More carnage

[turbodan]

I figured I blew another HG at the dragstrip a few weeks ago. I've been driving the car a little, but the coolant level has been dropping, so It came apart last night. I got the intake off, and I went down the head one port at a time with a flashlight, just checkin it out. I get to number five and whats this? Layers of delicious frosting? No...



I was thinking the combustion chamber in the cylinder was going to really look like hell, but when I got in there, not really. The head has heavy wet carbon deposits, but no real signs of coolant leakage. It just looks like a cylinder thats been running low on compression, which figures since the MLS blew out between both 4 and 5 and 5 and 6. I had a few weak cylinders in there, which is good, because I thought the car felt faster than 110 traps before this little spat of engine failure.



As opposed to a healthy cylinder:



I'll probably clean up the pistons and run it. I'm a little worried about broken ring lands, but I dont know how to check that with everything together. We'll see how it goes with a new head...

[///ARINUTS...]

How does an MLS HG blow? Do you reuse it now or do you have to get another one? or parts of another one?

[turbodan]

In this case the head lifted off or deformed and allowed combustion gases to pass between the cylinders and into the water jacket. With an MLS, this destroys the Viton coating and can even crack the spring steel layers if they get hot enough.

I was planning on going back to the stock compression ratio anyway, so this isn't a big deal. I'll just buy another gasket.

[M. Holtmeier]

Man you are pretty insistent on wringing every last drop of worth from that short block!

It seems you had better luck with a stock gasket, eh? Any problems that may exist out of sight would be evident in the cylinder wall.

[turbodan]

The stock gasket never pissed coolant into the motor. The MLS seems to be a total failure when it does blow.

I'm still not sure the block is alright. If it is, the coolant in the oil would have had to get past the rings. Thats possible I suppose, especially if it was just sitting in the chamber and it drained down in there. Its either that or theres a crack in the cylinder wall. I dont see any imperfections, and the amount of coolant in the oil this time was slight. Not a milkshake like last time with the cracked head.

I'll take a few more hard looks at the cylinder wall before it goes back together.

[///ARINUTS...]

perhaps O-ring with the stock gasket would be better?

[turbodan]

I'm thinking about it. The MLS was doing great until I ran it through the 1/4 four times with severe detonation. I'm not disappointed, but I dont know what I'll do yet.

[GregATL]

For comparison my MLS did not blow during this event.


Initially I thought I had a cracked cylinder wall but now with the engine apart it's obvious that it's just melted piston that has grafted itself onto the cylinder wall.


My concern at this point would be cylinder head clamping. You seem to lift it quite easily. Keeping the head in place is probably more of an issue than what type of headgasket you're running. I understand it's detonation related. I would be looking at knock sensing to help avoid this situation again.

My .02.

[turbodan]

I was definitely hearing it. I didn't think it was detonation though, because the tune works fine everywhere in the state, apparently just not at the dragstrip. I figured it had to be something else. Bad call. Should have throttled back...

I'll try a $30 stock HG this time with the Raceware studs at 50 ft-lbs. I've wondered how well the stock HG and studs combo would work, so I'll give it a try.

[M. Holtmeier]

Weren't you using studs and a stock HG before? What are your boost levels at these days?

[turbodan]

This carnage occured with Raceware studs at 45 ft-lbs and a Cometic 3mm MLS.

I had a stock gasket and studs in there when I assembled it with the cracked head. That one didn't run very long, as you can probably imagine.

[Bill in MN]

45 ft lb for your head torque specs? M30 torque specs are 80 for a Cometic MLS and ARP studs. I don't claim to be anything close to a know-it-all but it seems those specs are quite low.

[turbodan]

The Raceware stuff has very fine threads, so I believe they generate more clamping force for the same amount of torque.

[Brian D]

The Raceware stuff has very fine threads, so I believe they generate more clamping force for the same amount of torque.

I would look very closely at that, it is hard to believe you can gain the same clamping force with nearly 50% less torque simply through thread pitch. What is the pitch of the Raceware stud versus the ARP? Did you lubricate the threads when you torqued the head down?

Edit-this link shows ARP's recommendations for bolt and stud torques. Notice the spread between pitch differences.
http://www.arp-bolts.com/catalog/Catalo ... g_0024.jpg

[turbodan]

I'm no engineer, so I can really draw any conclusions from comparison. I'm sure there are a lot o factors that come into play with this hardware. I dont know the thread pitch on the raceware studs, though its quite fine. Probably twice as fine as the threads going into the block, if that makes sense. I could possibly take a picture of one of them.

[Brian D]

I'm not an expert at this either, but 45 ft/lbs just seems real low. I haven't seen M30 studs, but small block chevy head studs are the same way (course into block, fine for the nuts). The torque for those is close to the stock figure, IIRC.

I'd just look real close at what you've got. Where did you get the torque spec from?

[turbodan]

Its as per the manufacturer. They actually suggest 15 ft-lbs, then 30, then 42 for the final torque. I went with 45 because it did seem low, but I didn't want to overtorque them too much. I should be able to get away with 50.

[GregATL]

As I spent part of my day reassembling my motor this is all fresh in my mind. I am using ARP studs with their moly lube. The torque spec is 85 ft lbs. If using oil it is 95 ft lbs. This is for an M30. If you encounter a stud that is not torqueing smoothly, ie grabbing or popping, untorque them all and re-lubricate your studs. You will not have even torque figures if you try to torque them under these conditions. (not trying to be condescending just sharing things I've noticed)

Dan like you mentioned with the raceware studs the ARP have a much finer thread on the nut end than the block end. What size are the studs? M30 uses M12 x 1.75 threads in the block. I would have to go out to the shop to get the figure for the nut but that would be tomorrow. Edit M12 x 1.25

I would also torque in 5 lb increments if only going up to 45-50 ft lbs. I also wait at least 15 minutes (longer if I have time) between steps to give everything time to settle in. For example today after 2+ hours of torqueing down the head I am only @ 70 ft lbs. I am letting it sit tonight and will finish it tomorrow. Going to go to 90 for a final torque this time. 4 more steps.

You may be able to go much higher depending on the stud size, insertion depth in the block, and strength of the stud material. On the diesel I am going to build next (6.9 for my truck) the studs used are 7/16" and torqued to 110 ft lbs (ARP studs and lubricant). Compare that to a 12mm (equals > 7/16") @ 85-95 ft lbs. There is room for higher torque values as long as the block is capable of the additional pull on it.

And I can relate to thinking detonation was something else. When I nailed the throttle on my car the fan would occasionally touch the radiator (better than 1/2" clearance otherwise) and it would make an extremely similar noise. Hard to tell the difference.

And thanks Dan for sharing the carnage. It's always helpful to see how things break and attempt to not do the same.




Edited for accuracy. Insomnia does not make you wise.

[turbodan]

I thought it HAD to be something else since the tune works so well everywhere else. It was very steady too. Not an occasional ping or rattle, just constant, loud detonation at all times under boost. Thats severe stuff.

[russc]

The real problem(while audible detonation is very bad also) is the knock you can't hear. Thats where you really need some sort of sensor w/control. This was pounded into me from Dinan. Thats why all his systems came with either thier unit or J&S's control unit. With the J&S unit, there was lots of pre-det it could hear but my ear couldn't. I would suggest that all invest in some kind of knock control, especially if you have MS! Theres almost no reason why you shouldn't.

RussC

I thought it HAD to be something else since the tune works so well everywhere else. It was very steady too. Not an occasional ping or rattle, just constant, loud detonation at all times under boost. Thats severe stuff.

[turbodan]

I may. I dont know how much good it can do with slight knock on an engine with "relaxed fit" pistons and rocker arms. I dont know if it could be sensitive enough to pick up knock I wouldn't be hearing anyway.

I always leave margins in my ignition map. I dont tune it down to a tenth of a degree of audible knock. I'll usually run at least a degree or two away from that threshold. That seems to work pretty well.

There are a few other things I really should implement with MS. Idle control for example. If I'm doing anything else, thats next. Knock sensing would be neat, but I think I can get by without it. The only knock I've ever had problems with is the bb's under the car knock. If I can keep that under control I think I'll be okay.

[Brad D.]

I may. I dont know how much good it can do with slight knock on an engine with "relaxed fit" pistons and rocker arms. I dont know if it could be sensitive enough to pick up knock I wouldn't be hearing anyway.

I always leave margins in my ignition map. I dont tune it down to a tenth of a degree of audible knock. I'll usually run at least a degree or two away from that threshold. That seems to work pretty well.

There are a few other things I really should implement with MS. Idle control for example. If I'm doing anything else, thats next. Knock sensing would be neat, but I think I can get by without it. The only knock I've ever had problems with is the bb's under the car knock. If I can keep that under control I think I'll be okay.

We usually tune engines on the engine dyno by listening to knock through headphones and a modded knock sensor. When you hear knock with the phones it is still not audible from in the test cell. You can pick it up with phones about a degree before its audible. We find that point and then take maybe 2 degrees out. Reliabilty is of utmost importance.
Dan, setting up the idle control is really pretty easy, especially if you use the Glen's Garage idle board.

[Maddog]

I feel like I must be getting lucky with my car. 18psi without any detonation....only a slipping clutch that keeps me from doing any heavy boosting in anything other than 1st gear....which is all just wheel spin Anyway.

I'll have to continue praying to the head gasket gods.

[turbodan]

You'll usually get it when you start to hook up. Third gear and up are the detonation zone for me. If it going to happen, thats when I hear it.

So far I'm having no problems with a stock M20 head gasket and studs at 1.3 bar. I didn't even resurface the head. Just did a little cleaning and slapped it back on. I think as long as I stay out of detonation it'll be alright.