2 Cometic Head Gaskets Fail the Same Way - Ideas?

[MY1GDSM]

Gasket Surfaces aside for a minute...

Have you considered using a different Head gasket? Personally there is only 2 MLS gaskets I would ever use OEM an The Felpro Perma-torque...

I had some issues close to this with Titan ISC Copper gasket years ago an Switched it out for a OEM Composite gasket copper sprayed with Regular APR's an never had any issues running 30psi on E85...

I also had a different machinist surface the head though as well... .

 

[VETDRMS]

I haven't been able to find the JV311 paper locally, NAPA no longer sells Victor. CarQuest can get it but it would take 5-7 days.

Gasket Surfaces aside for a minute...

Have you considered using a different Head gasket? Personally there is only 2 MLS gaskets I would ever use OEM an The Felpro Perma-torque...

I had some issues close to this with Titan ISC Copper gasket years ago an Switched it out for a OEM Composite gasket copper sprayed with Regular APR's an never had any issues running 30ps on E85...

I also had a different machinist surface the head though as well... .

I have considered the Felpro PermaTorque gasket. The main issue is I really need a 87.5mm bore due to the material taken out of the chamber. At 87mm there may be just a hair of overhang into a couple spots on the intake side of the chamber. I could use the 4G64 DOHC OEM composite gasket as well. These are options I am considering but I will check the surfaces first. I honestly don't feel like using another Cometic.

Update:

I think I found the problem.

I checked the deck of the block and overall it is very flat. In the dark with a flashlight nearly no light shines through with the straight edge straight across the block in the back, middle, and front.

Checking diagonally from the front left to the back right I could fit a 0.0015" feeler under the bar between cylinders 2 and 3 with some drag, a 0.002" feeler would not fit. This was the only bar orientation that had any gap. I checked end-to-end in the back, middle, and front as well as front to back and the 0.0015" gauge had heavy drag under the bar at all spots checked. If I went diagonally from back left to right front it the 0.0015" feeler had heavy drag.

I moved the bar in from the top right corner when check diagonally to identify the high spot. The high spot is marked out with sharpie in the picture below. If the end of the bar was not in this area there was no gap between 2 and 3. This was the one place I could not get the large lapping block into very well due to the timing cover and motor mount. I think this is the cause of the high spot on the block, but overall it is very flat.

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I then checked the head and it was immediately obvious there was a big dip from the outer edge of cylinder 2 to the outer edge of cylinder 3. With the bar end-to-end there was a 0.004" gap at the outer edges of 2 and 3 and up to 0.005" in the middle, which would explain the failure at the front/back of 2 and 3.

Diagonally there was a 0.006" gap between cylinders 2 and 3!

The dip was caused by the amount of lapping that had to be done to remove the cut marks from the decking. The head is being taken to a machine shop that can cut to the required 50RA or smoother finish tomorrow. Unfortunately, after all this cutting/lapping there is very little left to cut off the deck before it is into the service buttons. This will likely be the last time the head can be refinished, which sucks for how much work has been put into it.

The chambers are going to end up smaller, I might use the FelPro PermaTorque, which is 0.055" compared to the 0.066" gasket that was on there, so my compression may be as high as 10.2:1, which just puts more stress on the gasket.

I'm just glad I can point to something as the culprit and hopefully remedying it will fix the issue.

Thanks everyone!

Update 2

Some days the DSM gods just give you the finger.

I dropped the head off to be decked this morning but after we looked a little closer there was an issue with the exhaust seats. The head was just repaired and all new seats were installed. I thought we were putting 7000 series powdered metal seats in but apparently some chrome-nickel seats were installed (for turbo application), but it looks like they were just too soft, a few of them got pounded pretty good and I am lucky I didn't burn a valve.

I could re-do the seats but this cut would be the last that could be done on this head before it hit the service limit, and my compression ratio is already too high. It looks like I am building a new head, starting with a virgin core, which should drop my compression at least a half point. I will probably use the Supertech coated intake and Inconel exhaust valves on this one.

I will be buying my own straight edge to check things in the future, thanks for the help.

 

[BogusSVO]

Glad you found the issues!

now here is a bit more info.
I think that you say you have hit the service limit, that you are refering to the "Cast injection points" on the bottom of the head.

If that is the case, please read this thread
http://www.dsmtuners.com/forums/cylinder-head-short-block/408333-thinking-buying-head.html
look at the pics posted in #6 and #7 they are circled in red, these are the cast injection points, my reply is #9

the ONLY way to figure if you are at or past the service limit, is to measure the head thickness (post #9 has that info)

For a straight edge, I would recomend that get a machinist "round bar" it will be of more use when dealing with OHC engines
here is a link....
2011 Full Line Catalog | Goodson Tools & Supplies for Engine Builders
page 130 bottom left corner of the page

 

[VETDRMS]

There are three reasons to make the decision to go with a new head. The first being the chamber size from the machine work and wanting to lower compression with a stock sized chamber. When this head was first cut the chambers were 43.5cc, they haven't been measured since but another 0.0035" had to come off the head after the first time it was cut to clean up. If I switch to the FelPro PermaTorque gasket my compression ratio would be almost 10.2:1, if I build a new stock-chamber head it will drop it to 9.6:1, which will help with the pump gas tune.

The second is that this cut would be the 4th time it has been decked to my knowledge, possibly more. Being that the head is 0.006" out at the middle it would take a pretty significant cut to get the deck flat.

The third reason is that the chambers were enlarged in diameter when the chambers were cut with a flycutter to unshroud the valves. This was welded and filled but the diameter is still slightly larger than stock, so even with an 87mm gasket there is a very slight amount of chamber overhang on the intake side, which required a custom 87.5mm gasket. With a new stock head I can use the PermaTorque 87mm gasket with no overhang.

I am disapointed, for sure, but this seems like the best solution at this point. I really wanted to get some dyno/track time with this head as it ran very good and I think the port work was good.

Thanks for the link to the round bar, I might get one of those.

 

[BogusSVO]

the combustion chamber closes up appox 1cc per .007 cut

measure the head thickness from the valve cover rail to the head deck surface

measure all for corners

new head thickness is 5.200-5.202

 

[VETDRMS]

I will check it when I get a chance, thanks.

On a slightly different topic I am trying to decide which valves to put in the new head. I am leaning toward using the Engnbldr valves again. These are the same EV8 material used in the Ferrea 6000 series valves. Another alternative would be the Supertech coated intake and Inconel exhaust valves. The Engnbldr valves were in the last hood and looked good upon disassembly, considering how beat up the seats were.

 

[BogusSVO]

I have no probles out of the engbldr valves, I have installed at a min of 50 sets, not Just the 4g valves, but small block ford, 2300 ford, and small block chevy

get the valves ground and see how they fair, if they grind out good, use them, if not order another set.
when I spoke with him a few days ago, he was out of stock 4g valves and had a few sets of the 1mm os still instock ( the 1mm os are my faves, if you are replacing the valves you may as well go larger)
He ordered some more at the end of march but they are still a month or so out before he can get them.

 

[VETDRMS]

The new head should be done tomorrow. I spent some time this weekend cleaning up the deck surface and checking it for flatness.

I started with 400grit and ran the lapping block over the deck until most of the marks where it failed had cleaned up. I then checked flatness and there were no points a 0.0015" feeler gauge would slide. I then shut off all the lights and looked for light under the straight edge and I could see no visible light under the straight edge anywhere on the deck other than at the spot the gasket failed the worst. It wasn't rough but you could see where the little tracks were cut into the deck from where it was leaking. The light coming through at this point was split up like it was coming through those little tracks.

After that I went over the deck one last time with 600grit until the main failure point was almost not visible. I then checked the deck for flatness once more, but this time I took the back half of my 0.0015" gauge and lapped it down to between 0.0005" and 0.001". There was one spot on the deck where it would slide at the 0.0005" thickness.

However, when checked with a light nearly no light was visible at the main point of failure, just a few faint beams. Just looking at it you couldn't see any light either time, the only way it was visible if I had my eye level with the block and a few inches away. I decided to stop lapping at this point as I didn't want to remove much material.

This is where the straight edge was when checking for light at the front failure points.

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However, once it was all cleaned up I could get the 0.0005" feeler gauge to slide under the straight edge between cylinders 2 and 3 when the bar was like this:

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With the straight edge in the following pictures the 0.0005" feeler gauge wouldn't slide in the middle or any other spots.

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Here is a picture of the deck without the straight edge:

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At this point I don't think there is really anything else I can do. The head should be perfectly flat this time instead of the 0.006" runout the other one had. Hopefully these surfaces are good enough to seal with the FelPro PermaTorque head gasket, which got here Friday.

Hopefully I will be following up with successful results once this is done, which should be this week.

Thanks for the help.

 

[BogusSVO]

sounds like you have covered it all, and checked it all thourghly, last thing I would check is the piston(TDC) to deck clearance. to see how much in the hole or out the hole the poston is.