it on the block or head. Follow instructions on the can and spray lightly and evenly from about 12 inches away. Use multiple coats if a thicker coating is desired. Do not spray so heavily that the spray runs off. If it does, wipe it all off and start over. Be careful not to get a buildup of spray between the layers of the HG.

Headbolt/ stud torque technique. I'm not going to write it all here, I just wanted to emphasize the importance of proper torque sequence, torque up to full pressure in steps of about 15 to 20 ft-lbs each, and cycle the studs/bolts through 3 cycles while untorquing in steps also. Oh, and the first time the head is torqued it should be at a very light torque, about 10 ft-lbs, and the torque sequence should be repeated at the same torque setting since the HG will crush down as you go, leaving the first bolt in the torque sequence looser than it was when you first started.

Good? any additions to this?

 

[Spoolin98]

pneumo "cycle the studs/bolts through 3 cycles while untorquing in steps also. Oh, and the first time the head is torqued it should be at a very light torque, about 10 ft-lbs, and the torque sequence should be repeated at the same torque setting since the HG will crush down as you go, leaving the first bolt in the torque sequence looser than it was when you first started."

Can you explain this better, I'm a bit confused?

 

[pneumo]

pneumo "cycle the studs/bolts through 3 cycles while untorquing in steps also. Oh, and the first time the head is torqued it should be at a very light torque, about 10 ft-lbs, and the torque sequence should be repeated at the same torque setting since the HG will crush down as you go, leaving the first bolt in the torque sequence looser than it was when you first started."

Can you explain this better, I'm a bit confused?

OK. The idea behind it is that the MLS HG have beads rolled into the edges of every hole, and these edges are raised up. When you tighten the first bolt the HG crushes down slightly, then as you tighten the other bolts the HG will crush down a little more, leaving the first bolt loose. The idea behind the torque sequence is that the inner bolts should be tightened first so the gasket stays flat. That's why the torque sequence starts from the inside and goes out. It's sort of like a rolling pin flattening dough, you want to squeeze it from the inside out so any irregularities are squeezed out. If the bolts at the outside ends of the head are tighter than the inside bolts the gasket might arch and wrinkle slightly. By going over them again at about 10 ft-lbs you're making sure that every bolt/stud is starting with the same torque. You don't want the outer half of the bolts to be tighter than the inside bolts.

Untorqing should be done in steps, too. The untorque sequence is the opposite of the torque sequence. It's in the manual.

I also like to clean the block and head with a clean, lint free rag and some kind of non-residue cleaner like acetone or brake parts cleaner, and I'll clean it until a white cloth doesn't show anymore dirt. I like to make sure the coating on the HG has every chance to bond with bare metal. I handle the HG by the edges, like an old vinyl record, so I don't get any dirt, oil, or even fingerprints on the HG. Bare metal on virgin HG. :thumbup:

PS I dont use copper spray anymore. For someone who doesn't have the time to pay close attention to details spray may be a quick and easy way. For me, I'm an enthusiast, I don't make a living by working on others cars, so when I work on my car I can take as much time as I need and sweat the finer details all I want because that's what makes me happy.

So far this method has held my Cometic HG up to 25 psi of boost on a daily basis for about 8 months plus a trip to the track where it saw 28 psi with a 30 psi boost spike. Best MPH was 123.7 in a 3160 pound car including my 175 pound butt. HP calcs put that around 465 HP.

 

[Doug99RS]

So it seems DCX has designed the HG, block and deck surfaces and installation technique to work together as a system. Perhaps the spray is another uncontrolled variable that they designed to eliminate.

I think we might be able to make some general recomendations for the DSM HG. What do you think of these:

1. Stock unsurfaced head and block- use Mitsu composite HG.
2. Resurfaced block and head with smooth finish- use MLS HG.
3. Resurfaced head/stock block or resurfaced block/stock head- use magic enchantations and voodoo dolls?

Whether to spray it or not is optional. If copper spray is used, do not spray it on the block or head. Follow instructions on the can and spray lightly and evenly from about 12 inches away. Use multiple coats if a thicker coating is desired. Do not spray so heavily that the spray runs off. If it does, wipe it all off and start over. Be careful not to get a buildup of spray between the layers of the HG.

Headbolt/ stud torque technique. I'm not going to write it all here, I just wanted to emphasize the importance of proper torque sequence, torque up to full pressure in steps of about 15 to 20 ft-lbs each, and cycle the studs/bolts through 3 cycles while untorquing in steps also. Oh, and the first time the head is torqued it should be at a very light torque, about 10 ft-lbs, and the torque sequence should be repeated at the same torque setting since the HG will crush down as you go, leaving the first bolt in the torque sequence looser than it was when you first started.

Good? any additions to this?

I wish there were more dealership technicians on the forum that could speak for other manufacturers as well. While I seem to be the only one bringing this up from DCX training I DON'T think it's going to be a DCX only procedure in the coming months and years.

If I had to make a change to your numbered suggestions it would probably be something more like this:
1. Stock unsurfaced head and block- use MLS with spray
2. Resurfaced block and head with smooth finish- use MLS HG.
3. Resurfaced head/stock block or resurfaced block/stock head- MLS with spray.

Also, I would not recomend wiping the headgasket. It may put debris from the rag on the gasket and most shop rags are cleaned with an oil based solvent. I've drowned many a HG and never saw them come back and I don't think wiping it once sprayed would be a good idea.

Now one might say "Why did you bring this up if you're just going to promote spraying it unless in ideal/perfect conditions?" and the only thing I can answer with is that in all the cases where I've read an MLS leaking/seaping none of them were sprayed. I think there's too many variables out there to include the "Fully blown" category of MLS's because we can always go back to boost levels, surface prep procedures and so on. But it seems like not spraying promotes minor failures/nuisances.

I also think that for the audience this is also the best recomendation given the fact that most people out here are NOT going to mill the head, block, use MLS and torque everything EXACTLY like you're supposed to. I think they might get 2/4 or 3/4 but not all of them. As such I think that's the best suggestion to try and stand behind.

Edit: also on the torque step procedures, metals change shape when torqued down (ie. dodge viper makes about 20 extra horsepower by having a dummy head torqued down before machining the cylinder walls). When you untorque the head or any component in the reverse order you releive pressure properly which helps prevent warpage.

 

[Spoolin98]

Thanks guys, well put.

 

[insanewayne]

If anyone here is pulling off there head, NOT getting it resurfaced and tossing it back on, they shouldn't be working on a car.

 

[pneumo]

Agreed, the factory tolerance for DSM head and block surface isn't that flat. The specs show the standard surface at 0.002", and the service limit is 0.008" of uneveness. Doug, what is the flatness for the new DCX motors? When I had my motor rebuilt I asked the machinist how flat he could make the surfaces, and he said he could get to 0.0005" (half a thou). seemed good to me

 

[Spoolin98]

0.0005" (half a thou)

Thats 5 ten-thousandths just to let you know.

 

[bjones18]

If anyone here is pulling off there (their) head, NOT getting it resurfaced and tossing it back on, they shouldn't be working on a car.

Interesting. Many people do just that without problems. Including professional builders. How do you plan to account for the change in compression and timing, thicker gasket each time? How many engines have you rebuilt to gain this perspective?

 

[Doug99RS]

Interesting. Many people do just that without problems. Including professional builders. How do you plan to account for the change in compression and timing, thicker gasket each time? How many engines have you rebuilt to gain this perspective?

Personally, and professionally I've pulled heads and NOT machined them either. There's only a few that I DO send out and that's when over-heating is suggested.

Obviously a head can't be milled but so much and but so many times. It's not really... that is it SHOULDN'T be a case of keep milling and stacking gaskets to compesate. I can't see someone pulling a head 3-4 times and expecting it to be good to use regardless of whether you mill it or not. If you pull it that many times in the life of the car I question the quality of ones work or choice of parts more than the manor in which this discussion was really brought about.

As for the new spec of the New World Engine they say there are numerous areas that are machined down to 25 microns or 0.0010" if I got my conversions right. Don't quote me and burn me at the stake if I'm wrong, I'm working on a short schedule tonight with no text books in site. But here's a write up I did on my local forum about the engine:
http://www.carolinadsm.com/forum/showthread.php?t=17239&highlight=GEMA

I'll check back later and see if I can't find the exact numbers for you.
Thanks,
Doug

 

[92awddsm]

Personally, and professionally I've pulled heads and NOT machined them either. There's only a few that I DO send out and that's when over-heating is suggested.

I can't see someone pulling a head 3-4 times and expecting it to be good to use regardless of whether you mill it or not. If you pull it that many times in the life of the car I question the quality of ones work or choice of parts more than the manor in which this discussion was really brought about.


Doug

If anyone here is pulling off there head, NOT getting it resurfaced and tossing it back on, they shouldn't be working on a car.

My head has been removed and reinstalled several times. First time, the block and head were machined during the rebuild. The second time was for swapping the composite hg out for a cometic hg. The third time was for a valve spring change. The fourth time was for an engine freshen up. The fith time was for a cometic hp hg. I have only machined my head once and it is still sealing pefectly. I dont see a need in surfacing unless you overheat and warp it, the gasket blows and you burn it betwen 2 cylinders, or corrosion from the water ports has gotten the best of the sealing surface. If the finish and tolerences check fine, there is no need to resuface.

 

[Suparata]

Personally, and professionally I've pulled heads and NOT machined them either. There's only a few that I DO send out and that's when over-heating is suggested.

A lot of people do that and that's not good. A head that has spent some time in service should be degreased and resurfaced no matter what. Even if it only means taking .002" it is still more than worth it. And a few thousands of the head surface does not mean anything.
It is funny that I was just working on a set of heads that pressurized the radiator and for the life of me I couldn't find any place where a .001" feeler gauge goes in. You could however see the marks around the fire ring so I made it another project. The pictures show 3 steps of machining: .001", .003" and .005" cuts.
You make your call.
http://www.engintecs.com/gallery2/main.php?g2_view=core.ShowItem&g2_itemId=3378

 

[Scrymerr]

Personally, and professionally I've pulled heads and NOT machined them either. There's only a few that I DO send out and that's when over-heating is suggested.

Obviously a head can't be milled but so much and but so many times. It's not really... that is it SHOULDN'T be a case of keep milling and stacking gaskets to compesate. I can't see someone pulling a head 3-4 times and expecting it to be good to use regardless of whether you mill it or not. If you pull it that many times in the life of the car I question the quality of ones work or choice of parts more than the manor in which this discussion was really brought about.

As for the new spec of the New World Engine they say there are numerous areas that are machined down to 25 microns or 0.0010" if I got my conversions right. Don't quote me and burn me at the stake if I'm wrong, I'm working on a short schedule tonight with no text books in site. But here's a write up I did on my local forum about the engine:
http://www.carolinadsm.com/forum/showthread.php?t=17239&highlight=GEMA

I'll check back later and see if I can't find the exact numbers for you.
Thanks,
Doug

I totally agree. I have pulled heads before and run them (although using composite HG) without having them decked. If the car has not overheated chances of it being fine are a lot greater than people think. I don't know why people think that every time you pull a head it has to be decked. I know aluminum is softer than iron, but if you follow torque/detorque sequences and specs, it shouldn't be a big deal.

Dan

 

[Doug99RS]

A lot of people do that and that's not good. A head that has spent some time in service should be degreased and resurfaced no matter what. Even if it only means taking .002" it is still more than worth it. And a few thousands of the head surface does not mean anything.
It is funny that I was just working on a set of heads that pressurized the radiator and for the life of me I couldn't find any place where a .001" feeler gauge goes in. You could however see the marks around the fire ring so I made it another project. The pictures show 3 steps of machining: .001", .003" and .005" cuts.
You make your call.
http://www.engintecs.com/gallery2/main.php?g2_view=core.ShowItem&g2_itemId=3378

I understand that even though we take measurements in certain spots it's not a perfect reflection of the entire surface being measured. But there are specifications out there saying what is acceptable and what isn't and how to correct the condition in the event it's not good. But at this point I can honestly say that 90% of the cylinder heads pulled off by myself and co-workers at various dealerships in two different states my last 8 years doing this have NOT been milled.

Now you could say everyone working at Chrysler/Jeep/Dodge dealerships are retards but honestly that would just be a diversion from the overall picture. The industry as a whole takes the same approach as I do. If it's not overheated and not a comeback after replacing the headgasket then we're going to do the checks as described in the service manual, as instructed by the older technicians that have been doing it 20+ years and by following the instructions given to us by the people entrusted by the manufacturer to train dealership mechanics.

Machining is the best way. It's the best for performance, it's the best for daily driven cars and it's simply the best way. But it's not the only way that works for the life of the car.
D

 

[bjones18]

A lot of people do that and that’s not good. A head that has spent some time in service should be degreased and resurfaced no matter what. ...

I am not a master builder. However, I talk to a few on a regular basis.

One guy (racing since '60s, builds/sells cars, races several rails and others 7-8 sec cars)sold his top-fuel dragster because to be competitive he had to rebuild after every race - $$$. He did not machine the heads for each rebuild.

By the way, he laughs at the guys who pour money into their engines to run 8 sec.

 

[TSIfreek]

Mitch was talking about a head that has been on the engine for a few seasons needs to be milled to get the best possible gasket seal not a motor that is taken apart every other race.

 

[insanewayne]

I wasn't mostly refering to a scenario where let's say you think you car is due for a HG...it's been over 100'000 Km's, or lets say you have a stock car...and are ready to throw in some ARP's.....

If you poppin your head 4-5 times a year for modifications then no, check the specs, and huck it back on.

Alot of people reading this are guys starting out, and giving the impression that you can take a talon, that you just bought, or have owned for a couple years and added a few bolt ons to, and pop the head on and off without machining it is bad.

 

[Doug99RS]

Alot of people reading this are guys starting out, and giving the impression that you can take a talon, that you just bought, or have owned for a couple years and added a few bolt ons to, and pop the head on and off without machining it is bad.

This is one of the reasons I try to go in to alot of detail and be very precise when explaining things. I wish more people would understand that it's not just the qualified mechanic or parts puller that is working on cars and advice needs to be worded to suggest the best idea for all viewers. If you want to get more technical then that's what alot of us like talking about. But a blanket suggestion should really cover EVERYONE and those who do pay attention to every detail. Kind of like why I moved this article in the first place from the tech articles because it didn't fit everyone.
Doug

 

[bjones18]

Mitch was talking about a head that has been on the engine for a few seasons needs to be milled to get the best possible gasket seal not a motor that is taken apart every other race.

There must be a difference.... can you predict which is harder on a head? I know which is harder on bearings, rings, valves, and pistons... hence the need to rebuild after every race. Wow that must be a HUGE thermal cycle on the head.

My point is... Many people including myself rebuild without resurfacing; for daily use, high performace, and extreme racing.

Rather than saying a person is stupid for not resurfacing (which may place the majority of successful rebuilds in the stupid category), a more helpful post would include specific information on when resurfacing is needed, and simple/accurate methods for measurment.

 

[insanewayne]

My bad

It's been discussed now, so I won't bother.

 

[Baron4406]

What about spraying with Hylomar?? I had a buddy who ran well into the 10's and he told me that was the stuff he used to stop head gasket failures. I used it and it worked well.