Yes my leaks started after the first warm up, so if you dynoed already, you should be fine.

What I did to solve my coolant seeping problems (which was only on one side, passenger fortunately) was to get back in there and break the head bolts loose about 1/8th thurn, then go back and retorque them all in sequence.

I ended up torquing them to the 85 ft lbs with the ARP bolts.

THe first time I only torqued them to ~80 ft lbs. Again this was fine for one side but not the other. I re torqued both sides to 85 ft lbs.

 

Getting the GM bolts torqued took a TON of effort.

 

I am pretty sure you would have noticed by now.

 

This is a re-post of a thread I posted back in November, 2003 which has fallen off the archive.

This is an anecdotal as well as informational post so take it for what it's worth. I wanted to share this with you guys as a heads-up and possibly help someone else avoid the same problem in the future.

Last Oct.-Nov., forum member and good buddy Wt99C5, (Al, as I like to call him) helped me install a h/c package in my '02 which had 2917 miles on it at the time. What we thought was going to take a couple of weekends to finish up ended taking many more weeks, including pulling the heads 4 times before this problem was resolved. Needless to say, we got good at pulling the motor apart and reassembling and readjusting everything.

I'll say up front that the tuner I bought the package from, MMS, was not at fault here. In fact, Mike was quite helpful and just as interested as we were to track down the problem. The problem was the Cometic gaskets that I ordered with the package. Mike recommended these but had never experienced the leak I had with them.

Here's what we installed:

> MMS ported and polished cylinder heads, milled .030" to bump compression up with 2.08" Intake valves / 1.58" Exhaust valves and Rev 1116 Dual valve springs/Titanium retaners
> 229/229/112 MMS cam
> Comp Cam Chromoly hardened pushrods (.050" shorter than stock)
> RollMaster (Australia) True Roller Dual Timing Chain / Sprocket set
> ASP Underdrive pulley (I had to modify slightly to account for the timing set spacer thickness)
> Ported oil pump
> ARP head studs (amazing quality and strength and fantastic when you need to remove heads again like we did)
> Cometic Multi-layer Steel (MLS) cylinder head gaskets (great quality but a big mistake ordering these)
> Ported and polished Throttle Body
> Crank seal and water pump gaskets

After the install, we discovered a leak at the front, outboard corner of the passenger head. Coolant would slowly ooze between the head and gasket after heat-cycling the engine.



We surmised that we had a faulty Cometic head gasket and replaced it with a new one a week or so later. No dice. The second one leaked exactly in the same spot as the first, which I had sent back to MMS for their analysis.

Mike emailed me back with his assesment. He told me to note that the stock metal gaskets use a sticky sealant around the cooling passages and that GM probably does this because they take note of what the aftermarket does and incorporate this into their assembly process. Mike said the Cometic gasket was out before GM's metal gaskets were and that they probably noticed that a lot of engine builders using the Cometics were using copper sealant spray to prevent leaking so they decided to use sealant on their metal gaskets as a matter of course. Mike recommended using K/W 1612-12 copper gasket spray on the entire surface of both sides of the gasket before putting it back on. The sealant flows during torqueing and fills any potential crevices. He felt this would very likely solve the problem. We tried the K/W sealant on the third go-round on the passenger head gasket and - it stopped the coolant leak. However, now I had an oil leak in the same exact spot. Strange, but true.


Al and I did some more extensive research and measurements and came up with some pretty conclusive results which indicate why the gasket was leaking. It explains how oil could have been leaking out of the gasket and why I hadn't been able to attain a seal in the same location for the past month using different, new gaskets and sealant.

1) The Cometic has a .090" land around it's perimeter that must be engaged by the edge of the head all the way around to contain fluids (pic below). The stock gasket seals a substantial distance from the edge so that where the edge of the head is has no bearing on the seal.



2) The Cometic does not isolate the oil return galleys where the pushrods protrude in the head from the rest of the gasket like the stock gasket does. This can allow oil to migrate throughout the recesses of the gasket. No problem if the perimeter is sealed but if any part of the perimeter is not sealed, oil or coolant can leak through that breach. You can actually trace a path where the oil can enter the valley areas of the Cometic between the high land areas and seep all the way down to the lower stud areas.

3) I measured .118" of gasket protruding beyond the edge of the passenger head (pic below). This is where it was leaking. The edge of the head was not engaging the .090" raised land that the Cometic depends on for a good seal. The driver-side head, on the other hand, appeared to be engaging that area on the gasket and it had no leaks.



4) Below is a pic showing the raised land used on the stock gasket to seal the head (in yellow), the raised perimeter land the Cometic uses superimposed over the stocker (in red) and the faint line (H arrow in blue pointing to it) where the stock head casting impresses on the gasket.



Based on the above, I concluded that it's a hit-or-miss proposition as to whether these heads (earlier heads with the notch) will seal with the Cometics. The Cometic gasket depends on the inaccurate head casting and whether or not it extends far enough out to meet the perimeter land to attain a seal. On my driver's side I lucked out and it sealed. On the passenger side it appears the edge of the head was recessed just far enough back to not want to seal. So, the variations in the casting can affect whether or not the gasket will seal - we're talking 0.25% shrinkage (.040"/16") of the casting upon cooling when pulled out of the mold. The K&W sealant helped couldn't compensate for the mis-match between the head and gasket. I never applied the sealant to the driver-side head and it sealed perfectly because the head edge matches the Cometic's.

What bolsters this explanation is the Cometic gasket I sent back to MMS as faulty. Al and I didn't realize the significance of it until later in the process, but the impression the corner of the head made on that gasket was inside the perimeter land within the valley area allowing passage of the coolant. There wasn't proper engagement of the head on the gasket so it's no wonder I hadn't been able to get a seal at this corner. GM got it right with the stock gasket because they don't depend on the rough, inaccurate outer edge of the gasket for seal integrity. The above pic shows that the raised land is well within the confines of the primary pressure region the stud nuts put on the head. Plus GM uses sealant along the entire length of the raised land at a generous thickness.

The significance of my long-winded explanation above is that I believed we needed to go to another type of gasket if we were ever going to get them to seal - preferably one configured like the stocker. The one gotcha' is the little edge recess at the #5 and #6 cylinders on my heads which create a seal problem for the '02 style of gasket.

We ended up using the composite, earlier style '97-'00 GM gasket which fixed the leak once and for all. We also used them on Al's heads when we subsequently did his MMS h/c install and they worked on his as well. We couldn't find the Felpro's for our app at the time and had to account for the notch in the heads. The composite gaskets met all our needs.

I'm not impuning Cometic gaskets here as many use them successfully in similar and much higher hp applications, namely big bore and FI motors. As I said, take it FWIW.

Many thanks to Al for the monumental help and patience. Thanks to MMS for responding with suggestions and crediting us for the gaskets.

 

Surely if there was an issue then Cometic has corrected it by now? What about all the people that don't have any issues?

 

I just completed my 02 Z06 head swap, .040 Cometics with Permatex copper spray (one good coat on both sides because I did not want to take the chance of doing the work twice), multiple heat cycles, no issues (and I really expected one - watched oil and water like a hawk).

So count me in as another successful Cometic install.

 

Dan,

What did you do to prep the block?

I have a new set of AFR's on my workbench I am hoping to install this fall.

 

wow thanks for the write up!

So far the fort retorque of the PASSENGER SIDE has stopped the problem without the copper gasket spray. (wish I had read that before)

Funny that it seems to be the passenger side that keeps leaking.

I had an oil leak on the drivers side but it appeared to be from the valve cover.

 

I have a stroked 403 LS2 build up with AFR 225 heads and I too use Cometic gaskets. I had slight coolant leaks after building this motor twice, Once for the initial build and then after crank issue. But I found that GM sells a coolant sealant for the system. It is little pills that are made up of pecan shells and wheat (no ****) I used them and that stopped the little coolant leaks seaping out of the heads. The oil issue I don't think is a headgasket problem

 

I like taking pills, seems like a good solution....

I think the smoke is unburnt or not completely combusted gas as my eyes were watering real bad, and my throat was stinging. My feet tingled a little too..... No, I did not take any pills....

 

So did the ARP

 

Well.. I did what you are not supposed to do I suppose..

I started out with the chemical (Permatex) gasket remover (did literally nothing to the original GM MLS gasket remnants), then HD plastic scrapper (again, no real progress).. Defaulted to the old stand-by, hand-held razor blade tool.

Very carefully (held at correct angle, using correct side, etc.) started from one side to the other while holding a running vacuum over the work area to insure the material would not fall into the block. Time consuming but very, very affective. Did not go crazy trying to get a shinny bare-metal surface but made sure there were no raised areas (if the imprint or micro-film of the old gasket remained - so be it). As you know Cometic provides a surface smoothness specification - I don't have a way to measure this so for me it was years of motor building experience and feeling the surface by touch to determine when an area was complete. I followed this with a brake cleaner on a rag wipe down just before setting the gaskets in place.

The biggest (potential) gotcha in my mind is if you can somehow guarantee (maybe have an assistant?) that the head will be placed on the block perfectly the first time.. On one side I had a very slight initial mis-alignment and of course even after 45 mins of drying time the copper spray was still tacky (maybe it always stays that way to an extent); when the head shifted I could see a bit of the spray on the top edge of the gasket (intake side) had peeled back. Ideally you want the head to be placed squarely one time. If you had to remove it you'd end up cleaning the copper spray off of everything it touched, no fun I am sure. **edit** I just remembered you have ARP studs, no need to worry about head alignment during installation.

BTW, I shimmed the YT's this time, so I hope I have regained some credibility with you.

 

same experience from the worthles permatex gasket remover to the razor blade.

I can't emphasize enough how helpful the shopvac was in this process. From sucking the majority of the coolant out of the heads through the waterpump ports to using a brass fitting and clear silicione tube to remove what little fluid was in the bolt holes, vacuuming up the gasket leavins and the metal after flycutting. I even pulled the fluid out of the water pump before the I disconnected it.

When it saved me the most was when I pinched my oil pump gasket. and just like someone posted a piece of the o ring drpopped in the sump pick up. There was absolutely nothing I could do to keep if from falling in. So I thought I would give the old shop vac a try before I dropped the oil pan to remove and clean out the sump.

I just put it on there for a quick second before I saw that it was pulling up the oil and pulled it off.

When I checked inside, ureaka! 1/4 O ring!